Quiz 2 (Lecture 9)

Question 1

Aging is the

Answer 1

decrease with age in intrinsic ability to survive and reproduce (i.e., an increase in intrinsic mortality rates or a decrease in reproductive rates)
- ageing is the decline
- age specific deterioation

Question 2

Aging (senescence) refers to

Answer 2

the general process of decline that ends in death
-track & field example

Question 3

Senescence is not an evolved developmental program:

Answer 3

it is NOT an adaptation in its own right

Question 4

Senescence is

Answer 4

a by-product of other adaptations (primarily traits that increase reproductive performance)
-aging happens as a result of selection on other things

Question 5

Rate-of-living hypothesis

Answer 5

-senescence is a result of physical wear and tear
-selection may slow down the rate of aging, but there is only so much it can do

Question 6

two testable predictions of the rate-of-living

Answer 6

1. There should be no genetic variability in the rate of aging (no heritability, everyone ages the same)
2. There should be a strong negative correlation between metabolic rate and rate of aging
   - intracellular damage due to oxidative stress should increase with metabolic rate
   (high metabolism, increase oxidative stress and aging)

Question 7

Rate-of-living hypothesis example

Answer 7

APOE2: is possible to increase life span through artificial selection in a number of model species (fruit fly)
APOE4: mutants of this lead to developing Alzheimer’s
Longevity mutations have been found
- lots of genetic variability for rate of aging

Question 8

Rate-of-living hypothesis problems

Answer 8

1. Longevity mutants (mutants that live longer than wild-type individuals of the same species) do not necessary show reduced metabolic rate relative to wild-type individuals
2. Within a species, longevity and metabolic rate are not associated
3. Frequent exercise increases metabolic rate but does not decrease longevity
4. Bird typically have much longer life spans than mammals of comparable metabolic rate

Question 9

Senescence is the simple consequence of the fact that

Answer 9

selection operates more strongly on traits that appear at young ages than on traits that appear at old ages because of extrinsic mortality

Question 10

Because of extrinsic mortality, natural selection selects

Answer 10

strongly against variants that have decreased survival or reproduction in early life, but selects only weakly against variants with decreased survival or reproduction later in life
- key insight behind our understanding

Question 11

Mutation accumulation hypothesis

Answer 11

-for late life traits, selection is simply not strong enough to purge deleterious mutations
- mutations that have deleterious effects later in life build up in the genome, whereas mutations with deleterious effects early in life are eliminated by natural selection

Question 12

Mutation accumulation hypothesis consequence

Answer 12

is that individual that live long enough will be plagued by a suite of late-acting deleterious mutations; senescence is the consequence of the effects of these mutations

Question 13

Antagonistic pleiotropy hypothesis

Answer 13

-natural selection will favor an allele which has beneficial effects early in life even if it has deleterious effects later in life
- a pleiotropic allele that confers even modest benefits at a young age might be favored despite having major deleterious consequences later in life
-opossum example (protected from predation = longer lifespan)

Question 14

Antagonistic pleiotropy hypothesis predictions

Answer 14

1. The higher the rate of extrinsic morality in a population, the more rapidly members of the populations should senesce
   - extrinsic morality increases, expected life span decreases and selection against late-appearing deleterious phenotypes is reduced
2. We should detect the existence of genes with antagonistically pleiotropic effects (+early, -late)