Download Topic Review Guide: Speciation

Adapted from The Biology Space (Lee Ferguson, Allen High School)
Topic Review Guide: Speciation
To Think About: How is natural selection a major mechanism of evolution?
Watch: Mr. Andersens”s Reproductive Isolation and Speciation video
Then: Mr. Andersen’s Speciation and Extinction video.
Read: Chapter 13 and 14
Supplementary Resources: click the links below for more information to help you learn more about
the lesson.
 Crash Course’s Speciation video
 Kimball’s Biology Pages: Speciation
 UC Berkeley’s Understanding Evolution: Speciation
 UC Berkeley’s Understanding Evolution: Evo-Devo
 University of Miami: Reproductive Isolation
 DNA from the Beginning: Master Genes Control Basic Body Plans
Listen and Look: Here is a list of key terms you will hear and see during this lesson. Get to know
them! Be able to connect them to one another using a concept map.
KEY TERMS:
Speciation
Speciation
Species
Polyploidy
Temporal isolation
Gradualism
Extinction
Pre-zygotic barrier
Gene flow
Behavioral isolation
Evo-devo
Reproductive isolation
Geographic isolation
Allopatric speciation
Mechanical isolation
Punctuated equilibrium
Adaptvie radiation
Post-zygotic barrier
Sympatric speciation
hybrid
hybrid stability
Recall and Review: Use the lecture in the videos and your textbook to help you answer these
questions in your BILL:
1. Explain what the biological species concept is. Why is this species concept inapplicable to
asexually reproducing organisms? A species is a group of individuals that can reproduce
together and produce fertile offspring. Asexually organisms do not apply here because they
do not reproduce with other members of their species.
2. In the “Speciation and Extinction” podcast, Mr. Andersen discusses speciation of two varieties
of stickleback fish. Describe the environmental pressure that drove the process of speciation
in these fish and the role that natural selection played in this process.
3. Explain why island systems are ideal locations for the process of adaptive radiation to take
place. Describe other situations that could create ideal conditions for adaptive radiation to
occur. They are ideal because the species are confined to the new islands and thus only those
fit for that specific environment can survive. The species will evolve quickly as the alleles that
cannot survive will die off quick.
4. Explain what makes reproductive isolation such an important component of the species
concepts discussed in the chapter. In order for a new species to form, there must be a small
number of alleles reproducing over and over together. When individuals of one species
become isolated from the rest of the population, they can only reproduce with others who are
separated thus separating them genetically from the original population.
Adapted from The Biology Space (Lee Ferguson, Allen High School)
5. Draw an example of each of the following examples of reproductive isolation. Your drawing
should explain how each type of isolation leads to the formation of a new species without
using any words.
a. Geographic isolation (live in two different regions)
b. Behavioral isolation (different dances or songs in birds)
c. Temporal isolation (reproducing in the spring vs fall)
d. Mechanical isolations (2 snails with opposite shell openings)
6. Explain why reproductive barriers evolve. Describe an example of the evolution of a
prezygotic barrier and the evolution of a postzygotic barrier.
They evolve because of the barriers listed above. Prezygotic barriers prevent the two
organisms from any chance of coming together to mate. Postzygotic barriers allow for
fertilization to occur. However, once it occurs, the zygote typically is not viable thus an
offspring does not form.
7. Explain why polyploidy is much more common in plant species than in animal species. How
can polyploidy lead to reproductive isolation?
Because of alternation of generation – since they have to already undergo a change in
chromosome number during the cycle. Also they have more flexible body plans than animals.
As polyploidy leads to a completely different number of chromosomes, it is likely it would lead
to reproductive isoloation.
8. Recall that sexual selection is the process by which females of a species seeing a mate select
the males of their species based on an attractive appearance or behavior. Explain how sexual
selection could lead to reproductive isolation.
If a sub population of females changes their preference of dance or color (even if it is a minute
change) they will begin to only reproduce with birds who do that dance and will refuse to
mate with the others.
9. Distinguish between allopatric and sympatric speciation. Give two examples of each type of
speciation. (Allopatric speciation is when there is some sort of geographic barrier that forms
and separates members of the same population. Ex: formation of a lake that separates
species of ground squirrel. Sympatric speciation is when there is no barrier between the
members of the population yet they quit reproducing with certain members. For example, a
group of trees separates in that the center trees begin reproducing together – maybe less
wind or mammals to spread the seeds to the outer trees.
10. Discuss the differences between the two schools of thought regarding the tempo of
evolutionary change: punctuated equilibrium versus gradualism.
11. Look at the DNA from the Beginning site that discusses the role of genetics in development of
embryos. Homeotic genes (Hox) are genes that control the basic body plan of an organism.
How do you think natural selection coupled with the expression of Hox genes in early animal
embryos played a role in tetrapod evolution.