Ecology

Question 1

Decay occurs in a compost heap.

https://cdn.discordapp.com/attachments/1072263133764268164/1225841067891363913/image.png?ex=66229875&is=66102375&hm=ac5cd68ec386dba1a8c567a7559ed28e2e82c4a5ad5e9cae54ada5d6f060fc46&

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. [6 marks]

Got 2/6 marks in the Easter holiday.

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

Level marked - 2 levels.
For Level 2 processes in microorganisms and in plants should be considered.

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. [2 marks]

Got 0/2 marks in the Easter holiday.

Answer 2

too few quadrats
or quadrat too small
allow sample size too small

sample may not be representative of the lawn
allow quadrats may not have been placed randomly

Question 3

Mackerel eat krill and squid.
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. [2 marks]

Got 1/2 marks in the Easter holidays.

Answer 3

any two from:
* (losses due to) non-eaten parts (of squid / krill)
* respiration or respiring (in mackerel)
* excretion (by mackerel)

Question 4

Too many herring were caught by fishermen between 1960 and 1977.
Herring can live for up to 12 years and begin to reproduce when 3 to 4 years old.
Laws have been introduced to help conserve herring:
* 1977 to 1981 – herring fishing was banned in the North Sea
* 1984 to present day – control of mesh size of fishing nets
* 1997 to present day – fishing quotas were introduced
* 1998 to present day – herring fishing was banned in breeding grounds during the breeding season.
Figure 12 shows how a minimum mesh size helps to conserve herring.

https://cdn.discordapp.com/attachments/1072263133764268164/1225845492806586418/image.png?ex=66229c94&is=66102794&hm=1ef21d3dfa9d39d0bdc40a00869ed2d438873e933243474d91ce9c46155b5e7d&

Evaluate the effect of these laws on the conservation of herring stocks.
Use data from Figure 11 and information from Figure 12 in your answer. [6 marks]

Got 3/6 marks in the Easter holidays.

Answer 4

figures may be given without units (million tonnes) throughout

points for:
* small fish are not caught so can live long enough to reproduce
* biomass / stocks have generally increased after these laws introduced
* ’77-’81 law (total ban) resulted in increase in biomass, eg 0.1 to 0.48 or to 0.9 by ’84
* ’84 law (mesh size) resulted in increase in biomass, eg 0.9 to 1.8 (by ’90)
* ’97 law (quotas) resulted in increase, eg 1.15 to 1.25
* ’98 law (ban in breeding season) resulted in increase, eg 1.25 to 2.5

points against:
* could be a cause other than the law or correlation does not necessarily indicate causal relationship or other factors
* laws superimposed so can’t necessarily tell the effect of each
* each law results in an increase followed by a decrease
* quotas lead to dead fish being thrown back into sea

Level marked - 3 levels.
For Level 3 points both for and against must be considered
together with appropriate use of data.