7.4 Populations

Question 1

Define community.

Answer 1

All the different species that live in one area and interact with each other

Question 2

Define ecosystem.

Answer 2

All the living organisms found in one area, combined with non-living aspects of their environment

Question 3

Define biotic factor.

Answer 3

Living feature of an ecosystem

Question 4

Define abiotic factor.

Answer 4

Non-living feature of an ecosystem

Question 5

Give examples of biotic factors.

Answer 5

Predators
Disease
Competition

Question 6

Give examples of abiotic factors.

Answer 6

Light
Temperature
Water

Question 7

Define habitat.

Answer 7

Where an organism lives within an ecosystem

Question 8

Define a niche.

Answer 8

The role of a species within its habitat, consisting of both biotic /abiotic interactions

Question 9

What is meant by carrying capacity?

Answer 9

The maximum population size an ecosystem can support

Question 10

Name four abiotic factors that can affect population growth.

Answer 10

Temperature
Light
pH
Water/humidity

Question 11

What is intraspecific competition?

Answer 11

Competition between organisms of the same species

Question 12

What is interspecific competition?

Answer 12

Competition between organisms of different species

Question 13

Give examples of resources organisms might compete for.

Answer 13

Food
Water
Shelter
Minerals
Light
Mates

Question 14

Describe the pattern of a typical predator-prey relationship in terms of population change.

Answer 14

Prey is eaten by predator, predator population increasing & prey population decreasing
Fewer prey means increased competition for food so predator population decreases
Fewer predators means more prey survives and cycle begins again

Question 15

How are quadrats used to estimate population size?

Answer 15

Can be placed on grid coordinates or intervals along a belt transect
Results reported as either percentage cover or frequency

Question 16

How is mark-release-recapture used for estimating population size?

Answer 16

A sample of a species is captured, marked and released back into the same area
After a certain period of time another sample is captured and the number of marked organisms are counted

Question 17

What type of organisms are quadrats used for?

Answer 17

Slow-moving or non-motile organisms

Question 18

What type of organism is mark-release-recapture used for?

Answer 18

Motile organisms

Question 19

What is the equation for mark-release-recapture?

Answer 19

Estimated population size = total individuals in first sample x total individuals in second sample / number of marked individuals recaptured

Question 20

What assumptions does the mark-release-recapture method make?

Answer 20

Marked individuals distribute evenly
No migration in or out of population
Few births or deaths
Method of marking does not affect survival
Mark remains

Question 21

Why are ecosystems described as dynamic?

Answer 21

Populations constantly rise and fall
Any small change can have large effect
Biotic/abiotic factors may alter conditions of ecosystem

Question 22

What is primary succession?

Answer 22

Where an area previously devoid of life is colonised by a community of organisms

Question 23

Summarise the process of primary succession.

Answer 23

Pioneer species can survive harsh conditions & colonise area
Species change abiotic factors of environment
Over time, allows more complex organisms to survive

Question 24

What is a climax community?

Answer 24

The final stage of succession
Where ecosystem is balanced & stable

Question 25

When is climax community reached?

Answer 25

When soil is rich enough to support large trees/shrubs and environment is no longer changing

Question 26

How might a species alter the environment that develops during succession?

Answer 26

A species may improve the environment to make it more suitable for other species
A species may worsen the environment by making it less suitable for other species

Question 27

Define conservation.

Answer 27

The protection and management of species and habitats, in order to maintain biodiversity
Methods need to be adapted to the ecosystem

Question 28

How might succession be managed in order to aid conservation?

Answer 28

Sometimes succession needs to be prevented in order to preserve an ecosystem at a certain point
Known as the plagioclimax