STB 112 Theory - Unesco

UNESCO-NIGERIA TECHNICAL & VOCATIONAL EDUCATION
REVITALISATION PROJECT-PHASE II
NATIONAL DIPLOMA IN
SCIENCE LABORATORY TECHNOLOGY
MORPHOLOGY AND PHYSIOLOGY
OF LIVING THINGS
COURSE CODE: STB 112
Version 1.0 December, 2008
YEAR I- SE MESTER I
THEORY
1
THEORY
TABLE OF CONTENT
WEEK 1: ANIMAL KINGDOM
WEEK 2: PHYLUM PLATYHELMINTHES (FLAT WORMS)
WEEK 3: PHYLUM COELENTRATA (CNIDARIA)
WEEK 4: PYLUM ANNELIDA (SEGMENTED WORKS)
WEEK 5: PHYLUM NEMATODA (ROUND WARMS)
WEEK 6: PHYLUM-CHORDATA
WEEK 7: MORPHOLOGY AND PHYSIOLOGY OF VARIOUS
ORGANS AND SYSTEMS IN ANIMALS
WEEK 8: THE CIRCULATORY/TRANSPORT SYSTEM
WEEK 9: EXCREORY SYSTEMS IN MSMMALS
WEEK 10: PHYCOPHYTA (ALGAE)
WEEK 11: MYCOPHYTA (FUNGI)
WEEK 12: LICHENS.
WEEK 13: THALLOPHYTA
WEEK 14: BRYOPHYTA
WEEK 15: SPERMATOPHYTA.
WEEK 1: ANIMAL KINGDOM
All animals belong to either subkingdom invertebrate or vertebrate.
Invertebrates are animals without backbones while vertebrates are those with
backbones.
CHARACTERISTICS OF INVERTEBRATES
-
They have no backbones
-
They have no internal skeleton
-
They are unicellular e.g. Amoeba, Plasmodium or multicellular
e.g. Hydra, Tapeworm etc.
-
They move by means of:
i.
Flagella e.g. trypanosome
ii.
Pseudopodia e.g. Amoeba
iii.
Cilia e.g. Paramecium
iv.
Whole body e.g. Tapeworm
v.
Jointed legs e.g. Crabs, Insects
-
They exist by either
-
i. Parasite e.g. Trypanosoma
-
ii. Free living e.g. Hydra, Earthworm
-
They reproduce
i. Asexually by binary fission, budding
or multiple fission
ii.
Sexually by conjugation or gamete production.
Sub-kingdom invertebrate is divided into 8:
Phyla
Protozoa
Coelentrata
Platyhelmithes
Nematoda
Annelida
Arthropoda
Mollusca
Echinodermata
PHYLUM PROTOZOA
CHARACTERISTICS
-
They are the most primitive in the animal kingdom
-
They are unicellular and microscopic.
-
There are free-living as well as parasitic forms.
-
Nuclei could be more than one in the cytoplasm e.g. monocystis.
-
Reproduction may be asexual or sexual.
They are represented by 5 classes based on their locomotory organelles
-
Sporozoa e.g. plasmodium, monocystis
-
Rhizopada (sacodina) e.g. Amoeba
-
Mastigophora (flagellata) e.g. Euglena
-
Ciliophora (ciliate) e.g. paramecium
-
Opalinata e.g. opalina
STRUCTURE
Locomotory organ is lobe-shaped pseudopodia. They are mostly free living.
The protoplasm is surrounded by a thin cell membrane. The cytoplasm is
divided into an outer ectoplasm and an inner endoplasm.
The endoplasm consist of single nucleus, a single or more contractile
vacuole which helps in maintaining the water balance by expelling out
excess water (i.e. osmo-regulation free living amoeba are found among
decaying vegetable matter, in ponds and slow-flow stream. They feed on
diatom, algae. There are captured and engulfed by means of pseudopia.
Once a prey is captured, a food vacuole is formed around it and its being
digested.
LIFE CYCLE
Reproduction is asexual and is by binary fission.
-
The nucleus of the parent cell divides into 2 with each, nucleus
moving to opposite ends of the cells, followed by a construction of
the cell into 2 new daughter cells each into own nucleus.
-
In difficult conditions, as well as when water freezes, Amoeba cell
secretes a thick resistant wall around itself. Within it, can survive
for a considerable length of time. This condition is referred to as
ecosystem. Within it, the amoeba divides repeatedly to release a
large number of daughter amoeba when it breeds.
STRUCTURE OF PARAMACIUM
When compared with the shape of amoeba, paramecium possesses a fixed or
definite shape.
This is because of its pellicle.
They have the shape of a slipper.
Radiating round the body are numerous hairs like structure called cilia which
are used in movement.
Within the pellicle and before the cytoplasm are found numerous rod-like
trichocysta. They are used by the animal when feeding helps it to anchor
itself and are also used for defense or capturing of prey in some species.
Within the cytoplasm are found 2 nuclei, a small micro nucleus and a mega
nucleus.
It also possess 2 star shaped contractile vacuole situated anteriorly and
posteriorly, located near the posterior and is a funnel shaped and groove. It is
ciliated.
LIFE CYCLE
Reproduction is either asexual or sexual. Asexual reproduction is by binary
fission, sexual reproduction is by conjugation and is as follows:
-
2 sexually compatible, same specie come together at their oral
region to become conjugant mega nucleus disappears.
-
Micronucleus then undergo 2 meiotic division to give 2 nuclei in
each.
-
One is stationery and referred to as a female while the other is
mobile and referred to as multi nucleus.
-
The niche nucleus migrate into opposite and fuses with the female
nucleus to form a “zygote nucleus”. Conjugant with its own zygote
nucleus separates and become known as ex-conjugant.
-
Zygote nucleus then divides 3x to give 8 nuclei, 4 of it forms mega
nucleus and the remaining 4 forms micronucleus.
-
Ex-conjugant then divides 2 x to give 4 new daughter cells.
ECONOMIC IMPORTANCE OF PROTOZOANS
-
As parasites causes the following disease to man and animal.
i.
Trypanosome sp causes trypanosomiasis (sleeping sickness)
ii.
Plasmodium species causes malaria
iii.
Entamoeba histolytica dysentery.
iv.
Eimeria causes coccidiosis in chicks
some are commensals or free living e.g. opalina, paramecium etc
Week 2
PHYLUM PLATYHELMINTHES (FLAT WORMS)
GENERAL CHARACTERISTICS:
-
They are flatworms, their body is dorso ventrally flattened,
elongated, covered by ciliated epidermis or by cuticle.
-
They are bilateral symmetrical, have no true body segmentation.
-
Some have external suckers or hooks, or both, digestive
system/tract is incomplete or none with
no anus. There is a
muscular pharynx which leads into the gastro vascular cavity, the
cavity is branched.
-
Muscle layer are well developed, have no body cavity i.e. they are
acoelomate spaces between internal organs organs is filled by
loose parenchymatos cells.
-
They have no skeleton, circulatory or respiratory systems,
excretion by flame cell or flame-bulb protonephridia with ducts.
-
Several longitudinal nerve cords run the length of the body and a
tiny ‘brain’ ganglion located in the head make up a central nervous
system.
-
There are well developed reproductive organs, both sexes are
usually united (monoecious). Fertilization is internal.
-
They are either free-living or parasitic.
They are divided into 3 classes
i.
Turbellaria
ii.
Tremotoda
iii.
Cestoda
CLASS TURBELLARIA:
-
They are free-living flatworms (non-parasitic)
-
They are freshener planarians
-
Their body is undivided, epidermis is with cilia and many mucous
glands, and usually pigmented.
-
They are usually with ventral mouth, no suckers.
-
Few are terrestrial while most are aquatic majority are marine.
-
They are oval or elongate in shape.
-
They are hermaphrodite, development is usually direct, some show
asexual reproduction. e.g. planaria.
CLASS TREMATODA
-
They are the flukes
-
Their body is undivided, covered by cuticle but no epidermis or
cilia.
-
They have 1 or more suckers for attachment.
-
Their mouth is usually positioned on the anterior end; digestive
tract is branched into 2.
-
They have 1 ovary
-
They are all parasitic.
They have 2 sub classes:
i.
Subclass: Monogyenea
ii.
Subclass: Digyenea
Sub class Monogenea
-
They have a weak oval sucker or none.
-
Their posterior end is with an adhesive disk and usually with
hooks.
-
They have 2 excretory pores.
-
They lay few eggs, their larva is ciliated, they have no intermediate
host.
-
They are mainly ectoparasitic on cold blooded vertebrate,
cephapoda and crustaceans. E.g. Gyrodactylus found on gills of
fresh water fishes, polystoma, found in gills of tadpole and bladder
of frog.
Sub class : Digenea
-
Have 2 strong suckers, 1 around mouth and 1 ventral, but no
hooks.
-
Have 1 excretory pore.
-
Have long uterus, lay many eggs, have 1 or more larval stages.
-
They reproduce inside their intermediate host before changing to
adult form.
-
They are mainly endoparasites, larva are found mainly in
mollusk’s, crustaceans and fishes, adult forms are found in
vertebrates e.g. Schistosoma, Fasciola, Hookworm, Tape worm
etc.
STRUCTURE OF PLANARIA
Planaria are all small free-living worms. They live in cool, clear and
permanent waters, e.g. streams, ponds, marshes, and springs where they
cling to the undersurface of submerged plants, rocks and logs and avoid
light.
The worm is thin, slender and soft and of about 15mm long, with a blunt
triangular anterior end (head0 and a tapered body with dark pigment.
The head region bears 2 black eye spots. Mouth is on the ventral surface
near the middle of the body. Through the mouth a pharynx or proboscis is
extended to capture food.
Excretory openings are minute, located laterally on the dorsal surface and
are difficult to see. Genital pare are found on the ventral surface behind
the mouth.
The body is covered by epidermis and its ciliated. They lock of mouth,
pharynx and intestines. There is no skeleton, no respiratory system.
Gaseous exchange is through the epidermis. Excretory system is made of
large flame cells. Nervous system is highly organized and forms a tiny
‘brain’ and the head region.
Sexually mature worm is monoecious. The male reproductive system
includes , many hundred of small tastes, on both sides of the body,
minute its efferens, a larger vas deferens, a median seminal vesicle and a
muscular penis. The female reproductive consist of2 rounded ovaries, 2
oviducts, many yolks, a median vagina, genital atrium, copulatory sec.
they avoid strong light intensity. Locomotion is by gliding with the
anterior end forward and slightly raised or by crawling.
LIFE CYCLE
Asexual reproduction is by transverse fission. A worm constricts into 2
usually behind the pharynx and the mission parts on each piece then grow
and differentiate. Planarians have great powers of regeneration when
injured, naturally or experimentally, any part of the body can be replaced
back.
In sexual reproduction, 2 planarians, come together through their
posterior ventral surfaces, and copulation is mutual, the penis of each is
inserted into the genital atrium of the other, sperm from the male system
of each passes to the female receptacle of the other. (cross-fertilization).
The worms then separate after mating. Many zygotes and yolk later
combine in a separate capsule or eggshell. Development is direct, no
larval stage.
STRUCTURE OF FASCIOLA HEPATICA
This is the common sheep liver fluke. It is found in the bile ducts and
some times in other organs. It causes the disease called ‘liver rot’.
The liver fluke has a leaf shaped body. It measures up to 30mm long. It
is rounded anteriorly and blunt posteriorly.
It has a terminal anterior sucker which surrounds the mouth and a ventral
sucker which is behind and serves for attachment in the host. Between
the 2 suckers id the genital opening.
Digestive system is made up to a mouth, pharynx, esophagus, 2-branched
enteron. (Stomach).
Excretory systems are highly developed in adult worm.
Male reproductive system has 2 many branched testes, vas deferens,
seminal vesicle, prostate gland and penis. Female system comprises a
branched ovary on the right side, oviduct, seminal receptacle, and
louver’s canal.
LIFE – CYCLE
Eggs are passed out with feasces through the bile duct and intestine of
sheep.
In worms and moist climate, the eggs hatched out about 9 days into larva.
The larva (miracidium) is barely visible. The miracidium is multicellular,
ciliated and with a pointed rostrum, with 2 eye spots. It hatches in water
and swims for not over 24hours, and dies unless it finds a certain suitable
kind of snails (bulimoides)species, if the snail is found, it burrows into
the soft tissues and lymph vessels of the snail enter, only one penetrates
it, should many miracidia enter, the snails dies. The larva loses its saclike sporocyst. Within the sporocyst another form of larva called redia are
formed. Each sporocyst produces 3-8 elongate sac-like rediae, with a
mouth and short gut. In about 8 days they burst out and migrate to
another organ (liver0. there, they produce other radiae for 1 or 2
generations, and finally each daughter redia produces several larva of a
new kind called cercaria. The cercaria has a slender tail and a disk-shaped
body, with both oral and ventral suckers.
The cercaria burrows out of the snail to swim through the water by use of
its tail.
Few hours later, the cerceria settles on a grass blade or other vegetation
near surface of water and losses its tails, and now become a metacercocia
found in a tough cyst.
The encysted larva (metacercaria) remain viable for weeks or months on
grass or damp hay. When such infected vegetation is eaten by a sheep or any
suitable host, the cyst are digested off and the larvae burrow into the
intestinal well and then to liver.
Week 3: PHYLUM COELENTRATA (CNIDARIA)
Characteristics:
-
They are multicellular organisms.
-
They are radially symmetrical.
-
They have no head or body segmentation.
-
They are diplobastic it have 2 body layers of cells, an external
epidermis and an glea between the 2 layers.
-
They have only one opening i.e. mouth, no anus which is
surrounded by soft tentacles and connected to a sac-like digestives
cavity. (enteron).
-
They have no blood, respiratory or excretory organs.
-
Reproduction is asexual by budding, sexual by gamete production
or by alteration of generations (metagenesis)
They are divided into 3 classes:
1.
Class: Hydrozoa
-
They exist in polyp form
-
Enteron or gastro vascular cavity lacks portion i.e. not septet.
-
Mesoglea is non cellular.
-
Mainly found in shallow saltwater or fresh
-
They are solitary (Hydra) or colonial (Obelia).
-
Reproduce asexual by budding or sexually by gamete production,
or with medusoid stage e.g. Hydra, Obelia.
ii. Class: Scyphozoa
-
They are the jelly fishes
-
They are chiefly free-swimming medusae of bell or umbrella form.
With strong 4-part radial symmetry.
-
They have central gestrovescular cavity with pouches or septa in
bell margin.
-
Have no polyp generation.
-
They are all marine e.g. Aurelia (common jellyfish).
-
They have separate sexes.
iii. Class: Anthozoa
-
They are the sea corals, or sea anemones.
-
They all exist is polyp form.
-
Mouth leads into stomodeum (gullet).
-
Enteron is divided by vertical septa.
-
Mesoglea is a connective tissue with or without skeleton.
-
They gonads are located in the septa
-
They are all marine found on coral reefs
-
They are either solitary or colonial e.g. red coral, sea pen.
Metridium etc.
STRUCTURE OF HYDRA
Hydra is a small, solitary polyp. It is slender flexible about 10-30mm
long, with 8-10 delicate tentacles at its oral end. It lives in cool clean and
usually permanent freshwater of lakes, pounds and streams, attaching
itself to stones, sticks, or vegetation. The body is a cylindrical tube with a
basal disk or foot. The mouth is a small opening on a conical hypos tome
surrounded by tentacles. The mouth leads into the digestive cavity called
enteron. The whole animal is very flexible the body may extend as a
slender tube, bed in any direction or contract to a short form. The side of
the body may bear lateral buds that take part in asexual reproduction at
times, it may bear other rounded projections it ovaries or testes for sexual
reproduction.
The well of the body and tentacles consist of 2w cell layers (diploblastis).
A thin epidermis, made of cuboidal cells, which is protective and
sensory, is function and inner thicker gestrodermis made of tall cells and
serves mainly in digestion. Between these two layers is a thin non
cellular mesoglea.
Which provides an elastics framework for both the body and the tentacles
(support)?
Hydra lives attached by its basal disk to objects in water, and still moves
freely. Hydra exhibits different modes of locomotion, i.e. walking
floating and climbing or fixed.
Hydra feeds mainly on minute crustaceans, insects larvae’s and similar
animals or even many swallow a prey bigger then itself.
LIFE CYCLE
Hydra produces new individuals by asexual budding or by sexual means
involving gametes.
During asexual reproduction, bud forms as a projection about midway on
the body wall. This lengthens acquires blunt tentacles and a mouth, later
hit constructs and detaches at the base to become an independent hydra.
Budding may occur at any season, with adequate supply of food and
water, it suitable normal condition.
Sexual reproduction, this takes place during unfavorable condition.
The gonads are the only reproductive organs these are temporary
structures on the sides of the body. The ovaries produces eggs, while
tastes produces sperm cells. Both gonads arise from cells in the
epidermis. Although Hydra is dioecious, cross fertilization is the rule.
The tastes of one hydra matures earlier that the ovaries and releases its
sperm cells which travels in the water and this then fertilizers the eggs
cells form a zygote which soon divides and ruptures and settles in the
bottom of the water till when the condition become more favorable it
emerges as a new hydra.
STRUCTURES OF OBELIA
Compared to the hydra, Obelia is colonial and passed through a medusoid
life cycle stage.
Obelia exist as a whitish or brownish colony which consist of a root-like
base called hydrorhiza with slender branched stems from which hundreds
of 2 kinds of polyps grows, these are the feeding polyp or hydranth, with
20 or more solid tentacles fixed in a transparent vase-shape hydrotheca
which houses and protects it. Hydranth captures small animals by use of
their tentacles.
The second type of polyps is the reproductive polyp or gonandium. It is
cylindrical and converted by a transparent gonotheca on which lateral
buds form from and develops into medusae.
LIFE CYCLE OF OBELIA
The reproductive polyp or ganangium give rise to medusoid form. The
medusae then escape to float and feed in the3 sea. The medusae are of 2
different sexes, and their gonads develop in the enteron where the eggs
and sperm are released into the water. There in water, each zygote
develops into a minute ciliated planula larva, which later grows to a small
polyp. The small polyp later grows to begin a new colony by asexual
budding. The alteration of sexual and asexual generations is referred to as
metagenesis.
ECONOMIC IMPORTANCE OF COELENTERATES
-
Serves as food for man e.g. Jelly fishes.
-
The skeleton of the red coral is usual for jewelry.
-
Some are commensal on the shells of hermit crab e.g. Actininica
Used in laboratories for research purpose.
-
Sea
anemone
is
used
to
decorate
Aquarians
at
homes/schools/offices.
DIFFERENECES BETWEEN HYDRA AND OBELIA
Hydra
Obelia
- it is solitary
- found in fresh water
It is colonial
Found in sea water
- polyp form with no nedusoid life Polyp form with medusoid life cycle
cycle stage
- No metagenesis in life cycle stage
stage.
Have metagenesis in life cycle stage.
Week 4
PYLUM ANNELIDA (SEGMENTED WORKS)
CHARACTERISTICS.
-
They have bilateral symmetry.
-
Their body is elongated and made of conspicuous segments, and are triploblastre.
-
Appendages are made of minute rod-like chitrinous setae, there are few to many
per somite.
-
The class polychaeta have fleshy tertacles on the head and their setae are borne on
lateral fleshy parapodia, but most Hirudinea lack the setae.
-
Body is covered by thin moist cutide.
-
They have a well development coelom, it is divided by septa (septed) in
oligocheata and polytaeta but hirudinea lacke coelom.
-
Digestive tract is complete, tubular and estends the whole length of the body.
-
They have a closed circulatory system, blood plasma contains dissolved
heamoglobm and free amoebacytes.
-
Resperation is by epidermis or gills
-
Excretory system is of a pair of nephrodia per somite.
-
Nervans system is with pair of cerebral ganglia (brain), in each segment.
-
Sexes are united, development, is direct in oligocheata, and hirudinae, but sexes
may be separate and with trochophave level state in polychaeta.
They are represented by 3 classes.
i.
Polycheata, e.g. chlamoorm.
ii.
Ohgochaeta. e.g. earthworm
iii.
Hirudinea. e.g. leech.
Structure of a Clamworm (Nerers)
Clamworm lives near the low-trade line. It is nocturnal and hides by day time beneath
stones or in a temporary hole, only bringing crawls over the sand, or swims by lateral
wriggling of the body.
It has a long, slender, greenish body, round above and flattered ventually. It is compose
of 200 or more similar somites.
The head is district and is formed by the prostomium and peristomium. Within the body
well is the coelome cavity liend by peritone and divided by septa between the somites.
Digestive tract is made up of the month, protrusible pharynx with 2 horny- toothed jows
and groups of chitinus ‘teeth’ a short oesophayus joined by 2 large glands, stomach,
intestive and crus.
The cirenlatory system consist of a dorsal and ventral vessel which branes into glit,
nephridia, body well and parapodia.
Respiration is by capillaries in the parapodia and body well.
Excretion is by pared nephirodia, but differs from those of the earthworms.
Nervus system includes, a brain, nerves in the head and tentacles and a pair of ganglia
and lateral nerves in each sominte.
The prostomium bears 2 short prostomiel tentacles, a pair of stubby conicol palps
laterally located and 2 pairs of small eyes.
The peristomium surrounds the ventral mouth and bears 4 pairs of peristomiel tentacles.
The are sensory organs of touch, smell and sight. They help in finding food as well as
avoiding predators.
On both side of each somite is a flat parapodium. The parapodia are used for locomotion.
Anus is located in the lost somite, on it are 2 soft sensory and cirri sexes are separate, and
forms gonads only during breeding season. Eggs and sperm are formed from cells of the
loelomic peritoneum, fertilization occurs in the see. Zygote develops into a cilicted
trochophore larve.
Structure of Lumbricus Terrestris (earthworm)
They have few satae per segment.
The body of Lumbricus terrestris is long and cylindreal, topered at both adg. It has no
district head mature worm is divided into 115-200 segments/somites.
Maith is located on the 1st somite and is surrounded by a fleshy lobe (prostomium), while
the annus is on the last somite.
Clittelum is a conspicuous glandular swelling over somites 32-37, it secretes material that
form cocoons to contern eggs.
On each somite with the exception of the 1st and last are 4 pairs of minute britle like setae
that project slightly on the ventral and lateral surfaces. Satae serve as hold fast devices
when a worm is in its burrow or morning on grand.
There are other openings on the body other than the month and arun, and these are dorsal
pore on somite 7 or 9 down to the oral end, these connect the body cavity to the exterior.
i.
A Nephridiopora (excretony opening)
ii.
Openings of seminal receptacles.
iii.
Openings of the 2 oviducts.
iv.
Openings of paired sperm ducts.
The body is covered by a thin transparent cutide, it is secreted by the epidermis, beneath
it are many unicellular glands which produce mucus. The inner body well is collered by a
thin smooth epithelium (peritoneum).
The body form is maintained by the elasticity of the body well over the organs and fluids
within it. The characteristics. Movement of the earthworm is due to contraction of the
corruler muscles which elongates the body and contraction of the longitudinal muscles
which shortest it.
A cross section of the body wall show 2 concentric tubes i.e an onter body well and a
straight digestive tract within space in between them is the body cavity (coelom) which is
divided into compartments by septa. The coelom contains watery coelomic fluid with free
amoebocytes.
Digestive tract is of month, buccalcevity, pharynx, oesophaysn, cropper proventriculus,
gizzard, san intestive and an ams food is mainly dead leaves, gresses t.e.c.
Circulatory system consists of blood which consists of a fluid plasma that contains free
colourless amoebocyts. The plasma is red in colour. Blood flows to and from all parts of
the body in a system of closed blood vessels with capillaries.
It has no organized respiratory system. Blood in capillaries close to the cutide receives
oxygen and gives up C02.
Excretory system is made of a pair of nephodia, which opens into a nephodia nervous
system is made of a ‘bran’ and a ventral nerve card.
Life-Cycle
Earthworm is monoecious, both sex organs are ventrally and anterrorly located.
The male gonads include 2 pairs of minute testes, a cilicted sperm funnel connected to a
short vas afferens, connected also to a vas deferens that leads to the male pore.
The female gonads include a pair of overses that discharges nature ova into the coelom
and are collected by 2 oviducal funnels with egg SCCS, connected to the oviducts. The
system also includes 2 pairs of seminal receptacles where sperm received are stored until
need to fertilizer eggs in cocoons.
They reproduce through much of the year, mostly in worm moist weather.
Mutiny occurs at night and takes 2-3hrs 2 worms stretch out from their burrous and bring
their vsentral anterior surfaces together, with the anterior aids pointing in opposite
direction.
The clitellum on each, grips somite 7-12 of the other and less contact of somite 26 on
each is made with 15 of the other.
Each worm secretes a slime tube about itself, and on each worm a pair of seminal
grooves forms along which mosses of sperm pess to enter the seminal receptacles of the
other, aster this, the worms separate.
Each worm later produces cocoons containing eygs for each cocoon, a slime tube is
secreted. Around the citellum and within the cocoon forms a separate secretion over the
clitellum. The tube and cocoon then slip forward, to be fertilized while passing over the
seminal receptacles, and as the worm withdraws from the tube, the cocoon closes into a
lemon-shaped case. That is then deposited in damp earth.
Phylum arthropoda
Characteristics
-
They are bilaterally symmetrical.
-
They are tribloblestic, body is usually segmented and jointed externally (head,
thorax & abdomen)
-
They have a pair of walking appendages per segment.
-
Their body is covered by a herdered exostecleton containing cliton which is
secreted by the epidermis.
-
Digestive tract is complete, mouth parts is made of lateral jows, adopted for
chewing or suckining annu is terminal.
-
Circulatory system is oopen, heart is dorsal, body space is heomocoel, coelom is
reduced.
-
Respiration is by gills, tracece, book hugs or body surface.
-
Exretion is by coxal or green glands or by 2 or many malpighian tubules.
-
Sexest usually separate, female and male not similar.
-
Fertilization mostly internal.
They are divided into the following subphylum
1.
Sub-phylum chedicerate classes
i.
Merostomata e.g. horseshoe crebs
ii.
Pycognodie e.g. see spides.
iii.
Arechnidan e.g. spiders
2.
Sub-phylum mandibulate (antennate) classes
i.
Crustecea e.g. creb, crayfish, water flease etc
ii.
Insect e.g. housefly, mosquito etc
iii.
Chilopoda e.g. centripede
iv.
Diplopoda e.g. millipede
v.
Pauropoda e.g. pauropus resembles millipede.
vi.
Symphyla e.g. garden centipede.
Class insects is the largest and has the largest representatives.
Class insect/hexapoda
Sub-class – Aptergygota
-
Wingless
-
Little or no metamorphosis.
-
Abdoma with ventral appendages.
i.
Order portura e.g. Acerentulus barberi
ii.
Order – collembolan (springtails) e.g. garden flea, snow flea etc
iii.
Order- diplura (japugids) e.g. japyx
iv.
Order-thysanura (bristletaits) e.g. silverfish, firebrat.
Subclass- pterygota.
-
Winged insects
-
Noabdomind appendages
-
Metemerphosis gradual.
i.
Order – odonate e.g. dragonflies, damselflies etc
ii.
Order- ephemeropter e.g mayflies.
iii.
Order – orthoptera e.g. gresshoppes, crickets etc.
iv.
Order- dermaptera e.g. earwigs
v.
Order-plecoptera, e.g. stonflies
vi.
Order- isopteran e.g. termintes
vii.
Order- embioptera e.g embids
viii.
Order-mallophage e.g chewing irea.
ix.
Order- Anoplura e.g sucking lice
x.
Order- psocoptera e.g. booklice.
xi.
Order-hempitera e.g. tine bugs
xii.
Order- homoptera e.g. aphids, scale insects etc
xiii.
Order – thysanoptera e.g thrips
xiv.
Order- mecoptera e.g. scorpion flies
xv.
Order- newropera e.g. ant lions etc
xvi.
Order – Lepidoptera e.g moths, butterflies
xvii.
Order- diptera e.g. trueflies, mosquitoes, gnats
xviii. Order- siphonaptera e.g. flease.
xix.
Order- coleopteran e.g. beetles, weexils etc
xx.
Order- hymenoptera e.g. wasps, ant, bees.
Phylum echinodermata
-
Radially symmetrical in adults, bitoteral in larvoe.
-
Triboblestre, organs ciliated, no head, brain or segmentatia.
-
Body surface is of 5 radiating areas or ambulacra.
-
Body covered by delicate epidermis with spmes.
-
Digestive tract is simple, usually complete but some lack anus.
-
Curculatory system radiate, reduced.
-
Resporation is y minutes gills or populace, tube feet or closscal respiratory trees.
-
Nervans system with curcumoral riny and radial nerves.
-
Sexes separate, alike, with large goricals larvae micrsopre, cilicted, transparent
and usually free- swimming with conspicuous metamorphosis, fertilization in the
see.
Subphlylum pelmatozoa.
-
Mouth and ams on upper surface
-
Body in cup or calyx – shaped skeleton, usually attached by aboral stalk or
surface.
i.
Class cerpordea.
ii.
Class cystoidea.
iii.
“ blastoidea
iv.
“ edrroasteriodea
v.
“ helicophecoidea
vi.
“ crinoidea e.g. seacilies, feather stars.
Subphylum eleutherozoa.
-
Mouth on lower surface
-
No stalks.
i.
Class holothuriodea e.g. sea cucumbers
ii.
“ echinoidea e.g. sec urchins, said dollars
iii.
“ asteroidean e.g. startoshes/sea starts.
iv.
“ ophiuriodea e.g. brittle starts.
Structure of starfish (asterias vulgaris)
The body consists of a central disk and fice tapering rayws, or arms. The axes of the aims
and termed radi, and the spaces between them are called inter-radi. On the upper or
aborel surface are many calcareaous spines, which ae parts of the skeleton. The anus is a
minute opening near the centre of the abord surface.
The mouth is in the middle of the lower or orel surface, surrounded by a soft peristomieal
membrane. A media ambularel groove, borded by large sines, extends along the oral
surface of each arm, and from it many slender tube feet extends in 4-2 rows. On tip of
each arm is a small soft tentacle and light sensitive eyespot.
The whole body of the animal is covered by ciliate epidermis, beneath it is the
endoskeleton inside the skeletom is the large coelom which is fileld with a lymph-like
fluid containing free amoebocyles that helps in circulation, respiration and excretion.
Digestive system is made up of mouth stomach, a short intestine and arms. Nerves system
is a circumorel nerve running and nerve cords in the arms. Sexes are separate. A pair of
guide is in the coelom of every arm, and a minute duct from each opens aborally on the
central disk.
WEEK 5: PHYLUM NEMATODA (ROUND WARMS)
CHARACTERISTICS
-
their body is slender and cylindrical.
-
They have blateral symmetry
-
They have 3 body layer (triploblastic)
-
They have no true body segment
-
Their body is covered with tough resisted cutide
-
They have complete digestive tract (mouth and anus)
-
Body is filled with space i.e psendocoel
-
Have no circulatory or respiratory organs excretory organs are of 1,2or none
simple flame cells.
-
Sexes are usually separate, with the male smaller than female
-
Fertilization is internal, eggs are microscopie, each covered by a chitinous
shell
-
Development is direct with several moths, no sexeual reproduction or
regeneration.
-
They differ from fletroorms in shape absorce of citic and suckers presence of
a complete digestive tract and a body cavity and also having separate sexes.
-
They are represented by 2 classes.
i.
Adenophorea (Aphasmiodia)
ii.
Secernentea (Phasmidia)
e.g whipwon, heteroderg, gruines warm asceris, etc.
STRUCTURE OF ASCARIS LUMBRICOIDES
Ascaris Lumbricoides: is the common intestinal roundworm of man and prg it
shows the general features of nematodes the female is 8-16 inches long and about ¼
inches in diamale is lesser in size, 6-10 inches long. When fresh the speeimen is
yellow purple in colour.
The body is slender and round, temporary at both sides, covered with smooth tough
elastic cutide which bears minute structure along its body externals 4 while long one
on dorsal are vertral and 2 cm lateral sides.
Mouth opens at the anterior end, between 3 rounded fleshing lips ams is a transverse
slot close to the posterior and of the vertral surface.
Male has a sharp curved posterior end and 2 penial spiculae projecting from the male
genital pore just within the anus female is straighter and her gaital pure or vulra is
midvertrailly located on the body at about 1/3 the distance from the anteeror end he
body wall is thin and consists of cutide, epidermis and muscle layer.
Digestive tract is straight and extends the length of the body it consists of mouth,
local cavity phary/oesophagus in testine rectum and anus. No circultatory or
respiratory organs
LIFE – CYCLE
Male and female worms copulate within the host’s intestine the eggs are fertilized in
the oviducts of the female and covered by a tough shell.
A nature female may contain 23million of eggs at a time and lay 200,000 or more per
day. The eggs pass out of the female into the host’s intestine and leave with feeces in
warm. Moist, shady site fevelopment requires 3-4 weeks if such embryonated eggs
(emugo worms) are swallowed by a suitable host through food or water they hotel in
the intestine burrow into venis/lymph vessels of the intestine then travel thrugh the
heart to the lungs and grawing in size in few days they break into the air possesses
and move to the trachea oesophagus and stomach then back again to the intestine
where they finally graw to maternity.
No intermediate host is needed to complete the cycle. Pigs usually pick the leavee
from infected soil or in dirt on the sow’s udder dunny nursing.
ECONOMIC IMPORTANCE
-
They are peresitre in man, animals and plants
-
Do little or no damage but some cause impared efficiency illressor death of lost
-
passage of many larve through the lungs causes inflemation and may lead to other
infectures
-
Adult ascarids in nitestrie may produce toxic to the host and when numerous
many obstruct the intesture and lead to surgery.
-
in cultivated plants causes ‘root nots which causes weeking or death of plant othe
disese in men is elephantiasis
Week 6
SUB-KINGDOM VERTEBRATA
PHYLUM-CHORDATA
CHRACTERISTICS
-
The are all bilaterally symmetrical.
-
They have segmented body with 3 germ layers (tribloblestic)
-
Their digestive system is complete and also have a well developed coelom.
-
They have a single, dorsal, hollow, tubular nerve cord.
-
They have notochord at some stages of their life cycle this may persisit in the
primitive lower chordates e.g amphioxus.
-
They have endo skeleton
-
They have back bone which replaced the notochord in hgher vertebrates
-
They have pair gill slits in their phargux
-
They have segmented canal tail the phylum is divided into 3 sub-phylale tunicate,
cephalochordate (lower chordotes) and craniata (higher chordotes)
SUB-PHYLUM TUNICATA
-
They are also called urochordetes (tunicctes)
-
They have notochord and nerve card in their tail region (larva form)
-
They larval form is also free-living minute, tadpole like and with gill slits.
-
Adult are tubuler globose or pregular in form and covered with tunic (test)
which is often transparent.
-
Adult are with out notochord, nerve card is rechaced no coelom segmentation
or nephridie.
-
They are represented by the following classes I lervaces (appendicalaria).
-
These are about 5mm long lerva form in adult and also in structure.
-
Their notochord and nerve cord persists
-
They have 2 gill slits their tunic is not persists.
-
They are free living e.g oikopleura and appendicularies
Class (ii) assidiaces
-
they have various sizes and form
-
they are either solitary colonial
-
they have many gill slits which persists
-
tunic is well developed and permanent e.g ciona ascidia
Class (iii) thaliacea
-
these are of various sizes
-
adults lack notochord and tail
-
their gill slits varies
-
tunic is permanent with arcular muscle bads
-
adult are free living or pelagia e.g salpa etc.
(ii)
SUB-PHYLUM CEPHALOCHORDATA
-
Their body is slender and looks like fish
-
Body is segmented with i-layered epidomis
-
They have no scales
-
Their notochord and nerve cord runs along he either body and persist so also
the many gill slits e.g. amphioxus (lancelets)
(iii)
SUB-PHYLUM (CRANIATA)
-
These form the major phylum choosota cligher chardotes
-
Thy all have enlarged brain enclosed in a brain case (cranium).
-
They have segmented spinal column or V.C that supports the body.
-
Their body is segmented into head, neck trunk and tail.
-
Their body covering is stratified into epidermis and dermis fishes and repliles
have protective sects.
-
They have endo and jointed skeleton of cartilage and bone.
-
They have 2 pairs of limbs (funs in fishes) and limbs articulates with the V.C.
through the limb grandness.
-
On their skeleton are muscles that move the parts for locomotion.
-
They have a long digestive tract, marth contain a tougue and usually with
teets.
-
Conculatory system is closed and included a well developed heart either 2, 3
or 4 chambered.
-
They are either poikilotlernic or lomothermic
-
Respiration is by gills or lungs
-
Excretion is by kidneys
-
Sexes are separate
-
They are represented by the following classes.
i.
cyclostomate
ii.
chondriclitlyes
iii.
osteichitlyes
iv.
amphibic
v.
reptilic
vi.
aves
vii.
mammies
CLASS PISCES
-
They have body covered with most skin and protected by scales of either placard
genoid, cyclord or tenoid or more
-
some have bath median and paired this and some lack paird fin
-
body is streamlined
-
They have a termind month and as us
-
Respiration is by gills, gills are protected by operenlum but some lck the
operaculum covering e.g dog fish they only have gill slits.
-
they are poikilothermie
-
sexes are separate some are oriparans ovoviviparans fertilization is external
development is direct
CLASS-CYCLOSTOMATA
They have long slender and cylindrical body with compressed tail region.
Their median fins is supported by cortilagince u in rays.
They have soft, smooth skin with many unicellular masus glands but no scale no true
jows and no paired funs
Their math is ventronteriorly located
They olfactory organs are pared but with single median operating on smooth
Their skill and visveral arcles are carto laginous
Notochared persists
They have 2 chamered heart
They have 5-16 pairs of gills in latoel saclike pauches
They have 2 kidneys
Theie brain is different treted with 8 or 10 pairs of cranial nerves.
They are poikilothermic
Have separate sexes hsve single gonad without duct, fertilization is external, development
is direct in Hagfishes while Lampreys have long larval stage. E.g. hagfish (Eptatretus
stout), Lamprey(Entosphems tridentatus)
CLASS CHONDRICHTYES
-
Their skin is tough and covered with minute placoid scales, they also have
many mucus.
-
They have both median and paired fins, and are supported byfin rays. In
males,the pelvic fins are with claspers.
-
Their muoth is ventrally located and its with enamel-capped teeth, intestines
with spinal valves.
-
They hsve two or one nostril, which is not connected to mouth cavity.
-
They have both lower and upper jaws.
-
Skeleton is cartilaginous,they have no true bone, notochord persists.
-
They have many vertebrae, with both pectoral and pelvic girdles.
-
Their heart is 2 chambered.
-
Respiration is by 5 – 7 pairs of gills
-
Thy are poikilothermic
-
Sexes are separate, gonad are paired, fertilization is internal, they are
oviparous or ovoviviparous, development is direct e.g shark, dogfish, ray etc.
CLASS-OSTEICHTHYES
-
Their skin is with many mucus gland, and usually with embedded bony
dermal scales (gonard, but mostly of cyclord or ctenoid) some are scales
(neked).
-
They have both median and paired fins supported by fin rays of cartilage of
bone.
-
Their mouth is usually terminal and with teeth.
-
Their jaws are well developed, articulates with the skull.
-
They have eyes (well developed) with no lids.
-
Their skeleton is mainly of bone, they have many vertebrae.
-
Their tail is usually homocercal
-
They have 2-chambered heart.
-
Respiration is by gill, covered by operculum and also with swim bladders.
-
They have 10 pairs of cranial nerves
-
They are poikilothermie
-
Sexes are separate, gonads are paired, oviparous, ovoviviparous or viviparous
ferterlization is external development is direct.
CLASS AMPHIBIANS
-
Have moist and glandular skin, no scale
-
Have 2 pairs of limbs for walking or swimming toes are 4-5 or fewer or more
-
Have 2 nostrils connected to mouth cavity and aid lung respiration.
-
Eyes are with moveable eye lids, eardrums are external, mouth with fine teeth,
tongue is protrusible.
-
Skeleton is large and bony, skill with 2 occipital condyles
-
Heart is 3-chambered 2 atria and 1 ventricle red blood cells nucleated and oval
-
Respiration is by gills, lungs, skin or mouth lining.
-
Brain with 10pairs of cranial nerves
-
They are poikilothermic
-
Fertilization is external, they are oviparous eggs with yolk and enclosed in
gelatinous coverings. e.g frog, toad, salamander, caecilian etc
-
They are represented by 3 orders
i.
Anura
ii.
Candeta
iii.
Apoda/Gymnophiona
CLASS REPTHLIA
-
Body covered with dry cornified skin, usually with scales or scutes.
-
They have 2 pars of limbs, each with 5 toes ending in boney claws and
adopted for running, crawling or climbing or none.
-
Skeleton is completely ossified, skull has 1 occipital condyle.
-
Heart is imperfectly 4-chambered red blood cells, nucleated biconvex and
oval
-
Respiration is lungs, or cloacal respiration in some aquatic turtles.
-
They have brain with 12 pairs of cranial nerves
-
They are poikilothermic
-
Fertilization is internal, have copulatory organs egg are large, much yolk and
in lecthery or slimg shell usually laid but retained for development in some
lizards and snakes they are represented by orders.
i.
Chelonia
ii.
Squamata
iii.
Crocodilia
e.g Tortoises, lizards, geckos, snckes, crocodiles, alligators etc.
CLASS AVES
Body covered with feathers have 2 pairs pf limbs fore limbs modifies as wngs for
flight and hand limbs for perchaing walking or wimming each foot usually with 4 tres
shanks and toes shecthed with cornified skin.
-
Skeleton is delicate, strong, fully ossified
-
Mouth projects as beak or bill with horny sheath, no teeth, skull with 1 occipital
condyle neck flexible pelvis is fusel stonum enlarged, have meelian keel tail with
few bones.
-
Heart is 4-chambered, Redblood cells is nucleated oval and biconvex
-
Respiration by compact lungs attached to ribs and connected to thun-walled
consees.
-
Have no urinary bladder, excretions is semisolied
-
Females with only left overy and oriduct
-
Brain with 12 pairs of cranial nerves
-
They are homorothermie
-
Fertilization is internal, eggs with large yolk, coveel with hard ling shall,
deposited for incubation.
CLASS MAMMALIA
-
Body usually covered with hair fur
-
Skin with many glands e.g sebaceous scent sweet and mammary.
-
Skull with 2 occipital condyles
-
Mouth with teeth, movable touque, eyes with movable eyelids, ears with
external panna.
-
Have 4 limbs, some lack hand limbs each, foot with 5 or fever roes and
adqotel for walking, running climbing burrowing swimming or flying, toes
with horny deros nail, hoofs or flesty pads.
-
Heart completely 4-chambered
-
Respiration by lungs, a dicphragsn separates the lungs
and heart from
abdomud cavity.
-
Have urmary bledder excretions is fluid
-
Have a highly developed brain with 12 pairs of cranial nerves.
-
They are homothermie
-
Mole with copuletory organ (pens), testes in a scrotum which lungs,
fertilization is runterial egg are minute with no shell and retained in the uterms
of the female for development.
-
Females secretes mlk from the mammany gland to nourish the young.
They are divided into the following subclasses and orders.
i.
sub-class prototheria: order monotremata e.g duck-billed platypus.
ii.
Sub-class theria: order marsupiala (pouched mammals) e.g kangaron
iii.
Sub-class: Eutherra (placental mammals)
Order: insectivore e.g moles, shrews
Order: Dermoptera e.g flying lemurs
Order: Chiroptera e.g Bets
Order: Primates e.g lemurs, monkeys, apes man
Order: Pholidote e.g pangolin/scaly an teeter
Order: Lagomorpha e.g hares, rabbits
Order: Rochertra e.g squirrels, mrce, parcupines gumea prys etc.
Order: Cetacea, e.g whales, dolphins
Order: Carnivare e.g dog, cets, lions etc.
Order: pinnipecdia e.g seels see irons
Order: proboscides e.g elephants cardvereles
Order: Srewe e.g manatees/sea cows
Order: Hyracordea e.g tree acid rock hyrax
Order: Perissodactly (oddtoed) e.g horses, zebras asses,
rhinoceroses etc.
order: Artrodactyle (even toed) e.g prys hippopotenis camels, lows
sleeps, goots gazelles etc.
PHYLUM MOLLUSCA
CHARACTERISTICS
-
They are bilaterally symmetrical.
-
They are tribloblastic, epithelium is single layered, mostly cilicted with
mucons glands.
-
Their body is usually short, enclosed in a thin dorsal manthe which secretes a
shell of 1,2 or 8 parts.
-
Their head region is well developed except in classes of (scaphopeda and
bivalvia).
-
They have a ventral muscular foot modified for crawling, burrowing or
swimming.
-
Digestives tract is complete, usually u-shaped or coiled, their mouth is with a
radula which bears transverse rows of minute chitinous teeth, except in
bivalvia, anus is on mouth.
-
Circulatory system includes a dorsal heart with 1 or 2 artria and 1 ventricle.
-
Respiration is by 1to many gills(ctenidia)or along in the manthe cavity or by
ephidermis.
-
Excretion is by kidneys (nephridia), eider 1,2 or 6 pairs, usually connected to
pericardial cavity.
-
Coelom is reduced.
-
Nervous system is of 3 pairs of ganglis sexes are usually separate, but some
are monnoecius, gonads are 4,2 or 1 fertilization is external or internal. They
are mostly oviparous, have a trochopore and veligar larvae or parasite stage.
-
They have no a exual reproduction.
Have the following classes
i.
Class monoplacophora e.g Neopiling galatheae
ii.
Class Aplacophora e.g lepidomenic .
iii.
Class polyplacophora e.g Crypidomenic.
iv.
Class caphophoda e.g Dentalium.
v.
Class gastropoda e.g snail, slugs, limpets, whelks e.t.c
vi.
Class Bivalvia e.g Nucula, clama, e.t.c.
STRUTURE OF LAND SNAIL (GASTROPODA).
Helix asperses is the common garden snail it has a fleshy heed which bears 2 pairs of
retractile
The head jons directly to a muscular foot on top of which as the shell the genital pore
opers on the right side of the body besides the head, also there is a small anus and a larger
respiratory pore located in the soft mantle margn at the edge of the shell.
Digestive system includes the mouth, pharyx with a dorsal horny, stomach, intestine and
an anus land snail has a lung for respiration which repleces the gill of other gastropods
and mothus.
The heart has I aurich and I vertricle. A single kindney dreams from the pericardial cavity
around the heart and discharges into the mouth cavity.
Each individual is with a combined male and female reproductive system. They are
nocturcl, most active at night.
LIFE-CYCLE
Mating takes place between 2 snails, during which a ‘dart’ from each is discharge into the
body of the other. Copulation is reciprocal the penis of each is reserted into the vagina of
the other for transfer of a spermatophore, the snails the separate.
Each, later deposits 1 or more beetles of geletinais covered eggs in demp places or
shallow slantory burrows development needs many days and its direct the young emerges
as minute snails.
Week 7
MORPHOLOGY AND PHYSIOLOGY OF VARIOUS ORGANS AND SYSTEMS
IN ANIMALS
Morphology: (structure of organisms).
This is the form and structure of an organism or of a part of an organism it is the study of
the form and structure of organisms.
PHYSIOLOGY
This is the study of functioning of living things the branch of biology that deals with the
internal workings of living things including functions such as metabolism respiration and
reproduction, rather than with shape pr structure.
NERVOUS SYSTEM
The nervous system, are those elements within the animals that are concerned with the
reception of stimuler the transmission of nerve impulses or the actoration of
muscleonechanisms.
ANATOMY AND FUNCTION OF NERVOUS SYSTEM
The reception of stimuli is the function of special sensory cells the conducting elements
of the nervous system are cells called nervous, the specific response of the nervous i.e
nerve impulse and the capacity of the cell to be stimulated make this cells a receiving and
treasmithing unit capable of treasferring information from one part of the body to
another. This stimuli are either external derived from temperature, moisture light, gravity,
contect, pressure, oxygen supply, salt concentrations, and odors or internal stimuli
resulting from the quality of food, water or wastes in the body and from factoghe pain,
disease, etc some stimuli act directly on cells or issues and elicit a direct response e.g.
sunburn.
A receptor is a cell or organ having a special sensitivity to some kinds of stimulus e.g. the
eye to light and ear to sound.
NERVES AND NEURONS
Nervos systems are composed of nerve cells called neurons. Each nerve cell consists of a
ventral portion containing the nucleus, known as the cell body and one or more structures
known as axons and dendrites the dendrites (afferent) are short extersions of the cell body
and are involved in the reception of stimuli.
The exon (efferent) on the other hand, is usually a single elongated extension it is
especially important in the transmission of nerve impulses from the region of the cell
body to other cells.
In all vertebrates, the nervous system has a comparable embryonic origin and is always
single, hollow and dorsal to the digestive tract.
The vertebrate nervous system is divided into 2.
i.
The central nervous system (C.N.S) with large anterror brain and a spinal cord
ii.
The peripheral nervous system consisting of the cranial and spinal nerves.
The cranial nerves connect to the brain by passing through openings in the skill, or
cranium.
THE BRAIN
This is the portion of the C.N.S contained within the skill. It is the most specialized organ
of the human body. It is the control center for movement, sleep, hunger, thirst, and other
vital activities necessary for survival. All human emotions, including love, hote, feor,
anger, election and scdness are controlled by the brain. The brain makes us conscious,
emotional, and intelligent.
An adult human brain is a 1.3kg mass of pinkish-grey jellylike tissue made up of
approximately 100 billion of nerve cells collect neurons and 3 membranes colled
meninges (dure meter, arachnoid meter and pia meter).
The brain is divided into 3 orations i.e. fore brain mind brain and hand brain. The fore
brain consist of the offertory lobes, cerebrum and hypothalamus.
The mid brain narrow and short with thick walls which connects the hindbrain and
forebrain together. It consist of the optic lobes.
The hindbrain consist of 3parts i.e cerebellum, inedulla oblongate and pons vorolli.
THE SPINAL CORD
The spinal cord is an extension from the medulla oblongate and passes through the neural
conal of the vertebral column which protects it and ends in the secrumi the spinal cord is
protected by 3 layer meninges i.e. dure mater, arechnoid meter and pre meter. The
process occupied by cerebrospind flaid.
A cross section of the spinal cords it is divided into 2 partias, an outer and inner partions.
The outer pation contens white metter consisting of axons and dedrites. The inner partion
is H-shape, it contains grey matter and cell bodies of meter neurous. Each spind nerve,
before it attelles to the spinal cord, divides into dorsal root contens nerve cells and before
it enters the spinal cord form a ganglion containing cell bodies of nerve cells (sensory
heureus ). The dorsal root carries impulses from the body to the spinal cord.to the body.
FUNCTIONS OF THE NERVOUS SYSTEM
-
The fore brain is concerned with receiving sensory impulses from the
olfactory organs and making the odour in its environment.
-
The cerebrum is the sect of consciouness, in tellingerce, memory judgement,
learining, section and imaginction.
-
It also seat all voluntary action.
-
The thdcmus is the certre of poin, touch and anger.
-
It relcys motor implses to the spinal cord from the cerebrum.
-
The hypothdomus regulates body temperature, water balance, steep and blood
pressure.
-
It is the center of appetity.
-
It controls the pituitary gland.
-
The midbran is concerned with the sight.
-
The hand bran is concerned with the balance and positionary of the body.
-
It also cooramates various actions of muscles in voluntary responses e.g
walking, talking and sitting.
-
Medulla oblongata control respiration hearbect and all involuntary actions.
-
The pains varolli carries impulses from one hemisphere of the cerebellum to
the after i.e coorducting muscular movement in the 2 sides of the body.
-
The spinal cord is the site of reflex i.e involuntary actions.
-
It sends impulses to the brain and carries responses from the brain to the
muscles.
THE PERIPHERAL NERVOUS SYSTEM
It communicates action between the brain, spinal cord and the entire body it consist of 12
pairs of cranrel and 31 pairs of spinal nerves.
The creniel nerves crise from the brain, while the spinal nerves crise from the spinal cord.
The peripheral nervous system consists of somotic nerves system and autonomic nerves
system.
SOMATIC NERVOUS SYSTEM
Nerves from the brain are led through the spinal cord to skeletal muscles. The nerves
sends impulses from the external stimuli to the C.N.S and relay responses from the C.N.S
to the skeletal muscles of the body i.e causing body movement it is concerned with the
conscous awareness of the external movement to the brain.
AUTONOMIC NERVOUS SYSTEM
This is made up to the sensory and motor neurons it arises from the C.N.S and connects
to different internal organ. The autonomic nervous system consists of 2 parts i.e
sympathetic and paresypethetic nervous system.
These consists of 2 rows of nerve tissues or ganglia immg the sides of the spinal column
the 2 systems helps in checks and balances of some vital organs such as heart, eye, lungs,
kidney etc.
REFLEX ACTION (INVOLUNTARY ACTION)
A reflex action is an involuntary or automatic response of the body to a stimulus
involving the spinal cord or the brain. After the reflex action is completed, the impulse
reaches the brain e.g. pulling off year hand immediately from a hot object when you
accidentally touch it when you accidentally touch a hot object the sensory cells (pam
receptors) in the skin are stimulated by the hot pain.
The stimulus (hot pains) then initictecs nerve impulses which are sent through the
sensory neurone (afferent) in the nerve cord. The impulses are then transmitted through
synapse into the intermediate neurone in the spinal cord, form thre into the motor neurons
which then transmit the impulses to the muscles the impulses cause stimulation of the
boceps muscles (flexor) to contract and the triceps muscles to relex the hot object is
immediately dropped this action takes a fraction of second to complete. Examples of
reflex actions are here sneezing, canling etc.
VOLUNTARY ACTION
These are actions initiated and controlled by the conscious part of the brain we think and
reason before voluntary action are carried out e.g writing, walking, reading talking etc. in
voluntary action, sensory neurons send ompulses to the spinal cord and from it to the
brain for interpretation and sent through the motor neurons to the effectors
DIFFERENCES.
Reflex action
Voluntary action
Action in the spinal cord or hard brain
action in the forebrain
Response isuncuscias and not under control it is under control of
Of will
will
Actions are not learnt they are in brain
they are mostly heart
Response is quick and automatic
response not
Automatic
It is delayed
Few neurons are involved path is
path is longer
many neuronse are involved,
Week 8
THE CIRCULATORY/TRANSPORT SYSTEM
Circulatory system or cardrovascular system, in humans is the combined function of the
heart blood, and blood vessels to transport oxygen and nutrients to organs and tissues
thought the body and carry away waste products.
MEDIA OF TRANSPORTATION
These are cytoplasm, water, body fluid, blood and lymph. In invertebrates such as those
in the phyla of platyheliumathes nemctode, aunelida to the arthropoda, large voluje of
body fluid flow and battle numeranus cells, these serve as their transport medium. The
food and oxygen needed for these crimids ids distributed in the body fluid to all living
cells the waste products is then carried also in the body fluid to the excretory organs for
excretion. Their excretory organs lie freely in the body space coelom therefore their
excretory organ is not supplied by blood vessels as seen in vertebrates.
COMPONENTS OF THE CIRCULATORY SYSTEM
The transport system in man and other vertebrates comprises of the blood, heart, and
blood vessels (arteries, vems and capillaries).
The heart is the ergne of the covenlertary system it is divided into 4 chambers up the right
and left atrium, and the right and left ventricle the walls of these chambers are made of a
special muscle called mydar-dium which contains continusly and rlythmically to pump
blood.
The blood is a fluid issue made up of about 55% flud called plasma and 45% cells the
blood consists of 3 types of cells oxygen-beorny red blood cells disease figlitry white
blood cells blood clottry platelets.
Plasma is the fluid portion of the blood it is yellowish and made up of 90% waste and
10% dissolved substances such as selts, proterns vitermis minerals hormores dissolved
geses and fets.
BLOOD CELLS
Red blood cells (erythrocytes)
These are red in colour minute biconccive and disc-shaped they contain hcemoglobum
which carries oxygen from the lungs to the living cells.
They lack miclens, they live for short time theylive for about 3 maths, they are destroyed
by the cells of the liver spleen and renewed in the nicorrow of the long bones the are the
mostnumeras of the blood cells.
WHITE BLOOD CELLS (LEUCOCYTES)
Each has a nucleus and lacks hcemoglobom they are large and more active than the
R.B.C they are capable of amoeboid movement and can squeeze through narrow speces
from the blood vessels into body issues they are fewer than the R.B.C they can move into
the site of infection, eight becteria, and produces cutitoxm which neutralizes poisers
produced by disease producing crganisms that infect the body.
PLATELETES (THICMBOCYTES).
These are ling fragment of cells, they are nan unclected, and colourless. They are formed
in the bone marrow. They are the surce of thromboplastion which mitetes blood clotting.
THE HEART
It is a muscular pumping organ of the blood it lies at the centre of the thoracre cavity in
the pericardid cavity the heart of man is can-shaped and divided into 4 cham,bers, 2 atric
and 2 ventricles below the right auride leads into the right ventride and guarded by the
tricuspid valve, while the left circle leads into the ventride and gucruded by the bicuspred
or mitred velve these valves prevent blood rom flowing backwerks.
There is no communication between the right and left sides of the heart, this makes the
heart to fuction as a dumple pump. The right ide pumps deoxyge rated blood to the lungs,
while the left side pumps oxygen feet blood from the arota to all parts o the body. During
each heartbeat about 60-90 of blood are pumped out of the heart.
Three types of blood vessels form a complex network of tubes through the body. Arteries
carry blood crocy rom the heart and vens carry it toward the heart capillaries are the troy
liks between the conteries and vens where oxygen and nutrients diffuse to body tissues.
Arteries have thicker wells than vens to withstand the pressure of blood beny pumped
from the heart blood in the vens is at a lower pressure, and so vens have valves to prevent
blood from lowing backwards the smallest are the capillaries and only visible by
microscope.
CIRCULATION OF BLOOD
There are 2 plans or types of blood circulation in human bengs these are pulmonary
systemic circulation. Pulmonary circulation.
In pulmancry circulation deoxygencted blood from the heart and upper limbs and tissues
of the body trevels from the right atrium of the heart to the right vetride from there it is
puscled through the pulmoncry certery to the lung in the lung the pulmoncry cirtery
divides to form pulmonary capillary region of the lung, to be oxygencted Newly
oxygencted blood the flows into the pulmacy vens, to the left trium of the heart function
to the left ventride the contraction of the left ventrice sends blood into the aorta,
campletry the conculation.
System circulation
The heart ejects oxygen rich blood under high pressure out of the left ventride through
the largest cirtery the aorta smaller arteries branch off from the aorta to various parts of
the body this oxygenated blood trevels to various organs and issues of the body as such
losing its oxygen to become deoxygenated before retuning back to the heart and the circle
start all over agen.
CIRCULATORY SYSTEMS IN NON-HUMANS.
Unicellular and some multicelled animals, such as sponge, jellyfish, sea anemone, flat
wormes, and roundiomd, do not have a circulatory system. All their cells are able to
abserb nutriets, exchange gesses, and expel wases through firect contact with either the
outside or with a digestive tract.
In more complex invertebrates, they have a wide range of circulatory system designs their
circulatory systems are classifies as either open or closed. Example, open system is found
in seasters, spoders, and certipedes these all lack capillaries, the blood bothers the issues
directly in closed systems, the blood is confored to a system of blood vessels.
Invertebrates with closed systems include segmented worms squids and octopuses.
All vertebrates have closed circulatory systems. These systems are classified by the
number of chambers in the heart, which determines the basic configuration of blood flow
fish for instance have 2 chambered hearts with one strium and one vertricle.
The blood pumped from the vertride trevels through arteries to the gills, where it diverges
into capillaries and exchanges geses leaving the gills, the capillaries reconvese into blood
vessels carrying oxygected blood to the rest of the body, where the vessels cyam diverge
into capillaries before recovering again into vens carrying deoxygercted blood that return
to the heart.
From and other amphibians have 3 chambers hearts, 2 atriums and are vertride blood
pumped from the vertride enters a forket artery one fork, i.e the pulmoncy circulation
leads to the lung. The other for systemic circulation, leads to the rest of the body, blood
from the point monoy circulation enters the atrium, while blood from the systemic
circulation enters the right strim. Although there is some mixing of oxygended and
deoxygencted blood in the ventricle, there is a ridge with the vertride which assures that
most of the oxygected blood is diverted to the systemic arculation and most of the
deoxygenated blood goes to the joulmanary circulation in reptiles this rige is more
developed, forming a partial wall. In crocodiles the well is complete, forming a four
chambered heart like that found in mammds and buds.
Week 9
EXCREORY SYSTEMS IN MSMMALS
Excretion is the process of getting nel of metabolic wastes such as, urine, gases, urea,
salts etc. From the body of animals.
An impotent function of excretion is to dispose off waste nitrogenous materials
A second function is to regulate water balance.
Living organisms produce many excretory products during there metabolic activities.
Some are harmful if left to remain in the bodies of living organisms.
EXCRETORY ORGAN:
Contractile vacuole, flame cell, nephritis, malt pighian tubules and kidneys, lungs, skin
are the excretory structures n animals.
Excretion protozoans, excretion is by contractile vacuole. It is a small cavity found in the
cell of fresh water protozoa,it helps to flatworms such as planana, tapeworms and
sckistosme, the organ of excretion is the flame cell. The flanecell cnsists of two
longitudinal concls with network of ducts which branch to all parts of the body.
Other invertebrates such as the ecrthworms the organs of excretion are the Nephridis. A
pair of nephridis is located in each segment except the 1st 3 and the last segments.
Each nephridium consists of five particus namely nephrostome, narrow tube, middle tube,
wide tube and muscular tube. Each nephrostone is located in the body cavity coedom of
one segment while the rest coiled parts of nephridum are embedded in the body cavity of
the segment behind it.
In risects such as the cockroaches malpighicu tibules is the excretory organs arises from
the junction between the midgut and lindgut. Each tubute cousists of two perts, the distel
and proximal end.
Internally, mdpighian tubule is lined by glandular epillelium with a layer of microvillo
mclpighicu tubules lie in the body cavity (hcemocoel) and are bothed by blood.
In vertebrates such as mammals (mam), kidneys are the organs for the excretiin of all
nitrogenus wastes from the body structure of kidney.
There are 2 kidney which lie in the abdominal well the left kidney is slightly higher in
position than the right one. Each kidney is bear shaped and dare red in colour and is
surrounded by librous capsule and fets which keep it in position.
A cross-section of the kidney shows that it consists of three particules cortex medulla and
pelris.
The cortex is the outer layer consisting of molpighian bodies and tubules medulla is the
inner layer consisting of uriniferans tubules. The medulla projects inwords to form 15-16
pyramids the niferaus tubules open into the pelvis thragh the pyramids.
Pelvis leads into the ureter. The ureter leads into the urinary bladder and the urinary
bladder leads into the urethra the structure responsible for the formation of urin is the
nephron (kidney tubule).
STRUCTURE OF A NEPHRON/URINIFEROUS TIBULE
Each nephron is made up of a cup shaped and hollow structure celled Bowman’s capsule
and a narrow, coiled and long tube colled uriniferans tubule. Each Bow man’s capsule is
supplied with a branch of rend artery which divides severd times forming ting capillaries.
These capillaries write at one end to form an efferent arteriole, cadled glomerulus.
The wells of the glomerulus and Bowmai’s capsule have ting pores which anlyallow
small molecules to pass through. The nephran consisits of 3 partians called, proximid
convoluted tubule, loop of heile and distel convoluted tubule.
URINE FORMATION
He liver changes all nitrogenous waste matter in the body to urea. Urea is soluble in
water and is carried in solution in the plasma to the kidneys by rend artery.
Blood under high pressure flows into the Bowman’s capsule through the afferent arteriole
in the Bowman’s capsule, substances of small molecules size such as urea, glucose water,
mineral salts, vitamins harmaues, and amino acids are filtered into the cavity of
Bowman’s capsule. This process is called ultrafiltration and the fluid in the Bowman’s
capsule is known as glomeruler filtrate.
These filtrate passes into the proximal tubule where all amino acids glucose and large
hormoues, vitamins, water and mineral selts are recbserbed into the body. After this
recbscrption the filtrate passes into the loop of henle where much of the water is
recbsorbed to the body (osmotic regulation of the body fluid). The filtrate continues its
journey to the distel convoluted tubule and collecting duct where further recbsortion of
water and selt takes place. This process selecting what to return to the body is called
selective recbsorption. After this recbsorption, theflowd in the kidney tubule is called
urine.
The urine is emptied into the pelvis, from the pelvis, the ureter posses the urine into a
mascular urinary bladder where it is stored temporarily and leter disschcrged through the
urethra to thr artside function of the kidneys.
-
Osmoregulation
-
Excretion
-
Acid bae bakce (PH)
LIVER:
The liver is the largest gland in the body of vertebrates it is darle-red, spongy and lobed.
The liver is hung from the postenor surface of the diaphragm by a ligament and overlaps
the stomach. Underside of the right lobe is the gall bladder which contains the bile the is
secreted from the bile duct which leads from the liver to the duodenum.
The liver perverts organic toxims produced by bacteria from reaching toxic levels in the
body it converts the toxre products to non-toxie compound which are later excreted by
the kidneys.
THE SKIN:
This is the surface coveny of the body in man, it is about 1-2mm thick except that of the
palm and soles which are about 6mm thick the skin is the most extensive organ in the
body.
It consists of 2 layers if epidermis and an inner derms the epidermis is divided into 3
layers cornitied granular and malpighicu kyer the derms is a thick layer of connective
issues. It consists of blood vessels swect glads, sebacews glads, har follicles seory cells
and fotty cells.
Functions of the skin.
-
Protection
-
Sensitivity
-
Excretion and osmoregulation
The swect glands of the skin excrete excess water containing salts and waste nitragenus
substances urea
-
Maintainance of constant body temperature
-
Storage of reserved food
-
Manufactures and stores vit D.
Week 10
PHYCOPHYTA (ALGAE)
General characteristics:-
The body of the plants is not differentiated into roots, stem and leaves.
-
They contain the green pigment called chlorophyll.
-
Some of the members/algae have other pigments like blue, yellow, brown e.t.c in
addition to the chlorophyll.
-
They exhibit autotrophic nutrition
-
Any excess glucose is stored as starch
-
Reproduction is by fragmentation, spore formation or conjugation.
-
Cell wall is made up cellulose.
-
The body made up of true pareachyamaton cells.
-
Some algae are unicellular. Others are multicellular. The multicellular are either
filamentons or colong.
-
They are mainly aquatic.
Classification
The division phycophyta is divided into the following classes:1.
2.
Myxophyceac/Cynophyceac (blue-green algae)
-
Contain blue pigment (phycocyamin) in addition to chlorophyll.
-
E.g Nostoc,
Euglenophyceac
Oscillatoria,
-
Anabaena e.t.c.
Simple organisms (protists) from which all other
plants have been though to evolved e.g. Eug/ena.
3.
Chlorophyceac (green algae). Possess only green pigment.
e.g. Volvox,
4.
Spirogyra, Chlomydomonas, etc.
Bacillario Phyceac (Diatoms). Mosthly free-floating, boat shaped, rod-shaped
disc-shaped e.g. diatom.
5.
Phaeophyceac (brown). Possess brown pigment (fucoxan thin) e.g. Fucus,
Laminaria.
6.
Rhodophyceac (red). Possess red pigment (phyco-erythrin). e.g. polysiphonia.
Batrachospernum.
Diatoms
These are mostly one-called and of variety of forms. The single cells may form filaments
or colonies. They are found in fresh as well as salt water and in ground.
Structure.
Diatoms are boat – shapped, rod-shaped, disx-shaped, wedge- shaped, oval- shaped
rectangular-shaped e.t.c.
The wall of the diatom cell is made of two halves or values, an older one called eqitheca
fitting closely over the younger value called hypotheca (inner value).
The valves are made of pectin impregnated with silica. They have numerous fine lines
which are really very fine dats which are radially symmetrical in the centric (round)
diatoms (Centrales) and bilaterally symmetrical in the elongated diatoms (pennales). In
some general, there are ingrowths of the wall called central or polar module according to
position. A line (actually series of minute openings) called raphextends from central to
the polar module.
The protoplasm consists of a thin layer of cytoplasm within the cell wall. One large or
many small yellow to golden-brown plastids of varied shaped and sizes, a central nucleus
suspended by cytoplasmic threads or a broad cytoplasmic band, and a central vacuole.
The colour of plastids is due to a pigment called diatomin in addition to chlorophyll.
Pyrenoids may or may not be present. If present, they are without the starchy envelope.
Reserve foods are globules of fats and insoluble complex substance called volution. No
starch in diatom.
Reproduction:1.
Vegetative – usually occur at might the protophlasm grows and divides into two
resulting in the separation of the two valves. Each of the half cell forms a new
valve against the old one fitting into it, division and valve-formation continue one
after the other. The result is one set of cells gradually become smaller and smaller.
2.
Asexually- this is by formation of auxospore. When a particular minimum size is
reached, a reversion to original size takes place through the formation and activity
of a special cell called auxospore, which is produced in variety of ways:a.
When valves separates, the protoplast escapes and become an auxospore.
It grow to its max, size then form new valves.
b.
The protoplast divides into 2, each daughter protoplast (an auxospore)
grows and form new valves.
3.
Sexual- this is by conjugation. The protoplast of two cells escape and act as
gametes. They fuse to produce a zygote which behaves as an auxospore. It grows
and produce valves. Alternatively, two contiguous diatom cells form two gamtes
each.
The gamete fuse in pairs forming two zygotes which act as auxospores. The
auxospores grow and help the diatoms to return to their original sizes.
Englena.
This is a unicellular organisms with one end blunt (anterior) and the other tapering
(posterior). There is a single flagellum at the blunt end. The body is covered by pellicle
consisting of non-living material secreted by the cytoplasm. Rod-shaped chloroplasts
radiating from a central. The central zone has a mass of paramylum granules consisting
of polysac chandes. Similar granules are scattered throughout the cytoplasm. A large
nucleus is found near to the posterior end. A narrow gullet lead into a spherical reservoir.
In the cytoplasm near base of the gullet is a prominent red pigment spot called stigma
(eye spot), and just behind the gullet but slightly out of the centre is a small vacuo
contractile threads called myonemes can be seen. Divides transversely to give rise to a
new filament.
2.
Sexual- this is by conjugation and consists of fusion of 2 identical gametes
(=isogamy), there are 2 types of conjugation.
a.
Scalariform (Ladder-like) conjugation. This takes place between the cells
of 2 or 3 filaments. Two filaments (or 3) come to lie in contact in the
parallel direction and then repel each other. As a result of repulsion,
tubular outgrowths develop from corresponding points of contract of the
filaments. These outgrowth joined to form conjugation tubes.
Meanwhile, the protoplasmic contents of each of the cell lose water
contract and become rounded off to form a gamete. The gametes of one
filament creep through the conjugation tubes into the corresponding cells
of the adjoining filament and fuse with it to form a zygote. The zygote
clothes itself in a thick dark wall to form a zygospore. The gametes of one
filament pass into the gametes of the other filament. Thus one filament
remains empty while the other has a row of zygospores. If 3 filaments are
involved, the zygospores are formed in the middle filament.
Reproduction:
Englena reproduces in 2 ways.
1.
Binary fission – the organisms comes to rest and secrets a mucilaginous covering.
Flagellum is withdrawn and it doesn’t divide the nucleus divides by mitosis. The
cytoplasm also divides longitudinally sometimes one daughter cells retains old
flagellum, and the other development new ones.
2.
Spore formation when food supply is exhausted, the protoplasmic contents
contract and become surrounded by a thick wall. This is called a cyst/resting
spore. The cyst can resist nufavourable condition. When conditions become
favourable again, the cyst germinate and the protoplasm divides into 2,4 or more.
The divided bodies (= spores) are set free as maked, unicellular organism.
Spirogyra_
Spirogyra plant is an umbranched filament consisting of a single row of cylindrical cells
joined end o end each cells is surrounded by a membra and a cell wall made of cellulose
and pectin. A thin layer of mucilage covers the cell wall making it shiny to touch. The
filament is not differentiated into a base an apex.
Each cell has a thin layer of cytoplasm in which 2 or more spiral chloroplast are
embedded. A nucleus lies in the centre of the cell and is suspended by cytoplasm threads.
A large vacuole occupies the centre of the cell. On the chloroplasts are a number of small
nodular protoplasmic bodies called pyrenoids, and around them, minute starch gains are
deposited.
Reproduction:There are 2 methods.
a.
Vegetative:- this is by fragmentation when filament is broken off into individual
cells or small pieces, each
b.
Lateral conjugation:- this takes place between the cells of the same filament there
are 2 types:-
i)
Chain type conjugation:- here conjugation tube is formed on one side of the
partition wall, and the gamete passes through the tube.
ii)
Direct lateral conjugation:- here, the “male” gamete perfortes the wall to pass into
the cell and fuse with the “female” gamete. No formation of conjugation tube.
In lateral conjugation, the gametes of alternate cells only move to the
neighbouring cells. This later on, zygote-bearing cells are seen to alternate with
empty cells in the same filament.
Economic importance of algae.
1.
Serve as producers in food chains/webs.
2.
Provide O2 to aquatic animals for respiration.
3.
Serve as food for humans and livestock providing CH20, proteins minerals (K.I)
and vitamins.
4.
Serve as fertilizers.
5.
Source of substances like agar which is used in various wap.
a)
6.
As laxatine (b) Textile sizing (c)
Thicken food like ice cream, cheese,
soup and bakery products. (d)
Growth medium for bacteria.
Carrageemin obtained from irish moss (an alga) is (a) used in chaculate milk to
hold the cocoa particles in suspension. (b) used in syrups, toothpaste, cosmetics,
shampoos, sauces, e.t.c.
7.
Algin, another substance obtained from kelpond is used in making ice cream,
salad dressing, paints, printing inks, cosmetics e.t.c.
8.
Diatoms’ shells form diatomite which is mined and processed to be use.
(a)
As filtering medium in swimming pools public water supplies, sugar
processing, drugs, and beverages.
(b)
As filler in paints, asphalt, paper and plastic.
(c)
In detergents and fertilizers.
(d)
As heat insulator in boilers and furnaces because of its bulkiness &
lightness.
9.
Algae can be a nuisance in reservoir swimming pools.
Week 11
MYCOPHYTA (FUNGI)
General characteristics.
*
The body of the fungus is composed of threat – like structure called hyphae
(collectively called my celium).
*
It is not differentiated into roots, stem and leaves.
*
Fungi lack chlorophyll.
*
And so they exhibit heterotrophic mode of feeding either as parasites/saprophytes
*
Excess sugar is stored in form of glycogen.
*
The body of fungus is composed of false or pseudoparenchymatous tissues
*
With cell wall made of cellulose mixed with the chitin.
*
Although they lack chlorophyll, many contain other pigments in the cell wall or in
the cavity.
Classes
1.
Myxomycetes (slime fungi)
*
They grow in damp, shady places in soil rich in humus.
*
They require moisture and darkness for normal growth.
*
They contain pigments like yellow orange, brown, red or colourless.
*
They are animal-like in their vegetative stages and plant- like in their reproductive
stages.
2.
Phycomycetes.
*
The mycelium is unseptate and coenocytic.
*
Sporangium has many sporangiospores.
*
Sexual reproduction is either oogamous or isogamous
e.g. pythium, phytophtora, mucor, e.t.c.
3.
Ascomy cete.
*
They are terrestrial parasites or saprophytes
*
The mycelium is of septate hyphae
*
The protoplast is uninucleate or binuecleate
*
Reproductive structures are asci.
e.g. sachromyces, penicillium claviceps e.t.c
4.
Basidiomy cetes (club fungi).
*
They are saprophytes or parasites
*
The mycelium is of septate hyphae
*
The cells are usually binucleate with haploid nuclei.
e.g. Agaricus, puccima, ustilago.
5.
Deutromycetes (Fungi imperfecti)
*
They are saprophytes or parasites
*
Reproductive structures are the conidia
*
They have an imperfect life- history.
e.g. fusarium, Helmin thosporium.
Mucor (A Saprophytic Fungus)
Structure:
Mucor grows on animal dungs, went shoes, moist bread, e.t.c. spreading like a cobwebs.
The body is composed of white delicate, cottony threads called mycelium. The hyphae
are very much branched, but are coenocytic (i.e unseptate and having many nuclei).
Reproduction.
It reproduces in two ways:
1.
Asexual- by the means of spores which develop in sporangium under favourable
conditions of moisture and temperature.
The mycelium gives off erect hypae called sporangiosphores, each ending in
spherical
head called
sporangium. The
protoplasmic contents
of the
sporangiosphore migrate to its tip, but accumulate more densely towards the
periphery, the central part, remains vacuolate. The denser outer portion and the
thinner inner portions are separated.
The central sterile portion is called columella. The peripheral protoplasm gives
rise to a number of small, multinucleate, angular mosses each rounded off and
covered by a wall to form a spore. Finally the columella swells as a result of
accumulation of fluid in it. This exerts pressure which causes the sporangium to
burst. The spores are released, carried about by the wind and germinate under
favourable conditions.
2.
Sexual- by conjugation when food supply is exhausted. This involves fusion of
two identical gametes (i.e isogamy). Two hypae borne by two different plants of
opposite sexes (i.e train & strain) come close together and send out protuberances
to form conjugating tubes or progamets. Each progamete enlarges and become
club-shaped. A wall partitions into a basal suspensor and a terminal gametangium.
The protoplasmic contents of each gametangium.
Mycophya
Phythium (A parasitic fungus)
The mycelium has hypae that are long, slender, branched unseptate and coenocytic. It
causes “damping off” disease in crops like tobacco, mustard, ginger, cress etc. under
conditions cover crowding and over watering. The fungus attacks the bases of the
seedlings which become weak and soon fall over. After the death of the seedlings, it will
feed on them saprophytically. This shows that phythium is a facultative parasite. The
mycelium of the fungus runs in all directions through the intercellular spaces and into the
living cells of the host (i.e seedling). Later, white threads (hypae) may be seen on the
surface of the seedings.
Reproduction.
The fungus reproduces both asexually and sexually,
1.
Asexual reproduction:- the mycelium sends out aerial hyphae through the stomata
or lenticels. These hyphae may bear short lateral branches each swelling into a
spherical head. The lead is partitioned at the base by a septum to form either a
comdium (or conidiospore), under dry condition or to form zoosporangium under
moist condition. The condium directly infects a new seedling and produce a germ
tube which branches freely with in the tissue of the host.
The zoosporangium protrudes and bulges out into a bladder- like resicle. The
protoplasm migrates into it and divides to form a number of small, naked,
umnucleate and bicilate zoospores which when set free swin about in water for a
short time. They then withdraw their cilia and develop walls around them.
The infect new seedlings and germinate by sending out germ tubes which run
throughout the tissue of the host.
2.
Sexual reproduction:- this takes place after the death of the host plant. Hyphal end
swells into a spherical head called ooganium (-female organ) because of the
accumulation of protoplasm.
It is then partitioned off by a wall or septum. The cytoplasms of the ooganium
differentiate into a central denser region with a nucleus forming the egg
(oosphere) and a peripheral region with many small nuclei constituting the
periplasm.
A branch arises from the same hypha that produced ooganium or another hypha
close to it (ooganium). It swells and become club- shaped, and it cut off by a
septum. This forms the antheridia (male organ). Its protoplams becomes
differentiated into a central male gamete which is uninucleate and a periplams
which is multicleate.
Nuclei of periplam degenerate. An theridium bends towards ooganium and comes
in contact with it. A short cylindrical tube called ferterlization tube or beak is
produced.
This pieces the oogonium. Male gamete passes into it and fuses with, the egg
nucleus of oosphere. Fertilization with the antheridium and oogonium lying side
by side on same stalk is known as paragynous. The fertilized oospore form a thick
wall and rest in soil. The oospore germinates into a germ tube or it forms a
zoosporangium which divides to form a number of zoospores.
Economic importance of fungi.
1.
They act as decomposers converting dead organic matter into humus e.g. mucor.
2.
Some are edible providing protein and vitamins to humans e.g. yeast.
3.
Some fungi are used as control agent against parasites and pests.
4.
Yest is used in chiary products, bakery and brewery.
5.
Parasitic fungi cause diseases to plants and animals
6.
Some can be used to clarify fruit juices that may contain suspended pectic
materials e.g. Aspergillus.
7.
Some are used in the production of antibiotics e.g. Penicillium.
8.
Some produce toxic substances in food (food poisioning) e.g. Ergot.
9.
They are used in waste management (i.e compost making)
10.
Ergot poisoning causes paralysis, nervous disorders and abortion.
11.
Ergot, in medicinal does, can be wed to stop haemorhage and induced uterine
contraction after birth.
Week 12
Lichens.
Lichens are associations of specific fungi and algae, the former constituting the greater
part of the lichen’s body. The species of lichen is determined by the different fungi and
algae that association. Lichens commonly occur as grayish-green, greenish-white or
brightly coloured incrustations, one to several C.M. in diameter, on the stems and
branches of shrubs and trees, wooden posts, rocks, old walls and on the ground.
Somptimes, they hang in shaggy tufts a few to several cm long from the branches of frees
and shrubs. They could also be colured such as white, yellow, orange, brown, red or
black. Many grow under extreme conditions of humidity and temperature, and many
survive long periods of desiccation. They are found in cold regions and high altitude, as
well as in the tropical rain forests.
In lichens, fungi and algae live in a symbiotic relationship. The fungi absorb water and
mineral matter from the substratum and supply these to the algae, while the algae prepare
food and supply it to the fungi.
Classification.
Lichens have been classified into 2 main groups.
1.
Ascolichen – fungi are members of the ascomycetes, reproduce by means of
ascopores. They are further divided into.
2.
a.
Discolichen – produce open, cup, or saucer shaped apothecia.
b.
Pyrenocichens- produce closed, flask-shaped perithesia.
Basicholichens fungi are members of agaricales, reproduce by means of
basidiospores.
Thallus.
The thalli of lichens follow 3 different patterns of growths.
1.
Crustose lichens:- form hard, granular crust and adhere very tenaciously to rocks,
barks of shrubs and trees and certain soils e.g. Graphis, Leconora. These show
very little differentiation into upper lower surface.
2.
Foliose lichens form definite, flattened leaf like thalli with lobed margins. They
adhere to the substrate (e.g rocks, tree trunks, walls) by means of rhizoids (=
rhizines). They show clear distincton into upper and lower surface e.g. parmelia,
physica.
3.
Fruticose lichens:- form much branched, shrub like bodies attached to substrate by
means of their narrow basal portion only. Branches may be flat and ribibon, like
or slender and filamentions. Such lichen many stand erect (e.g. cladonia or
reindeer moss) or hang on the branches of shrubs ands trees (e.g. usnea or old
man’s board).
The main framework of the thallus is made of interwoven mass of the hyphea of
fungus ascolicheral enclose mostly unicellular or sometime filamentous bluegreen algae. Basidiolichens enclose similar blue-green algae. The type of fungus
and algae associated in a lichens is always constant. In some lichens the algae are
scattered in the thallus, while in o thers, they occur in one or two layers.
Structure:
A section through the thallus of a folloise lichen shows a loose mass of hyphae in the
centre (=medulla) and compact mass of hypae in the peripheral region. (= cortex).
Between these two regions lies the algae layer (=gomdial layer). This layer has many
algae cells (=gonidia) held together in the meshes of the hyphae. In usnea (a fruticose
lichen) the thallus is differentiated into a central, compact core of hyphas a region of
loosely interwoven hyphae, an algal region and externally, another compact region of
hyphae.
Reproduction:
Reproduction is predominantly fungal in character and is divided into vegetative, a sexual
and sexual.
1.
Vegetative :- There are different methods.
2.
By soredia:- These are tiny, granular bodies occurring on the upper surface of
thallus as grey powder each
Lichens
a.
Soredium consists of oen to many algal cells wrapped up in a weft of fungal
huphe. Soredia are blown away by wind and germinate directly into lichen thalli
or form new serodia under appropriate conditions.
b.
Isidia are tiny outgrowth on the surface of the thallus. Each isidium consists of
algal cells and fungal hyuphoe surrounded by a layer of cortex.
They are primarily photosynthetic in function but at times get detached from the
parent thallus and development into new thalli.
c.
Cephalodia:- Dark swellings on the surface of thallus (sx internally two). The
algal cells are different from those that normally occur in the thallus i.e they are
foreign cells carried over to the young lichen cells.
d.
Oidia- The hypea may break up into short segments called oidia. An oidium
germinates like a spore and give rise to normal hyphae.
e.
Fragmentation:- The thallus is divided into long or short fragments by the wind.
Each fragment many grow to the size of the parent thallus e.g. usnea.
Asexual reproduction.
In ascolichens, it is by means of spores formed by the fungal partner. The spore
germinates by sending out hyphae in all direction. When a hypha comes in contact with
the requisite alga, it branches and cover the algal cell. The two then grow into a lichen
tallus some spacies of lichen produce large numbers of small, spore-like bodies within a
flask-shaped cavity called phycnidum. The bodies area called phycindiospores or
phycnospores. Pycnidia usually appear as black dots on thallus or as tiny protuberances
on the margin. Pycindiospores are known to germinate in certain species, producing a
hypa. When it comes in contact with appropriate alga, the combined body grow and
forms a lichen thallus.
Organs (=spermogania), pycnidiospores.
In basidiolichens, it is by means of basidiospores, very much like in Agaricus.
Asexual reproduction in Agaricus is by vidia which are small unicellular fragments of the
hyphae. The oidia grow into primary or secondary mycelia. A uninucleat oidium may
also directly fuse with a primary mycelium. In some species, a basidiospore may give rise
to a large number of conidia by budding each conidium then germinates into a mycelium.
Another method of asexual reproduction is by chlamydospores. These are enlarged, thick,
walked vegetative cells that act as “testing” spores which occur singly or in chains, and
germinate by producing a germ tube.
Sexual reproduction.
Only the fungus takes part in the process. Sexual reproduction results in the formation of
ascocapr with many asci the male and female organ are in close priximaty to facilitate
fertilization. The female organ (= carporgonium) is multicelluar, shout filament of large
cells. It has a coiled basal portion (=spermogonium) is flask shaped with an apical
opening called ostiole. The minute, non-motive male cells (spermatia) are formed within
it large numbers. These are discharge through the ostiole in shiny mosses to float on the
thallus.
Fertilization:- Occurs when a spermetium comes in contact with a tnuchogyne. Its
protoplasm migrates into the trichogyne and fuses with the ascogonium nucleus. This is
fertilization. From the base of ascogonium, several hyphae begin to grow and develop,
an ascus at the end of each branch. A mature ascus contains 1-8 ascopspores. On
liberation, the mature ascopsores germinate, producing hyphae. Those coming in contact
with the right type of alga grow rapidly and eventually produce lichen thalli.
Uses (Ecological & Economical)
-
Distingrate rocks to form soil. Thus preparing ground for mosses later higher
plants.
-
As food for wild animals & catle (+human)
-
As medicine
-
Some yield bentiful dyes for production of litmos.
-
Some are used in cosmetics, perfume and soaps.
-
Some are used in brewing liquor
-
Some containing tannins are used in tanning hide into leather.
Week 13: Thallophyta
Classification of thallophyta
Thallophyta are plant that has a simple body structure and they lack definite
organs. (Roots, stem, leaves etc.) it is further divided into the 2 division
namely
Division 1: phycophyta
Class I cyanophyta or blue green algae,
Example nostoc, anabaena.
Class ii euglenophyta or euglenoid
Example, euglena
Class iii bacillarioophyta or diatoms
Class iv chlorohyta or green algae
Order i volvocales, volvox.
Order ii conjugales (or zygnamates)
Class rhodophyta
Division ii mycophyta or fungi
Class i schizomycophta or bacteria
Class ii myxomyco[phyta or slime fungi
Classs iii eumycophyta or true fungi
Gentral charactieristics of the algae
1. Algae are green thalophytes containing the green colouring matter
chlorophyll in many algae, the green colour may be makined by other
colours, but in all of them chlorophyll is always present.
2. Algae are autotrophic plants i.e. they manufacture their own food with
the help of chlorophyll contained in them.
3. The body of an algae is composed of a true parenchymatous tissue.
4. The cell wall of an alga is composed of true cellulose.
5. Some algae are unicellular while other is multicellular organism.
6. Reserve carbohydrates in algae are usually the starch.
Morphology of spirogyra
Spirogyra belongs to the family class chlorophyceae or green algae. It also
belongs to the larger of conjugales. It is a green filamentous algae which is
seen floating about freely in water. It is usually found growing abundantly in
ponds, spring, slow running steam etc. the commonest species includes
spirogyra maxim, spirogyra longata, and Spirogyra nitida. It is a
multicellular plant.
Structure of spirogyra
Each spirogyra plant is an unbranched filament. The walls are made of
cellulose and pectin. It is slimy in a nature and the filaments show no
differentiation into the base and the apex. Each cell has a living layer of
cytoplasm in which one or usually more spiral bands of chloroplast makes
the plant to obtain its name. The nucleus is situated in the centre and there is
one large central vacuole. Chloroplast varying number from 1 to 14 in each
cell. Also pyrenoids are found in the body of spirogyra. These pyrenoids
store excess food in the form of starch. There is usually one large nucleolus
in each nucleus, but frequently more.
Reproduction
Spirogyra reproduces both asexually and sexually.
a. ASEXUALLY REPRODUCTION
This occurs by fragmentation. This occurs when the filament breaks
upon into a number of pieces consisting of one or several cells.
Nucleus of each cell now divides into two and a cross wall is formed.
The two daughters’ cells remain attached to each other and grow in
length. New filaments will be formed and the length will increase.
This is referred to as vegetative reproduction.
b. SEXUAL REPRODUCTIONS
Sexual reproduction in spirogyra consists in the fusion of two similar
reproductive units or gametes. This is referred to as isogametes and
process involved is called conjugation
Conjugation can take place in two ways; it can take place between the
cells of two filaments or three and is referred to as scalari form or
ladder like conjugation. Some times however, conjugation takes place
between the cells of the same filament and is referred to as lateral
conjugation.
1. SCALAR FORM CONJUGATION.
When two filaments come to lie in contract in the parallel direction,
they repel each other. As a result of the repulsion, tubular outgrowths
develop from the opposite or corresponding points of contact of the
filaments. These tubular outgrowths are called conjugation tube.
When all or most of the cells of the two filaments have formed such
tubules, the whole structure looks more or less like a ladder and hence
the name scalar form or ladders like conjugation.
In the meantime the protoplasmic content of each cell lose water,
contract and become rounded off in the centre. Every contracted mass
of protoplasm form a gamete. All gametes are alike in appearance and
therefore, they are known as isogametes. By a kind of amoeboid
movement the gamete of one filament creeps through the conjugation
tubes into the corresponding cells of the adjoining filament and fuse
with the gametes of that filament. The formation of a zygote. The
zygote clothes itself with a thick dark wall and is known as the
zygospore. Sometimes the gametes meet and fuse in the conjugation
tubes. The wall of the zygospore is thick and black. Normally, the
gamete of one filament pass onto the gametes of the other filament.
2. lateral conjugatin
this takes place between the cells of the same filament. Lateral
conjugation can take place in two ways.
i.
chain type
an outgrowth or conjugatin tube is formed on one side of the
partition wall, and through the passage thuus formed, the
gamete (male) of one cell passed into the gamete (femal) of
the neighbouring cell. In spirogyra there is no distinction
between male and female gamete so far as their shape and
structure are concerned, but there is some difference in their
behaviour. One is active, motile and initiative and may be
regarded as male, while other is passive and receptive and
may be regarded as female
ii.
direct lateral conjugation
direct lateral conjugation occurs when the male gamete
passes into the female gamete by performing the septum in
its centre. The protoplast of one cell (male) tapers towards
the next cell (female), which now swells considerably. The
tapering and pushes and pierce the septum in between these
two cells and the whole protoplast of the male cell moves
into the female cell through the perforation and fuses with
the female gamete. After fusion a zygospore is formed.
There is no formation of conjugation tube in this case
germination of zygospore
the zygospore is provided with a thick cellulose wall, composed of three
layers of which the middle one contains some clusion with the rapid decay
of the parent filament all the zygospore are sew free anf they sink to the
bottom of the pool of the water. They undergo a period of rest till the next
favourable season and then they germinate, the protoplat of ech zygospore at
first increase in size, then its outer layers burst and the inner one with the
protoplast grows out in the lform oa a short tube which ultimately forms into
a new filament . the filament escapes and floats on the surface of the water.
Cells divide and the filament increase in length. Between male and female
games so far as their shape and structure are concerned, but there is some
difference in their behaviour. One is active, motile and initiative and may be
regarded as male, while other is passive and receptive and may be regarded
as female.
b. Direct lateral conjugation
Direct lateral conjugation occurs when the male gamele passes into the
female gamete by performing the septum in its centre. The protoplast of one
cell (male) tapers towards the next cell (female) which now swells
considerably. The tapering end pushes and piece the septum between these 2
cells, reduction division.
A zygote is formed as a result of fusion of two gametes, each with
chromosomes and therefore the nucleun of the zygote out first undergoes a
reduction division, the resulting nucteic dwide again so as to form four
nuclei, each will in chromosomes. Three of these nuclei degeneracy so that
the mature zygote contains a single nucleus n chromosomes.
Economic importance of the phycophe
1. Algae are the primary producer since it can manufacture its own fovel
using chlorophyll.
2. They are symptom (It is the association of algae and fungi, the algae
prepares food and shares it with the fungus while the fungus absorbs
water and mineral salts from the surroundings and also approach
protection to the algae).
3. Some algae example, brown algae and red algae are sources of food
for the consisted people in chiria and Japan.
4. Diatomaceous earth is use in making metal polish, paint plastic etc.
5. An important commercial product known as Agar – Agar is obtained
from some red algae and is universally used in the labouratories as a
medium of culture for fungi and bacteria.
6. Red algae (e.g porphyra and chodrum are used as medicimes).
7. Gelatine obtained from red-algae is used as a base for shoe polish,
shaving cream, cosmetic etc.
8. Algar is also used in textile sizing; it is also used to thicken food ice
cream, cheese, and soup and bakery products.
9. It is also used as growth medium for bacteria in the laboratory.
10.carrageen derived from an algar (irish moss) is used in chocolate to
hold the cocoa particles in suspension
11.Algae can be a nuisance in reservoir and swimming pool.
Classification of fungi
Class i myxomycytes or slime fungi
Class ii phycomycetes or alga like fungi
Sub class I Oomycetes
Order I saprotegniales e.g. saprohegnia
Order ii perenosparales e.g. phythum
Phytophthora, albujo and peremoxpora
Sub class ii zygomycetes or aplanatae.
Order iii mucurales e.g. mucor, rhizopus
Class iii ascomycetes or sac fungi
Sub class i protoascomycetes (no ascocarp)
Order i saccharomycetes e.g. yeast
Subclass ii euascomycetes (asci in ascocarp)
Order ii asperillales e.g. penicillum and aspergillus.
Order iii erysiphates e.g. erysiphe
Order iv sphaeriales e.g. neurospora, xyloric
Order v hypocreates e.g. claviceps
Order vi pezizales e.g. peziza, ascobdus
Class iv nasidiomycetes or club fungi
Sub class I hemi basidomycetes
Order i ustilajinates or smuts e.g. ustilag
Order ii uredinales or rusts e.g. puccinia
Sub class ii holobasidomycetes
Order iii agaricale e.g. mushrooms.
Order iv lycoperdales e.g. puff halls. (lycoperdon)
Order v phallales e.g. stinkhorms
Order vi nidullariales e.g. birde rest fung
(nidularia and cyathus).
Class v deuteromycete or fungi imperfect
i.e. fungi with imperfect life history.
e.g. helminthosporm and fusarim
characteristics of the main group
1. phycomycetes (alga like fungi)
a. the mycellum is unseptate and multi nucleate, i.e has no cross
walls divide ot up into cells and contain numerous nuclei.
b. Sporagum with innumerable sporangiospore
c. Sexual reproduction is either Oogamous in Omycetes or
isogamous in zygomycete. E.g. phythum, phytophtora, mucor
etc.
2. ascomycete
a. they are levastial saprophytes or parasites.
b. Mycelium is made up of septate hyphae.
c. Protoplast in uninuclate or bi-nuclate.
d. Reproductive structure are the asci
e.g. sacchromycete,
penicillin.
3. basidiomycetes (club fungi)
a. saprophytic or parasitic.
b. The cells are usually buncleate with haploid nuclei.
General characteristics of fungi
1. The body of a fungi is not dyferentiated into roots, steams and leaves.
2. They lack chlorophyll
3. They are heteotrophic organ. They feed cyther saprophyrically or
parasitically.
4. Body is composed of false tissue or sends parachy mature tissue.
5. The reserve/store carbohydrate as glycogen.
6. The body of a fungi contain other pigments in the cell-wall or cell
cavily
7. The body is made of intermovein mass of thread called hyphare
(collectively called mycellum).
Mucor (a saprophytic fungus)
Occurance
Mucor belong to the family mucoracea. It is commonly called “pin
mauld and grows on animal day, moist bread, well shoes, decaying
vegetables and other organic media. It spread like a cobweb.
Morphology – the body is composed of a mass white delicate controlling
threads collectively know as the mycelium. It is very much branched but is
coevaytic i.e unseptate and multimedeate.
Each individual thread of the mycelium is known as the hyphae (plural
hyphae).
The mycelium is made up of sorts of hyphae which includes the stolans,
rhzords and the sporangrophes.
Reproduction
This takes place by two methods viz. a sexual and sexual. The a sexual
method is most common.
1. A sexual mode of reproduction
This method of reproduction take place by means of spores which
develop in sporangium under favourable conditions of moisture and
temperature the mycetia give off here and there numerous slender
erect hyphae, called sporangiosphores, each ending in a spherical head
called sporangium the protoplasmic contents of the sporangiophore
ungrate to its tips, but accumulate more densely towards the
periphery, the central part remain thin and vacuolate. The denser outer
portion and inner thurner portion is called columella. The peripheral
protoplasm gives rise to a number of small, multinucleate, angular
masses each rounded off and covered by wall to form a spore. Finally
the columella swells as a result pf accumulation of fluid in it. this evil
exert pressure which causes the sporangium to burst the spore, one
related, carried about by the wind and germinate under favourable
conditions.
2. Sexual Reproduction
Sexual reproduction takes place by conjugation when food supply is
exhausted. It involves the fusion of two identical gametes (i.e
isogamy)
Two hyphae borne by two different plants of opposite sexes i.e strain
and strain come close together and send out protuberances to form
conjugation tubes or programmes. Each progamete enlarges and
become club-shaped. A wall partitions it into a basal suspensor and a
terminal gametangium constitute a gamete and is multinucleate. The
end walls of the gametagia dissolve and the gametes fuse to form a
hygospore. The zygospore swells into a round body and its wall
thickens, turns black and becomes (small hard, dry) wanted
The zygospore undergoes a period of rest and then germinates. The
outer wall breaks and an inner wall grows into a tube called
promycelium (sporangiophore) which end in a single sporangium. The
promycelium may be branched, each branch bearing a sporangium
which contains many spores but no columyella. Each spore
germinates into a mucor plant.
Sometimes it so happens that although the conjugation hyphae meet,
no fusion of gametes take place. The gametegia then develop
parthenogenetically into a thickwalled bodies called azygospores or
parthenospores. The azygospore looks similar to the zygospore.
2. pythium
It belongs to the family pythiaceae and is a parasitic fungus. Pythium causes
the disease known as damping off in crops, like in tobacco, ginger and
mutard under conditions of overcrowding and over watering. It attack the
bases of the seedling soon fall over after the death of the seedling. It will
feed on them saprohytically. The mycellum verifies in all directions through
the intercellul;ar spaces and into the living cell. L;ater white threads hyphae
mayseen on the surface of the seedling. The hypae aare long, slender,
branched,unseptate and coenocytic.
Reproduction.
The fungus commonly reproduces asexually and sexually though not
common.
Asexual reproduction:
Mycelium sends out aerial hyphae through stomata/cuticle, which bear short
lateral branches each swelling into a spherical head. This head is partitioned
off at the at the base bya septum to form either a condium (or conidiospore)
under dry conditions ortoform a zoosporangium under moist condition. The
conidium directly infects a new seedling and produces a germ tube which
branches freely within the tissue of the host.
The zoosporangium protrudes and bulges out inopt bladder like vesicle the
protoplasm migrates into it and divides to form a rio of small, naked
uninucleate and biciliate zoospore which when set free swim about in water
for a short time. They then withdrawn their cilia and develop a wall round
them. They infect a new seedling germinate by sending out a germtube
which verifies through the tissue of the host.
Sexual reproduction
This take place bymeans of Oogonia (female) and antheridia (male) which
develop form two neighbouring hypae. The Oognium is spherical or pear
shaped with a smooth reddish brown wall. It contains a large Oosphere or
egg-cell, lying loose and free within it surrounded by a scarity zone of
protoplasm called the periplasm. All the nuclei of the Oogonium except one
egg-nucleus of the Oosphere degenerate.
The anthemdum in the other hand is broadly chloroshaped and develops
before the Oogonium. It also contain many nucleus but finally one male
nucleus persists while others originally present, degenerate. Lthe Oogonium
as it grows penetrate through the antheridium and swells above it, becoming
spherical or pear shaped.
The antheridium also swells and form a funnel shaped collar around the base
of the Oogonium. This is known as the fertilization tube and it pierces the
Oogonium. Male gametes passes into the Oogonium and fuses with the egg
nucleus of the Oosphere. Fetrtilization with the
WEEK 14: PTERIDOPHYTE
14.1: Pteridophytes (Tracheophytes Without Seeds)
14.2: Division Lycophyta
14.3: Order Lycopodiales
Figure 14.1: structure of Lycopodium
clavatum
A club moss (Lycopodium clavatum) from Oregon. The upright stalk
bears a spore-bearing, cone-like structure (strobilus) at its tip. The
strobilus is composed of numerous scale-like sporophylls, each bearing
sporangia in the axils. The stem and leaves are vascular, unlike true
mosses. Lycopodium has only one type of spore, a condition termed
homosporous. This genus is considered more primitive than the
heterosporous genus Selaginella.
Order Selaginellales
Figure 14.1: structure of Selaginella bigelovii
Selaginella bigelovii, a common member of the division Lycophyta in dry
chaparral areas of southern California. It often grows on bare ground and
rock, and superficially resembles a true moss from a distance. Unlike
Lycopodium, it is heterosporous with two types of spores. Right: Close-up
view of the sporangia-bearing leaves (sporophylls). The upper greenish
megasporangium contains 4 female megaspores. The orange
microsporangia contain numerous, minute male microspores. The stem
and scale-like leaves are vascular (with xylem tissue), unlike true mosses.
Figure 14.1: structure of ash coloured Selaginella
A low-growing, ash-colored species of Selaginella (S. cinerascens), a
member of the division Lycophyta in dry, clay soils of southern California.
It sometimes appears in the beds of vernal pools after they have dried up.
The stem and minute scale-like leaves are vascular, unlike true mosses.
The reptile in photo is a coastal horned lizard (Phrynosoma coronatum).
Week 15
SPERMATOPHYTA.
General characteristics.
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Body of the plant is differentiated into roots, stein, leaves.
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Have the highest degree of internal tissue differentiation with well defined
conducting elements.
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Xylem elements are tracheid or vessels
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Growth is from an apical meristein.
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Secondary thickening is common.
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Pigments are cholophylls a and b with carotenoids.
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Have well defined sexual reproduction with alternation of generation.
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Reproductive parts are borne in specialized structures – flowers/strobili in lower
forms
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Seeds are born naked or in closed structures to form true fruits.
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They are chiefly terrestrial but with source obviously derived aquatic
representatives.
Classes.
1.
Pteridoespermae (seed-bearing ferns)
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Have vegetative xtics of pteridophytes, but bear seed-like reproductive structure.
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Form a link between true ferns and the flowering plants.
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All are extinct (no longer in existance).
2.
Gymnospermae.
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Mostly trees and shrubs.
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Xylen elements always tracheids except one order- primitive vessels are found.
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Flowers are mostly of strobiloid construct on and unisexual.
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Seeds with one intergment and naked. E.g. Zamia, Cycad, Pinns, Taxus.
3.
Angiospermae.
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Worlds dominant vegetation in all habitats.
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Adapted to life on land
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Possess true xylem vases.
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Flower consisting of whorls of sterile and fertile parts.
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Male gametophyte represented by pollen grain, female by embryo-sac with 8inclei.
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Endospermed formed as a result of triple fusion.
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Seed, has 2 integuments enclosed in specialized carpels called overy which repens
into a true fruits.
Sub-class monocotyledons
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Mostly herbaceous, few palm, but no tree.
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Adventitions root system.
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Usually paralled-veined leaves.
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Vascular bundles irregularly arranged in the stem.
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Secondary growth is rare.
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Flower parts are in threes or multiple of threes.
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Single cotytedon in the seed.
e.g. maize, corn, wheat etc.
Sub-class: dicotyledons.
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Mostly herbs, shrubs and trees
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Tap-root system
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Net- veined leaves.
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Vascular bundless arranged in rings in the stein.
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Secondary growth is usual.
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Flower parts are in fours or fives (45/55) or multiple of these.
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Two cotylodons in the seed (rarely one by reduction).
Pinus plant (A gymnosperm)
Structure.
Pine or pinus is a tall, erect, evergreen true sometimes growing to a height of 45m. it has
well – developed tap-root and numerous aerial branches with needle – like leaves. The
stem is rugged and covered with scale bark. Branches are of 2 kinds:-
1)
Long branches (of unlimited growth) in apparent whorls developing from lateral
buds and.
2)
Dwarf branches (of limited growth). Leaves are also of 2 kids:1.
Long, green, neele- like foliage leaves collect needles borne only on dwarf
branches (=foliar spurs) and.
2.
Small, brown, scally leaves borne one both kids of branches. The number
of needles (leaves) in a cluster varies from 1 to 5 depending on the
species.
Reproduction:
Asexual reproduction (Sporophyth generation).
The pinus plant is the sporophyth. It bears two kinds of cones (stobili)s- male and female
cones- on separate branches of the microsporophylls (stamens) and the female cone
consists of megasporohylls (carpels). Male cones develop much earlier than the female
cones. Flower have no perianth.
Male Cone:
Male cone is made of a no of microsporophylls (stamens) each differentiated into a stalk
(filament) ands a terminal leafy expansion (another) with two micro sporongia (pollen
sac) on its undersurface. Each pollen sac microsoporangium produces tetrads of
microsopores (pollen grains) each with two coats exine and intine.
The exitne forms two wings, one on each side.
Pinus
Female cone.
Female cone consists of bract scales or carpels (megasporophylls). On t he upper surface
of each bract scale is a triangular structure called oruliferous scale at the base of which
there are 2 sessile orules with their micropyles towards the axis of the cone. Eash ovule
has a central mass of tissue called nucellus (megasporangium) surrounded by a single
intergument made of 3 layers. A megaspore mother cell in the nucellus undergoes
reduction division to produce 4 megaspores, 3 degenerate one remain functional.
Sexual production (Gametophyte generation).
Male gametophyte:The microspore (pollena grain) gives rise to a male gametohyte or prothallus, within the
microspore loat. The prothallus consists of (1) 2 or 3 small cells called prothallus cell
with soon degenerate (2) an antheridial cell which divides to form a generative cell and
tube cell.
The pollen grains are shed at this stage.
The generative call later divides into 2 (=male gametes).
Female gametophyte:
The megaspore gives rise to the female gametophyte or prothallus within the nucellus. At
the micropylar end of the prothallus develop 2 to 5 archegonia each consisting of a venter
enclosing a large egg-cell and a distinct egg-nucleus.
The archegonia slowly mature and become ready for fertilization in the following year.
Pollination:
Pollination take place through the agency of wind soon after the female cone emerges
from the bud. The pollen grains pass between the two slightly opened scales and are
deported at their base.
The microspores get entangted in mucilage deposited at the micropyle. The mucilage is
drawn in by the nucleus together with the microspores (spollen grains). Fertilization takes
place in the following year at about the same time when the archegonia mature.
Fertilization:
The exine bursts and intine grows out into a pollen tube which finally reach the neck of
archgonium. The pollen tube bursts at the apex of archegonium and the two male gametes
are liberated. The nucleus of one of the gametes slips out of the cytoplasm and passes
unto the egg-nucleus. The other male gamete and t he tube nucleus become disorganized.
After fertilization ovules develop into seeds and the whole flower into a dry brown
woody cone. The fully developed embrayo of the seed consists of an axis with
ahypocotyls, a radicle, a plumule with a number of cotyledons (2 to 5) surrounding it.
Under suitable conditions, the seed germinates (epigeal germination) into a sporophyte.
Life Cycle of an Angiosperm.
A zygote develops into an embrayo which later develops into a plant with roots, stem,
leaves and flowers. This is the sporophyte generation. The flowers have stamens
(microsporophylls) and carpels (megasporophylls) the stamens bear pollen sacs
(microsporangium) within the ovule which again develops within the overay.
The pollen sacs produce the pollen (microspore) mother cells which by reduction division
give rise to pollen grains (microspore). The nucellus produces the embryo-sac
(megaspore) mother cells which by reduction division give rise to a megaspore (note: 3
megasores will degenerate).
Gametophyte:
Male gametophyte: pollen grain germinates on the stigma of carpel to give rise to a male
gametophyte (=pollen tune with the 3 nuclei in it i.e. the tube nucleus, and 2 male
gametes.
Female gametophyte: the megaspore gives rise to female gametsophyt (i.e. embryo-sac
with eight nuclei in it). Both gametophytes are extremely reduced in size.
Female gametophyte is completely endosporous and dependant on the sporohyte for
protection and nutrition. Antheridia and archegonia are absent.
Pollination and fertilization.
Pollination mainly takes place through the agencies of insects, wind, water, birds and
boats. This is followed by fertilization one of the male gametes fuses with the egg-cell
and the other fuses with 2 pola nuclei or their fusion product (= definitive nucleus) with
2nd chromosomes. The fertilized egg-cell becomes the zygote (oospore) which grows into
and embroyo, the triple fusion nucleus grows into the endosperm (with 3n chromosomes).
The ovule and overy develop into seed and fruit respectively.
Differences between Gymnosperms and Angiosperms.
Gymnosperms
1.
Xylem exclusively made of
Angiosperms
1.
Xylem mainly composed
Tracheids.
of vessels.
2.
Phoem contains no companion cells 2.
Phloem contains companion cells.
3.
Flowers are simple-non calyxon
3.
Flowers are complex.
Corolla
4.
Flowers always unisexual
4.
Flowers unisexual or bisexual
5.
Air-current is the only pollinating
5.
There are many different pollinating
Agent
6.
Ovules are freely exposed on the
agents.
6.
Ovules remain enclosed in the ovary.
Megasporophyll (carpel)
7.
8.
During pollination, pollen grains enter 7.
Pollen grains are deposited on the
The microphly
stigmen.
Male gametophyte is represented by a 8.
Male gametrophyte reduced to 2
few cells usually 2 or 3
nuclei only tube nucleus and
- a vestigial prothallus
generative nucleus.
9.
Female gametophyte is a large
9.
Female gametrophyte is represented
Structure with archegonia ambedded
by an 8- nucleate embryo-sac and
in it, each with an oven
the ovun (egg cell) is free in it
without any archegonia.
10.
11.
Endosperm formed from vegetative 10.
Endosperm is formed from definitive
of female prothallus before fertilization
nucleus only after fertilization and is
and is haploid (n)
triploid (3n)
Cotyledons are 2 to 5
11.
Cotyledons are 1 or 2