Exam 1 Study Guide: Life Histories

Question 1

Define Life History

Answer 1

Schedule of an organisms growth, development, reproduction, and longevity. Can vary within (intra) and between (inter) species

Question 2

Life History 5 Components

Answer 2

1. Time to reach maturity (1st reproduction)
2. Fecundity (# of offspring/ reproductive event)
3. Parity (# of reproductive events like semelparous and iteroparous)
4. Parental investment (how much invested in per offspring)
5. Longevity (life expectancy)

Growth rate: trees vs sunflowers

Age at maturity: when it first reproduces–frogs take months, elephants take years

reproductive effort: how much energy is invested in reproduction – salmon invest everything into a single spawning event

Number of offspring: many small vs few large

Longevity: how long an organism lives

Question 3

Slow-To-Fast life history continuum (R-K)

Answer 3

R-selected species (fast) : High offspring mortality & fast growing populations

EX: mouse

K-selected species (slow) : low offspring mortality & populations nearing carrying capacity

EX: elephant

Question 4

Characteristics of Slow-To-Fast life history continuum (R-K)

Answer 4

R-selected species:

-Faster growth
-Shorter life span
-Earlier reproduction
-Earlier sexual maturation
-Smaller parental investment
-Large number of offspring

K-relayed species:

-Fewer spring
-Longer lifespan
-Slower growth
-Delayed reproduction
-Later sexual maturation
-Greater parental investment

Question 5

Explain Grime’s triangle, comparing life history traits among stress tolerators,
competitors, and ruderals.

Answer 5

Stress tolerance: survive in extreme conditions, grow slowly and reproduce infrequently

Competitors: thrive in stable resource rich environments, invest in growth and dominance over others

Ruderals: seed production, dispersal are important to quickly colonize new habitat, weedy plants

Question 6

Ideas behind “optimal clutch size”

Answer 6

The number of offspring that maximises parental fitness by balancing survival and reproduction

Question 7

From clutch size, what are the tradeoffs between offspring number and offspring size

Answer 7

-Many small offspring: lower survival per individual but higher total reproductive output

-Few large offspring: higher survival per individual but lower reproductive output

Question 8

Describes the ideas behind the tradeoffs between current vs. future reproduction

Answer 8

organisms must balance resources between reproducing now or saving energy for future production

-High adult mortality: favor early, high reproductive effort

-Low adult mortality: favor delayed, repeated reproduction

EX: turtles delay reproduction for years

Question 9

When do you expect to see semelparous vs. iteroparous reproduction

Answer 9

Semelparous: reproduce once THEN die – common in harsh to unpredictable environments

Iteroparous species: reproduce multiple times throughout life – common in stable environments

Question 10

Summarize the principle of allocation and relate it to the lifetime reproductive success

Answer 10

resources allocated to one function can’t be spent on another. Birds laying more eggs may have reduced survival due to energy demands.