TOPIC 7 - 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

living and non living aspects of the environment found in one area

Question 3

describe biotic and abiotic factors.

Answer 3

biotic - living features of an ecosystem eg. predators, disease

abiotic - non-living features of an ecosystem eg. light, temperature

Question 4

define habitat.

Answer 4

the place where an organism lives within an ecosystem

Question 5

define niche.

Answer 5

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

Question 6

what is meant by carrying capacity?

Answer 6

the max size of population an ecosystem can support

Question 7

4 abioitic factors that may affect population growth?

Answer 7

pH
temperature
light intensity
humidity/water

Question 8

what is meant by intraspecific and interspecific competition?

Answer 8

Intraspecific = competition between organisms of the same species
Interspecific = competition between organisms of different species

Question 9

what resources might organisms compete for?

Answer 9

food, water, shelter, minerals, lights, mates

Question 10

describe 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 mean more prey survives, and the cycle begins again

Question 11

how are quadrats used for estimating population size?

Answer 11

• placed at grid coordinates
• placed at intervals along a line transect
• for slow moving or non mobile organisms

Question 12

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

Answer 12

• sample of species is captured, marked and released back into the same area they were caught from
• after certain period of time = another sample is captured and number of marked organisms are counted

Question 13

equation for mark-release-recapture?

Answer 13

total no of individuals in first sample x total number of individuals in second sample / number of marked individuals recaptured

Question 14

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

Answer 14

• marked individuals distribute evenly
• no migration in or out of the population
  -few births or deaths
  -method of marking doesn’t 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 + abiotic factors may alter the conditions of the system

Question 16

what is meant by primary succession?

Answer 16

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 abiotic factors of their environment
• overtime, this allows more complex organisms to survive

Question 18

what is the climax community and how is it reached?

Answer 18

final stage of succession where ecosystem is balanced and stable = soil is rich enough to support large shrubs or trees + environment is no longer changing

Question 19

how might species alter the environment that develops during succession?

Answer 19

may alter it to make it more suitable for other species or worsen environment making it less suitable for other species

Question 20

what is secondary succession?

Answer 20

• starts from land where vegetations has been cleared
  eg human deforestation
• less harsh abiotic conditions
• faster
• pioneer species can be larger

Question 21

define conservation.

Answer 21

protection of species and habitats in order to maintain biodiversity

Question 22

how might succession be managed in order to aid conservation?

Answer 22

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