Sexual selection
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Sexual Selection. How it happens…. Aka, what stressors are put on by organisms to choose the best mate Sexual selection’s goal is to unite and pass on the best possible combination of genes Fitness of an organism may depend on several factors, which we will discuss. They are.

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How it happens
How it happens…

  • Aka, what stressors are put on by organisms to choose the best mate

  • Sexual selection’s goal is to unite and pass on the best possible combination of genes

  • Fitness of an organism may depend on several factors, which we will discuss.


They are
They are

  • Sexual Dimorphism

  • Male- Male Competition

  • Female Choice

  • Diversity in Sex Roles


Sexual dimorphism
Sexual Dimorphism

  • The differences between the males and females of a species

  • May include

    • body size

    • Coloring

    • Patterns

    • Length or size of appendages or parts of an organism ( thumbs on toads or feathers on birds)


Sexual dimorphism1
Sexual Dimorphism

  • May be several reasons why there are differences, but all relate in that its all about finding a mate.

  • Body size may make a better fighter, or coloring may be flashy enough to attract a female


Male male competition
Male- Male Competition

  • There are a few subtopics here:

    • Combat

    • Sperm Competition

    • Infantcide


Combat
Combat

  • Males often possess the tools needed to fight with other males in hopes of getting the lady

  • This may mean a larger body size, larger antlers, longer fins, or even longer necks (giraffes)

  • By fighting (and winning) a male shows dominance over other males and gains the attention of the female


Combat1
Combat

  • Sometimes this leads to dimorphism among males of the same species.

  • One is not big enough, strong enough, or armed enough to win a competition

    • So it uses stealth like tactics of completing the task at hand and getting out unnoticed.


Sperm competition
Sperm Competition

  • Males of sexually reproducing species produce sperm (the gamete that holds the male’s genes)

  • In the case of female promiscuity (a female mating as much as possible) you often see some form of sperm competiotion


Sperm competition1
Sperm Competition

  • This may lead to many types of competition

    • Larger amounts of sperm

    • Nuptial gifts- may include amounts of food for the female or the offspring

    • Insertion of a copulatory plug- a literal plug inserted to block other male’s attempts at sex

    • Application of pheremones – decreases the attractiveness to other males

    • Male guarding the female, or prolonging copulation


Infanticide
Infanticide

  • When the male of a species consumes the offspring of a female which he has not fathered.

  • Most notable in lions

  • Goal is to pass on your own genes.

  • Any offspring that a male has not fathered shares no genes

    • Furthermore, any young males may present a challenge down the road

  • Best option for a male lion?

    • Eat all other cubs


Female choice
Female Choice

  • In a lot of situations it is up to the female to find a mate

    • All a male can do is advertise

      • Say “look at me! Look at meeeeee!”

  • Females then can pick and choose the male they feel possesses the best set of genes.

  • Basically saying, most anything a male does to stand out to a female also makes him stand out to predators

    • But, if that male can survive, and reproduce the rest of his genes must be really good.


Diversity in sex roles
Diversity in Sex Roles

  • Most of the time, in most organisms, the female carries most of the cost of offspring (producing and watching over eggs, carrying babies, and/or care for the young)

  • Sometimes this is not the case


Diversity in sex roles1
Diversity in Sex Roles

  • In humans, fish, some frogs, and most birds the male may take on as much of a burden (if not more) compared to the female.


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