Interdependence

Question 1

What do plants need to compete for in order to survive and reproduce?

Answer 1

• light
• space
• water
• minerals (nutrients) from the soil

Question 2

In what ways do environmental changes affect communities?

Answer 2

• population size increases: e.g. if number of prey increase, there is more food available for predators, so more predators survive and reproduce, increasing their numbers
• population size decreases: e.g. US number of bees are falling rapidly - due to pesticides, less nectar-rich food available, more disease
• population distribution changes: - a change in where an organism lives
• e.g. European bee-eater is a Mediterranean species but now present in Germany

Question 3

What are indicator species?

Answer 3

• organisms that are very sensitive to changes in their environment, so can be studied to see the effect of human activities

Question 4

What are the living and non-living factors that causes environmental changes?

Answer 4

Living factor:
- a change in the number or types of competitors

Non-living factors:

• a change in average temperature
• a change in availability of nutrients
• a change in the amount of light
• a change in average rainfall
• a change in availability of oxygen and carbon dioxide
• a change in the availability of nesting sites, shelter and habitats

Question 5

How do you work out population size?

Answer 5

1. work out the number of organism per m^2
2. multiply the mean by the total area of the habitat
3. e.g. total area is 800m^2 and there are 22 daisies per m^2 22 x 800 = 17600

Question 6

How can you make sure results are more valid?

Answer 6

• they must be repeatable, reproducible and answer the original question
• more likely to be valid if you use random samples, so that it’s not all one spot

Question 7

Give examples of non-living indicators of environmental change

Answer 7

• satellites: measure the temperature of the sea surface. they are accurate, modern and give global coverage
• automatic weather stations: tell us the atmospheric temperature. they contain sensitive and accurate thermometers and can measure to very small fractions of a degree
• rain gauges: measure rainfall, to see how much average rainfall changes year on year
• dissolved oxygen meters: measure concentration of dissolved oxygen in water. sees how water pollution is changing

Question 8

Give examples of living indicators of environmental change

Answer 8

• lichens: air pollution indicators as they are sensitive to the concentration of sulphur dioxide in the atmosphere. Air is clean when there are lots of lichen
• invertebrate animals: such as mayfly larvae, are present when water is clean. rat-tailed maggots, sludge worms have adapted to live in polluted conditions so high level of pollution

Question 9

What do animals need to compete for in order to survive and reproduce?

Answer 9

• space (territory)
• food
• water
• mates

Question 10

How can you make sure results are more reproducible?

Answer 10

• use a large sample size (e.g. as many quadrats and transects as possible in your sample area)
• bigger samples are more representative of the whole population, so more reproducible

Question 11

How do you use quadrats to study the distribution of small organisms using random sampling?

Answer 11

1. place a 1m^2 quadrat on the ground at a random point within the first sample area (using a random number generator)
2. count all the organism within the quadrat
3. repeat 1 and 2 as many times as possible
4. work out the mean number of organism per quadrat within the first sample area, median, mode also
5. repeat in the second sample area
6. compare the two means

Question 12

What are the pros and cons of using non-living indicators?

Answer 12

Pros:

• directly measuring pollutants of environmental change gives reliable, numerical data that’s easy to compare between different sites
• the exact pollutants can be identified and their concentrations measured

Cons:

• requires expensive equipment
• trained workers needed to operate
• only gives a snapshot of conditions at the time measurements were taken

Question 13

What are the pros and cons of using living indicator species?

Answer 13

Pros:

• relatively quick, cheap and easy to see whether an area is polluted or not
• gives a long term view because organisms change relatively slowly as the environment changes

Cons:
- it isn’t always reliable because their survival can be affected by other factors (e.g. temperature)

Question 14

How do you use transects to study the distribution of organisms along a line?

Answer 14

1. mark out a line in the area you want to study using a tape measure
2. collect data along the line
3. you can do this by counting the organism that you’re interested in that touch the line
4. or you can use quadrats and place them next to each other or at intervals.