24.1 - Population Size

Question 1

Define limiting factors

Answer 1

Limiting factors (biotic or abiotic component that limits further population growth) determine final size

Question 2

Outline the phases of a sigmoidal population growth curve

Answer 2

1. Slow growth (lag phase) - small numbers of individuals. Birth rate>death rate = population increases
2. Exponential Growth Phase - breeding numbers increase, population multiplies exponentially. No constraints on population expansion
3. Stable state (limiting factors come into effect). Further population growth limited by external constrain. Population generally fluctuates but remains stable over time.

Question 3

Define carrying capacity

Answer 3

Maximum population size that can be sustained by its environment, this is reached in the final stage of the sigmoidal population growth curve

Question 4

Give examples of biotic limiting factors.

Answer 4

• Predator number
• Disease
• Competition

Question 5

Give examples of abiotic limiting factors.

Answer 5

• Resource availability (food, water, light, oxygen, space)
• Natural disaster
• Weather/climate change

Question 6

What is the difference between immigration and emmigration.

Answer 6

Immigration: Movement of individuals to an area which increases its population size

Emigration: Movement of individuals away from an area, reducing its population size

Question 7

What are density independant factors?

Answer 7

Factors that have an effect on the whole population regardless of size.

• They dramatically change population size.

E.g. earthquakes, fires, volcanic eruptions, storms.