Ecology Revision Structured Questions

1. The humpback whale, Megaptera novaeangliae, is one of the world’s largest aquatic mammals. It can grow to a length of up to 15 metres and a mass of up to 36 000 kg. A large proportion of the mass of a humpback whale is a very thick layer of fat-filled cells stored under the skin, called blubber.
The humpback whales are seasonal feeders. They feed in polar regions during the summer
and then migrate to warmer temperate and tropical waters to mate and have their young during the polar winter.
(a) The figure below shows the organism in the food web. The humpback whale is a carnivore, feeding on krill and herring. The herring feeds on krill. Both the krill and herring feed on phytoplankton. Add arrows on the figure to show the direction of energy flow in the food web.

chij katong q7.PNG

(b) Construct a food chain in which the humpback whale is a tertiary consumer.

(c) Draw and label a pyramid of numbers that comprises three trophic levels.

(d)  One reason that the humpback whale has managed to reach its enormous size is
because it is a member of a simple food web.
In terms of energy transfer, explain how the humpback whale is able to reach such a large size.

2. The figure below shows the feeding relationships of organisms in a food web found in the South Pole region.

northland q6.PNG

(a) With reference to the figure above, draw a pyramid of biomass with 4 trophic levels.

(b)  Explain your answer to part (a).

(c)  Explain why large amounts of pesticides are found in the bodies of penguins despite no farming activity in the South Pole region.

3.  The figure below shows how the energy flows through part of the food chain.

serangoon q3.PNG

(a) (i)  What is the source of energy input in the above system?

(ii)  Write an equation to show how the animal receives energy from the food when oxygen is present.

(b) State and explain how energy is lost from the cow at B and C.

(c) What percentage of the energy is available to consumers and decomposers? Show your working.

(d)  The figure below shows a hom fly, a parasite which feeds on the blood of the cattle. lt leads to lower weight and milk production in the cattle. There can be up to 50,000 horn flies feeding on one cattle.serangoon q3 b.PNG

(i)  Draw a food chain of the above situation when the cow is infested with the hom flies. Also indicate where in the food chain does enter.

(ii)  Draw a Pyramid of numbers and a Pyramid of biomass of the above food chain.

(e) What is a carbon sink? Give an example of a carbon sink.



1. (a) phytoplankton to herring / krill, krill to herring, herring and krill to whale

(b) phytoplankton –> krill –> herring –> humpback whale

(c)  correct labels (phytoplankton/ krill/ humpback whale); correct shape


abundant food available

– feeding on more than one trophic level;
– phytoplankton efficient at converting light energy –> can support large population of primary consumers;
– no competition from other predators for food
– efficient feeding mechanism
– food consumed has few indigestible / inedible parts/ contains high calories;

efficient energy transfer
– less energy lost in short food chains 9 more energy reaches the top consumer
– example of how energy is lost – energy used to support the organisms in the different trophic levels, energy lost to surrounding as heat

2. (a)

northland q6 ans.PNG

(b) Trophic level 1 has a smaller biomass than trophic level 2 because microscopic algae are extremely small and hence the total biomass is small;

Lesser energy is transferred from one trophic level to the next because energy is lost through heat by respiration;

As lesser energy is transferred, it can only support a smaller biomass, hence biomass decreases from trophic level 2 to 4

(c) The microscopic algae may have absorbed large amounts of insecticides at an area outside the south pole region;

The shrimp feeds on the algae, squid feeds on the algae and the insecticides accumulates in the body of the squid and is not excreted;

Penguin may feed many squids which contains insecticides and insecticides accumulate and amplifies in concentration

3. (a) (i) The Sun

(ii) Glucose + oxygen –> carbon dioxide + water + energy


  • Energy is lost as heat energy in respiration at B
  • And as waste e.g urea and faeces in excretion / egestion at C

(c)  4+62= 66 J ; 66/100 x100= 66%

(d) (i) Light energy from the sun –> grass –> cow –> horn flies

(ii) serangoon q3 ans.PNG

(e) A carbon sink is an area that stores carbon compounds for an infinite period. lt stores more carbon than it releases. e.g Forest , ocean



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