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BIO220 Midterm Review.docx

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University of Toronto St. George
Locke Rowe

BIO220 Midterm Review Lecture 1: Genes, Environment & behavior  Environmental effects on trait values can be described as “plasticity”, and these responses can be adaptive  The influence of genes and environment can be visualized with plots of the “reaction norm” o Natural selection shapes the reaction norm  Bees and wasps behavior in the fall o Drunken behavior due to an adaptation for locating ripen fruit, flowers attract bees from nectar containing alcohol.  Genetic and environmental variation o Phenotypes reflect both genetic and environmental effects  Z(phenotype) = G (genes) + E (environment)  Evolution by natural selection... o Variation in a trait o Variation in fitness for the trait o Genetic basis for the trait Experiment 1: Rover-Sitter polymorphism  Rover/sitter foraging polymorphism found in the fruit fly, Drosophila melanogaster and discovered by Marla Sokolowski in the early 1980s. Under the presence patchy food, Rovers eat less but move more than sitters during foraging and they are more likely to explore new food patches than sitters. o Rovers and sitters move for similar distance in the absence of food.  Genetic analysis these behavioural differences arise mainly from allelic variation in foraging (for), which encodes a cGMP-dependent protein kinase (PKG). An enzyme involved in cell signaling, (located in nervous system and the gut), Rovers are have the dominant alleles. o By inserting “rover” alleles in “sitter” larvae, able to change the behavior of sitter.  Under environment changes, food deprivationboth moves less, Rover slowly behaves like Sitter. o Phenotypic plasticity, Phenotypic plasticity  Daphnia Morphological response to predators (grow helmets)  Tadpole under harsh environment, changes to cannibalism Reaction Norms  Describes the effect of some environmental variable on the phenotype of a single genotype. Experiment 2: Daphnia Genetic variation and evolution of reaction norms  Daphnia tends to be attracted to lights (food is in the light, so are predators), Assayed 10 genotypes from each of 3 lakes with many, few to no predators. Tested with and without fish smell. o Daphnia population with a selective history of predation risks have evolved to avoid habitats with high risks of predationevolution of a reaction norm shaped by natural selection. Lecture 2: The Evolution of Sexual Differences (Dimorphisms)  Males and females shared a large portion of the autosomes (90%), but they are very different. Why? o Different in the expression of genomes, significant sexual difference at the genetic level. Sexual dimorphism: conspicuous ornaments  Big red pound in male frigate bird  Long tail variation in male widow birds o No diversity in females. Huge diversity in mating males. Evolutionary biology need to account for diversity.  Sage-grouse o Males with big pouches doing dance with tail feathers.  Elephant seals, beetles fighting, stalk-eyed flies  Peacock displaying o Why do males have huge tails? Terrible idea considers the survival of the fittest.  Bad for survival, but it will be good for increasing mating success.  Natural selection is about survival (everything about fitness); sexual selection is just about mating success. Sexual selection  Depends on the advantage which certain individuals have over other individuals of the same sex and species, in exclusive relation to reproduction (mating). o Sexual selective traits enhance mating successcontribute to fitness  Subset of natural selection. Can be useful to consider them separately.  Natural selection  increase survival, increase reproductive rate increase fitness. o Sexual selectionincrease the number of matesincrease fitness Fitness in males and females  FemalesFitness will be comprised of survival and reproductive rate.  Malefitness will be compered of survival, and access to eggs. **sex roles can reverse in special cases. Why do we have two sexes?  Fundamental difference is anisogamyunequal size gametes.  Femaleclass of individual produce large gametes o Large resource rich eggloaded with energy, few of them  Male produce small gametes. o No resource, inexpensive, can produce many of them (average ejaculate to fertilize all America )  Consequence of interaction in sexes. Parental investment theory  Sexes are different in reproductive investment. There will be competition in those invest little for access to fewer resource rich egg.  Members of the sex with low investments with compete among each other for high investment eggs. The sex involve more in offspring, their gametes are limited resource. o Males: tiny mobile games, fitness limited by access to eggs.  Male fitness depends on how many egg can he fertilize.  Expect competition of males for access to femalesmale-male competition o Female: resource rich gametes  Fitness limited by the resource they access to build gametes  Choosy among males to mate, choosing the best sperm/malefemale choice o Special cases when male taking care of the gametes after fertilizationfemales competing for males  Mating rates o Relationship between mate and number of offspring.  Since males are limited by access to egg, by giving them eggs, they can reproduce unlimitedly.  Females are limited by resource, but eggs are limiting their mating rateweak relationship between mates and number of offspring. Experiment 3: Bateman Curves  Set-up: a set of females mate one with male, twice with males, etc. And have males mate once, twice with females etc. o By recording the number of offspring, this provides the idea that females are limited by resource; males are limited by access to eggs.  In many organisms, females are inseminated, and they store it. In flies, they mated once, and they store the sperms. No matter how many times they mate, it will not increase the number of offspring they produce since it is limited by egg numbers. o Strong selection on male to mate more, no strong selection on females to mate more.  Asymmetry created  Data on max. number of offspring produce during lifetime. o Elephant seal: male100, female8 o Red deer life-long monogamous, not significant difference. o Man888 Women69 offspring in 27 pregnancies Sexual Selection Intra-sexual selectionmale competition  Competing among each other for eggs. o Pre-copulatory (before mating happen, number of copulations) o Post-copulatory (after mating happens, competition in sperms, given the number of copulationsthe probability of fertilization)  Fighting behaviors (prevent others have access)  Territorialities (fight to setup territories)  Social status o Males walrus competing for status, females come and watch the males sing. Most females will mate with the dominant male. o Elephant sealsmales fight for beach, females want beach for pups.  Bigger beach gives more mates.  Males had no territories try to sneak in and mate.  Dominant males inseminated 50 females, lot of variation in mating success.  Strong selection, traits allow you to be dominant can allow you to reproduce 50X, this selection cause such bazaar traits.  Sperm competition (post-copulation) o Mate guarding  Females store sperm, males mate female, and it pays for them to guard the female. o Sperm removal & copulation duration  A female mated, another come in, wanted to remove the sperm of the other male, increase copulation durationincrease number of sperm transmitted. o Sperm plug  Sperm plugs in lobsters male seals the pores of the female make it difficult for others to mate. o Traumatic insemination  Bed bugsmales inseminate females by stabbing in the stomach, and sperms flow thru the blood stream to the reproductive organs o Anti-aphrodisiacs  A butterfly put a scent on the female to tell others that this female is mated.  Damselflies o Male clasping the female's thorax (behind the head), prior grasping, males transport sperm to the abdomen area. If the female want to be inseminated, she brings the tip of abdomen to the male and gets the sperm. Then the male will guard the females. Females store sperms in the abdomens; egg moves down the tubes, squirts the stored sperms on the egg and lays the egg. In other case, male continue to hold the female.  In the storage organ of sperm in male, they had another organ, inflated with hocks, it will first pull out the stored sperm in female horns, whip and barbs o In dragon fly, males lift the females up, and hit the water surface, every time she hit the water surface, egg comes out.  Bluegill Sunfish (alternative reproductive strategies) o Large males can guard eggs and provide territories for femalesfemale want  External fertilizer o Intermediate males pretend to be females. o Smaller males comes out of the blue and shoot sperms. Experiment 4: Rock-Paper-Scissors Game in Nature (frequency dependent selection)  If everyone playing rock, the fitness of scissors loose, and ones that play paper will win most of time.  Three strategies in side-blotched lizard (genetic basis)frequency changes overtime o Orange  Defend large territories  Extremely aggressive towards all males o Blue  Defend smaller territories (not going to have high quality female)  Detect and root-out yellow males o Yellow  ‘Sneaker’ male (on orange males)  Mimic throat colour and behaviour of receptive females.  If there are lot of orange, yellow will success. The fitness of each type depends on the frequency of other.  Prediction: o if blue is high, orange will increase o If orange high, yellow will increase o If yellow high, blue will increase  Result: o Blue numerically dominant in 1991 o Orange begins increasing at the expense of blue in 1992 o Yellow begins reducing orange by 1994 o Blue returns to numerical dominance by 1995 Required Reading #1-2:  A successful male can potentially sire many offspring. If a male gains a disproportionate share of reproduction, he will take away reproductive opportunities from other males, leading to a high reproductive variance among males. A successful female, on the other hand, will not take away reproductive opportunities from other females, leading to a smaller variance in reproductive success. o The higher the reproductive variance, the stronger the effects of sexual selection.  If females provide more parental care than males, the variance in male reproductive success can be expected to be large, since females providing offspring care will not be immediately available for further reproduction and competition for available females will increase among males.  Females can directly increase their reproductive success by mating with certain, select males and acquiring direct benefits. o “Good genes”differences among males provide females with information about the genetic qualities of the different males that can be inherited by the offspring o Fisherian Arbitrary Choice female preference can evolve for arbitrary traits that do not provide information about the male's quality, and that therefore do no reinforce the effects of natural selection.  Females gain the indirect benefits of producing offspring that will be more sexually attractive to females that carry the preference, result in a positive feedback loop, whereby the trait becomes more exaggerated as selection on the preference increases.  Although both sexes are seeking to optimize their reproductive success, their genetic interests are not aligned, resulting in sexual conflict o Some trains of male will increase his mating success at the expense of female, this can spread across the population  Evolutionary arms raceharm traits induce counter-traits in other sex.  Harem: A group of females associated with a single male. Typically the male in the harem defends his group of females.  Lek: A mating system which consists of an aggregation of males where each is seeking to attract a mate. Leks are not associated with resources; however it is thought that leks attract more females than a single male would attract.  Resource defense polygyny: A mating systems in which males establish a territory around resources needed for mating success. In this system multiple females will join the male in his territory.  Polyandry: A mating system where one female pairs with many males.  Polygyny: A mating system where one male is associated with many females.  Promiscuity: A mating system where there are no pair bonds. In this case is seems that males and females mate randomly.  Serial monogamy: A mating system in animals where they pair with a mate for one mating season but change mates over the course of a lifetime.  Social monogamy: The behavioral pairing of a single female with a single male. Lecture 3: Sexual Selection and Female Choice  Satin Bowerbird: Males set-up bowers and decorates them with colorful objects (especially blue and yellow). Females would then inspect the bowers and go in the backdoor to mate.  Sage GrouseLek o Strong selection, large variationdraws bazaar differences among males Female choice  Any female traits (behaviors, morphology) that biases the mating success of males toward the preferred type  Visual Stimulation o Satin bower bird o Widow birds  Acoustical stimulation o Tungara frogs  Tactile stimulation o Sierra dome spider play the web  Olfactory stimulation o Mouse (pheromone) Experiment 5: Tail manipulation experiment  Set up: manipulate tail length of widow birds to ask are long tails preferred by females. o Nnatural tail length o Rreduced tail length o Lelongated tail length o Ssham surgery (see if cutting and gluing will affect mating success, first cut and then glue back. )  Hypothesis: L > N> R and N=S.  Result: Prior to treatment, relatively same mating success, after the treatment, natural and sham are almost the same. The reduced tail reduces in mating success. And elongated increase in matting success, this suggest that tail length itself lead directly to mating success. Experiment 6: Female preference of eyespots in peacock tails  After treatment of removing eyespots, it significantly decreased mating success in peacock. Experiment 7: Female preference of complex calls in Tungara frog  Tungara have 2 part in mating calls whining & chucks. o Whining first attracts females. The more Chucks the betterFemales go for more complex chuck.  Reasons why not all males have chucks? o Predators like bats are can also be attracted to complex calls.  Therefore, 2 forces pushing the trait. Sexual selection driving it up and predator driving it down. Hypothesis for female choices  Direct benefitsdirect natural selection on the female o Female preferences are side effects of other forces (those traits are indicator of parental investment )  Selection of resources rather than male attributes  Male traits act as an indicator of parental investment (PI)  Territory quality  Parental care  Ornamentsprotection for female  Colorful furhealthier, free parasites o Female preference for males with resources  Spermatophore in katydid or Mormon cricket: protein-rich capsule produced by male that can weigh up to 25% of his weight. Containing spermatozoa and transferred in entirety to the female's ovipore during copulation. Female consume the protein mass, by mating, female receive a huge resource.  Female prefers larger male for bigger spermataphores.  Hanging fly: Females attracted by pheromone, and checks the food male has. While mating occurring, she is consuming the food. In some species, they get things are not food and trick the female. Longer the female eats, the longer the male can mate.  More foodlonger copulation durationmore sperm transferred  Indirect benefitsfemales prefer male traits indicate high genetic qualityher offspring will have a higher fitness. o Goof genesnumber of eyespot in peacock as an indicator of good genes  Larger display sizes tend to give genes to female that increase the survival of offspring, choosing those male increases the fitness of her offspring. Parental Investment (PI) Theory  Members of the sex that invest little in offspring will compete among themselves to mate with members of the sex that invest more in offspring o Difference in sex of the reproductive investments  When male have to invest more in parental care, then sexual role reversal o Giant water bug, pipefishHigh male PI  Water bugfemale lay eggs on the back of the male, so the male transfer oxygen to the eggsMale back is the limited resources. Pipefish sex role and mating system  During copulation, females dump eggs into the brood pouch in male, eggs get fertilized. Pouch is sealed until the babies are born. o Male’s reproductive success is limited by size of their brood pouch o Females’ reproductive success is limited by access to male  Female compete for access to male  Sexual selection on female size and ornamentation.  Small, weed-looking male  Large, ornamented femaleindicate good eggs. Experiment 8: Experiment evidence of sex role reversal  Question: do males exercise mate choice?  Result: males prefer larger highly fecund females in pipefish population. o Longer length, larger fold size. Experiment 9: Relative PI and flexible sex role in Katydids  When food is abundant, males call for female, but females does not want to mate with male because they have food in the nature. At this time, male tend to mate with any female.  When food is in decline, males don't often call female. But females need food from male. Therefore, male choice of females and female-female competition happens. Mate choice in Mice and Humans  Human tend to favor symmetrical faces  Major Histocompatibility Complex (MHC)codes for antigen recognition for immunity response, more genetic variation at MHC the better. o HLA in human  Mice choose mates based on MHCto avoid inbreeding, to increase genetic variation at MHC loci for their offspring.  Females can detect MHC; they tend to mate with males with different MHC. Females and males are choosing mate due to their difference, human chose among MHC for the same reason. o Experiments in human have males wear the same T-shirt for 2days, and bags are choices from female. (Female prefers the ones with difference MHC-type). However, Females tends to prefer the same MHC when they are on birth control pill. Lecture 4: Social Behavior (good for individuals to good for genes)  Alarm calls o Ground squirrels and Meerkats stands up and guard for others  Individual gives alarm call making itself seen by predator, increase the probability being eaten, decrease the probability of others being eating, altruistic behavior.  This behavior can only be explained on a genetic level.  Cooperative breeding o In population of meerkats , Some individuals are producing offspring, others are helping to breed offspringaltruistic  decrease their own fitness, increase fitness of the group  unbreeding individual lactate to help feed the offspring in the group  Eusociality o Multiple generations with different reproductive role in a group.  Wasp, ant mount Definitions in social behaviors  Social behaviors: The interaction with and responses to other individuals of the same species  Altruistic behaviors: the behavior increases another individual’s reproductive success at a cost to one’s own reproductive success  Cooperative: Behaviour that, if adopted by two (or more) individuals, benefits both. o Understand why there are no cheaters? Cooperation and natural selection  Hard to understand altruistic behavior with natural selection, if genes are selfish (replicate at the cost of alternate alleles), how can we explain cooperation? Game theory  Developed in the cold war. Post-secondary world understand how to interact each other, favor themselves but does not involve destroy the world.  Hawk-dove Gave o Imagining hawk-like behavior and dove-like behavior in the same species, having them interact each other over food. Ask when two individuals come for the food, what do they do. Act hawk or dove?  When two doves come, they work out, split the resource. The payoff is R/2.  If dove against hawk, the dove have nothing.  If a hawk plays against dove, the hawk gets everything.  If hawk play against hawk, the resource be divided, and cost them the energy for fighting. The question is what should you play? o Evolutionary explanation of cooperative behavior  Reciprocity (相互作用) o If you know the other will cooperate, and then you would want to cooperate, if you don't know, you might not cooperate. o Imagine a game two individual are communicating, compete strategies to explain this, the best strategy is “Tit for Tat”  Cooperate on the first encounter. Copy your opponents’ last move thereafter. Being nice first, and if the other did not being cooperative, you do the same.  Nicestart by cooperation  Retaliatorystop if partner stops  Forgivingif partner has cheated in past but changed, then cooperate  Experiment 10: Predator Inspection in Guppies o In population of guppies, few individuals inspect for predators for group of fishes  The two approach of fish are cooperating and can be viewed as an iterated prisoner’s dilemma o Question: Do guppies play Tit-for-Tat during predator inspection?  Examine predator inspection behaviour with “cooperating” and with “defecting”partner Kin selection o Results: If there is a cooperating mirror, overtime, it gets closer. With defecting mirror, it stays the same distance away.  Group selection o Reduce the frequency of male in the population, every male fertilize many eggs, females producing fewer eggs. Imagine there is an alleles produces more male, those male will be successful, because they can then fertilize a lot of females  Group selection does not work because is invasible by cheaters. o Special case when group selection works  Crows have alarm calls, and have dialogue. How can we account for such altruistic behavior?  In a population, two genotype, calling genotype and non-calling genotype. Callers appear altruistic. When selection happens, reduction in a caller. This removed the frequency of caller gene.  Add social groups into this case. They gather on tress interacting with each other, imagine groups have no caller, many caller, and intermediate caller. They interact, and mixed up in breeding season, they redistribute again randomly again.  Instead of having one group, we will have three groups with different number of callers.  In the absent of caller, high mortality, they get eaten,  In a group that all are caller, low mortality.  In intermediate, the increase frequency in non-caller.  Non-caller decrease in frequency after breeding season, within group, caller is always worse than non-caller, but a group with all no caller is the worst. Experiment 11: Evidence for group selection (Impatiens Capensis )  Large plants out-compete small plant, but small plants are still common  Question: how are small plants still around? Why don’t large plants take over the population?  Hypothesis: Groups with many large “selfish” plants do worse than groups with many small “cooperative” plants  Result: o Large individuals in well-spaced groups tended to have high fitness. o Groups consisting of many small individuals tended to have high fitness. o These two effects tend to cancel one another out. Reasons why small still exist. o 2 force of selection: group effect push the size down, and individual effect push it up.  Kin selection o Selection applies to the family. o Under normal circumstance, presence of altruistic alleles. And it gives benefit to everyone, and it pays a cost every time. All recipients get that benefit. Non- altruists do best and we will eventually lose the altruist alleles. o In altruism among related individuals, the cost and benefit only felt by altruist, this might work when the benefit is higher than cost. Hamilton’s Rule c = Cost of altruism to the actor b = Benefit of altruism to the recipient R = Genetic coefficient of relatedness (Probability that the recipient carries the altruist gene) Altruism can evolve, if the benefit of recipient multiplied by the genetic coefficient and it’s larger than the cost of altruism. Experiment 12: Alarm Calling In Ground Squirrels  Question: Do squirrels with close relatives nearby give more calls than those without?  Result: compare group relatedness, if there are no close relatives, low proportion of time calling. Alleles for calling are directed to other individuals having these alleles. The benefits is felt by caller themselves Evolution by natural selection  Natural selection cannot favor sacrificial genes, in contrasts, natural selection favor individuals that self-sacrifice.  Trade one sacrificial allele to three more sacrificial alleles o Although the individuals’ action is altruistic. Overall picture, the allele increase in frequency. Favoured genes ALWAYS increase in frequency each generation Required Reading #3:  Animals living in groups, however, benefit from many more pairs of eyes to provide vigilance or help forage. But living in groups may also confer costs to members.  Although choosing not to help is typically the best choice for an individual’s fi tness in the short-term, it could mean that the individual will not receive reciprocal help from others when it is needed in the future. This provides incentive for altruistic behavior in situations where individuals interact repeatedly, which typically occurs when animals live in stable groups.  These groups are called eusocial (i.e., truly social) because they share three key criteria: 1. cooperative care of young; 2. Overlapping generations (i.e., parents and offspring cohabitating); and 3. a reproductive division of labor, often culminating in caste development  Hamilton's rule details the conditions under which altruistic behavior should evolve. It weighs the benefits and costs (in terms of reproductive benefits, or offspring produced) of a donor performing an altruistic behavior towards a recipient. According to Hamilton's rule, the donor receives a direct cost C (in terms of lost direct fitness) for cooperating, whereas the recipient receives an additional benefit B (in terms of increased direct fitness). However, the donor also receives a portion of the benefit B that is discounted by the genetic relatedness r (i.e., degree of shared genes) between the two individuals. This discounted portion of the benefit is equivalent to the donor's indirect fitness gain.  Cooperation and sociality are widespread in animals. Seemingly altruistic behaviors, like raising the offspring of others instead of trying to reproduce, can largely be explained by the shared genetic heritage between interacting individuals.  The cooperative and often complex collective action that arises from such family groups is a product of the interaction of individuals seeking to maximize their own evolutionary fitness. Lecture 5: Parent-Offspring Conflict  Trade-off between parents and offspring o Provision of food increase fitness of the offspring, decrease the number of future offspring o Offspring want food, parent provide food In offspringthe cost provided now will not be provide for future offspring, need to discount by a half due to sibs. B minus C is the optimal provision rate. ParentsBeneficial discounted by a half and the cost is discounted by a half, The optimal provision rate in offspring is higher than parent. Expect to have conflict. Optimal provision rate in Conflict, this conflict can be resolved in many ways 1) Parent wins 2) Offspring wins 3) Compromise Parent-Parent conflict  Parents are equally related to their offspring, who should provide care?  Why don't all parents desert their offspring immediately? Experiment 13: Kentish Plover experiment  Question: can we account for the pattern of predominately male care in terms of cost and benefits?  Part 1(benefits of deserting)Catch both parents, remove the nest, remove either the mother or father, and test how long it is to re-mate. o Fast re-mate time means the benefit of desertion is high. o Females can mate very fast the benefit of desertion is high in female  This suggests a bias in sex ratio. Hard for male to pair with female. Easy for female.  Part 2(Cost of deserting)In some nests, you take male away, in others take female. Measure brood survival. o When female is taken away, the survival rate is high, suggest the male is providing the resource. Survivorship decrease when male removed.  Male provide better care, bi-parental care had no different as male care. The cost in female exerting is no cost, but high cost in male. Overall, since there are high benefits but low cost to desert offspring, females does not provide care for offspring. Lecture 6: Evolutionary Medicine and an Introduction to Aging  Evolutionary medicine  application of evolutionary principle to the health problems  Asks why (ultimate) rather than how (proximate) o Why do we age? o When do we expect resistance to evolve? Reasons why we are vulnerable to disease  Trade-off: structures and systems must balance conflicting demands o We are accumulating mutation, the cost to repairing them is expensive, it may decrease reproductive rate.  Environmental changes: o Change that exceed the rate of our evolution, if it slow done, see matching phenotypes. If the environment fast, mismatch with the environment.  Pathogen evolution: they evolve faster than we do, their generation time is rapid, with each generation, and evolution happens faster, we are constantly behind.  Historical contingency (意外事故) Definition of aging or senescence  Progressive decline in somatic function reflected in reductions in fertility as well as survivorship  Proximate cause: Progressive degeneration of the soma Manifestation of aging  General degeneration of the soma o Impaired function (speed, strength, sight, etc.) o Increased disease (cancer, organ failure)  Mortality rate increases with age For 45-55, the rate of death is increasing. An individual of 65 have a high probability suffering from cancer than a 30 years old. As we age, the probability of mortality increases. And age specific fitness declining Free Radicals and Vitamins  Molecules containing at least one unpaired electrons  Attack and modify macromolecules o “Oxidation” of DNA, proteins, lipids  We have our own defenses (various amino acids that act as antioxidants)  Vitamins E and C act as antioxidants Why not enough repair?  As you increase DNA repair, decrease fecundity, if DNA repair is resource-expensive, you are not using these resource for reproduction, your fitness will depend on reproductive rate and longevity, there will be a balance point that balance both factors. Constraints  Cannot have free repair mechanism, taking in the forms of trade-offs. o Balance of conflicting forces. Trade-off affects the evolution of all traits  Display size (morphological traits) o Tail length in peacock  Foraging rate (behavioral traits) o The best habitat with more food will have more predators  Longevity (life history traits) Cost of reproduction  Higher reproductive rates accelerate senescence and thereby shorten lifespan. o More offspring you have at a higher rate, the more reduction in longevity. o Investment in reproduction increase reproductive rate, if you do that , you decrease longevityrelated to why we age Experiment 14: Reproductive costs in water striders  Male spend time little eating, and mating  Female avoid male, and collect the food, turn it into egg. o If there is reproductive cost, if we induce female to reproduce at a high rate, we should see them die faster.  Hypothesis: High reproductive rates accelerate senescence and thereby shorten life span.  Set-up: manipulated reproductive rate of females by changing food ration o Female reproductive rate is limited by food supplies. Decrease food supply, decrease egg produce. Collect data of reproductive rate and the side effect of that on longevity. o Those reproducing at a low rate live for a long time. Those who get a lot of food, and reproduce at a high rate will live shorter, die faster.  It appears there are costs of reproduction, females that reproduce faster die fast.  Over the course of days, egg develops. And burst with baby strider, early eggs go through regular reproduction; later egg by older female has problems in the egg, in really old female, they produce egg that produces poorly, or part of the embryo develops. o Egg quality can be a measure of the quality of her soma, because her whole life is used to develop egg. Poor eggspoor soma Graph: when the 30 day old, 100% alive, and they start dying, before they die, they stop reproducing. Prior to stop producing, their egg develops abnormally. This suggest the soma is decline before they actually die, just like in human The time female start to produce bad egg is early if they reproduce at a high rate. Later in life if they reproduce at low rate. Hence higher reproductive rate increase the decline of the soma. Different ways to modify test method, showing same result (high reproductive rate, low longevity) Taxa Methods  Crustaceans  Diet restriction  Insects  Egg addition  Fish  Removal of oviposition sites (sites to put eggs)  Birds  Delay of reproduction  Mammals There is a cost of reproduction, and it is wide spread, increase reproduction decrease longevity, implication is that traded-off are involved in the evolution of senescence. Experiment 15: A Study of Reproductive Costs in British Aristocracy  Record goes back 200 years in the royal family. o In that data set, do we see a correlation between longevity and number of individual produced?  Look at probability of death across ages.  Mothers born before 1700, 2.8 offspring each, probability of death increase, the old it is, the higher chance she die, high fetal mortality  Mother born between 1700-1875, similar shapes, but below the other one. Relate to the fact that they are producing less offspring; problem with correlation maybe due to the advancement in medicine.  Within the period, mother produce one children live longer than mother produce two children Sex differences in aging and cost of reproduction  In high birth rate population, females live similar age as male  In low birth rate, females outlives male.  This suggest reproductive cost Theorized of senescence  Mutation accumulation: Deleterious mutations with age-specific effects accumulate at late ages o If a gene is expressed late in life, selection does not remove it, stays in the population. You expressed deleterious genes as you age, that is why it harms soma.  Antagonistic pleiotropy: Genes with beneficial effects early in life will be favoured in spite of negative effects late in life o A gene early in life will be negative in later life. Pleitropy suggest a gene with 2 effects. The strength of selection decline with age Age specific survivorship  Accumulation of probability  this suggest few individuals will live a long age, this is independent from aging. It’s just the longer you live, the higher change you will be eaten Mutation accumulation Theory  Imagine a deleterious gene, if the gene is expressed early in life, then more people will die, and that the gene might not accumulate. However, if the gene express later in life, then the individual carry this gene may already reproduced, passed on the genes. o Strength of selection decline with age. Old age is a dust bin of late acting deleterious mutation
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