Populations Flashcards – Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028)

What is a population?

A group of organisms of one species living in the same area at the same time.

What is a community in an ecosystem?

All the populations of different species in the ecosystem.

What is an ecosystem?

A community and its environment functioning as an interacting unit.

What four factors can affect the rate of population growth?

Food supply, competition, predation and disease.

How can food availability affect population growth?

It can support or limit organisms’ survival and reproduction.

How can competition for limited resources affect population growth?

It can reduce population growth.

How can predation and disease affect population growth?

They can increase deaths, slowing growth or causing population decline.

What does a population growth graph show?

How population size changes over time.

How does population size change during the lag phase?

It increases slowly.

How does population size change during the exponential or log phase?

It increases rapidly.

What happens to population size during the stationary phase?

It levels off, remaining approximately stable.

Why does population growth level off in the stationary phase of a resource-limited environment?

Limited resources constrain further growth.

What happens to population size during the death phase?

It decreases.

What do the direction and levelness of a population growth curve indicate about population size?

An upward curve indicates an increase, a level curve indicates approximate stability, and a downward curve indicates a decrease.

What does the steepness of a population growth curve indicate?

How quickly population size is changing: a steeper curve means a faster change.

Why is population growth slow during the lag phase?

The population is small, so few organisms are reproducing.

What resource and limiting-factor conditions support the exponential phase of population growth?

Resources are readily available, and limiting factors have relatively little effect.

How do births and deaths compare during the exponential phase, and what happens to population size?

Births exceed deaths, so population size increases rapidly.

How do food availability and competition change as population size increases?

Food becomes more limited, and competition intensifies.

Why does population size remain approximately stable during the stationary phase?

Limiting factors constrain growth, so births and deaths are approximately balanced.

How do births and deaths compare during the death phase, and what happens to population size?

Deaths exceed births, so population size falls.

Name four factors that can reduce survival or reproduction in a population.

Food shortage, competition, predation and disease.