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Announcements. Test Results for Exam 2 are in! Behavior movie tonight at 7pm in Evert 151. Exam 2 Results. Mean = 41. Parental care Very costly behavior - time - energy - vulnerable to predation. emperor penguin. red shouldered hawk. earwig. tarantula hawk.
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Announcements Test Results for Exam 2 are in! Behavior movie tonight at 7pm in Evert 151 Exam 2 Results Mean = 41 Parental care Very costly behavior - time - energy - vulnerable to predation emperor penguin red shouldered hawk earwig tarantula hawk Types of investment protection from predation protection from elements provisioning - feeding, host emperor penguin red shouldered hawk earwig tarantula hawk Bigger gametes (increase zygote size and survival) More gametes (increase potential number of offspring) Females initial investment more than males (larger gamete size, internal development in some animals) Do females have a greater incentive to make sure their initial investment is not wasted? If so, females should provide the majority of parental care. Investment on current offspring Increased investment = increased probability of young surviving = increased fitness for parents Trade off between current and future reproduction? Time, energy, risks spent by parent on current offspring (parental investment) can influence possibility of having future offspring. Potential tradeoff: More energy invested now, less energy available for future reproductive efforts. Increased parental investment can affect survival of adults. (potentially decreasing fitness) Therefore, each increment of parental care is subject to selection. cichlid - St. Peter’s fish Life history traits –characteristics of an individual that influence survival and reproduction Age at maturity Atlantic Salmon African elephant House Mouse 3-6 years 2 months 11 - 20 years Life history traits –characteristics of an individual that influence survival and reproduction Number of offspring produced Atlantic Salmon African elephant House Mouse 1 calf every 3-8 years 5-8 young every month 1,500 to 8,000 eggs once Life history traits –characteristics of an individual that influence survival and reproduction Number of reproductive events Atlantic Salmon African elephant House Mouse ~6-12 1 ~3 - 10 (interoparous > 1) (semelparous = 1) Life history traits –characteristics of an individual that influence survival and reproduction Lifespan Atlantic Salmon African elephant House Mouse 60 - 70 years 3-6 years ~2 years Remember EPCs… Parental care should be proportional to probability offspring are yours. Females can be quite confident of maternity, males (when females mate multiply) are less confident of paternity. - cost / benefit ratio for parenting different between sexes
  • Variance in reproductive success usually greater for males than females (for example in polygynous, lekking species).
  • Times spent caring for offspring = less time getting more mates.
  • The potential reproductive rate is greater for males than females,
  • cost / benefit ratio for parenting different between sexes
  • Cost of parental care is greater for males.
  • Operational Sex ratio (ratio of sexually receptive males to receptive females at any time) Females limited by number of eggs, gestation, so ratio often male biased. cichlid - St. Peter’s fish However, bi-parental care is common (particularly in birds). In many species, males provide more care than females. Australian mallee fowl African cichlids greater rhea seahorses A female (left) and male (right) Solenosteira macrospira . The male's shell is covered with numerous egg cases After mating, females deposit egg cases on their mate's shell, and the males carry this burden (which can exceed 50% of the male's wet mass) until the eggs hatch Giant water bugs (Belostomatidae) Large bugs, eggs also larger than typical aquatic insect. Need to exchange gases (CO2 out, O2 in) which is easier out of water. males moisten eggs laid out of water males carry eggs glued to back no parental care Giant water bugs Are these really the exceptions to the rule? If males help rear young, fitness increases through increased young survival. Parental care is driven by the distribution of resources, operational sex ratio, previous investment, ecological conditions… Caring for the right offspring. Offspring recognition in colonial species Mexican free tailed bat Caring for the right offspring. Offspring recognition in colonial species Cliff swallows can recognize own young, rough winged swallows cannot colonial cliff swallows solitary rough winged cliff swallows Caring for the right offspring. Offspring recognition in colonial species colonial cliff swallows solitary rough winged cliff swallows Caring for the wrong offspring It is not worth making a mistake and not caring for your own offspring! (recognition systems are not perfect) Communal care of offspring common in some species that live in groups. dwarf mongoose Optimal Threshold Model signals you want to accept signals you want to reject rejection errors acceptance errors adapted from Reeve 1989, Starks 2003 Caring for the wrong offspring - the extreme Brood parasites - cowbirds, cuckoos Caring for the wrong offspring - the extreme Brood parasites - cowbirds, cuckoos brown-headed cowbird screaming cowbird bronzed cowbird shiny cowbird 3 species of cowbirds in northern Argentina bay-winged cowbird screaming cowbird shiny cowbird colonial, builds own nests. Egg dumping? lays eggs in nests of 1 species - the bay winged cowbird lays eggs in nests of 176 species Sibling conflict Sibling aggression and siblicide Occurs when resources are variable or in short supply? Offspring compete for resources (they only share 50% of genes) Galapagos blue-footed booby have two eggs, often raise two young masked booby have two eggs, first hatched chick always kills second chick Parent offspring conflict (Trivers) Selection may act on parents and offspring differently. Some actions that increase fitness of offspring may reduce fitness of parents. Parental favoritism Likely occurs when resources are variable and adults have more young than they can raise (bet hedging) Females can invest in eggs differently (even choose sex in some species). Young can be fed preferentially. Seychelles warbler Parental favoritism Honest signals of quality in offspring? barn swallows Asynchrony in hatching (birth order) can promote or reduce sibling conflict and parental favoritism great egret Can parents control sex of offspring? Seychelles Warbler Can parents control sex of offspring? Haplo / diploid organisms (like ants, bees and wasps) fertilized egg = female ; un-fertilized egg = male Temperature Dependant Sex Determination (TSD) many reptiles Helpers at the nest In some animals, juveniles stay to help second nesting effort. More often female juveniles. Both direct and indirect benefits. Direct (learning about maternal care) Indirect (inclusive fitness by helping rear related offspring magpie jays voles Helpers at the nest Leads to overlapping generations Key step in the evolution of sociality? Genetics basis for mating systems / parental care. prairie voles Monogamous, male parental care meadow voles polygynous, no male parental care In male prairie voles, vasopressin and dopamine in the forebrain regulate affiliation between mates (bond formation). Vasopressin receptor is expressed at higher levels in monogamous species than polygynous species. Lim and colleagues, used a viral vector to transfer the vasopressin receptor gene from the monogamous species into the polygynous species. With this change in a single gene, the polygynous species essentially becoming monogamous.
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