19. populations in ecosystems

Question 1

Population

Answer 1

Group of organisms of the same species living in the same habitat.

Question 2

Habitat

Answer 2

Part of an ecosystem in which particular organisms live.

Question 3

Community

Answer 3

Populations of different species in the same area at the same time

Question 4

Ecosystem

Answer 4

A community and the abiotic factors.

Question 5

Niche

Answer 5

An organisms role in an ecosystem.

Question 6

Carrying Capacity

Answer 6

Maximum population size an ecosystem can support

Question 7

Interspecific competition

Answer 7

Members of DIFFERENT species in competition for resources.

Question 8

Intraspecific competition

Answer 8

Members of the SAME species are in competition for resources or mates.

Question 9

What three things can be said about all predator-prey graphs?

Answer 9

• the size of both populations fluctuate
• there will always be more prey than predators
• size of population changes for prey before predators

Question 10

Explain the mark and release technique.
+ give equation

Answer 10

A known number of animals are caught and marked, then released. After time a given number of individuals is captured, number of marked animals recaptures is recorded.

Estimated population size = (total no. in 1st sample x total no. in 2nd sample) / no. of marked individuals recaptured.

Question 11

What assumptions are made when carrying out capture-mark-recapture? (5)

Answer 11

• proportion of marked and to unmarked in sample match whole population
• marked individuals distribute evenly
• size of population stays the same (emigration, immigration, death, birth)
• nothing has made marked sample more likely to be re-captured
• mark(s) have not been removed

Question 12

Succession

Answer 12

Change in an ecological community over time.

Question 13

Explain primary succession.

Answer 13

• PIONEER species (eg. lichen) colonise bare rock or sand
• Death and decomposition of pioneer species cause abiotic factors to become LESS HARSH, forming a layer of soil (humus).
• Mosses and small plants can now grow on soil, increasing the NUTRIENT CONTENT of soil.
• New species OUTCOMPETES previous species
• less hostile environment, higher biodiversity

Question 14

What is meant by ‘climax community’?

Answer 14

• final stage of succession, dominated by trees

Question 15

Secondary succession.

Answer 15

Succession is disrupted and plants are destroyed. The succession begins again. Does not have to start from bare rock, soil is already created.

Question 16

Why and how does succession get managed?

Answer 16

• To conserve habitats.
• early stages of succession maintained, preventing climax community.
• allowing for a greater range of species

Question 17

What is meant by choppicing?

Answer 17

• cutting trees at their base, allowing them to survive.

Question 18

two types of transect

Answer 18

belt
interrupted belt