Interpreting Dog Evolution – Part 1. Appearance



Interpreting Dog Evolution – Part 1. Appearance
Interpreting Dog Evolution – Part 1. Appearance
Integrated Science 4
Lineage from Ancestor Wolf
It is widely accepted that the domestic dog originated from the wild gray wolf (Canis lupus). While some still
debate where and when exactly this happened, the general idea is that perhaps certain populations of wolves
recognized that humans could serve as a means to obtain food. In turn, the humans may have recognized that
the wolves were good companions and could ward off other predators in the wild. It is conceivable that the
humans began to care for and travel with tame wolves. These wolves would breed, and perhaps their docile
and trusting character traits were passed on to future generations. At some point, humans began to see other
desirable traits in the domesticated wolves that led to directed breeding in the hopes of gaining traits beneficial
to the humans – the ability to herd, hunt and do work. Eventually the focus then changed to appearance of the
domesticated dog and the formation of different breeds.
Think about the dogs in your life – your dog, your friend’s dog, or your neighbor’s dog. There are plenty of
them to consider, as 46% of United States households own at least one dog (Humane Society, 2014). Surely you
can envision the differences between a golden retriever and a poodle. It isn’t as easy, however, to list the
differences between a rough collie and a Shetland sheepdog. Evolutionary biologists have used many different
methods to study and describe the evolutionary relationships of organisms. One method relies on careful
observation of the appearance of the organisms. This method is founded upon the idea that closely related
organisms will have more features in common than those that are distantly related. If you consider the rough
collie and the Shetland sheepdog in terms of their evolutionary relatedness, one might think they are closely
related... but what about other breeds? In this activity, you will be studying the evolutionary history of 7 dog
breeds and the gray wolf. These breeds include: basset hound, cairn terrier, collie, German shepherd, Labrador
retriever, pug and Siberian husky.
Based on archaeological evidence, the dog was the first animal to be domesticated by humans.
Conflicting archaeological evidence estimates that the dog was domesticated in Germany around 14,000
B.C. or even earlier, around 135,000 years ago. Still other scientific data suggest origins in either East Asia
or Eastern Europe.
There are currently 200-400 breeds of domestic dog worldwide.
When comparing the heads of wolves and dogs of similar height and weight, the head of the dog is smaller
than the head of the wolf.
1. Look at the various animals on the sheet provided by your instructor.
2. Fill in the Data Table 1 using the guideline of noting the presence (“+”) or absence (“-”) of the trait. Real
phylogeneticists would actually take measurements and use numerical data, when or if possible.
3. Use the data collected and recorded in Data Table 1 to determine the number of similarities between each
pair of animals. Record this information in Data Table 2.
4. Create a cladogram for the various dog breeds being analyzed based on their morphology (appearance.)
Note the presence (“+”) or absence (“-”) of the trait. Record this data in Data Table 1.
It may be helpful to use the following definitions:
 Short Legs – Are legs well proportioned with the body or are they shorter than they should be to be in
proportion? Use a “+” if short legs are present.
Skin Wrinkling – Is there an excess of skin such that folds and wrinkles are present? Use a “+” if skin
wrinkling is present.
Curly Hair – Use a “+” if the hairs of the coat are tightly curled.
Floppy Ears – Are ears erect or floppy (laying alongside the head)? Use a “+” if floppy ears are present.
Size – Is the overall size of the dog “large” – height greater than 20”, weight greater than 50 lbs? Use a “+”
if the size ears are large.
Short snout – The veterinary term for this condition is brachycephaly. It is characterized by a snout that
accounts for a small percentage of the length of the head (nose to back of the head). Use a “+” if a short
snout is present.
Furnishings – Long mustache and eyebrow growth. Use a “+” if furnishings are present.
Coat color – Is the color is “blended” (more than one color mixed throughout)? Use a “+” if a blended coat
is present.
Curly Tail - Use a “+” if the tail is not straight and curls around itself.
Data Table 1 - Presence (+) or Absence (-) of Traits in each type of Animal
Data Table 2 – The number of similarities between each pair of animals.
1. Describe the evolutionary relationships represented in the phylogeny based on appearance.

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