3.7.4 populations in ecosystems

Question 1

Population

Answer 1

Group of organisms of same species, living in same place (habitat) at the same time

Question 2

Community

Answer 2

All the populations of different species living in same place (habitat) at the same time

Question 3

Ecosystem

Answer 3

Community with the abiotic interactions with the environment

Question 4

Niche

Answer 4

Role of species within its habitat

If 2 species have the same niche, one will outcompete other

Question 5

Abiotic conditions

Answer 5

Non-living features of ecosystem

E..g temp or pH

Question 6

Biotic conditions

Answer 6

Living features of the ecosystem

E.g. predation, food supply

Question 7

Ecologists studied a community of fish in a lake. They found that each species of fish had adaptations to its niche. One of these adaptations was the shape of its mouth.

Suggest how the shape of mouth is an adaptation to its niche. (2 marks)

Answer 7

Different mouth eats different food

Competition between species (interspecific) reduced

Question 8

Suggest and explain one advantage to the fish of occupying different depths in the lake. (2 marks)

Answer 8

Less/no competition

For food/prey/O2

Question 9

Carrying capacity

Answer 9

Maximum stable population size an ecosystem can support

Question 10

Interspecific competition

Answer 10

Competition between species

Reduces resources available to both > limits both pop

If one species better adapted, it will outcompete others

Question 11

Intraspecific competition

Answer 11

Competition within a species

Smaller population = less competition > better for growth and reproduction

Larger population = more competition > less growth and reproduction > smaller pop

Question 12

Predation

Answer 12

Population sizes of predators and prey are interlinked

Increased predator population size> more prey eaten > prey population falls

Less food for predators > predator pop size falls > prey pop rises > predator pop rises again

Question 13

Random quadrats

Answer 13

2 tape measures at right angles

Randomly generate coordinates and place quadrat there

Count frequency of species in quadrat

Calculate mean per quadrat

Calc pop size by mean x no quadrats

Question 14

Quadrants along belt transect

Answer 14

Used to look at changes in distribution

Lay tape ensure along gradient

Place quadrats at regular intervals

Count frequency/percentage cover in quadrats

Question 15

Mark release capture

Answer 15

Capture, mark (discrete, nontoxic), release

Leave enough time for organisms to randomly distribute before collecting 2nd sample

Pop size = (sample 1 x sample 2) / number marked in sample 2

Question 16

Assumptions made for mark release capture

Answer 16

Sufficient time for marked individuals to mix within pop

Mark not removed/ doesnt affect chances of survival

No immigration

No births/deaths

Question 17

Succession

Answer 17

Colonisation by pioneer species

Pioneer species change abiotic conditions and make env less hostile e.g. dies and decomposes to form soil that can retain water

Env becomes more suitable for other species with different adaptations and may be less suitable for the previous species - better adapted species outcompetes previous species

As succession goes on, biodiversity increases

Climax community: final, stable community

Question 18

Conservation of habitats

Answer 18

Prevent succession and stop a climax community from forming: plagioclimax

Ensure ecosystem is preserved