Gametes - Sex cells
- Ova - largest cells in the human body, 1-2 a month released until all run out
- Sperm - 40-600 million released per ejaculate
Sexes and Sex Selection
- Female - sex that makes the larger parental
Why Is There Sex?
Hedge against environmental change
No current reason for humans phylogenetic inertia
Protection against pathogens Red Queen hypothesis
The Sexes and Sexual Selection
Female sex that makes the larger parental investment per gamete.
Male sex that makes the smaller parental investment per gamete.
Sexual selection a type of natural selection in which members of one sex compete
reproductive access to members of the other sex.
The means of competition can be structural or behavioral, and often lead to sexual
dimorphism. Why is there sex?
- no current reason for humans - phylogenetic inertia
- Protection against pathogens
- In most of animal kingdom, females are much bigger than males.
- One major exception is in species with proportionally large brains.
- humans males are bigger
- In those species, males compete for females with displays of strength and
- Females choose mates based in part on these displays
- Overt female choice
- Cryptic female choice Mating Systems
- Sexual selection - male behavior displays
- males fight so they can mate withdominant female
- Structual displays - peacock tail, antlers on bucks, claws on crabs
- Incitement - femalerhesus money tail turns red and they secrete vaginals
fluids - wags
in males face and then dances off and will keep doing until the male shows
- In humans females usually initiate mating process
- Monogamy - pair-bonding
- Polygamy one animal has ma