Populations In Ecosystems

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. Can vary from very large to very small

Question 3

Describe biotic and abiotic factors, give examples.

Answer 3

Biotic = living features of an ecosystem e.g predators, disease

Abiotic = non-living features of an ecosystem e.g light, temperature

Question 4

Define habitat

Answer 4

The place where an organism lives within an ecosystem

Question 5

Define a niche

Answer 5

The role of a species within its habitat, consisting of both its biotic interactions e.g what it eats and abiotic interactions e.g time of day its active

Question 6

What is meant by carrying capacity?

Answer 6

The maximum size of population an ecosystem can support

Question 7

Name four abiotic factors that affect population growth

Answer 7

1. Temperature
2. Light
3. pH
4. Water / humidity

Question 8

What is meant by intraspecific and interspecific competition?

Answer 8

Intraspecific = competition between organisms of the same species

Interspecfiic = competition between organisms of different species

Question 9

What resource might organisms compete for?

Answer 9

Food, water, shelter, mineral, light, mates

Question 10

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

Answer 10

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

Question 11

How are quadrats used for estimating population size?

Answer 11

Can be placed on grid coordinates or at intervals along a belt transect. Results reported as either percentage cover or frequency. For slow moving or non-motile organisms

Question 12

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

Answer 12

A sample of a species is captured, marked then released back into the same area they were caught

After a certain period of time another sample is captured and the number of marked organisms are counted

For motile organisms

Question 13

What is the equation for mark-release-capture?

Answer 13

Estimated population size =

total number of individuals in the first sample x total number of individuals in second sample / number of marked individuals recaptured

Question 14

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

Answer 14

Marked individuals distribute evenly

No migration in or out of the population

Few births or deaths

Method or marking does not affect survival

Mark does not come off

Question 15

Why are ecosystems described as being dynamic?

Answer 15

Populations constantly rise and fall

Any small change can have a large effect

Biotic and abiotic factors may alter the conditions of the ecosystem

Question 16

What is meant by primary succession?

Answer 16

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

Question 17

Summarise the process of primary succession

Answer 17

Pioneer species can survive harsh conditions and colonise the area

They change the abiotic factors e.g decomposition adds nutrients to the ground

Over time this allows more complex organisms to survive

Question 18

What is the climax community and how is it reached?

Answer 18

The final stage of succession, where the ecosystem is balanced and stable. It is reached when the soil is rich enough to support large trees or shrubs and the environment is no longer changing

Question 19

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

Answer 19

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 20

Define conservation

Answer 20

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

Question 21

How might succession be managed in order to aid conservation?

Answer 21

Sometimes succession needs to be prevented in order to preserve an ecosystem at a certain point