Topic 11: Population Ecology (continued)

Question 1

What 2 fields apply population ecology?

Answer 1

1. Bioeconomics. Managing exploited populations.
2. Conservation. Conserving endangered or threatened populations.

Question 2

What is the largest harvesting rate that can be maintained indefinitely?

Answer 2

The Maximum Sustaining Yield (MSY)

Question 3

When is the MSY applied?

Answer 3

When the rate of harvest is less than the rate at which the population can grow.

Question 4

What are two outcomes of Maximum Sustainable Yield (MSY) harvesting?

Answer 4

1. If the population is growing rapidly, we can harvest, and the population will replace itself rapidly.
2. If the population growth is low, harvesting risks the population not being able to replace itself and crashing.

Question 5

When does population growth = 0?

Answer 5

When population is at 0 or K (carrying capacity).

Question 6

What is the population numbers (N) at maximum growth rate?

Answer 6

N = 1/2 K (carrying capacity)

Question 7

What are 2 ecological problems with harvesting at MSY?

Answer 7

1. Biological parameters are often not well known. MSY assumes that population growth rate is known
2. Environmental fluctuations mean that carrying capacity is not constant.

Question 8

When will a MSY population decline?

Answer 8

If harvest > population growth rate

Question 9

How is MSY obtained?

Answer 9

By harvesting at maximum growth rate while maintaining 1/2 K

Question 10

What are 3 economic problems with MSY?

Answer 10

1. Fluctuations in K will impact quotas and incomes for harvesters.
2. There is greater short-term gain by overharvesting.
3. The tragedy of the commons. If one harvester does not exploit the resource, it is likely that another will.

Question 11

What is the wisest harvest rates?

Answer 11

Below MSY

Question 12

What is Minimal Viable Population Size (MVP)?

Answer 12

The population size above which a species must be maintained to ensure its long-term survival.

Question 13

What is an example of ‘no population size can guarantee persistence of a species indefinitely’?

Answer 13

Passenger Pigeons in North America

Question 14

What must be determined for MVP estimation?

Answer 14

An acceptable probability of extinction over fixed time intervals.
e.g. 2% over 1000 years, 1% over 100 years

Question 15

Is there a single MVP to apply to all species under all circumstances?

Answer 15

No.

Question 16

What 2 broad factors determine the likelihood of extinction?

Answer 16

1. Deterministic factors.
2. Stochastic (chance) processes.

Question 17

What does MVP of a species depend on?

Answer 17

1. Ecological characteristics of a species. e.g. longevity, birth and death rates, dispersal
2. Environmental conditions.

Question 18

What are deterministic processes?

Answer 18

Ongoing processes with relatively predictable consequences.
e.g logging forests removes the largest and oldest trees, so it can be predicted that there will be fewer large old trees available for habitats

Question 19

What are stochastic processes?

Answer 19

Processes that happen by chance and have an outcome that is difficult to predict.

Question 20

Variations in processes have a large effect on what populations?

Answer 20

On small populations.
Chance variations in processes can affect population structure and capacity for population growth.

Question 21

What are the 4 types of stochastic processes?

Answer 21

1. Genetic. loss of genetic diversity including inbreeding and genetic drift
2. Demographic. e.g. sex ratio, birth rates
3. Environmental. e.g. change in climate, food available, or predator numbers
4. Catastrophic. e.g. fire, flood and drought

Question 22

What is population viability analysis?

Answer 22

The species-specific risk assessment of the probability of extinction within a specific time frame.