1. Intraspecific Competition

2. Intraspecific Competition
=Competition between members of the same species for resources
Competition for individual survival
e.g. food, space, sunlight, shelter, oxygen, water
2. Competition for reproductive success

3. SEXUAL SELCTION

4. SEXUAL SELECTION

5. Sexual Selection=
Competition among individuals of the same sex for reproductive success
Two types of sexual selection:
Male competition
Female choice

6. Sexual Selection=
Competition among individuals of the same sex for reproductive success.
This is different from natural selection
which is a battle for survival.
This is a battle for reproductive rights.

7. Male Competition (“Breeding Rights”)
Males fighting
e.g. Elephant
seals

8. Male Competition Leads to Sexual dimorphism 2) Threat Displays
Fighting should be
avoided
Leads to
Sexual dimorphism

9. Male Competition 3) Sperm Competition Fire ant = 3 sperm/egg
Honey bee = 25
Gorilla = million
Human = million
Chimpanzee = 600 million
Horse = billion
Pig = billion

10. Reproductive Competitive Among Primates

11. Reproductive Competitive Among Primates

12. Reproductive Competitive Among Primates

13. Male Competition 4) Sperm removal
e.g. Insect barbed penises scoop out competitor’s sperm.
e.g. Damselfly

14. Male Competition
5) Male guarding of female
laying eggs
e.g. Dragonfly

15. FEMALE CHOICE
e.g. Female blackbirds choose males with
good territory

16. FEMALE CHOICE
e.g. Female Barn swallows choose males with the longest tails

17. College Survey
e.g. Humans

18. FEMALE CHOICE How are mate preferences developed? Some are learned
e.g. Imprinting in turkeys

19. FEMALE CHOICE How are mate preferences developed? Some are learned
e.g. Eye ring in
sea gulls

20. Are some preferences genetic?
Swordtail platyfish
Some species with swords and some without.
Females of the swordtail species prefer individuals with the longest tails.
Is this genetic or learned?

21. Experiment with Platyfish
Genetic?
Species A
Male with Sword
Species A
Female
Species A
Male without Sword

22. How would you test the idea that the female swordtails’ preference is genetically determined?

23. Experiment with different species
Platyfish
Species A
Male with Sword
Species B
Female
Species B
Male without Sword

24. Experiment
Platyfish
ALL female platyfish prefer males with tails regardless of species! Appears to be gentic.
Species X
Male with Sword
Female
Species Y
Species Y
Male without Sword

25. Experiment Genetic: Platyfish toward the swordtail condition
Females have a genetic predisposition
toward the swordtail condition
But why? Is the tail a signal for some other
beneficial trait?

26. What traits are selected for? Selective Advantage Hypothesis
a. Traits selected with potential for reproductive success:
“Health, wealth, & power”
e.g. Territoriality of black birds
Males are less discriminating than females
Males have a low cost of reproduction
Females have a high parental investment

27. But why would she prefer some traits over others?
Selective Advantage Hypothesis:
a. The trait shows health
b. Handicap hypothesis: She is choosing those which have survived even in spite of possible disadvantages. It shows they are extraordinarily fit.
2) Beauty hypothesis: She is choosing simply because she thinks the male is beautiful

28. Traits without apparent survival value:
How can this happen?

29. FEMALE CHOICE “Runaway Selection”
Female chooses males with fancy tails
Sons get fancy tails
Daughters get tendency
to select fancy tails
But why would she prefer some traits over others—ones with no apparent advantage?

30. Intraspecific Cooperation

31. Why do individuals Cooperate?
Food capture
Predator avoidance
Protection
Build shelters
Care giving
Reproduction
Altruism ?
Kin selection

32. KIN SELECTION

33. KIN SELECTION=
= “a form of natural selection that favors traits that increase survival or reproduction of an individual’s kin at the expense of an individual”

34. KIN SELECTION It involves altruism or self sacrifice
--an act by one individual that increases fitness of others at that individual’s expense benefits close relatives

35. But what possible selective advantage would there be to self sacrifice----for that matter, any altruistic act?

36. KIN SELECTION “Inclusive fitness”=
Sum of the reproductive success of individuals sharing a genotype

37. KIN SELECTION
An altruistic act may increase the chances your genes will survive.
If you save 2 brothers or sisters you will save your genes (They each share ½ of your genes.)

38. KIN SELECTION
“I would lay down my life for two brothers or eight first cousins”
J.B.S. Haldane

39. KIN SELECTION
Individual fitness= determined by the # of an individual’s offspring.
Inclusive fitness= determined by the sum total of reproductive success of all individuals sharing a genotype

40. Next Time
Predators & Parasites