REPRODUCTION

1. REPRODUCTION Biol 101: Humans in Nature Fall 2010 Neil Greenberg

2. REPRODUCTION Biol 101: Humans in Nature Fall 2010 Neil Greenberg

3. Costs and Benefits of Sex • budding • Fragmentation and regeneration • If the geneotype works, why fix it? BUT, • Doesn’t enable genetic compensation for variable or changing environments • Enables isolated or non-moving organisms to reproduce • Rapid reproduction an advantage in a stable environment

4. Costs and Benefits of Sex • 1. gametes wasted • 2. offspring wasted (or sacrificed by effort expended in competition) variations in offspring quality or quantity • 3. Cost of meiosis- genetic material wasted=50% • 4. Time and energy spent courting, mating, and caring for offspring • Searching & signaling • Egg carrying, incubation

5. Costs and Benefits of Sex: Sperm wars • behavioral; for example, males frequently guard females to prevent other males from also mating with them and gaining paternity of the offspring (e.g. elephant seals keep harems; insects such as damselflies). • produce more than one sperm type, typically a fertile type and a "helper" or "worker" caste that may help males win (or avoid) sperm competition.

6. Costs and Benefits of Sex • Risks of Reproduction • The cost of copulation (mating, physical coupling). The assumption that the expenses of copulation include: • (a) increased conspicuousness to predators • (b) distraction from vigilance for predators • (c) decreased ability to escape while coupled

7. Switch hitters EXAMPLES • Sea anemones … asexual when variability is not an advantage, sexual when environmental stressors are present • Earthworms … are hermaphrodites

8. Sexual selection • Good Genes: exaggerated sexual signals are so expensive, in order to be successful, the male that bears them must have a superior genetic constitution: good genes. So any female that chooses them will add those genes to hers where they will contribute to the success of both her male and female offspring.

9. Sexual selection • Handicap hypothesis: • apparently some secondary sexual characteristics can be harmful traits in males but become attractive to females because they indicate the male's capacity to cope with them (Zahavi) or because they represent the valuable trait of enhanced immunocompetence … sometimes reflected in unexpected ways such as singing ability

10. Sexual selection • Runaway sexual selection (Fisher): • positive feedback between an ornamental trait in a male and the female preference for the trait -- can lead to very elaborate traits: • females prefer males with traits that confer an initial survival or reproductive advantage. • The male's trait becomes exaggerated as the female's preference for it is enhanced. • At some point the cost to males outweighs the benefit.

11. Communication within & between cells, tissues, organs, organisms • Only by communicating can cells, tissues and organisms coordinate their activities. • tissues & organs – a prime example of specialized form for exchanging substances with the external (or adjacent) environment (e.g., membranes maximize exchange, neurons focus exchange)

12. Communication within & between cells, tissues, organs, organisms 3. Organisms – by means of senses, including detection of specialized chemical signals (e.g., cAMP (affects gene activity) or pheromones (organisms affect each other to cause (e.g.,) aggregation, alarm, territories, trails – menstrual synchrony, mother-baby identification)

13. SAMPLES OF NATURE • palolo worms in Samoa • Barnacles and their extremely long ... uhmm ... reproductive devices … triggered by scent released in water. . “Barnacles cannot move, but each has both male and female sex cells, allowing each neighbor to be a potential mate.” • Wrasse can change from female to male … males can fertilize more eggs

14. SAMPLES OF NATURE • Madagascan tortoises making a porn film (judging by the explicit grunts the male is making!) triggered by a “perfume” • Elephants … female investment: 22 month pregnancies, 3-4 years of nursing; multiple males tolerated, but the last one is best: males signal by seeping gland behind eye and genitals dripping • Chinchilla – female “rejects an unwanted suitor by squirting urine in its face.”

15. SAMPLES OF NATURE • Tarantula male s are very careful … male approaches while female is eating • Cockroach... he can copulate while she’s distracted by his secretions • Dusky salamander males chin glands secrete aphrodisiac • Crabs can only do it when the female is shedding her shell & there’s a unique “taste” in the water . • Butterfly – mated female is smeared with male’s scent which other males find repugnant

16. SAMPLES OF NATURE A wolf … genital lock assures no other male can fertilize her before sperm has time to reach the egg. • Blue gill sunfish dancing around the eggs, plus a female impersonator! Large male who made nest … about 2/3rd of babies are his • Role reversals with the jacanas … females mate with 3-4 males; will smash rival female’s eggs if possible • Sea louse … after parasitizing a fish, bloated female will look for a male

17. SAMPLES OF NATURE • sea lions in Patagonia “are shown fighting over a HAREM, and some use the battle to their advantage by making off with reluctant females.” • Royal albatrosses mating for life … met at a dance when they were about 5; found each other every year & after about 4 years they might copulate … couple on vide has been together 20 years. • Attenborough comments on culture as complement to genes