Lecture 2- Life history strategies I

Question 1

what is a life history strategy?

Answer 1

an organism’s unique combination of investment in survival, development, and reproduction

Question 2

3 examples of life history traits

Answer 2

-age of maturity
-reproductive window
-frequency of reproduction

Question 3

what is a ‘darwinian demon’?

Answer 3

hypothetical species where there are no life-history trade-offs- doesn’t exist, there are always limitations (physiological, resource-related etc)

Question 4

what is a longitudinal cohort study?

Answer 4

looks at organisms across their lifetimes, observing growth/reproduction/survival- can infer where investment is from this

Question 5

what is a cross-sectional cohort study?

Answer 5

looking at a snapshot of a population, and determining the stages of each individual at a point in time- can infer general information about a species

Question 6

how might a cross-sectional study operate?

Answer 6

taking ages from ring dating, e.g. in plants or some animas such as some sharks which have calcified rings on their fins. looking at this age and current reproductive stage can allow inferences about life history

Question 7

how can you quantify life-history traits from an individual?

Answer 7

track age of maturity, development, reproductive window etc- gives a general idea of a species’ strategies

Question 8

what is cole’s paradox?

Answer 8

the gain from switching to 2 reproductions from 1 should be the same as adding 1 to the average litter size, which should lead to semelparity being favoured

Question 9

iteroparous

Answer 9

multiple birth- multiple reproductions before death

Question 10

semelparous

Answer 10

reproduction once then death- always in octopi, guppies etc but can happen more rarely

Question 11

issues with cole’s paradox

Answer 11

assumes there are no costs of reproduction, and that juveniles will survive at a similar rate to adults, no stage-specific density dependence

Question 12

resolution of cole’s paradox

Answer 12

Charnov and Schaffer- noted that differences in adult and juvenile mortality create significant costs of semelparity that stop it from evolving more

Question 13

what are reproductive hypotheses?

Answer 13

predictions of where itero- and semelparity will evolve

Question 14

advantage of iteroparity

Answer 14

some offspring are more likely to survive, can put in relatively little effort and still have some success

Question 15

advantage of semelparity

Answer 15

can have quite successful offspring, but requires a lot of effort- higher reproductive success per unit reproductive effort

Question 16

demographic hypothesis

Answer 16

preferred strategy is related to mortality risk, which determines reproductive window- high mortality risk = shorter rep window = semelparity

Question 17

factors determining point of reproduction within a lifetime

Answer 17

chances of being able to reproduce multiple times- increased by early reproduction
investment- can invest more resources into a later reproduction, but may die before the chance