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19. Behavior

19. Behavior The necessary conflict Is Sex Necessary? The sexes Males: sperm are cheap and plentiful humans: 300 million sperm per ejaculate, make more continuo usly goal: mate with lots of females Females: eggs are in limited supply, offspring costly

Mercy
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19. Behavior

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  1. 19. Behavior The necessary conflict

  2. Is Sex Necessary?

  3. The sexes Males: sperm are cheap and plentiful humans: 300 million sperm per ejaculate, make more continuously goal: mate with lots of females Females: eggs are in limited supply, offspring costly humans: 400,000 eggs post puberty (many die daily), degrade with time, born with all her sex cells intact goal: get best male available Sets up conflict!

  4. Operational Sex Ratio (OSR) • Predicts who will do the fighting • Ratio between receptive males to receptive females • More males = female choice • More females = male choice • Males are an extension of their gametes! • Males almost always sexually receptive • 96% males, 54% female college students said they thought about sex in any hour

  5. Mate Competition

  6. Tactics of Male Competition Physical contact: Ibex Providing resources: Red back spider Physical display: birds Although competition occurs among males, females still choose This choice drives the competition! Females are choosing genes!

  7. Physical contact: Ibex

  8. http://www.dkimages.com/discover/previews/1239/10140550.JPG http://imagecache2.allposters.com/images/pic/LPIPOD/BN233_601-FB~Gorilla-Gorillagorilla-Baring-Its-Teeth-Africa-Posters.jpg Physical contact Ibex, Mountain Goat from East Africa, Middle East Males fight for the right to mate Males usually larger than females Specialized structure for fighting

  9. Resources: Red Back Spider

  10. Hanging flies (males give female insect prey before mating http://www.elkhornslough.org/journal/journalpix/050309dance-flies.jpg Providing Resources Red back spider: male forfeits life to the female to increase sperm transfer Nuptial gifts: Common in insects, seen in birds

  11. Physical display All female choice Males “displays” his quality (genes) Good skills – Bower birds building and selecting objects Good looks – Bird of Paradise plumage and dancing Good performers – Manakins coordination and dancing two males are necessary

  12. Good skills: Bowerbirds

  13. Good looks: Bird’s of Paradise

  14. Good performance: Manakins

  15. Irish Elk http://cas.bellarmine.edu/tietjen/Ethology/Irish_Elk.jpg Sexual Selection Competition for mates between individuals of the same sex drives evolution of certain traits Individuals with desired trait will get to mate Desired trait = better fitness = offspring will have advantage Fitness: reproductive output Genes for favorable trait are passed on to next generation Runaway selection: trait that females like gets exagarrated example: Irish Elk Female choice of large antlers Antlers got so big they were detrimental to males Species is now extinct

  16. Environmental influence on mating: Jacana

  17. Environmental influence on mating Jacana: birds lives in streams, ponds crocodile predation leads to high loss of eggs, young females larger males tend the eggs, young frees the female to keep laying

  18. Mating systems Polygamy: one individual mates with multiple members of the opposite sex at the same time 97% mammals about 100% invertebrates 6% birds Forms: Polygyny: 1 female, > 1 male Polyandry: 1 male, > 1 female Monogamy: one individual of each sex mates exclusively with one another 3% mammals (humans?)

  19. Male Parenting

  20. Choose Good Parenting Partners Male assistance in raising the young When do males help? Environment makes is difficult for female alone to raise offspring (offspring die)

  21. Titi Monkey monogamy

  22. Choose Good Parenting Partners Titi monkeys: South America Father helps raise young Mother feeds constantly to produce milk How to ensure monogamy? Courtship: elaborate behaviors to bond a pair Courtship ensures shared foraging, nest building, defense, parenting

  23. Wandering Albatross: Prolonged Courtship

  24. http://www.animalpicturesarchive.com/ArchOLD-7/1188739447.jpghttp://www.animalpicturesarchive.com/ArchOLD-7/1188739447.jpg Wandering Albatross Spend most of their life at sea Courtship lasts several years (prior to sexual maturity) Chick takes 1 year to fledge One parent must stay with the young Other parent finds food Monogamy assures the success of the offspring

  25. Monogamy 94% of birds, 3% mammals Types: Life-long: exclusive breeding for entire life ex: Wandering Albatross Serial: partners together one or more breeding seasons Social: partners breed and raise offspring together, but still breed with other individuals (90% of monogamous birds)

  26. Summary: Males and females have different goals defined by their gametes This conflict creates competition Sexual selection leads to the evolution of sexual traits Mating systems are diverse and are shaped by the environment Courtship bonds individuals together Next time: EXAM 3 Population Readings: 27.3, 27.4

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