3.2 Distribution of organisms

Question 1

Name 5 Biotic factors.

Answer 1

Competition, disease, food availability, grazing and predation

Question 2

Name 4 Abiotic factors.

Answer 2

Light intensity, moisture, pH and temperature.

Question 3

What is an indicator species?

Answer 3

Species that by their presence or absence indicates environmental quality.

Question 4

What device can we use to measure Light intensity?

Answer 4

Light meter.

Question 5

What device can we use to measure moisture in soil?

Answer 5

Moisture meter.

Question 6

What device can we use to measure pH in soil or water?

Answer 6

pH meter or Universal Indicator and a pH scale.

Question 7

What are some possible errors when measuring light intensity and how can we minimise them?

Answer 7

• May cast a shadow, to prevent this stand to one side.

- Changing cloud cover, repeat readings to improve reliability

Question 8

What are some possible errors when measuring moisture in the soil and how can we minimise them?

Answer 8

• Moisture left on probe, to prevent this dry the probe between readings.
• Too small sample size, to prevent this repeat readings to improve reliability.

Question 9

What are some possible errors when measuring pH in soil and how can we minimise them?

Answer 9

• Contamination of sample, to prevent this dry probe between readings.
• Too small sample size, to prevent this repeat readings to improve reliability.

Question 10

What is a quadrat used to sample?

Answer 10

Plants and slow moving animals

Question 11

What are some possible errors which can occur when using quadrats and how can we minimise them?

Answer 11

• Estimate is not representative of the area. Make sure the quadrat is placed randomly.
• Organisms mis-identified. Use an identification key to identify organisms.
• organisms are double counted. Establish a rule to only count plants inside and touching left and bottom of quadrat.

Question 12

What are some possible errors when using pitfall traps and how can we minimise them?

Answer 12

• Birds or other animals may eat what has been trapped - camouflage the trap.
• organisms don’t fall in the trap. Make sure it is level with the soil.
• some animals may eat others, check trap regularly.

Question 13

What is a biotic factor

Answer 13

A living factor affecting an ecosystem

Question 14

What is an abiotic factor?

Answer 14

A non living factor affecting an ecosystem

Question 15

What is a pitfall trap used to sample?

Answer 15

Crawling invertebrates found in the soil.

Question 16

How can the RELIABILITY of an investigation be improved?

Answer 16

Repeat the independent variable e.g sample more quadrats in an area.

Question 17

How can the VALIDITY of an investigation be improved?

Answer 17

Reduce any errors e.g. make sure to check traps regularly.

Question 18

The absence of which species can indicate high levels of sulphur dioxide in the atmosphere?

Answer 18

Lichens

Question 19

The presence of freshwater invertebrates like mayfly nymph indicates what about water quality?

Answer 19

There is a lot of dissolved oxygen in the water.