Key area 2- Distribution of Organisms

Question 1

What are biotic factors? Give examples.

Answer 1

Living factors e.g. competition for resources, disease, food availability, grazing and predation.

Question 2

What are abiotic factors? Give examples.

Answer 2

Non-living factors e.g. light intensity, moisture, pH and temperature.

Question 3

Give examples of factors that increase and decrease the biodiversity of an ecosystem.

Answer 3

Some factors such as warm temperatures increase the biodiversity of an ecosystem while others such as low levels of grazing decrease the biodiversity of an ecosystem.

Question 4

What can both biotic and abiotic factors affect?

Answer 4

The biodiversity and the distribution of organisms.

Question 5

How is light intensity measured?

Answer 5

Light intensity is measured using a light meter, the sensor is held upwards and a reading is taken from the scale. The light sensor may be inadvertently shaded so it is important to ensure all users stand clear.

Question 6

How is soil moisture and pH measured?

Answer 6

Soil moisture and pH are measured using a moisture meter or pH meter, the probe is inserted into the ground and a reading is taken from the scale. The probe on the meter may retain soil from a previous sample so it is important to wipe the probe in between readings.

Question 7

How is temperature measured?

Answer 7

Temperature is measured using a thermometer, the thermometer is placed in an open area and a reading is taken from the scale. Placing the thermometer in direct sunlight or holding it in a warm hand may provide an inaccurate reading so it is important to place the thermometer in a shaded area.

Question 8

What are some ways to sample animals and plants?

Answer 8

Quadrats, pitfall traps, branch/tree beating and tullgren funnels.

Question 9

How can quadrats be used for sampling?

Answer 9

Quadrats are thrown randomly and the number of squares containing the organism of interest are counted. Quadrats only sample a small proportion of the investigated area therefore it is important to throw the quadrat randomly, several times and calculate an average.

Question 10

How can pitfall traps be used for sampling?

Answer 10

Pitfall traps are sunk into the ground and camouflaged to allow invertebrates to fall in. It is important to ensure the trap is level with the soil and camouflaged so insects will fall in.

Question 11

What are indicator species?

Answer 11

Indicator species are species that by their presence or absence indicate environmental quality/levels of pollution.