4.1 Ecosystems

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Question 17

Ecologists are investigating the role of detritivores in the decomposition of leaf litter in a temperate deciduous woodland. They placed identical samples of beech leaves into two types of litter bags with different mesh sizes:

Fine mesh bag (0.5 mm mesh): Excludes larger detritivores, allowing only microscopic decomposers (bacteria and fungi) to enter.
Coarse mesh bag (5.0 mm mesh): Allows both detritivores (such as earthworms and woodlice) and microscopic decomposers to enter.

They recorded the mass of the leaf litter in each bag at the start of the investigation and after 6 months.

Table 1: Mass of leaf litter during decomposition

Mesh type in bag	Mass at start ( $g\text{g}$ )	Mass after 6 months ( $g\text{g}$ )
Fine mesh	$125$	$89$
Coarse mesh	$125$	$53$

Calculate the percentage decrease in the mass of the leaf litter in the Fine mesh bag. Give your answer to 2 significant figures.

[3]

Calculate the percentage decrease in the mass of the leaf litter in the Coarse mesh bag. Give your answer to 2 significant figures.

[3]

Suggest why the presence of detritivores in the Coarse mesh bag leads to a higher rate of decomposition.

[2]

4.1 Ecosystems

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Question 17

Fine mesh bag (0.5 mm mesh): Excludes larger detritivores, allowing only microscopic decomposers (bacteria and fungi) to enter.
Coarse mesh bag (5.0 mm mesh): Allows both detritivores (such as earthworms and woodlice) and microscopic decomposers to enter.

They recorded the mass of the leaf litter in each bag at the start of the investigation and after 6 months.

Table 1: Mass of leaf litter during decomposition

Mesh type in bag	Mass at start ( $g\text{g}$ )	Mass after 6 months ( $g\text{g}$ )
Fine mesh	$125$	$89$
Coarse mesh	$125$	$53$

Calculate the percentage decrease in the mass of the leaf litter in the Fine mesh bag. Give your answer to 2 significant figures.

[3]

Calculate the percentage decrease in the mass of the leaf litter in the Coarse mesh bag. Give your answer to 2 significant figures.

[3]

Suggest why the presence of detritivores in the Coarse mesh bag leads to a higher rate of decomposition.

[2]

4.1 Ecosystems

Question 17

Table 1: Mass of leaf litter during decomposition

Markscheme

4.1 Ecosystems

Question 17

Table 1: Mass of leaf litter during decomposition

Markscheme

4.1 Ecosystems

Question 17

Table 1: Mass of leaf litter during decomposition

4.1 Ecosystems Questions

4.1 Ecosystems

Question 17

Table 1: Mass of leaf litter during decomposition

4.1 Ecosystems Questions