3.2 Distributions of organisms

Question 1

Two factors which can affect the distribution of organisms

Answer 1

Biotic
Abiotic

Question 2

Biotic factor

Answer 2

Factors in the ecosystem related to biological living things

Examples :
Food availability
Predation
Grazing
Disease
Competition

Question 3

Light intensity

Answer 3

Measure: Light metre
Error: There may be a shadow cast over it
How to fix: Move away and don’t stand over it

Question 3

pH

Answer 3

Measure: Soil pH metre
Error: There may be some soil left from past site on it
How to fix: Wipe and clean between uses

Question 3

Temperature

Answer 3

Measure: Thermometer
Error: Wrong reading as it is still the previous reading
How to fix: Give it time to go back to normal

Question 4

Predator-prey interaction

Answer 4

A) Predator numbers are low, prey numbers are high. Predator numbers start to increase due to their being more prey available
B) Predator numbers increase which prey numbers decrease due to more prey being eaten
C) Due to low numbers of prey, predator numbers start decreasing
D) Due to low numbers of predators, prey species numbers start to increase

Question 4

Abiotic factors

Answer 4

Non-living factors in the ecosystem that can be measured

Examples :
Light intensity
Temperature
Moisture
pH

Question 5

Soil moisture

Answer 5

Measure: Moisture metre
Error: If the readings are from previous site
How to fix: Wipe and clean between uses

Question 6

Two sampling methods

Answer 6

Pitfall traps
Quadrats

Question 7

Pitfall traps

Answer 7

They are used to measure ground dwelling invertebrates

Source of error
-No drainage holes: they could flood causing drowning
-Not level to ground: they won’t fall in trap
-Not covered: predators may eat invertebrates

Question 8

Quadrats

Answer 8

They are used to sample low growing plants such as clovers and daisies

Source of error
-Not thrown randomly: throwing randomly eliminates bias
-Size: small quadrats may lead to results that aren’t representable

Reliability
The reliability of sampling can be increased by repeating the technique multiple times

Validity
The validity of quadrat experiment can be increased by randomly throwing the quadrat. This eliminates bias and provides a more representative sample

Question 9

Indicator species

Answer 9

They are organisms that by its presence or absence indicates the level of pollution in the area. Examples include lichens, mayfly nymphs and sludge worms

Question 9

Paired statement keys

Answer 9

They can help identify unknown organisms based upon their characteristics. To use, you must star5t at the first statement and work your way through.