BMAT 2020 - Biomass Q

Could someone show me the calculation for this question?

I used the following approach to solve this question:
the question is asking about the % of biomass transferred to secondary consumer(i.e from rose bush---->ladybird)
there was total of just one rose bush so x% of 800=10/50(considering there are a total of 50 ladybirds)
Hope this helps.


How did you decide the order of the trophic levels???
Because at the top there should be less biomass and less organisms

if you arrange by biomass: 1 ladybird - 2 aphid - 3 rosebud
if you arrange by number org: 1 rosebud - 2 ladybird - 3 aphid

I know we have to arrange by number of organisms here to solve, i’m confused as to why?

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I decided the trophic levels on the basis of given mass of a single organism in a particular trophic level as we know that when we move up the trophic level there’s a general gradation in the energy as well as biomass.
I don’t know whether i’m completely right but question also says we are moving from roses to ladybirds(rose bush----->aphid---->ladybird).
please correct me if i’m thinking wrong.


less biomass doesn’t necessarily mean less organisms, it depends on the surface area of the food! I think that’s the explanation haha

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