1. Types of Natural Selection
Section 21.4

2. A. Natural Selection review
1) NS only gets rid of things that are BAD. Neutral or useless traits will not be removed
a. (see vestigial structures)
b. NOT like use / disuse from Lamark
2) For Natural selection to take place…
a. Trait must be genetic (not acquired)
b. Must have more than 1 allele
c. More individuals born than can live
d. One allele must result in greater fitness

3. 3) Natural Selection = the ONLY mechanism of evolution that leads to adaptation
a. Evolutionary Adaptation = Δ gene ƒ to better match environment

4. B. Types of Adaptations
1) morphological = physical form
dimorphism & polymorphism
2) physiological = how body functions internally
3) behavioral = behaviors that are not learned but are instinctual are inherited and can undergo evolution

5. C. Types of Natural Selection
1) Balancing Selection – balanced polymorphism due to heterozygote advantage maintains 2 phenotypes.
2) Stabilizing Selection – selective advantage of Median variation
3) Directional Selection – selective advantage of one extreme
4) Disruptive Selection – selective advantage of Both extremes
5) Sexual Selection – any type of selection that is based on ability to mate

6. 1.Balancing Selelection: Sickle Cell Anemia
a)point mutation(a 1 base substitution)
b) result = abnormal hemoglobin that makes RBC sickle in low O2 conditions
c) sickled cells block capillaries
d) co-dominant Hbn and Hbs
e) Malaria caused by protist Plasmodium an endoparasite of RBC
f)Heterozygous condition
reduces effects of malaria

7. g)heterozygote advantage creates…
h) a balanced polymorphism
i) balance between the 2 alleles
j) explains prevalence of sickle cell anemia in high malaria areas
sickle cell malaria

8. Frequency Dependent selection
May also create balanced polymorphism (balancing selection)
Scale eating fish
side-blotched lizard

9. 2. Stabilizing Selection : Human babies
Low birth weight = more complications
High birth weight =more complications
Medium weight =
Best chance for
survival

10. 4. Disruptive Selection
Wasp lays eggs only at base of spines
Peccary likes to eat leaves with few spines

11. 3.Directional Selection: Grant’s finches

12. 4. Disruptive selection: Peppered Moth
Moths in polluted area selected for dark color
Moths in clean area selected for light color
All same inbreeding population

13. Rock Pocket Mouse
/biointeractive/films/n atural_selection.html

14. 6. Sexual Selection Lecking behavior Greater prairie chicken
Greater prairie chicken
Wild Turkey
Timberdoodle
White tail deer
Bat behavior
big horn sheep 1:18

15. D. Adaptations are NOT perfect
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