Chapter 10 - The Evolution of Sex

Notes for Evolution - The Triumph of an Idea - Chapter 10

Click link to return to Biology 409 Schedule
or back to Chapter 9 or ahead to Chapter 11

General guide on these review questions here

Chapter 10 - Passion's Logic - The Evolution of Sex

Objectives:

a) Gain an overview of the way natural selection can promote behaviors that lead to enhanced reproductive success

b) Consider that sex involves considerable cost to an individual, yet might have some benefits that are not as obvious as they might at first seem.

c) Be able to characterize, in general terms, what male vs. female strategies involve and imply.

d) Be able to characterize why sexual selection seems to be a paradox at odds with natural selection yet is driven by female choice.

e) Learn some examples of competition between males, both behavioral and at the level of sperm competition.

f) Contrast situations under which a female might have reason to bias the sex ration of her offspring, either towards males or females.

g) Use natural selection to understand infanticide in lions and other animals with certain kinds of social groups.

h) Use natural selection to explain why animals might behave altruistically, either to promote their own inclusive fitness or because of potential return benefits.

i) Contrast chimp and bonobo social groups and the selective forces that might have shaped the differences.

I. Introduction

Featured Scientist: William D. Hamilton
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Links: 1 - 2 - 3 - 4

II. Why Sex?

61 Lecture Slides or PDF Handout on "Why Sex?"
(Detailed notes from Website by Edmund Brodie III)
Two recent Scientific American articles: 1 - 2

Key Terms: Red Queen hypothesis

RQ Ev-10.1: Why is the analogy of Alice and the Red Queen used in relation to the possible advantages of sex given the risk that parasites pose?

III. Sperm and Egg

RQ Ev-10.3: Contrast in the most general terms possible how female and male roles differ in sexual reproduction.

IV. Female Choice

Key Terms: sexual selection

PBS Website Sexual Selection

RQ Ev-10.4: Using peacocks and peahens or your own original choice of animals as an example, explain why sexual selection seems a paradox compared to how natural selection normally acts, and then use the notion of female choice to explain how traits that seem maladaptive are indeed favored by natural selection.

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RQ Ev-10.5: Explain how Marion Petrie tested the effectiveness of female choice in peahens.

V. Battle of the Sperm

RQ Ev-10.6: Give three examples from the book or elsewhere that illustrate how males can compete with each other to ensure that their sperm are most likely to fertilize a female's eggs.

VI. Chemical Warfare of the Sexes

RQ Ev-10.7: What evidence did William Rice collect that suggested that fruit flies are in a chemical arms race between and within the sexes?

VII. Tug of War, In Utero

VIII. Maternal Investments

RQ Ev-10.8: What evidence did Jan Komdeur collect to suggest that warblers from the Seychelles could manipulate the sex ratio of their offspring, depending on conditions? (open pdf of review article here)

IX. Darwinian Family Life

RQ Ev-10.9: Even though it seems cruel to humans, under what circumstances might natural selection favor a male lion to act homicidally towards cubs in a pride?

X. For the Good of the Gene

Link to Introduction to Social Evolution from Here

Key Terms: inclusive fitness (More Links: 1 - 2 - 3)

RQ Ev-10.10: Use the notion of inclusive fitness to explain how an act of altruism (acting to benefit the reproductive success of another individual at some cost to one's own future reproductive success) might actually be favored by natural selection.

RQ Ev-10.11: Why should a female bee work so hard to help raise more sisters instead of reproducing herself, and why are male bees not apt to help out in the hive?

XI. The Generosity of Peacocks

RQ Ev-10.12: Why should a female bee work so hard to help raise more sisters instead of reproducing herself, and why are male bees not apt to help out in the hive?

XII. Sexual Politics of the Chimpanzees

Featured Scientist: Robert Trivers
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Links: 1 - 2 - 3 - 4 - 5 - 6

Download Triver's classic 1971 article on reciprocal altruism here (pdf format)

RQ Ev-10.13: How can chimpanzee males gain benefits by helping out other males that are unrelated to themselves, and when are they unlikely to help?

XIII. Love, Not War

Featured Animal : Bonobos
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Links: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8

PBS Website Chimps and Bonobos

RQ Ev-10.14: Contrast the social structure and activities of chimp and bonobos, together with some ideas about why such differences might have evolved and are still maintained by natural selection.

Click link to return to Biology 409 Schedule
or back to Chapter 9 or ahead to Chapter 11