Edexcel Biology IGCSE 2B Unofficial Mark Scheme 10th June 2016

Tell me the questions which I'm missing out - I'll add them in.

1.a)
Respiration. (1)

1.b)
[Wind] pollination. (1)

1.c)
Producer and consumer. (2)

1.d)
Advantages of brushing hairs twice before closing:
Ensures the insect is there hence can catch it for a source of food hence energy for respiration.
Plant is efficient as it prevents wasting of energy by closing trap when no insects are present. (2)

1.e)
Protease enzyme pepsin etc. (1)

1.f)
Issue with microbes entering plant:
Can cause disease hence cause plant to die.
Can use up all the nutrients etc. by decomposing the food ingested by the plant. (2)

2.a)
Fish have different amounts of nitrogenous excretory products because they may be different species, have eaten different quantities and type of food etc. (1)

2.b)
Eutrophication when organic matter is leached into aquatic environment, decomposers e.g bacteria decompose the matter, releasing high concentration of nutrients and mineral ions hence algal bloom (rapidly growing algae population). Hence algae at surface block light from reaching algae at bottom of river/lake hence can't photosynthesise hence die hence large biomass which is decomposed by bacteria, using all the oxygen in the water, hence lack of oxygen for respiration in fish hence fish kill.

(Maybe) Could also talk about the ammonia being converted into nitrates and then hence amino acids and protein hence increasing growth and obviously the death of plants hence producers have negative effect on food chain. Main points however are above. (5)

3.a)
Independent variable is the type of plastic. (1)

3.b)
29.2 cm. (2)

3.c)
Reliable as repeats (equivalent) were used as he used 10 trays for each, used a variety of different independent variables and grew the plants for a long enough time (3 months). (2)

3.d)
Abiotic factors:
Temperature.
Type of soil.
Concentrations of CO2 and O2 for photosynthesis and respiration. (3)

6.a)
7mm. (1)

6.b)
Retinal cells in the back of the eye. (1)

6.c)
The pupil dilates to allow more light to enter the eye as the antagonistic radial muscles contract and circular muscles relax, allowing the diameter of the pupil to expand. (3)

I believe it was (insect) pollination rather than (wind) pollination, as it asked why the insects were needed. Also I put secondary consumer instead of just consumer - do you think it will count? Also for 6b I just got retina. What was the answer for 'suggest why the black sheet meant the plant grew faster' (or something like that)
Overally I defo found this paper easier than paper 1 but then again I think I made a lot of mistakes and strange answers

f-or trophic level I put a number so for example: trophic level 1 (for producer)
-I also put pH for question 3d)
-question 3c) average of results
-2a) on top of what you put i think (not sure) you can talk about different metabolism/digestive system as different species.

the placenta question is missing and the cholesterol in artery question

can you please remind me what was the question for 1b)

I believe it was (insect) pollination rather than (wind) pollination, as it asked why the insects were needed. Also I put secondary consumer instead of just consumer - do you think it will count? Also for 6b I just got retina. What was the answer for 'suggest why the black sheet meant the plant grew faster' (or something like that)
Overally I defo found this paper easier than paper 1 but then again I think I made a lot of mistakes and strange answers

Great haha literally all those points I wrote additionally as well but forgot to write them. Im not sure you'd get the mark for putting a number.

1.b) Why do other plants need to attract insects?

ok cool and do you know how many points the insect question was on

Tell me the questions which I'm missing out - I'll add them in.

1.a)
Respiration. (1)

1.b)
[Insect] pollination. (1)

1.c)
Producer and consumer. (2)

1.d)
Advantages of brushing hairs twice before closing:
Ensures the insect is there hence can catch it for a source of food hence energy for respiration.
Plant is efficient as it prevents wasting of energy by closing trap when no insects are present. (2)

1.e)
Protease enzyme pepsin etc. (1)

1.f)
Issue with microbes entering plant:
Can cause disease hence cause plant to die.
Can use up all the nutrients etc. by decomposing the food ingested by the plant. (2)

2.a)
Fish have different amounts of nitrogenous excretory products because they may be different species, have eaten different quantities and type of food etc. (1)

2.b)
Eutrophication when organic matter is leached into aquatic environment, decomposers e.g bacteria decompose the matter, releasing high concentration of nutrients and mineral ions hence algal bloom (rapidly growing algae population). Hence algae at surface block light from reaching algae at bottom of river/lake hence can't photosynthesise hence die hence large biomass which is decomposed by bacteria, using all the oxygen in the water, hence lack of oxygen for respiration in fish hence fish kill.

(Maybe) Could also talk about the ammonia being converted into nitrates and then hence amino acids and protein hence increasing growth and obviously the death of plants hence producers have negative effect on food chain. Main points however are above. (5)

3.a)
Independent variable is the type of plastic. (1)

3.b)
29.2 cm. (2)

3.c)
Reliable as repeats (equivalent) were used as he used 10 trays for each, used a variety of different independent variables and grew the plants for a long enough time (3 months). (2)

3.d)
Abiotic factors:
Temperature.
Type of soil.
Concentrations of CO2 and O2 for photosynthesis and respiration. (3)

3.e)
Why the black sheet resulted in faster growth:
Black is a good absorber of thermal radiation from the sun hence increases temperature to the optimal temperature for enzyme activity hence increase in photosynthesis and respiration rate.
Also prevents other organisms getting into soil and taking nutrients hence decreases competition. Also helps prevent growth of weeds etc. (4)

6.a)
7mm. (1)
e6.b)
Retinal cells in the back of the eye. (1)

6.c)
The pupil dilates to allow more light to enter the eye as the antagonistic radial muscles contract and circular muscles relax, allowing the diameter of the pupil to expand. (3)

for 3b) i thought it was 29.28 which i rounded to 29.3 since the results had one decimal place. I did 73.2/1000 and multiplied the result by 400

No, I forgot the calculation but the answer was like 29.21 or 29.23 and hence you rounded down. I checked with people on this as well.

to get 29.2 you must have done 73/1000 rather than 73.2. 73/1000 x 400 would give 29.3 whereas 73.2/1000 x 400 would give 29.28 (29.3)

why do i remember getting 28.9?