Intraspecific Competition Lecture - Intraspecific Competition =Competition between members of the same species for resources 1 Competition for

Intraspecific Competition Lecture - Intraspecific...

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Unformatted text preview: Intraspecific Competition =Competition between members of the same species for resources 1) Competition for individual survival e.g. food, space, sunlight, shelter, oxygen, water 2. Competition for reproductive success SEXUAL SELCTION SEXUAL SELECTION Sexual Selection= Competition among individuals of the same sex for reproductive success – Two types of sexual selection: Male competition Female choice 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. Male Competition (“Breeding Rights”) 1) Males fighting e.g. Elephant seals Male Competition 2) Threat Displays Fighting should be avoided Leads to Sexual dimorphism Male Competition 3) Sperm Competition Fire ant = 3 sperm/egg Honey bee = 25 Human = 450 million Horse = 7 billion Pig = 20 billion Reproductive Competitive Among Primates Male Competition 4) Sperm removal e.g. Insect barbed penises scoop out competitor’s sperm. e.g. Damselfly Male Competition 5) Male guarding of female laying eggs e.g. Dragonfly FEMALE CHOICE e.g. Female blackbirds choose males with good territory FEMALE CHOICE e.g. Female Barn swallows choose males with the longest tails Clicker Question for Women Which of the following traits do you rank most highly for a mate? 1) 2) 3) 4) 5) 6) College graduate Good health Physical attractiveness Desire for children Religious orientation Good earning capacity Clicker Question for Men Which of the following traits do you rank most highly for a mate? 1) 2) 3) 4) 5) 6) College graduate Good health Physical attractiveness Desire for children Religious orientation Good earning capacity FEMALE CHOICE Cont.’ What traits are selected for? Traits selected with potential for reproductive success: – “Health, wealth, & power” Males are less discriminating than females – Males have a low cost of reproduction – Females have a high parental investment FEMALE CHOICE Traits without apparent survival value: 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? FEMALE CHOICE How are mate preferences developed? 1) Some are learned e.g. Imprinting in turkeys FEMALE CHOICE How are mate preferences developed? 1) Some are learned e.g. Eye ring in sea gulls 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? Experiment with Platyfish Genetic? Species A Male with Sword Species A Female Species A Male without Sword How would you test the idea that the female swordtails’ preference is genetically determined? 1.Food capture gathering 2.Predator avoidance 3.Protection 4.Build shelters 5.Care giving 6.Reproduction 7.Altruism ? 8.Kin selection KIN SELECTION 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” 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 But what possible selective advantage would there be to self sacrifice----for that matter, any altruistic act? KIN SELECTION “Inclusive fitness”= Sum of the reproductive success of individuals sharing a genotype 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.) KIN SELECTION “I would lay down my life for two brothers or eight first cousins” J.B.S. Haldane 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 ...
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