CAIE IGCSE Biology 19 Organisms & Their Environment
Practise tracing energy, constructing food webs, explaining nutrient cycles and interpreting changes in ecosystem populations.
- Syllabus
- 2026–2028
- Course
- Biology 0610
Covered syllabus points
19. Organisms and their environment question 1
The dominant grass species in an African grassland ecosystem are star grass and red oat grass.
- Star grass is eaten by antelope species, such as topi and Thomson's gazelle.
- Smaller animals such as mice and grasshoppers feed on red oat grass.
- Topi and Thomson's gazelle are eaten by predators such as cheetahs, lions and serval cats.
- Grasshoppers and mice are eaten by serval cats and tawny eagles.
- Vultures feed on dead mammals.
Fig. 1.1 shows part of the food web for this ecosystem.
Fig. 1.1
Question (a)
(a)
Complete the food web by writing the names of the correct organisms in the boxes in Fig. 1.1.
[ 3 ]
Question (b)
(b)
Name the trophic level of the following species.
star grass
topi
[ 2 ]
Question (c)
(c)
State the principal source of energy for the food web shown in Fig. 1.1.
[ 1 ]
Question (d)
(d)
State what happens to energy when it leaves a food web.
[ 1 ]
Question (e)
(e)
Explain why there are no more than four trophic levels in the food web shown in Fig. 1.1.
[ 3 ]
19. Organisms and their environment question 2
The diagram shows a food web.
What do the arrows represent?
A
the absorption of oxygen
B
the absorption of water
C
the flow of energy
D
the release of carbon dioxide
19. Organisms and their environment question 3
Question (a)
(a)
Fig. 6.1 shows part of the carbon cycle in the ocean.
Fig. 6.1 (not to scale)
[ 5 ]
Question (i)
(i)
Phytoplankton contain chlorophyll.
Explain how phytoplankton lower carbon dioxide concentrations in the atmosphere.
[ 2 ]
Question (ii)
(ii)
Suggest the role of zooplankton in this ecosystem.
[ 1 ]
Question (iii)
(iii)
State the names of two processes that add carbon dioxide to the atmosphere.
1
2
[ 2 ]
Question (b)
(b)
Fig. 6.2 shows the pyramid of energy for a food chain in an ocean ecosystem.
Fig. 6.2
[ 6 ]
Question (i)
(i)
On Fig. 6.2, label the trophic level containing herbivores.
[ 1 ]
Question (ii)
(ii)
Explain why pyramids of energy usually have fewer than five trophic levels.
[ 3 ]
Question (iii)
(iii)
State two advantages of using a pyramid of energy rather than a pyramid of biomass to represent a food chain.
1
2
[ 2 ]
19. Organisms and their environment question 4
Carp are a type of fish. Researchers in Brazil measured the body lengths of a population of carp in a river in 1998 and again in 2008.
Histograms of their results are shown in Fig. 2.1.
Fig. 2.1
Define the term population.
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