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AQA A Level Biology - Populations in Ecosystems Mark Scheme ()

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A useful mark scheme for the separate Populations in Ecosystems workbook for students to check and improve their answers and understanding.

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Cardinal Newman College
POPULATIONS PPQ MS




M1.(a) All the fish / all the species / all the populations / all the organisms;
Must indicate all / every species.
Reject answers that suggest other fish / organisms might be
present.
1




(b) (i) 1. Capture sample, mark and release;

2. Appropriate method of marking suggested / method of marking
does not harm fish;
2. E.g. Cutting a fin / attaching a tag / paint/marker.

3. Take second sample and count marked organisms;
3. May be awarded from equation if not given here.




4.
4. Accept any valid alternative to equation or answer
expressed
as a ratio.
3 max




(ii) One suitable reason;
Accept other valid answers, which must, however, relate to
breeding / only works if population constant.

E.g. population increases / changes (between first and second sample)
1




(c) 1. With different mouth eats different food / has different way of feeding /
specific mouth shape for specific food;
1. Catches more food and gas exchange are neutral

2. Competition between species / interspecific competition is reduced;
2. Reject intraspecific
2
[7]




M2. (a) Two marks for correct answer of 59/60 ((28 x 38) / 18);;


Page 1

, Cardinal Newman College
One mark for incorrect answer clearly derived from figures of 18, 28
and 38;
Ignore: any figures after decimal point.
2




(b) (i) Population changes;
Reject: population decreases

As young birds leave nest/join population;
Reject first point if (young) birds are leaving
population/migrating
2




(ii) (Would be likely to) catch all birds (again) in second
sample/sample sizes are the same;
Neutral: references to breeding

Birds (in territories and) not mixing with population;
Accept: idea of the population is divided

Only estimates number of birds in territories sampled/territory
sample not representative (of population);
2 max




(c) (Recording) DNA/base sequence is like marking
(animal)/wouldn’t need to mark;

(Finding identical/same base sequence) would show animal has
been caught/recorded before;
2
[8]




M3. (a) use of random numbers to place quadrats;
number of individuals counted in large number of quadrats;
little variation random, large variation - clustered;
3

(b) new plants grow attached to parent;
1

(c) less competition;

Page 2

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October 4, 2022
Number of pages
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Written in
2021/2022
Type
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