Unit 1 - Population Dynamics - (Week 6)

Question 1

Define “density-dependent factor”, give examples of one and describe how it affects
population growth.

Answer 1

They are factors which reduce a population when numbers are high and allow a population to increase when numbers are low

Predador-Prey cycle and Competition for space and food

Density-dependent factors: competition for resources (eg food, light, water, space, mates, territory)

Question 2

Define “density-independent factor”, give examples and describe how it affects
population growth.

Answer 2

Fcators that affect population number regardless of the population’s size i.e. natural disasters e.g. fire

Density-independent factors (tend to be abiotic in nature) eg weather (short term), climate (long term), volcanic eruptions, landslides, floods, fires ie natural events

Question 3

Explain what the “carrying capacity” of a population is.

Answer 3

the maximum level of population which an ecosystem can sustainably support.

Question 4

Describe the “exponential model” of population growth.

Answer 4

• population increases over time
  regardless of limits on resources
• less sustainable
• has a characteristic J-shape

Question 5

Describe the “logistic model” of population growth.

Answer 5

population grows until it reaches
* carrying capacity
* more sustainable
* has a characteristic S-shape

Question 6

Explain why oscillations in population size may occur.

Question 7

Describe inter-specific competion from density dependant factors

Answer 7

Occurs when individuals of different species require similar resources e.g. red and grey squirrels competing for food.

Question 8

Describe intra-specific competion from density dependant factors

Answer 8

Occurs when individuals of the same species require the same resource e.g. red deer competing for a mate. It is more intense than interspecific.