Unit 7 Populations in ecosystems

Question 1

@Define population and community

Answer 1

Population
Group of organisms of the same species living in the same habitat
Community
- All of the populations of different species in the same area at the same time

Question 2

Define ecosystem and habitat

Answer 2

Ecosystem
- Community and non living components of an environment can vary from small to large
Habitat
- Part of ecosystem which particular organisms live

Question 3

Define biotic and abiotic factors

Answer 3

Abiotic
- Non living conditions of an ecosystem
Biotic
- Impact of interactions between organisms

Question 4

@Describe the reason why populations vary in size
1

Answer 4

Abiotic Factors
- Temperature, oxygen and carbon dioxide concentration, light intensity, pH and soil conditions.
- The less harsh the abiotic factors (plenty of water and light) the larger the range of species and the larger the population sizes.

Question 5

@Describe the reason why populations vary in size
2

Answer 5

Biotic factors
- Interspecific competition is when members of different species are in competition for the same limited resource e.g food water
- Intraspecific competition is when members of the same species are in competition for resources and a mate
FOR BOTH
Individual better adapted to the environment is more likely to succeed in the competition.

Question 6

@Outline the interaction between predator and prey

Answer 6

The size of the population will always change in the prey first and after a lag period, the predator population changes.

Question 7

@Outline how the size of a population can be measure using sampling
for slow moving or non motile

Answer 7

TO ACCURATELY REPRESENT POPULATION
- Use uniform areas to eliminate bias
- Line transects to examine change over a distance
OR
- Divide area into grids/ sections
- Use a random generator for obtaining random coordinates
- Count number of species in a quadrat and percentage cover should be estimated
- Large sample should be used. and calculate average number per
section
- Valid method of calculating total number of plant, e.g.
mean number of plants per section multiplied by number of quadrats

% cover divide % by number of wuadrates

Question 8

@Outline the use of a belt transect

Answer 8

• A belt transect is when the tape measure is placed through an ecosystem that is not uniform, such as a rocky shore.
• Quadrat can be placed at intervals along the transect to measure the impact of the changes in the environment.

Question 9

@Outline how the size of a population can be measure using mark release recapture for active organims

Answer 9

• Capture and collect sample of population mark and release, number caught recorded
• Ensure marking is not harmful to animal
• Allow time for animal to randomly distribute before collecting a second sample
• Size of Population = number in first sample × number in second
  sample divided+ by number of marked fish in second
  sample

Question 10

@Outline assumptions of mark release recapture

Answer 10

Estimate may not be accurate due to:
- Population size not constant
- Animals always redsitribute evenly

Question 11

@Outline primary succession

Answer 11

• Colonisation by pioneer species
• Pioneer species change the environmental factors
• Environment becomes less hostile for other species
• Change/increase in biodiversity
• To climax community

Question 12

Outline the advantage of succession

Answer 12

As succession occurs, the species richness and number of organisms increase (biodiversity increases).

Question 13

Outline conservation of habitats

Answer 13

• The destruction of habitats esults in a loss of food and space for organisms and can lead to extinction.
• By maintaining earlier stages in succession, and preventing a climax community, a greater variety of habitats are conserved and therefore a greater range of species.