Life History Evolution

Question 1

Allocation trade-offs

Answer 1

• Virgina Opossum: female reproduces sooner, smaller litters, more likely to reproduce; females waits longer (tissue repair) less to give to reproduction, live longer
• Sand Crickets: short wing females devote more energy to reproduction, dont disperse well; long wing females – devote to flight muscles, reproduce later in life, can disperse well in poor environments

Question 2

Senescene

Answer 2

A decline with age in reproductive performance, physiological function, or probability of survival

Question 3

___ reduces an individual’s fitness

Answer 3

senescence

Question 4

Mutation Accumulation Hypothesis

Answer 4

that mutations that affect an organism’s fitness later in life are subject to weaker natural selection –as individuals age, they have already reproduced and passed on their genes to the next generation.

Question 5

Selection on _______-acting mutations is strong

Answer 5

early

Question 6

Mutation Accumulation Hypothesis: weak selection allows ______ to accumulate, contributing to __________ __________

Answer 6

deleterious mutations; age-related decline

Question 7

Explain Inbreeding depression & Age

Answer 7

the reduced fitness (health, survival, reproductive success) of individuals resulting from mating between closely related individuals

• inbreeding depression caused by deleterious recessive alleles
• late-acting deleterious alleles at higher frequency under mutation-selection balance –> selection is weaker on deleterious alleles

= severity of inbreeding depression increases with age

Question 8

Substitution Rate (K)

Answer 8

the rate at which a mutation that arises in an individual will eventually spread through the entire population and become established

Question 9

Neutral theory of molecular evolution

Answer 9

The substitution rate K = mutation rate μ in neutral evolution because neutral mutations fix in the population at a rate that is determined by how often mutations occur, rather than how large the population is.

Regardless of whether the population is large or small, the rate of genetic substitution in the long term is controlled by the mutation rate and is independent of the effective population size Ne.

Question 10

Antagonistic pleiotropy hypothesis

Answer 10

Mutations with fitness benefits early in life, fitness costs later in life –> positive selection when benefits outweigh the costs

Question 11

Pleiotropy

Answer 11

when a single gene influences multiple traits

Ex - frizzle mutation in chickens; feather curl outward, but also have high metabolic rate/body temper/digestive capacity, lay fewer eggs, etc

Question 12

Populations with lower rates of ecological mortality (due to predation, disease, etc.) should evolve delayed senescence (later aging or slower decline in fitness) to both the Mutation Accumulation Hypothesis and the Antagonistic Pleiotropy Hypothesis

Answer 12

Both of these theories predict that natural selection will be stronger in environments where individuals live longer, which leads to evolutionary changes in aging patterns.

Question 13

How big should offspring be?

Answer 13

trade-off between the size vs. number of offspring ; smaller size –> more offspring, vice versa

trade-off size vs. survival; smaller size –> less likely to survive, larger –> more likely to survive

Question 14

What is the optimal solution for offspring size?

Answer 14

Number of offspring * expected survival

Question 15

How many offspring? Lack’s (1947) hypothesis

Answer 15

Natural selection will favor the clutch size that maximizes the number of surviving offspring