1. Sex

2. Outline What is sex? Cost/Benefits of Sex What defines the sexes?
Sexual Origins
Sexual Conflict
Male-male Competition
Female Choice
Cryptic Female Choice
*Sperm Competition
Where is this leading?

3. What is Sex? Sex: Meiosis and Syngamy Meiosis - Reduction
Syngamy - Fusion

4. Syngamy Fusion of gametes 2 kinds: Isogamy- protists, fungi, algae
costs
Anisogamy
beneficial

5. Benefits of Having Sex
Traditional: increase the rate of adaptive evolution --> decreases extinction risk
Creates genetic variation
spread of advantageous traits and elimination of deleterious genes
Resistance to parasites (Red Queen hypothesis)
Repair of damaged DNA via recombination

6. Costs of Sex Only one sex can bear young
Asexual population: both “sexes” can bear young, so population increases more rapidly
Males and females must find each other to mate
Predation risk

7. What defines the sexes? Gamete size! This defines Anisogamy
Larger gamete = Female
Increase zygote size
Zygote fitness
Smaller gamete = Male
Get more for less, just like Walmart!
This defines Anisogamy
There is variation in gamete size though…

8. Giant Sperm
Drosophila bifurca

9. Sexual Origin
Giardia lamblia
Very primitive group

10. Sexual Conflict Male-Male Competition Female Choice
Cryptic Female Choice
Sperm Competition

11. Male-Male Competition
Can lead to extravagant characters and sexual dimorphism
Territory size and quality
Ornaments vs. Armaments
Mate Gaurding

13. Female Choice
Females preferentially mate with males that have larger or more intense exaggerated characters
Morphological characteristics, display behaviors, territory size, nuptial gifts
Honest indicators, sensory bias

14. Indirect Benefits of Mate Choice
Sexy sons: female preferences are inherited
Runaway selection
Good Genes
Handicap Principle

15. Cryptic Female Choice
Female chooses which sperm will fertilize her eggs after mating with several males
Denial of deeper genetalic access
Discharge or digestion of sperm
Breaking copulation

16. Cryptic Female Choice
If females do these things non-randomly then it is cryptic female choice

17. Sperm Competition
Sperm from two or more males compete inside the female
Calopteryx
Number of Sperm
Sperm Quality
Mating Order

18. Sperm Competition Sperm Displacement Producing more sperm
Copulatory organ modifications
Humans
Genital plugging and removal

19. Where is this leading us?
Mating Systems
Monogamy
Polyandry
Polygyny
Promiscuity
Life History Evolution