LEC18

Question 1

Define

Population state

Answer 1

Snapshot of the number of individuals and their spread, at a given point in time

Question 2

Define

Population dynamics

Answer 2

Biotic and abiotic factors that cause population states to change with time

Question 3

Describe

What members of a population do

Answer 3

• Rely on same resources
• Influenced by similar environmental factors
• Likely to interact and breed

Although ecologists are less concerned about whether pop. members breed

Question 4

Define

Population abundance

Answer 4

Number of individuals in the population

Question 5

Define

Population density

Answer 5

• Number of individuals per unit area (how individuals are spread out in space)
• Not a static property

Question 6

Define

Biomass density

Answer 6

Total weight of organisms in an area

Question 7

Describe

The consequences of low population density

Answer 7

• More resources for each individual
• Individuals less likely to encounter one another (spread disease, fight, mate)

Question 8

What are the two types of competition?

Answer 8

• Interference competition: overt, like two bears fighting
• Exploitation competition: covert, like two bears trying to eat all the berries in a bush

Question 9

Describe

Mark-recapture

Answer 9

1. Capture individuals, mark them, release them
2. Capture 2nd set of individuals, determine how many have been marked already
3. Calculate N, from M/N = R/C

Question 10

What are the three types of population dispersion?

Answer 10

Clumped, uniform, random

Question 11

Describe the causes of

A clumped dispersion

Answer 11

• Babies tend to stay near their parents
• Localized suitable environmental conditions
• When animals travel in groups

Question 12

Describe the causes of

A uniform dispersion

Answer 12

• Results from direct interactions between individuals (territoriality)
• Death of individuals when competitors are too close
• When individuals move from one another (ex: territorial wolf-packs)

Question 13

Describe the causes of

A random dispersion

Answer 13

• Individuals arriving at locations randomly when there are no spatial interactions or when there are multiple different spacial interaction functions

Question 14

What is the formula for changes in population size (for a short period of time)?

Answer 14

ΔN/Δt = B(t) - D(t) + I(t) - E(t)
ΔN: change in population density

Question 15

What are the two factors determining change in population size, in populatons not experiencing large amounts of immi/emigration?

Answer 15

Reproductive state and survivorship curves

Question 16

What are the links between carrying capacity and growth rate?

Answer 16

• Over carrying capacity: positive growth rate
• Under carrying capacity: negative growth rate
• At carrying capacity: neutral growth rate

Question 17

What is Type I survivorship curve?

Answer 17

• Low death rate when young
• High death rate when old
• Happens in large species

Shape: –\

Question 18

What is Type II survivorship curve?

Answer 18

• Constant death rate
• Happens when large percentage of mortality comes from predation

Shape: \

Question 19

What is Type III survivorship curve?

Answer 19

• High death rates when young
• Low death rates when old
• Seen in organisms that produce large amount of offspring but offer little care

Shape: __/