Name _______________________________
Date __________________
Ch 21 reading guide – Biology in Focus
(Adapted from Fred and Theresa Holtzclaw’s reading guides)
(www.bozemanscience videos that go with this chapter 003 – genetic drift, 009 Evolution Continues)
Concept 21.1 Genetic variation makes evolution possible
2. Explain genetic variation and give an example not given in this section.
3. Explain the difference between a locus and an allele.
4. Explain the difference between a heterozygous and a homozygous organism.
5. Phenotype is the product of ______________
________________ ___________________.
_______________
and
many
6. What are three sources of genetic variation? Explain each.
a.
b.
c.
7. What is a mutation? What is the result of a mutation?
8. Refer to p. 288, Figure 13.25. Explain how one “point mutation” affects normal hemoglobin to
become sickle cell.
9. Explain how the duplication of genes can be beneficial.
10. Where does genetic variation come from in sexual reproduction?
Concept 21.2
11. What is a gene pool?
12. What is the purpose of the Hardy-Weinberg principle?
13. Explain what each of the components of the following equation mean.
P2 + 2pq + q2 = 1
a. p2
b. 2pq
c. q2
14. List and explain the five conditions of the Hardy-Weinberg Equilibrium
15. What does the Hardy=Weinberg equilibrium prove?
Read carefully through this section – we will be doing many math problems using this formula.
Concept 21.3 Natural Selection, genetic drift, and gene flow can alter allele frequencies in a
population
Bozeman science video 003 discusses Genetic drift – make sure you have watched it – so I won’t
repeat it here.
16. What is gene flow? Give an example.
17. What is relative fitness? Give an example of how relative fitness is an advantage.
18. What do you think the relative fitness of a sterile mule is? ______
19. Explain sexual selection and give an example.
20. Explain sexual dimorphism and what is the advantage of it?
21. Explain heterozygote advantage. Give an example.
22. List and explain the four reasons natural selection can’t fashion perfect organisms.
On p. 417 answer Focus Big Idea 1