Unit 1.3 Review Answer Key
Name______________________________
Period_______________
1. Define a species
Members of a population that can reproduce and produce viable, fertile offspring
2. List the two main types of speciation
Allopatric and sympatric speciation
3. Explain allopatric speciation
A geographic barrier separates a population into two subpopulations. These
subpopulations cannot cross the barrier and mate, and therefore undergo speciation
Note: a barrier is something that can’t be crossed…. i.e. birds can fly over a river or a
canyon, but land-bound animals cannot
4. Provide an example of allopatric speciation
Grand Canyon squirrels (refer to the slides for more details). They once belonged to
one species but then the Grand Canyon split into two, and the squirrels on either side
could not cross the chasm. They became geographically isolated and formed two
different species
5. Explain sympatric speciation
Speciation that occurs without a geographic barrier. A population can live in the same
place and undergo sympatric speciation due to mutations, genetic drift and
reproductive isolation
6. Explain ecological isolation and provide an example
Two organisms occupy/live in the same geographic area, but don’t come into contact
with one another… this could be because they live in different habitats (for instance,
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maybe one species of blue bird prefers certain trees that are only found in particular
parts of a forest)
7. Explain temporal isolation and provide an example
Two organisms do not come into contact with one another because they mate and
reproduce at different times of day (i.e. owls mate at night, pigeons in the day time).
Another example would be a species of toad that mates during the spring, while
another species of toad mates during the fall. If they mate during different seasons,
they won’t ever come into contact to reproduce.
8. Explain behavioral isolation and provide an example
Two organisms do not come into contact with one another because they don’t engage
in the same courtship rituals (i.e. peacocks show off their feathers, and other birds
like to sing)
9. Explain mechanical isolation and provide an example
Two organisms can’t reproduce because they are physically incompatible and will
hurt or even kill each other if they try to engage in sexual reproduction.
10. Explain gametic isolation and provide an example
Two organisms can engage in sexual intercourse, but their egg and sperm will not
fuse to create an embryo
11. Explain what reduced hybrid viability is and provide an example.
Two different species mate, their offspring has a reduced chance of survival and
living up to its full life-span
12. Explain what a reduced hybrid fertility is and provide an example.
Two different species mate, their offspring can’t produce offspring. Their babies can’t
have babies.
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13. Explain what will happen to a population that undergoes allopatric speciation
The two geographically isolated subpopulations will form two different species
14. Explain what will happen to a population that undergoes sympatric speciation
The two subpopulations will form two different species that coexist in the same
geographic area
15. Define phylogenetics
The study of evolutionary relationships between organisms
16. Describe a phylogenetic tree
Illustrates visually the evolutionary relationships between organisms
17. Define morphological evidence and provide an example
Evidence that looks at the structure and form of an organisms; great example –
fossils and the fossil record
18. Define molecular evidence and provide an example
Using the cells and DNA of species to compare their similarities
19. Define a clade
A monophyletic group composed of an ancestral species and all its descendents
20. What are clades used for?
To illustrate derived characters (traits that are passed down from generation to
generation), when they might have first appeared and which organisms are more
closely related
21. Describe the two steps to creating a cladogram.
Don’t worry about this; as long as you know how to do a cladogram, you will be fine!
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22. Use this cladogram to answer the following questions:
a. Which animals share a vertebrae?
Snake, horse, dog, cat
b. Which animals share toes?
Dog, cat
c. Which animals share fur?
Horse, dog, cat
25.
Use the below table to make a cladogram
Cladogram should have goldfish first, then lungfish and then lions. Goldfish has bony
skeleton, so write that before goldfish; then in between goldfish and lungfish you should
have humerus, ulna, and radius bones as well as lungs and a shoulder girdle. Then in
front of lions you should have hair.
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