ecosystem test

Question 1

Decay occurs in a compost heap.
FIGURE 7 shows a compost heap.
FIGURE 7
Describe:
* how microorganisms in the layers of soil help to
recycle chemicals in the dead plants
* how the chemicals are used again by living plants.

Answer 1

in microorganisms
* digestion or large molecules to small molecules
* enzymes or named example
* respiration
* production of carbon dioxide
* release of mineral ions or named example such as nitrate /
phosphate / magnesium
in plants
* carbon dioxide (from air) taken in by leaves
* by diffusion
* via stomata
* carbon dioxide used in photosynthesis
* making glucose / sugar / starch / cellulose or making other
correctly named example
* (named) ions taken in by roots
* by active transport
* nitrate ions for making amino acids / proteins / DNA / chlorophyll
* phosphate for making DNA

Question 2

Using the mean from this investigation to calculate the number of daisy plants on the
lawn may not be accurate.
Give two reasons why

Answer 2

too few quadrats
or quadrat too small
sample may not be
representative of the lawn

Question 3

How should the student decide where to place the quadrat?
Give the reason for your answe

Answer 3

(grid and) coordinates
to achieve randomness

Question 4

The animals in Figure 9 get their energy by eating other organisms.
Describe how the algae get energy.

Answer 4

from light / sunlight
absorbed by chlorophyll /
chloroplasts

Question 5

The biomass of mackerel is much less than the combined biomass of krill and squid.
One reason for this is that the mackerel cannot digest all parts of the krill and squid.
Give two other reasons.

Answer 5

respiration or respiring (in
mackerel)
* excretion (by mackerel)