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Questions | Answers

1. Primary sexual characteristics: reproductive organs
Secondary sexual characteristics: external features of an organism other than reproductive organs that differ between males and females.

2. Sexual dimorphism

3. Ecological selection: Selection for characteristics that improve survival.
Sexual selection
: selection for characteristics that improve reproductive success.

4. Intrasexual selection: within one sex. Usually male-male competition.
Intersexual selection: between sexes. Usually female choice.

5. Intrasexual Selection: Mate Defense (Whoever defends mates best against rivals gets to mate), Resource Defense (Whoever defends best resources (e.g., food, shelter, etc.) against rivals gets to mate), and Scramble Competition (Whoever gets to most mates first gets to mate).

6. Intersexual Selection: Lek (female chooses male holding best spot at ritual gathering place), Prenuptial Gifts (chooser selects mate who offers best "gifts"), Good Gene Selection (chooser selects mate with best genes), Runaway Selection (chooser selects mate with best sexual attractiveness -- not better genes for surviving, but better genes for being chosen as a mate).

7. Runaway selection often starts as good gene selection as the chooser selects a mate with a characteristic that indicates better genes (e.g., longer tail), but then selects mates with more and more extreme examples of the characteristic so that the extreme characteristic, while sexually attractive, is now a liability for survival.

8. Monogamy: single mate per mating season
Pros: two-parent care
Cons: out-reproduced

9. Polygamy: Multiple mates per mating season
Pros: choose best partners
Cons: single parent care

10. Three types of polygamy:
Polyandry: one female with multiple male mates
Polygyny: one male with multiple female mates
Promiscuity: males and females both have multiple mates.