distribution of organisms 3.2

Question 1

what are biotic factors

Answer 1

living factors which affects ecosystem

Question 2

the 5 biotic factors

Answer 2

competition for resources, disease, food availability, grazing and predation

Question 3

over-grazing

Answer 3

can lead to plant species being destroyed therefore biodiversity is medium

Question 4

under-grazing

Answer 4

can lead to a small number of very vigorous plants species becoming dominant therefore biodiversity is low

Question 5

moderate-grazing

Answer 5

leads to high biodiversity of plant species because faster growing plants that shade out light are held in check

Question 6

what are abiotic factors

Answer 6

non-living factors which affect ecosystems

Question 7

four abiotic factors

Answer 7

light intensity, moisture, pH and temperature

Question 8

predation

Answer 8

• as the predation of the hare increases there is more food for the lynx so their population also increases
• this reaches a point where too many hares are eaten and their population decreases
• now with less food to eat, the lynx population decreases allowing more hares to survive

Question 9

light intensity

Answer 9

• apparatus, light meter
• source of error, casting a shadow over meter, variation of light intensity and clouds during the day
• how to minimise error, ensure the light panel is not shaded, take several readings at the same time of day

Question 10

moisture

Answer 10

• apparatus, moisture meter
• source of error, probe might be damp or dirty from previous measurements
• how to minimise error, dry and clean probe before use

Question 11

temperature

Answer 11

• apparatus, thermometer
• source of error, probe not left long enough in soil
• how to minimise error, leave the probe for several minutes

Question 12

pH

Answer 12

• apparatus, pH meter
• source of error, probe isn’t fully inserted
• how to minimise error, insert probe fully

Question 13

line transect

Answer 13

can be used to investigate how abiotic factors can affect the biodiversity in a habitat

Question 14

sampling

Answer 14

when a small number of organisms are counted which is representative to a particular ecosystem and the total population can be estimated

Question 15

why do we sample an ecosystem

Answer 15

1) to investigate which organisms live there
2) to investigate how abundant these organisms are
3) to investigate the reasons why the organism lives there

Question 16

quadrat

Answer 16

-organisms being sampled, slow moving organisms and low growing plants

-possible sources of error, number of quadrants is too small
is the organism in or out of the quadrat
unfair representation

-ways to minimise error, use a large number of quadrats and place randomly
decide on a rule before sampling and apply consistently

Question 17

pitfall trap

Answer 17

-organism being sampled, small invertebrate rates

-possible sources of error, animals may avoid the trap
animals may escape or be eaten
some animals may be missed

-ways to minimise error, ensure trap is hidden
place alcohol in the trap which kills organisms
check trap regularly
set multiple traps

Question 18

quadrat problem solving

Answer 18

1) find the total area of the field
2) state the number of organisms being asked
3) calculate the estimate number of organisms asked

area of field x total number of (daisys)

Question 19

indicator species

Answer 19

species that by their presence or absence indicate environment quality/ levels of pollution