Download Adapted From: KVHS Biology - Kevin Gallant Rothesay, N.B.

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Campbell 7 - Chapter 24 - The Origin of Species
Note: The main things to understand in this chapter are what speciation is, the natural
barriers and the types of speciation. There are a number of terminologies that must be
understood in order to explain speciation and macroevolution.
1. Define the term species.
2. Suggest some cases in which the biological species does not work.
3. Why is the phrase "potential to interbreed" included in the biological species concept?
4. Barriers to reproduction fall into the categories of prezygotic and postzygotic barriers.
Describe each of the following; (The names of these may be difficult to differentiate but
use some common sense here and understand the concept – the names are
secondary – Figure 24.4 covers this. They are also referred to as prezygotic (before
fertilization) and postzygotic (after fertilization) isolation mechanisms.)
a) Prezygotic barriers: prezygotic barriers, habitat isolation, behavioral isolation, temporal
isolation, mechanical isolation, gametic isolation
b) Postzygotic barriers: reduced hybrid viablity, reduced hybrid fertility, hybrid breakdown
5. Identify and give an example of the two major types of speciation.
6. What conditions favor allopatric speciation?
7. Many plant species have arisen by sympatric speciation by means of autopolyploidy or
allopolyploidy. Explain.
8. Define and explain adaptive radiation. Is there evidence for it?
9. What is adaptive divergence?
10. Explain the differences between punctuated equilibrium and gradualism? (Important)
11. What is heterochrony and allometric growth? (Fig. 25.15 will help with this)
The Big Picture – Putting the Pieces Together and Making Connections
• Speciation can be linked to any type of evolution question. It can be the final result
in a natural selection question.
• It can also be tied into environment al changes occurring in a pond – increase in
temp example – leading to natural selection, microevolution, reproductive isolation
and speciation. Another example might be the drying up of a desert leading to gene
flow, microevolution and speciation.
***Please note the above big picture points are not made to make you study more. You
just have to take what you have learned and make the connections!!
Adapted From: KVHS Biology - Kevin Gallant
Rothesay, N.B.