Lecture 3- Life history strategies II

Question 1

what is the difference between ageing and senescence?

Answer 1

senescence refers to a decline in vitality and function with age, whereas ageing simply refers to the passage of time

Question 2

Weismann’s theory

Answer 2

group selection is the reason for senescence- non-reproductive, older members of the population take up resources, and their deaths helps ensure the population has enough resources to survive

Question 3

Medawar 1952

Answer 3

theory of mutation accumulation- mutation rate is faster than the rate of repair, and senescence exists because our repair processes are imperfect, leading to the accumulation of mutations

Question 4

Williams 1957

Answer 4

antagonistic pleiotropy- genes that were useful in younger life and are therefore selected for become deleterious in later life, leading to ageing processes

Question 5

example of antagonistic pleiotropy

Answer 5

high tesosterone levels- useful in human males in early life, as it aids in sperm production and is useful in sexual function, but becomes deleterious in later life as it increases the risk of prostate cancer

Question 6

hamilton 1966

Answer 6

mathematics of ageing- idea that senescence is inevitable, when it does not decrease fitness, due to NS. builds on Medawar/Williams

Question 7

Kirkwood 1977

Answer 7

disposable soma- damage repair is costly, and therefore cannot be invested in forever or for any longer than is necessary- this means not all damage can be repaired and senescence occurs

Question 8

there is a correlation between longevity and…

Answer 8

large body mass

Question 9

how does flying impact lifespan

Answer 9

flying animals tend to live relatively longer- related to resource access and escaping predation?

Question 10

other species which seem to live longer

Answer 10

tree-living and burrowing species
sea and cliff birds
social species
those which are active in either the day or night- encounter fewer predators?

Question 11

example of a species which does not senesce

Answer 11

hydra- have many totipotent cells, so just kinda lives until it gets eaten or something

Question 12

issues with hamilton’s ideas

Answer 12

senescence is not universal- can’t be simply explained by natural selection, need to bring in factors which cause species to differ

Question 13

examples of factors which can influence if senescence develops or not

Answer 13

-development and size, if growth continues throughout the lifespan (indeterminate) or not (determinate)
-body architecture- if there is a set developmental pathway (unitary) or this is more flexible and involves a unit replicating itself to form an organism (modular, which seems to help in avoiding senescence)
-regeneration ability- cell pluripotency etc

Question 14

examples of groups where senescence can vary between them and why

Answer 14

flatworms- only some species have totipotent cells
plants- some are more modular, which helps them senesce less, and some are more unitary