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Life history characteristics. Organisms face fundamental trade-offs in their use of energy and time Changes in life history are caused by changes in the.

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Presentation on theme: "Life history characteristics. Organisms face fundamental trade-offs in their use of energy and time Changes in life history are caused by changes in the."— Presentation transcript:

1 Life history characteristics

2 Organisms face fundamental trade-offs in their use of energy and time Changes in life history are caused by changes in the allocation of energy

3 Life history parameters Number & size of offspring Age distribution of reproduction Life span

4 Number & size of offspring

5

6 Age distribution of reproduction

7 Life span

8 tuna -many small eggs -grow quickly, reproduce young -reproduce daily dogshark -few large eggs -grow slowly, reproduce after 25 years -reproduce every few years

9 overlapping generations discrete generations Number & size of offspring Age distribution of reproduction Life span Differences in these parameters affect growth rate (fitness)

10 t = time (days or years) x = age of an individual (days or years) l x = proportion of newly laid eggs that survive to age x m x = expected # of offspring (fecundity) a = age at first reproduction z = age at last reproduction r = growth in population size per female per unit time Life history parameters

11 increased l x will increase r increased m x will increase r offspring produced earlier contribute more to population growth earlier reproduction begins, greater r Life history parameter conclusions

12 Characteristics that would maximize r (fitness): higher survival through reproductive ages higher fecundity at each reproductive age higher fecundity especially early in life longer reproductive lifespan earlier age of first reproductive Life history parameter characteristics

13 Constraints phylogenetic genetic physiological

14 Trouble with tribbles

15 Life history parameters Number & size of offspring Age distribution of reproduction Life span

16 Lack’s hypothesis selection will favor the clutch size that produces the most surviving offspring

17 assumes no trade-off between a parent’s reproductive effort 1 year and its survival or reproductive performance in future years Lack’s hypothesis

18 assumes only effect of clutch size on offspring is in determining whether the offspring survive

19 Lack’s hypothesis selection will favor the clutch size that produces the most surviving offspring Assumptions: assumes no trade-off between a parent’s reproductive effort 1 year and its survival or reproductive performance in future years assumes only effect of clutch size on offspring is in determining whether the offspring survive

20 Lack’s hypothesis

21 Organisms face a trade-off between making many low- quality offspring or a few high-quality offspring

22 fishinsects Size & number trade off

23 Optimum size & number compromise

24 Selection on parents favors a compromise between the quality and quantity of offspring, but selection on individual offspring favors high quality

25 Life history parameters Number & size of offspring Age distribution of reproduction Life span

26 In populations where mortality rates are high, individuals tend to breed earlier in life However, a trade-off exists between reproductive effort early in life and reproductive success late in life

27

28 Life history parameters Number & size of offspring Age distribution of reproduction Life span

29 Semelparity & iteroparity Semelparity -population growth rate is high -juvenile survival is high -adult survival is low Iteroparity -population growth rate is low -juvenile survival is low -adult survival is high

30 semelparity single reproductive event Pacific salmon iteroparity multiple reproductive events Atlantic salmon

31 Male reproductive success alternative mating tactics sneaker males sequential hermaphroditism protandry protogeny

32 protandry protogeny Sequential hermaphroditism

33 protandryprotogenyno change

34 When mates are not monogamous, the life history strategy that is optimal for one sex may be suboptimal for the other

35 Aging – late life decline in an individual’s fertility and probability of survival Why does aging persist? Rate of living theory - accumulation of irreparable damage to tissue Evolutionary theory - failure of organisms to completely repair damage Aging

36 Rate of living theory - accumulation of irreparable damage to tissue Aging

37 telomerase

38 Evolutionary theory - failure of organisms to completely repair damage -deleterious mutations -trade-offs between repair and reproduction Aging

39 Lifetime reproductive success: Aging Wildtype: first reproduction: 3, death: 16

40 Lifetime reproductive success: Aging Mutation: first reproduction: 3, death: 14

41 Lifetime reproductive success: Aging Mutation: first reproduction: 2, death: 10

42 Because natural selection is weaker late in life, alleles that enhance early-life reproduction may be favored even if they also hasten death Also, alleles that cause aging are only mildly deleterious Aging


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