5.3 Populations

Question 1

State the four factors affecting population size

Answer 1

Natality - increase through reproduction
Immigration - increase from external populations (moving in)
Mortality - decrease due to death
Emigration - decrease from loss to external populations (moving out)

Question 2

State the three phases of population growth

Answer 2

Exponential phase, Transitional phase, Plateau phase

Question 3

Explain the reasons for the Exponential phase

Answer 3

– Rapid population growth
– Natality exceeds mortality; immigration exceeds emigration
– Abundant resources (food, land) and limited environmental resistance (disease, predators)

Question 4

Explain the reasons for the Transitional phase

Answer 4

– Rate of population growth slows down

– Resources become more limited

Question 5

Explain the reasons for the Plateau phase

Answer 5

– Population stabilises, reaches a maximum population, which fluctuates slightly
– On average over a period of time, natality + immigration ≈ mortality + emigration
– Limited resources, high competition

Question 6

List 5 factors which limit population affected by population density

Answer 6

Predation and parasites
Availability of shelter and water
Nutrient supply (i.e. food source)
Disease
Accumulation of wastes