This tutorial looks at three subjects currently being actively researched in evolutionary biology - the reason for sexual reproduction, why the sexes differ and explaining the sex ratio favored by natural selection.

Key Questions:

• Why do organisms reproduce sexually?
• Can group selection explain sexual reproduction?
• Does sex reduce the effects of deleterious mutations?
• What environmental changes make sex advantageous?
• Why do the sexes differ?
• Why is a 50:50 sex ratio so prevalent in nature?
• Summary