Evolution of Aging

Question 1

What is senescence?

Answer 1

Senescence is deteriorative changes that occur in an individual with increasing age (age-specific survival probability, age-specific reproductive traits)

Question 2

Why is senescence an inherently evolutionary issue?

Answer 2

Part of “life history evolution,” the pattern of investment an organism makes in growth and reproduction. ie age of initial reproduction, duration of reproductive periods, lifespan. Decreases fitness

Question 3

What does variation in aging within and among species tell us?

Answer 3

Different species have evolved to have different lifespans, other factors contribute to lifespan within a species

Question 4

What is the difference between lifespan and life expectancy?

Answer 4

Lifespan- how long an organism survives

Life expectancy- prediction for how much longer an organism has left at a given age

Question 5

What is the rate-of-living hypothesis for aging and what are some predictions that it makes?

Answer 5

Rate-of-living- senescence is the result of wear and tear at a metabolic level. Predicts that there is a strong relationship between lifespan and metabolic rate, and if lifespan is set by physiological constraints then organisms are doing the best they can and therefore there should be no genetic variation in populations for lifespan

Question 6

How do rate-of-living predictions align with empirical evidence?

Answer 6

1) There is an apparent relationship between metabolism and lifespan but it is not straightforward
2) Populations do in fact contain additive genetic variance for lifespan

Question 7

What do telemores or mitochondria have to do with mechanisms of senescence?

Answer 7

Telomere length and rate of degradation may have an impact on lifespan.
Mitochondria and mtDNA accumulate mutations at a much higher rate

Question 8

Mutation accumulation

Answer 8

Due to the accumulation of deleterious alleles that take effect late in life on which natural selection works weakly. Evidence includes inbreeding depression due to high rate of deleterious recessive alleles that do not take effect in homozygous individuals

Question 9

Antagonistic pleiotropy

Answer 9

Allelic variation influencing more than one phenotype where the fitness consequences of the affected traits work against each other. (ie traits that are beneficial early in life become detrimental later in life) The earlier acting trait wins