Science C Lesson 2

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mineral, A16
root, A17
stem, A17
leaf, A18
energy, A18
oxygen, A19
A cactus lives in a hot, dry
desert. A pine tree grows on a
snowy mountain. A coconut
tree thrives on a sandy beach.
These three plants are very
different, yet they have the
same needs as all other
plants. Do you know what
plants need to live and grow?
Process Skill
You observe when you use
one or more of the senses to
identify or learn about an object.
A 14
Explore Activity
Materials
soaked pea
seeds from
Lesson 1
What Do Plants Need?
4 half-pint
cartons
• Procedure
Measure PlaceT cup of soil in each carton. Plant
the seeds, and cover them with a thin layer of soil.
3 cups of soil
water
Label the cartons Light, Water, No Light, and
A/o Water.
Put the carton labeled No Light in a dark place.
Put the remaining cartons in a sunny area. Water
the cartons labeled Light, No Light, and Water.
Observe Look at the plants twice a week.
Record what you see in a table like the
one shown here.
Drawing Conclusions
Q How many seeds in each
carton grew into plants?
Q Which plants looked
healthiest after two weeks?
Fl Interpret Data What do you conclude seeds
need to grow into healthy plants?
•
Q Going Further: Define Terms
What else do you think
plants need in order
to survive?
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No
N,
Read to Learn
Main Idea All plants have the
same basic needs.
What Are the Needs of Plants?
Like all living things, plants have certain
needs. Plants need sunlight, water, and air to
live. Plants also need minerals (MIN-uhr-uhlz).
A mineral is a naturally occurring substance
that is neither plant nor animal.
The parts of plants help them to get or make
what they need. What parts do you see on the
bean plant?
Stem
Field of bean plants
Roots
The roots, stem, and leaves
of this bean plant work
together to get what the
plant needs to live and grow.
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I
All plants get water and minerals from
the soil. The root is the plant part that grows
underground. Roots help hold the plant in the
ground. Roots also help take in water and
minerals that the plant needs.
The stem is the part that supports the plant.
It helps the plant stand upright. It carries
minerals and water from the roots. It also carries
food from the leaves to other parts of the plant.
Some plants, such as mosses, are simple
plants. They don't have real roots or stems.
These plants do not grow tall. Instead, they form
low-growing mats in damp places to get water
directly from the soil.
Other plants, such as the redwood tree, have
many roots and a large stem. They can grow
very tall.
The trunk of a redwood tree is
its stem. Its roots are spread
out underground. Why can
a redwood tree grow so tall?
What are the
needs of plants?
A moss plant uses
rootlike structures
to get the water it
needs. It grows
low to the ground
because it has no
stem to carry
water and minerals
to its leaves.
Tiny holes on the underside
of a leaf take in air.
Why Does a Plant Need Leaves?
The leaves (singular, leaf) are
the main food-making part of the
plant. Many leaves have broad, flat
surfaces that help them take in
sunlight. Leaves are green because
of chlorophyll. Chlorophyll traps the
energy (EN-uhr-jee) in sunlight for
the plant.
The leaf also helps the plant get
the air it needs. Each leaf has tiny
holes that take in air for the plant.
The leaf uses a gas in the air called
carbon dioxide. The plant uses the
Sun's energy to combine carbon
dioxide and water to make food.
The stem then carries the food
to the other parts of the plant.
A 18
FOR S C H O O L OR HOME
Watch Water
Travel Through
a Plant!
BE CARtFUt! Wear goggles.
Chloroplasts, shown here as small parts
inside a leaf cell, contain chlorophyll. This
is where the plant makes food.
Plants use the food they make
to stay alive. When we eat plants
or other animals that eat plants,
we use this food, too.
When leaves make food for a
plant, they give off oxygen
(AHK-suh-juhn). Oxygen is a gas
that is in air and water. People
and animals need oxygen to live.
You inhale the oxygen made by a
plant with each breath you take.
1. Measure Put about 5 cm
(2 in.) of water in a clearplastic glass. Add about ten
drops of food coloring.
2*
Predict Put a celery stalk in
the glass for two hours. What
do you think will happen?
3.
Observe What did you
observe after two hours?
4* Infer How does water
travel through a plant?
Why are leaves green?
A 19
/
How Do Plants Respond
to Their Environment?
Have you ever seen a
plant leaning toward a sunlit
window? This is one way
that plants respond to their
environment. A plant responds to
light by growing toward it.
Some trees and shrubs drop
their leaves as the days grow
Morning glories turn toward the Sun.
shorter and colder. These plants
respond to the change in seasons
READ NG I) raw Conclusions
from summer to winter.
How do plants respond to
Plants also respond to other things
sunlight?
in the environment. For example, roots
may grow toward water. The ability to
respond to the environment helps a
The trees in this grove are
plant to live, grow, and meet its needs.
responding to the cooler
temperatures of autumn.
Why It Matters
We depend on
plants for food.
We eat the roots,
stems, and leaves
of plants. The cereals we eat
are made from plants. We
eat animals that eat plants.
However, people need
plants for more than food.
We also breathe the oxygen
that plant leaves make. Visit
www.mhscience02.com to do
a research project on plants.
Think and Write
1 . What is oxygen?
2. What do plants need?
3* Why do most plants have
roots, a stem, and leaves?
4» What if you put a plant in
the middle of a room? The
room has walls on three
sides. On the fourth side,
there is a sunny window. In
which direction will the
plant grow? Why?
5. Critical Thinking The
saguaro cactus has no
leaves, but its stem is
green. Where do you think
the cactus makes its food?
MATH LINK
Make a bar graph. Go on a plant hunt.
Write down the different kinds of plants
you find. Then group them into categories,
such as grasses or trees. Make a graph
to show how many of each category
you found.
ART LINK
Leaf prints. Find several different leaves.
Paint the underside of each leaf. Then
press the painted part of each leaf on a
piece of paper to make a leaf painting.
What do you notice about the leaves?
LITERATURE LINK
Read Save Our Park
Trees to learn about a
tall, old oak tree that was
alive 200 years ago. When
you finish reading, think
about what you would tell
the people who would
want to cut down this
tree. Try the activities at
the end of the book.
TECHNOLOGY LINK
At the Computer Visit
www.mhscience02.com
for more links.
A 21
Scl
cience
ALIVE
Water, sunlight, and nutrients keep plants alive
and growing. Plant leaves absorb sunlight and use it
to make food. Trees grow tall and use their leaves to
get as much sunlight as possible. However, some
plants are equipped to live in places with very little
water, sunlight, or nutrients.
The cactus lives in the
desert, where there's
not much rain. The
plant's roots absorb
and store rainfall.
Some roots grow way
out to absorb as much
water as possible. The
cactus also stores
water in its thick stem
Ferns grow on the
ground, far from
sunlight. These
plants prefer the
shade. They don't
use as much
of the Sun's light to
make their food.
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