Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
76 Cards in this Set
- Front
- Back
|
What kinds of patterns are we looking for in a life history?
|
Repeated correlations among life history traits
|
|
|
Define life history trait
|
Traits whose variate directly influences life table schedules of fecundity and survival, and hence the population growth rate of individuals having particular values of those characters
|
|
|
Some examples of LHTs ...
|
- size a birth
- growth pattern - age and/or size at maturity - number, size, sex ratio of offspring - age and size schedules of reproduction and mortality - length of life |
|
|
If resources were unlimited what would natural selection favor?
|
Mature as quickly as possible, have as many offspring as possible, live as long as possible
|
|
|
Why do different trade-offs arise? What are the 2 most basic competing functions?
|
Resources are not unlimited and optimal allocation of resources depends wholly on the situation. Resources must be allocated between growth & survival vs. reproductive effort
|
|
|
What is a life history strategy/syndrome?
|
A combination of LHTs that are optimal for a given environment. Some combinations are not available to every organism.
|
|
|
What is optimal allocation of resources?
|
The allocation which maximizes fitness of an individual, and is what natural selection will favour
|
|
|
What are biomechanical constraints on LHT evolution?
|
law of thermodynamics/physics (insects must be small because they need so much oxygen)
|
|
|
What are phylogenetic constraints on LHT evolution?
|
restrictions by phylogeny (mammals must be born small enough to fit thru the birth canal)
|
|
|
What are systems constraints on LHT evolution?
|
events that happen at one point in the life cycle that close off other possibilities later in life (marsupials must have forelimbs, not wings or fins, because they need them to climb out before they are developed)
|
|
|
Define fitness (2 ways)
|
A RELATIVE measure of birth and death rates
DEMOGRAPHY of phenotypes; growth rate of a phenotype in a population |
|
|
What do the following things mean in a cohort life table ... X, Sx, Dx, dx, px, lx, mx, Ro.
|
X - age class
Sx - # survivors at the start of X Dx - # that die during X dx - death rate px - survival rate (dx + px = 1) lx - survival rate to age x mx - birth rate Ro = ∑lxmx - average lifetime reproductive success, lifetime expectation of female offspring |
|
|
What does Ro >, =, < 1 mean?
|
Ro = 1 - no population growth
Ro < 1 - exponential decrease Ro > 1 - exponential increase |
|
|
Cohort tables are only calculated for ...
|
FEMALES!!
|
|
|
What is the Euler equation and what does it tell us?
|
∑ e^(-rx) lxmx = 1
where x = age and we sum from age of 1st reproduction to age of last reproduction (α to ω) we can use it to calculate r, the intrinsic rate of increase |
|
|
The population which has the highest value of little r (intrinsic rate of increase)...
|
has the highest fitness!
|
|
|
Why is it the case the the population with the highest Ro (lifetime reproductive success) doesn't necessarily have the highest fitness?
|
Because not all reproduction is of equal value to increasing fitness
|
|
|
What are 3 assumption made by the Euler equation?
|
1. constant age-specific birth and death rates
2. age classes are of equal duration 3. stable age distribution |
|
|
What does this mean: Nt = N(t-X)*lxmx
|
It is the contribution of females to age class X
|
|
|
What is the importance of the Euler equation? Which LHTs does it incorporate?
|
It incorporates LHTs and relates those to r to measure fitness for a population of that phenotype. Age at first reproduction, age at last reproduction, probability of survival to a given age, and reproduction at a given age.
|
|
|
What does RV compare?
|
Compares the sensitivity of fitness to events at different ages.
|
|
|
What is the currency in which the worth of a life history is calculated?
|
RV
|
|
|
The RV of age class A = (describe equation in words)
|
birth rate in current age class
PLUS sum of expected reproduction of all subsequent age classes MODIFIED BY the effects of changing population size = SUM OF EXPECTED NUMBER OF OFFSPRING IN THE CURRENT PLUS FUTURE AGE CLASSES |
|
|
What is lx/la?
|
It is the probability of surviving to age X given that you have survived to age A
|
|
|
How does the stability of a population affect RV?
|
If a female is in a population that is increasing then her RV will (decrease?) but if she is in a population that is decreasing her RV will (increase?). If the population isn't changing then her RV will be constant.
|
|
|
When r ~ 0, fitness is sensitive to ...
|
changes in survival and fecundity, but not to changes in age of maturity
|
|
|
When r >> 0. fitness is sensitive to ...
|
changes in age of maturity, but selection on survival and fecundity is less strong
|
|
|
What is elasticity index λ?
|
measure of sensitivity of fitness to changes in fecundity or mortality
|
|
|
When a population is intrinsically growing fast, on what is selection stronger and less strong?
|
Stronger on age of maturity, less so on survival and fecundity.
|
|
|
In sexually dimorphic mammals, what 2 things influence cost of reproduction?
|
Litter size and sex ratio
in humans males are more costly |
|
|
What are some ways in which raising twins or males would cause future reproductive output to be reduced?
|
1. increased time to next birth
2. reduced probability to giving birth again 3. reduced probability of producing male offspring at next birth 4. reduced survival of subsequent offspring |
|
|
Having female twins results in a higher chance that the next offspring will be ... when does this also occur?
|
MALE
also happens when only a female out of male-female twins survives. if only the male survives there is only a 25% chance that the mother will have a male in her next birth. |
|
|
How does having twins affect the survival of the next offspring? Does it change depending on the sex of the twins?
|
Having twins makes it less likely that the offspring will survive, and survivorship of next offspring is lower if they were male twins.
|
|
|
How did the sex of an older sibling affect lifetime reproductive success?
|
Increased LRS for siblings with an older sister compared to an older brother (didn't affect survivorship)
|
|
|
What are some ways that costs of reproduction have been shown?
|
1. phenotypic correlations
2. experimental manipulations 3. genetic correlations (between reproductive effort and some component of fitness) by sib analysis 4. correlated response to selection between reproductive age schedule and components of fitness |
|
|
What is an income breeder? What does this mean for costs of reproduction?
|
Income breeders use current intake of energy and nutrients for reproduction.
Costs of reproduction are likely to be immediate. |
|
|
What is a capital breeder? What does this mean for costs of reproduction?
|
Capital breeders store energy reserves and use them for reproduction. Depleted stores affect future reproduction so costs will be delayed
|
|
|
Why is there so much variation between LHTs? 2 reasons
|
1. more than one way to maximize fitness! several combos of LTHs will result in the same r, there is no single ESS
2. intrinsic differences among individuals in LHTs, like the ability to rear young, so each individual will adopt the strategy best for them |
|
|
What is the individual optimization theory? An example? What is a key element we take from it?
|
That individuals will adopt LHTs that are suited to themselves, not necessarily to the population. Birds optimize their reproductive effort to match their parental quality.
This leads to the point that LHTs ARE characteristics of individuals - if you are talking about population LHTs you are actually talking about an average among individuals. |
|
|
What was the effect of clutch size manipulation on fledgling mass, number fledged, and recruitment?
|
Mass increased as clutch size decreased
Number fledged increased as clutch size increased but recruitment was maximized in un-manipulated clutches! |
|
|
What is the point of half-sib analysis?
|
To test the heritability of certain traits - I think. A trait can be deemed heritable if half-sibs are more similar than would be expected by chance.
|
|
|
What are the benefits of early maturation?
|
shorter generations (faster population growth rate), higher survival to maturity (because of a shorter period as a juvenile)
|
|
|
What are the benefits of late maturation?
|
Higher initial fecundity (mom is bigger when she gives birth so survives better), lower instantaneous juvenile death rates, higher later fecundity (females who wait longer might be better moms, even risking decreased survival)
|
|
|
Differences between age/size to maturity in sex depend on ...
Compare fish to birds/mammals |
the limiting factor in reproductive success. In fish it is how many eggs she can lay, which depends on her body size (bigger=more eggs) so females take longer to mature than males, but in birds/mammals the limiting factor is females so the males must be large enough to compete with one another for her, males will mature more slowly to be big enough to compete.
|
|
|
What are the 3 "rules" to deciding age at maturity for continuous growth? What are the downsides of the 1st two?
|
1. mature at consistent mass regardless of age (decreases chance of survival)
2. mature at consistent age regardless of mass (increased juvenile mortality) 3. optimal compromise |
|
|
What is a reaction norm?
|
A set of phenotypes produced by a single genotype under a range of environmental conditions
|
|
|
What 3 things are required to calculate the optimal age of maturity?
|
-growth function relating size to age
-relationship between fecundity and size -relationship between instantaneous mortality rates and age/growth rates |
|
|
What does it mean when a reaction norm of weight (y) vs. age (x) is nearly vertical? Horizontal? Which might be male and which one female, why?
|
Vertical: reach sexual maturity at the same age regardless of growth (rule 2)
Horizontal: reach sexual maturity at the same weight regardless of age (rule 1) Vertical = female, have enough experience to be a good mom (or just not worth it to keep waiting) Horizontal = male, large enough to compete for females |
|
|
What happened to age at maturity and size in exploited fisheries? Why?
|
Both decreased substantially! For size it's because of size-selective "predation". For age at maturity, if probability of survival is low then the best strategy is to live fast and die young!
|
|
|
What are the two main patterns we see with regards to size and number of offspring?
|
1. trade-off between number of offspring vs. quality of offspring, which generally means many small babies vs. a few large ones
2. huge intraspecific variation in number of offspring, but relatively little variation in offspring size |
|
|
What did Lack say that clutch size is determined by? In different countries? Is this right?
|
The average maximum number of young for which the parents can find enough food. Higher latitude = longer daylight = larger clutches. WRONG - it would be the most "productive" clutch size but it's not the most common.
|
|
|
What are some possible trade-offs that may determine clutch size?
|
Between # of fledgelings and ...
- fledgeling survival/reproductive success (fitness) - parental survival - future reproduction or genetic and/or environmental variation |
|
|
What is "bet-hedging" in birds of prey?
|
They lay an optimistically large clutch, because they cannot predict food supply at time of laying. In a good year they can rear most, but in a poor year there is brood reduction (asynchronous hatching so the big ones can take advantage)
|
|
|
What is the "insurance egg" hypothesis?
|
Since if only 1 egg is laid and that egg is lost thru breakage or infertility, birds lay an insurance egg. The first egg will hatch 2-3 days beforehand (asynchronous) and act aggressively towards the little guy.
|
|
|
How does sex ratio of offspring change as female mountain goats age? Why?
|
Sex ratio is skewed to the female side when young, but as the goats age they produce a higher proportion of males.
I actually have no idea why. Males disperse more, so maybe she doesn't want any competition with her sons, or maybe her daughters will take care of her? Maybe condition of mothers doesn't affect males as much as females so they produce females only when they can be high quality (like roe deer)? |
|
|
What is the sex ratio trend on warblers as they move from low quality to high quality territories? How does this change when there are helpers in the nest? Why?
|
Warblers in low quality nests produce a higher proportion of males, but in high quality nests almost no males are produced. If there are helpers (3+), however, sex ratio stays male-biased. I think males will compete with parents for resources but females will disperse, so in high quality territory you want to produce more females to disperse.
|
|
|
If male and females are equally costly to produce, what does the Fisher equilibrium predict?
|
EQUAL investment in the sexes, and EQUAL numbers of male and female offspring
|
|
|
If male and females are NOT equally costly to produce, what does the Fisher equilibrium predict?
|
EQUAL investment (?), and UNEQUAL numbers of male and female offspring
|
|
|
In birds vs. mammals, which sex disperses more? Why is this relevant?
|
Birds = females, mammals = males
Explains biased sex ratios in times of competition for the dispersing sex. |
|
|
What does a graph of proportion/frequency (y) vs. fitness in RS (x) look like for males and females? Why?
|
Females show a very tall pointy curve, indicating little variety in RS (most females are in the same range of RS), while males show a small curve with a shallow slope, indicating tons of variation in RS. Males vary more because they are the sex that invests less per gamete and because they much compete for babes. Females are the limiting factor in reproduction here so they are basically guaranteed a lay.
|
|
|
What does a graph of Fitness in RS (y) vs. "Quality" look like for males and females? Why?
|
Females of all different "qualities" have the same RS (horizontal line) but males RS increases as their quality increases. This is because females are the limiting factor for reproduction, so all females will be mated with, but males must compete for mates, and the higher quality males will sire more offspring.
|
|
|
Trivers and Willard figured that there might be selection for parental ability to vary sex ratio - what are 3 assumptions of their hypothesis?
|
1. mother's quality or resource availability translates into offspring quality at independence
2. offspring quality at independence translates into quality at sexual maturity 3. difference in quality has more effect on male LRS than on female LRS |
|
|
Why would female Red Deer of higher social rank be more likely to have males, knowing that larger females tend to have both higher rank and larger offspring?
|
Higher ranking females' offspring have higher LRS than subordinate offspring, and males have potential to have much higher LRS than females. Is this an answer? Damn I wish I had my notes.
|
|
|
The ability to provide high quality investment results in ....
What hypothesis is this? How was it shown in humans? |
MALE biased births!
Trivers-Willard Hypothesis. Census data showed that married, better-educated, younger mothers bore more sons and that infant deaths among unmarried young mothers were male biased. |
|
|
What might occur in differential sex allocation if the mother's weight affected female offspring but not male offspring? (Roe Deer)
|
Since at any weight she will have a male of the same "quality," she is more likely to have a male at low weights, but since her weight will affect the quality of her daughter, she will have female offspring at higher body weights. True story.
|
|
|
What is the mutation accumulation hypothesis?
|
That natural selection is ineffective at acting against mutations with late-acting deleterious effects so those mutations will accumulate in the population.
|
|
|
What is the agnostic pleiotropy hypothesis?
|
Something to do with the effects of increased early survival improving fitness drastically more than increased late life survival? Or that early reproducing organisms have shorter lives than late reproducing organisms?
|
|
|
What is the disposable soma hypothesis?
|
That there is a trade-off between somatic maintenance/repair and current reproduction.
|
|
|
What are some forms of somatic repairs we talk about?
|
Free radical prevention by producing antioxidants, telomerase to repair telomeres that are shortened in somatic cells with every mitotic division
|
|
|
If extrinsic mortality is high (parasitism, predation, adverse conditions) what two things are predicted to trade-off? Why?
|
Resources will be allocated to reproduction instead of survival. There is not a benefit to surviving to old age because nobody makes it there, it's not worth the cost of living forever.
|
|
|
What conditions would favour postponed senescence? An example of one way this happens?
|
Low extrinsic mortality - safer lives lead to longer lives. Increased antioxidant concentration, for example.
|
|
|
Why is there decreased force of selection for older individuals with increased extrinsic mortality? What does this result in?
|
Because what happens early in life affects fitness much more than what happens later in life - any cost of maintenance past a certain age is too high a cost so deleterious mutations accumulate and somatic maintenance is low. End result = life expectancy is reduced.
|
|
|
What do collagen fibers show?
|
Aging!
|
|
|
How are population growth rates found for semelparous and iteroparous organisms?
|
Semelparous:
Nt+1 = Nt*B*Pjuv Nt=#born, B=#births per female, Pjuv=juvenile survivorship Iteroparous: Nt+1 = Nt*B*Pjuv + Nt*Pad Pad=adult survivorship |
|
|
Rearranging for the equations of semelparous and iteroparous growth, what are the conditions that favour each?
|
Semelparity is favoured when there's high juvenile survivorship and low adult survivorship
Iteroparity is favoured when there's low juvenile survivorship and high adult survivorship |
|
|
Define senescence
|
progressive loss of function, accompanied by decreasing fertility and increasing mortality, with age
|
