Populations

Question 1

Using quadrats

Answer 1

Set up a grid
Choose random coordinates using a random number generator
Place a large number of quadrats on the coordinates
Measure the percentage cover or species frequency (say how you do this)
With a large number do the running mean until it stays stable and there’s enough for a statistical test

Question 2

Percentage cover

Answer 2

Measures abundance

An estimate of the area within a quadrat a specific plant species occupies

Question 3

Positive of percentage cover

Answer 3

Useful when counting individual organisms which is impractical

Question 4

Negative of percentage cover

Answer 4

Underestimates small organisms and overestimates large ones

Question 5

Species frequency

Answer 5

Number of individuals of each species in a quadrat

Question 6

Why use random sampling?

Answer 6

Avoids bias

Question 7

Deforestation/removal of hedges

Answer 7

Fewer species
Less habitats
Fewer food sources
Increase in CO2 in the air since less photosynthesis
Farmers often benefit from hedges as they have more predators for pests

Question 8

Transects

Answer 8

Should be used when there is a transition in the environment (systematic sampling)
Place quadrats at regular intervals along the line
Count plants/percentage cover (in quadrats)
Use several quadrats
May not be representative of area

Question 9

Mark-release recapture

Answer 9

Capture sample, mark and release
Appropriate method of marking suggested - doesn’t harm/rub off
Take second sample and count marked organisms
No. in sample 1 X no. in sample 2
Population =
Number marked in 2nd sample

Question 10

Assumptions of mark-release recapture: Population must remain stable

Answer 10

No emigration/immigration 
No losses to predation 
Marking does not affect survival 
Birth rate and death rate equal 
All belong to one population

Question 11

Community

Answer 11

All the populations of different organisms living and interacting in a particular place at the same time.

Question 12

Habitat

Answer 12

Place where an organism normally lives.

Question 13

Population

Answer 13

Group of individuals of the same species occupying same habitat at same time.

Question 14

Niche

Answer 14

All conditions and resources needed for an organism to survive and reproduce.
How an organism fits into the environment.
Governed by the abiotic and biotic conditions.

Question 15

Ecosystem

Answer 15

All the interacting biotic and abiotic features in a specific environment.

Question 16

Abiotic factors

Answer 16

Non-living features of an environment (e.g. Temperature, pH, light)

Question 17

Biotic factors

Answer 17

Living features of an environment.

Question 18

Carrying capacity

Answer 18

An ecosystem can only support populations of a certain size.
Affected by abiotic factors, inter and interspecific competition and predation.

Question 19

Intraspecific competition

Answer 19

Between members of the same species.

Question 20

Interspecific competition

Answer 20

Between members of different species.
Happens until one outcompetes another.
Compete for things such as food, space, light, breeding territory etc.

Question 21

Predator-prey relationships

Answer 21

Hard to show in lab.

Data from natural environments should be taken with caution.