20 - Evolution of Life Histories

Question 1

What does it mean to be semelparous?

Answer 1

produce young once and die. Can be annual or over several years

Question 2

What does it mean to iteroparous?

Answer 2

produce young multiple times. Can be seasonal (polar/temperate) or random (tropical regions)

Question 3

What are the 5 key points for when an organism starts reproducing?

Answer 3

• larger body size means greater fecundity (more offspring)
• there is a negative relationship between time and survival
• there is a trade of between offering investment and offspring number
• there is a trade off between offspring investment and offspring survival
• combines 3+4 - there is an optimal individual offspring investment for parents

Question 4

What are the benefits and costs to early maturation?

Answer 4

benefits
- shorter generation time (offspring reproduce earlier)
- high probability of surviving to maturity

Costs
- small size
- lower fecundity
- associated with a shorter time span with fewer breeding attempts

Question 5

What are the benefits to late maturation?

Answer 5

• larger size
• higher initial fecundity
• associated with longer life spans

Question 6

What is senescence?

Answer 6

deterioration with age

Question 7

What is intrinsic and extrinsic mortality?

Answer 7

intrinsic - mortality due to neglect of maintenance to the body. internal cause of death

extrinsic mortality - mortality due to stochastic or environmental factors

Question 8

What is the mutation accumulation theory?

Answer 8

Because selection weakens later in life, deleterious mutations that affect older individuals accumulate in populations.

Assumes 3 mutations
- deleterious to young not adults
- deleterious to old, not young
- deleterious to both

1 + 3 strongly selected against as they are young
2 has weak selection, there mutations will accumulate, leading to senescence

Question 9

What is the antagonistic pleiotropy theory?

Answer 9

• genes that have a positive effect in younger individuals will have a deleterious effect in older individuals

Question 10

What is the disposable soma theory?

Answer 10

Senescence is due to a trade off between allocation to reproduction and maintenance of the body

Question 11

What is environmental plasticity?

Answer 11

when organisms are able to adapt to changing environmental conditions. Happens within its lifespan

Question 12

What is ‘non-linear cost of reproduction’?

Answer 12

• if cost of producing offspring is constant - iteroparous as you might as well spread it out
• if there is a large upfront cost - semalparous as once you are over the hurdle Bette to make many at once than face that cost again

Question 13

What are the costs of reproduction?

Answer 13

• longevity
• growth

Question 14

Explain the fixed budget hypothesis

Answer 14

• life span negatively correlated with metabolic rate - too much variation in species
• longevity should not respond to selection - wrong it does

Question 15

What is the fresh blood hypothesis?

Answer 15

Old individuals die to make room for young
- if there is a selfish individual it ruins it all