Populations in Ecosystems

Question 1

define community

Answer 1

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

Question 2

define ecosystem

Answer 2

all living organisms found in one area, combined with non-living aspects of their environment. can very from very large to very small

Question 3

define a niche

Answer 3

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

Question 4

what is meant by carrying capacity

Answer 4

maximum size of population an ecosystem can support

Question 5

name four abiotic factors that affect population growth

Answer 5

1. temperature
2. light
3. pH
4. water/humidity

Question 6

what is intraspecific competition

Answer 6

competition between organisms of the same species

Question 7

what is interspecific

Answer 7

competition between organisms of different species

Question 8

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

Answer 8

• 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 9

how are quadrats used for estimating population size

Answer 9

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 10

how is mark-release-recapture used for estimated population size

Answer 10

• sample of a species is captured, marked and 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

(MOTILE ORGANISMS)

Question 11

equation for mark-release-recapture estimated population size

Answer 11

(total no. of individuals in sample 1 x total no. of individuals in sample 2) / number of marked individuals recaptured

Question 12

what assumptions does the mark-release-recapture method make

Answer 12

• marked individuals distribute evenly
• no migration in or out of population
• few births and deaths
• methods of marking does not affect survival
• mark does not come off

Question 13

why are ecosystems defined as dynamic

Answer 13

• 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 14

what is meant by primary succession

Answer 14

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

Question 15

summarise process of primary succession

Answer 15

• pioneer species can survive harsh conditions and colonise area
• they change abiotic factors of their environment e.g. decomposition adds nutrients to the ground
• over time, this allows more complex organisms to survive

Question 16

what is the climax community and how is it reached

Answer 16

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 17

how might a species alter the environment that develops during succession

Answer 17

species may improve the environment to make it more suitable for other species. alternatively, a species may worsen the environment by making it less suitable for other species

Question 18

define conservation

Answer 18

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

Question 19

how might succession be managed in order to aid conservation

Answer 19

sometimes succession needs to be prevented in order to preserve an ecosystem at a certain point, e.g. stopping moorland from progressing into spruce forest. this is called PLAGIOCLIMAX