Lecture 13: How Trade-offs Affect Life Histories

Question 1

What is the “Principle of Allocation”? What are some examples?

Answer 1

When energy and time is used up for one function, it reduces resources for others.

Examples:
- number of offspring vs. offspring size
- seed size vs. seed dispersal distance (weak trade-off)
- seed size vs. survival
- survival vs. age at maturity
- size vs. maturity and behaviour

Question 2

Define Life History

Answer 2

A description of the major characteristics of an organism throughout its life.

Question 3

Define Fecundity

Answer 3

Fecundity refers to the maximum possible number of offspring per fertility episode.

Question 4

Define Parity.
Define semelparous and iteroparous in plant species.

Answer 4

Parity refers to the number of reproduction episodes.

Question 5

Parity: Define semelparous and iteroparous in animal species.

Answer 5

An semelparous species only reproduces once in a lifetime, wheres an iterparous species reproduces multiple times throughout its lifetime.

Question 6

Parity: Define monocarpic and polycarpic in plant species.

Answer 6

A monocarpic plant produces one set of seeds and flowers, where as a polycarpic plant produces flowers and seeds multiple times.

Question 7

Define maturity of plants and animals

Answer 7

The age they are during their first reproduction.

Question 8

Define Allometry

Answer 8

The study of the change between body size and their biological traits and functions in order to maintain homeostasis.
When graphed, X axis refers to the body size and Y axis refers to the trait.

Question 9

Define gene flow

Answer 9

The transfer of genetic material across populations.

Question 10

How does gene flow affect “seed size vs. seed dispersal distance”?

Answer 10

According to a darter species study done by Turner and Trexler,

Smaller eggs = more eggs = farther dispersal = longer larval phases = high gene flow = low genetic isolation

Larger eggs = less eggs = shorter larval phase = low gene flow = more energy to maintain survival

Question 11

What is the trade-off for survival vs age at maturity?

Answer 11

Organisms that start reproducing at an early age, do not have enough energy to put into growth and survival.

Organisms that focus on survival, reproduce later in life.

Question 12

What are characteristics of an r selected species?

Answer 12

High potential of population growth rate, not competitive, fast development, early reproduction, small size, and semelparous.

Question 13

What are characteristics of a K selected species?

Answer 13

Low potential of population growth rate, larger size, late reproduction, highly competitive, slow development, and iteroparous.

Question 14

Grime’s Triangle: Explain the “competitive” category and provide an example.

Answer 14

Occupy environments of low disturbance and low stress.

Rapid development.

Example: Meadows, birch

Question 15

Grime’s Triangle: Explain the “ruderal” category and provide an example.

Answer 15

Occupy environments of high disturbance and low stress.

Rapid development, short lifespan, r-selcted species

Example: Weeds, annual grass

Question 16

Grime’s Triangle: Explain the “stress-tolerant” category and provide an example.

Answer 16

Occupy environments of high stress, low disturbance, and low competition.

Slow development as they invest more energy in being stress-tolerant.

Example: saline marshes, beech trees

Question 17

What are two ways that life histories are organized?

Answer 17

1. Grime’s Triangle
   Describing 3 evolutionary strategies in plants: competition (increasing disturbance) -> ruderal (increasing stress) -> and stress-tolerant (increasing competition) ->
2. EPO - Equilibrium, Periodic, and Opportunistic
   Strategies and adaptations due to life-history trade-offs: fecundity, juvenile survivorship, and age of maturity.