IBESS
2.1 Practice questions
1. For a named ecosystem you have studied, draw a food-web diagram. The diagram should show the names
of at least seven organisms belonging to at least three trophic levels. Clearly identify the trophic level to
which each organism belongs.
[5] (ES May05a p2 q1)
2. With the help of a diagram, explain the term pyramid of numbers.
3. Define the term ecosystem.
4.
[2]
[4]
(ES Nov04 p2 q7)
(ES May04a p2 q1a)
(a)With the help of examples, distinguish between a food chain and a food web. [5] (ES May04a p2 q6a)
(b) Explain, with the help of a diagram, how the flow of energy along a food-chain illustrates the first
law of thermodynamics. [8]
(ES May04a p2 q6b)
(c)Explain how the extinction of one species in an ecosystem can have an influence on the abundance
of many other species. [4] (ES May04a p2 q6c)
5. For a named species in an ecosystem you have studied,
state and explain how one biotic factor may 
have
influenced that species’ abundance.
[3] (ES May03a p2 q1d)
 diagram

6. The
below shows
the
energy flow in a river ecosystem in temperate latitudes. All energy values





are kJ m−2 yr−1. (ES May02a p2 q2a)










 
















 


















(a) Construct
food chain diagram of four trophic levels taken from this food web. [2]
a complete

7. Which statement about trophic levels is correct?
(ES May06a p1 q5)
A. The biomass per unit area usually increases with each trophic level.
B. A trophic level defines the feeding rate of an organism in a food chain.
C. No organism can occupy more than one trophic level in a food web.
D. Naturally occuring terrestrial food chains rarely have more than five trophic levels.

8. Which of the following are found at the second trophic level in a food chain? (ES May06a p1 q6)
A. Carnivores B. Herbivores C. Secondary consumers
D. Primary producers
9. Which of the following is the best definition of a population?
(ES May06a p1 q7)
A. The number of individuals of a given species
B. The number of individuals of the same species in a given area
C. The number of species in a given area
D. The number of individuals in a given area
10. Which unit is the most appropriate to express the gross primary productivity of an ecosystem?
A. kg
B. kg y-1 C. kg m-2
D. kg m-2 y-1
(ES May06a p1 q8)
11. Oxpeckers (tickbirds) are small birds that feed on ticks which infest large animals like rhinoceros.
(ES May06a p1 q24)
What are the relationships between these species?
12. What information is necessary to calculate the net primary productivity of an ecosystem?
(ES May06a p1 q26)
I.
II.
III.
IV.
The biomass produced by photosynthesis per unit area per unit time.
The biomass lost by the plant by respiration per unit area per unit time.
The biomass gained by heterotrophic organisms per unit area per unit time.
– 2 – per unit area
M06/4/ENVSY/SP2/ENG/TZ0/XX
The biomass potentially available to consumers
per unit time.
A. I only
B. I and II only
SECTION A
C. I, II and III only
D. I, II, III and IV
Answer all the questions in the spaces provided.
13. 1.
(a)The figure below represents a pyramid of biomass for a food chain in an aquatic ecosystem.
(ES May06a p2 q1ab)
Fish: 3.40 g m-2
Zooplankton: 2.25 g m-2
Phytoplankton: 3.75 g m-2
Suggest two reasons why the biomass of fish may be greater than the biomass of zooplankton.
(a)
Suggest two
zooplankton.
California - 14/412
.......................................................................
[2]
–3–
–3–
M06/4/ENVSY/SP2/ENG/TZ0/XX
M06/4/ENVSY/SP2/ENG/TZ0/XX
(Question 1 continued)
(Question 1 continued)
(b) The productivity: biomass ratio (P:B) represents the annual net productivity per unit of biomass. For
(b) the
The
productivity:
biomass
(P:B)
represents
the annual
productivity
unit of 2.2 g
example, from
P:B
ratios given
belowratio
it can
be seen
that each
gram net
of fish
biomassper
produces
(b) The productivity: biomass ratio (P:B) represents the annual net productivity per unit of
biomass. For example, from the P:B ratios given below it can be seen that each gram of
of new biomass biomass.
annually.
For example, from the P:B ratios given below it can be seen that each gram of
Using the data in (a) and the P:B ratios below, calculate the productivity for each trophic level and plot
Using the data
in (a)
and the P:B ratios
below, calculate the productivity for each trophic
a pyramid of productivity
on the
axes
[3] below,
Using the data
in (a)
andbelow.
the P:B ratios
calculate the productivity for each trophic
level and plot a pyramid of productivity on the axes below.
level and plot a pyramid of productivity on the axes below.
Trophic Level
Trophic Level
Fish
Fish
Zooplankton
Zooplankton
Phytoplankton
Phytoplankton
[3]
[3]
P:B ratio/yr-1-1
P:B ratio/yr
2.2
2.2
14.00
14.00
60.00
60.00
Fish:
Fish:
................................................................
................................................................
................................................................
................................................................
Zooplankton: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Zooplankton: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
................................................................
................................................................
Phytoplankton: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Phytoplankton: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
................................................................
................................................................
(This question continues on the following page)
(This question continues on the following page)
14. Which of the following are examples of mutualism? (ES May05a p1 q9)
I. Bacteria fixing nitrogen in the roots of plants
II. The pollination relationship between flowering plants and insects
III. Lions hunting zebras
IV. Mosquitos spreading malaria
2206-6411
A. I and II only
2206-6411
B. III and IV only
C. I, II and III only
0311
0311
Turn over
D. I, II, III and IVCalifornia - 19/412
Turn over
California - 19/412
15. If the producer biomass in an ecosystem is 300 kg ha-1, what is the approximate secondary consumer
biomass (kg ha-1) likely to be in the same ecosystem?
(ES May05a p1 q14)
A. 3000
B. 300
C. 30
D. 3