AQA June 2013 Paper. Is there a mistake? [pyramids of biomass]

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Adh231
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#1
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For the june 2013 paper for aqa (http://filestore.aqa.org.uk/subjects...P-QP-JUN13.PDF), question 9a asks you tick the correct pyramid of biomass (giving you 3 options) and the markscheme (http://filestore.aqa.org.uk/subjects...W-MS-JUN13.PDF) says the right answer is something which looks like a pyramid of numbers. I have always been taught that pyramid ofh biomass is pyramid shaped (there was a pyramid shaped option), the question also gives you a graph with the population of plant plankton. I think the question was meant to say tick the correct pyramid of numbers, but instead it says biomass.
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(Original post by Kartheyan)
For the june 2013 paper for aqa (http://filestore.aqa.org.uk/subjects...P-QP-JUN13.PDF), question 9a asks you tick the correct pyramid of biomass (giving you 3 options) and the markscheme (http://filestore.aqa.org.uk/subjects...W-MS-JUN13.PDF) says the right answer is something which looks like a pyramid of numbers. I have always been taught that pyramid ofh biomass is pyramid shaped (there was a pyramid shaped option), the question also gives you a graph with the population of plant plankton. I think the question was meant to say tick the correct pyramid of numbers, but instead it says biomass.
Uhm im pretty sure its the first one, like what? I'm retaking this in 4 days good luck!
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(Original post by Kartheyan)
For the june 2013 paper for aqa (http://filestore.aqa.org.uk/subjects...P-QP-JUN13.PDF), question 9a asks you tick the correct pyramid of biomass (giving you 3 options) and the markscheme (http://filestore.aqa.org.uk/subjects...W-MS-JUN13.PDF) says the right answer is something which looks like a pyramid of numbers. I have always been taught that pyramid ofh biomass is pyramid shaped (there was a pyramid shaped option), the question also gives you a graph with the population of plant plankton. I think the question was meant to say tick the correct pyramid of numbers, but instead it says biomass.
Sheesh this really does worry me
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LL92
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Pyramids of biomass do usually look like actual pyramids, you're right, but only under stable conditions, where the populations of predators and prey stay roughly in proportion with each other.

The graph of population sizes on the bottom of the page show that the population sizes don't stay in proportion though, there's a cycle. The number of plant plankton increase, which causes an increase in the number of animal plankton, which subsequently causes the plant plankton population to crash, at around June.

The question asks for the pyramid of biomass in June. So you need to look at the graph and see how the populations of animal and plant plankton are doing in relation to each other. I think the answer in the mark scheme is correct, in this case.
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Adh231
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(Original post by LL92)
Pyramids of biomass do usually look like actual pyramids, you're right, but only under stable conditions, where the populations of predators and prey stay roughly in proportion with each other.

The graph of population sizes on the bottom of the page show that the population sizes don't stay in proportion though, there's a cycle. The number of plant plankton increase, which causes an increase in the number of animal plankton, which subsequently causes the plant plankton population to crash, at around June.

The question asks for the pyramid of biomass in June. So you need to look at the graph and see how the populations of animal and plant plankton are doing in relation to each other. I think the answer in the mark scheme is correct, in this case.
Thanks for the reply, but I'm a bit confused. I thought pyramids of biomass shows energy transfer, for example in the first trophic level (producers) they photosynthesise converting light to glucose and then some of it to biomass, then herbivores eat the plants and convert some of the plant's biomass to their biomass. If the markscheme was right, that means that somehow animal plankton by eating the plant plankton has made more biomass than the plant plankton had. Also pyramids of biomass have nothing to do with population of animals.
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LL92
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(Original post by Kartheyan)
Thanks for the reply, but I'm a bit confused. I thought pyramids of biomass shows energy transfer, for example in the first trophic level (producers) they photosynthesise converting light to glucose and then some of it to biomass, then herbivores eat the plants and convert some of the plant's biomass to their biomass. If the markscheme was right, that means that somehow animal plankton by eating the plant plankton has made more biomass than the plant plankton had. Also pyramids of biomass have nothing to do with population of animals.
'Biomass' seems to mean different things depending on the subject in question, so I don't blame you for being confused! In the energy industry, biomass does mean the amount of energy that can be gained from burning biological mass, like wood. In biology though, biomass just means the mass of biological matter, which in this case is the mass of the plant plankton, animal plankton, and sharks. For example, if we had a block of solid wood with a volume of 5 meters cubed, the biomass here would be 5 meters cubed. So, the amount of biomass does have a relation to the population of the animals, since a population of 100 trees is going to have a larger biomass than a population of 10 trees (assuming the trees are always the same size).

The animal plankton have a higher biomass in June because they've consumed the biomass of plant plankton that was around in April. The biomass that was in the plant plankton has been transferred to the animal plankton biomass. The biomass pyramid would look like the first pyramid in April, but in June it looks like the third.

I hope that helps!
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Adh231
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(Original post by LL92)
'Biomass' seems to mean different things depending on the subject in question, so I don't blame you for being confused! In the energy industry, biomass does mean the amount of energy that can be gained from burning biological mass, like wood. In biology though, biomass just means the mass of biological matter, which in this case is the mass of the plant plankton, animal plankton, and sharks. For example, if we had a block of solid wood with a volume of 5 meters cubed, the biomass here would be 5 meters cubed. So, the amount of biomass does have a relation to the population of the animals, since a population of 100 trees is going to have a larger biomass than a population of 10 trees (assuming the trees are always the same size).

The animal plankton have a higher biomass in June because they've consumed the biomass of plant plankton that was around in April. The biomass that was in the plant plankton has been transferred to the animal plankton biomass. The biomass pyramid would look like the first pyramid in April, but in June it looks like the third.

I hope that helps!
Thanks for the help.
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