Chapter 8 - Life Histories

Question 1

What is a life history?

Answer 1

The schedule of an organism’s growth, development, reproduction, and survival.

Question 2

What is fecundity?

Answer 2

The number of offspring produced by an organism per reproductive episode.

Question 3

What is parity?

Answer 3

The number of reproductive episodes an organism experiences.

Question 4

What is parental investment?

Answer 4

The amount of time and energy given to an offspring by its parents.

Question 5

What is longevity/life expectancy?

Answer 5

The life span of an organism.

Question 6

What factors cause life history traits to vary?

Answer 6

Life form, habitat, environmental conditions.

Question 7

Do variations in life history traits occur in isolation?

Answer 7

No, they are often connected.

Question 8

What are traits of organisms at the slow end of the life history continuum? The fast end?

Answer 8

Slow: take a while to reach sexual maturity, long life spans, low number of offspring, large parental investment.
Fast: fast sexual maturity, short life spans, many offspring, low parental investment.

Question 9

Explain the principal of allocation.

Answer 9

The observation that when resources are devoted to one body structure, physiological function, or behaviour, they cannot be allotted to another.

Question 10

What would be considered an optimized life history?

Answer 10

One that resolves conflicts between the competing demands of survival and reproduction to the best advantage of the individual in terms of fitness.

Question 11

List some examples of trade-offs.

Answer 11

Offspring number vs. offspring size
Offspring number vs. parental care
Fecundity and parental care vs. parental survival
Growth vs. age of sexual maturity and life span

Question 12

What might affect the number of offspring an organism has in one reproductive event?

Answer 12

Low vs. high resource environments

Question 13

Why is there often a trade off between number of offspring and parental care?

Answer 13

As the number of offspring increases, the efforts of the parents to provide food and protection will increasingly be spread thin.

Question 14

What brood size has optimal fitness? Why?

Answer 14

Intermediate brood size because the parents are producing the maximum number of offspring they can care for.

Question 15

Differentiate between determinate and indeterminate growth.

Answer 15

D: A growth pattern in which an individual does not grow any more once it initiates reproduction.
I: A growth pattern in which an individual continues to grow after it initiates reproduction.

Question 16

What is the trade-off between determinate and indeterminate growth?

Answer 16

Organisms with large life spans should focus on growing in earlier years to then produce more offspring later on. Organisms with shorter life spans should focus on reproduction as opposed to growth.

Question 17

Differentiate between semelparity and iteroparity.

Answer 17

Semelparity: When organisms reproduce only once during their lifetime.
Iteroparity: When organisms reproduce multiple times during their life.

Question 18

Differentiate between annual and perennial life histories.

Answer 18

Annual: An organism has a life span of one year.
Perennial: An organism has a life span of more than one year.

Question 19

When does semelparity arise?

Answer 19

When there is a massive amount of energy required for reproduction.

Question 20

What is senescence?

Answer 20

A gradual decrease in fecundity and an increase in the probability of mortality.

Question 21

What factors may influence the timing of life history events?

Answer 21

Amount of resources available, temperature, presence of enemies.

Question 22

What is a photoperiod?

Answer 22

The amount of light that occurs each day.

Question 23

How can predators affect the timing of life history events?

Answer 23

Some species, such as the red-eyed tree frog, can sense the presence of predators as developing embryos. Development can then be sped up and the offspring can hatch before being caught by the predator.

Question 24

What is an example of temperature affecting life history events?

Answer 24

Plants flowering earlier due to global warming.

Question 25

Are trade-offs always passed on to offspring?

Answer 25

No. Trade-offs are responses to the environment and are not necessarily genetically coded.

Question 26

Can a trade-off be considered an adaptation?

Answer 26

The trade-off itself is not an adaptation. The genetic traits that are passed on to the offspring are the adaptations and may be passed on as a result of a trade-off.

Question 27

What trend was observed in the case study on big horn sheep and trophy hunting? What was a flaw discussed about this study?

Answer 27

Body size and horn length decreased. No other factors besides hunting were explored.

Question 28

What is the ideal free distribution model?

Answer 28

way in which a population’s individuals distribute themselves among several patches of resources within their environment, in order to minimize resource competition and maximize fitness

Question 29

What assumptions are made in the ideal free distribution model?

Answer 29

Animals are ideal (i.e., assess environment without error and do this in the quickest amount of time). Animals can move freely between habitats.

Question 30

What does it mean when a habitat is referred to as patchy?

Answer 30

The population is divided into subpopulations.