15. Population Structure

Question 1

As the size of an organism increases what happens to population density?

Answer 1

Density decreases, but there is variation between different animal groups

Question 2

Why does density decrease with increasing body mass?

Answer 2

1. Body scaling- not enough space for many large animals vs many small animals
2. Metabolic demand vs resource availability- not enough food for many animals who need to eat a lot

Question 3

What are the 5 animal groups

Answer 3

Pokiloderms
Aquatic invertibrates
Terrestrial invertibrates
Mammals
Birds

Question 4

Why do birds have higher population density than mammals?

Answer 4

Birds are more mobile (can forage over larger areas) and less social than mammals

Even though they occupy a similar range of body masses

Question 5

How does population density vary among plants?

Answer 5

Increasing biomass = lower density
(Duckweed has very high density vs redwoods have very low density)

Increasing age (larger mass)= lower density
(Seedlings have higher density than fully grown trees- competition, plants cannot move to find resources)
- self thinning

Question 6

How is rarity influenced?

Answer 6

Geographic range (vast vs restricted)

Habitat tolerance (broad vs narrow)

Local population size (large vs small)

Question 7

What are the most common and least common combinations of rarity?

Answer 7

Most common: Vast geographic range, broad habitat tolerance, large local population

Most rare: Restricted geographic range, narrow habitat tolerance, small local population

Question 8

IUCN red list categories

Answer 8

International Union for the Conservation of Nature

E- Extinct
EW- Extinct in the wild

CR- Critically endangered
EN- Endangered
VU- Vulnerable

NC- Not threatened
LC- Least concern

Question 9

Population dynamics

Answer 9

Change in population structure and size over time

Question 10

How do wolves hunt Dall sheep?

Answer 10

Targeting old and sick sheep

vs humans who go after healthy, strong, mature animals

Question 11

Life tables

Answer 11

Recording method to track births and deaths to estimate survival

Expressed in percentages

Survivorship: survivors / total pop
Mortality: deaths / total pop

Question 12

Survivorship curve

Answer 12

Graphic summary of a life table

Question 13

Cohort life table

Answer 13

Identify individuals born at the same time and record from birth

More accurate data and easier to interpret

Harder or impossibe to collect data because it requires tracking the individuals

Question 14

Static life table

Answer 14

Record age of death of many individuals in a narrow time span

Requires accurate age determination which can be difficult

Easier to collect data

Question 15

Age disribution

Answer 15

Calculate difference in proportions of individuals of each age class

Assumes differences are due to mortality instead of population growth, emmigration, immigration etc

Question 16

What are the 3 types of survivorship curves?

Answer 16

1. High survival of young- convex curve (large vertebrates, annual plants, rotifers, humans)
2. Constant rates of survival- linear decrease (birds, water snakes)
3. Low survival of young- concave curve (fish, trees, other plants)

Question 17

How does age distribution reflect species stability?

Answer 17

A higher proportion of young individuals to replace old and dying individuals reflects higher stability

Higher proportions of middle aged and old populations are less stable

Question 18

Why does monogamy produce a 1:1 sex ratio?

Answer 18

Females will always have high fitness and always reproduce

Only one male can reproduce with the female

The ability to produce female offspring is genetic, high fitness genotypes will be selected for more often

In a population with few females (high fitness) and many males (low fitness), females will be selected for, and increase in numbers over time until equilibrium is reached