Key Area 3.2 - Distribution Of Organisms

Question 1

Define the term abiotic factors

Answer 1

Non-living conditions which can influence where plants or animals live

Question 2

Define the term biotic factors

Answer 2

Factors in the ecosystem related to living things

Question 3

Give biotic factors that can affect the distribution of organisms in an ecosystem

Answer 3

Competition for resources 
Disease 
Food availability 
Predation 
Grazing

Question 4

Give abiotic factors that can affect the distribution of organisms in an ecosystem

Answer 4

Light intensity
Moisture
pH
Temperature

Question 5

Identify ways you can measure abiotic factors

Answer 5

Light meters to measure light intensity

Thermometer to measure temperature

Soil moisture metres and soil pH metres to measure the pH and moisture of the soil

Question 6

Describe how light metres can be used to measure light intensity

Answer 6

The metre is held at the soil surface and pointed in the direction of the maximum light intensity, then the metre is read

Question 7

Give possible sources of error of using light meters and how to minimise them

Answer 7

Inaccurate readings
- do not cast a shadow over the light meter

Unreliable results
- take more samples and calculate on average

Changing weather such as cloud cover
- all measurements should be taken at same time of day

Question 8

Identify what can be used to measure light intensity

Answer 8

Light meters

Question 9

Identify what can be used to measure the pH and moisture of the soil

Answer 9

Soil moisture meters and soil pH meters

Question 10

Describe how soil moisture meters and soil pH meters are used to measure the pH and moisture of the soil

Answer 10

Both are used by pushing the probe into the soil and reading the meter

Question 11

Give possible sources of error using soil moisture meters and soil pH meters and how to minimise them

Answer 11

Probe not dry at start
- wipe the probe between each reading

Unreliable results
- take more samples and calculate an average

Question 12

Identify what can measure the temperature of the air

Answer 12

Thermometer

Question 13

Identify what can be used to measure temperature of the soil

Answer 13

Temperature probe

Question 14

Identify what can be used to sample plants

Answer 14

Quadrat

Question 15

Describe how a quadrat is used

Answer 15

It marks off an exact area so that the plants in that area can be identified and counted

Question 16

Describe why a quadrat is used

Answer 16

It’s impossible to count all the plants in a habitat, so a sample is taken

A technique often used to sample plants is a quadrat

Question 17

Give sources of errors using a quadrat and how to minimise them

Answer 17

Sampling doesn’t represent entire field
- quadrats should be thrown RANDOMLY

Unreliable results
- take any quadrat samples and calculate an AVERAGE

Plants misidentified or overlooked
- use an identification key

Question 18

Identify what can be used to sample animals

Answer 18

Pitfall trap

Question 19

Describe how a pitfall trap is used

Answer 19

Often used to sample the small invertebrates living in the ground

Question 20

Give sources of errors using pitfall traps and how to minimise them

Answer 20

Birds eat trapped animals
- camouflage the opening of the trap

Within trap, some animals eat other animals
- check traps regularly, removing animals

Rainwater collects in trap killing animals
- punch holes in the base of the trap

Type of animals trapped may not be a representative of the area
- set up more pitfall traps

Question 21

Define the term indicator species

Answer 21

A species that by its presence or absence indicates the level of pollution in an ecosystem

Question 22

Give limitations for quadrat sampling

Answer 22

Generally only suitable for low-growing, rooted plants or for slow-moving or motionless animals

Quadrat size

Reliability limited by number of samples possible

Question 23

Give limitations of pitfall trap sampling

Answer 23

Generally only suitable for small, surface-crawling invertebrates

Pitfall trap size

Reliability limited by number of traps set

Question 24

Identify why identification keys are used

Answer 24

Keys are needed to easily identify unknown organisms

They are more reliable because an organism may be collected that doesn’t look identical to the picture

The numbers in the right hand side show which statement to use next until the name of the organism is found

Question 25

Identify factors affecting the biodiversity in an ecosystem

Answer 25

Abiotic factors Biotic factors Human influences which can be abiotic or biotic

Question 26

Identify abiotic factors that affect biodiversity and how they affect biodiversity

Answer 26

Pollution - such as burning of fossil fuels, polluting the atmosphere - loss of lichens and other plants which then affects food chains Discharging untreated sewage into waterways - deoxygenation of water and collapse of food chains

Question 27

Identify biotic factors that affect biodiversity and how they affect biodiversity

Answer 27

Hunting and fishing Overhunting of game animals - extinction of key species and wider effects on many food chains Overfishing for white fish - loss of fish stocks and collapse of marine food chains Conservation Captive breeding of endangered species - increases wild populations through release schemes

Question 28

Describe the use of freshwater invertebrates

Answer 28

Indicators of water pollution

Question 29

Describe the use of hairy leafy and crusty lichens

Answer 29

Indicators of air pollution

Question 30

What are indicators of water pollution

Answer 30

Freshwater invertebrates

Question 31

What are indicators of air pollution

Answer 31

Hairy, leafy and crusty lichens