KS4 Biology Test 1: Ecology
Please do not write on this question paper
1. This diagram shows a food web for some of the organisms that live in a freshwater
aquarium.
mites
loach
caddis larvae
mussels
snails
waterfleas
algae
diving beetles
hoglice
pondweed
water boatmen
plant debris
(a) From this food web name: a producer; a herbivore; a secondary consumer;
and an omnivore.
(4)
(b) Use the information from the food web to draw a food chain that contains four
organisms.
(2)
(c) Give two abiotic (physical) factors that might affect the size of the population
of algae in the aquarium.
(2)
(d) Explain how an increase in the population of algae might affect the
population of water fleas.
(2)
(e) Explain how a decrease in the population of snails might affect the population
of mussels.
(2)
(f) There are two loach in the aquarium. These are small fish about 50 mm in
length. There are 30 snails in the aquarium. These are about 5 mm in
diameter. The aquarium is full of algae, which are microscopic plants about
0.001 mm in diameter. Draw and label a pyramid of numbers for these three
organisms. The pyramid does not have to be drawn to scale.
(2)
14 marks
2. Forests all over the world are being cut down for timber and to provide land for
agriculture.
(a) Explain how this deforestation will lead to an increase in the amount of
carbon dioxide in the atmosphere.
(2)
(b) Carbon dioxide and methane are "greenhouse gases". Give two reasons why
the amount of methane in the atmosphere is increasing.
(2)
(c) What long-term effects will these gases have on the earth's climate?
(2)
(d) Some forests are managed instead of being cleared. As soon as trees have
been cut down, new trees are planted to replace them. How will this system
affect the amount of carbon dioxide in the atmosphere? Explain your answer.
(2)
8 marks
HGS Biology (NCM/9/99)
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3. Power stations and motor vehicles burn fossil fuels and release the waste gases
into the atmosphere.
(a) Name two gases that may be released into the atmosphere when fossil fuels
are burned, that cause acid rain.
(2)
(b) Describe how acid rain is formed from these gases.
(2)
(c) Describe two ways in which acid rain can damage the environment.
(2)
6 marks
4. An oak wood contains 200 oak trees, 150 000 primary consumers and 120 000
secondary consumers.
(a) Draw and label a pyramid of biomass for this wood. (Your pyramid does not
have to be drawn to scale).
(2)
A scientist estimated the total amount of energy flowing through the wood per
year. The results were:
Light energy incident on oak trees
4 600 000 kJ per m2 per year
Energy stored in cells of trees
44 000 kJ per m2 per year
Energy transferred to primary consumers
2 900 kJ per m2 per year
Energy transferred to secondary consumers
700 kJ per m2 per year
(b) Calculate the percentage of light energy landing on the trees that is captured
by photosynthesis in the cells of the trees. Show your working.
(2)
(c) Suggest two reasons why a large proportion of the light energy is not
transferred to sugars and other chemithe cells of the tree.
(2)
(d) Give three reasons why some of the energy in the primary consumers is not
passed on to the secondary consumers.
(3)
(e) Explain briefly why food chains with more than three levels are not common.
(1)
10 marks
HGS Biology (NCM/9/99)
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5. The diagram on the left shows a belt transect of the plants growing in the bottom
of a lake. The graph on the right shows how the concentration of nitrate dissolved
in the water of the lake changes with the time of year.
12
10
surface of lake
w ater
Eleocharis
nitrate
(mg/litre)
8
6
Lobelia
4
Potamogeton
2
Nitella
No plants
0
w inter
spring
summer
autumn
w inter
(a) Nitella is the only plant that can grow in deep water. Suggest two physical
factors that prevent the other plant species growing at this depth.
(2)
(b) The plants and animals in the lake need nitrogen to live and grow. What
precisely do they need it for?
(1)
(c) Explain why the concentration of nitrate in the lake falls during the spring.
(2)
(d) In the autumn many of the plants in the lake die. Explain, as fully as you can,
how this leads to an increase in nitrate in the lake.
(3)
(e) Fertilisers from farms near the lake are sometimes washed into the lake.
Explain, as fully as you can, how this can cause the fish living in the lake to
suffocate.
(4)
12 marks
6. The drawing shows a section through a well-designed compost heap.
dead plant material
soil
(a) What happens to the dead plant material in the compost heap?
(1)
(b) Why is soil put in with the dead plant material?
(2)
(c) Why does the compost heap have holes in the sides?
(1)
(d) The carbon in the dead plant material is eventually returned to the
atmosphere. Explain how this happens.
(2)
6 marks
HGS Biology (NCM/9/99)
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KS4 Biology Test 1: Ecology
Mark Scheme
1.
(a) producer:
algae / pondweed (not plant debris)
herbivore:
waterfleas / mussels / snails / hoglice / water boatmen
secondary cons:
mussels / caddis larvae / diving beetles / mites / loach
omnivore:
mussels
(b) algae  waterfleas  mussels  mites
etc (many others!)
(c) light, temperature, pollutants, space, etc
(d) increase; because there is more algae to eat.
(e) increase; because there is more algae for them to eat / fewer loach to eat them.
Or decrease; because loach have to eat more them
(f)
1
1
1
1
2
2
2
2
loach
snails
algae
2.
3.
4.
(a) Less CO2 is absorbed by fewer trees;
CO2 is released when trees are burned or decomposed.
(b) more cattle; more rice fields
(c) less energy radiated by the Earth / heat trapped; so make the Earth warmer; causing
specific climate change / rise in sea level.
(d) CO2 won't change;
since new trees absorb CO2, while burning old trees releases CO2.
(a) sulphur dioxide (SO2) and nitrogen oxides (NOx)
(b) The gases dissolve/react in water in the atmosphere/clouds;
to form acidic solutions;
which fall as acid rain.
(c) damage trees directly through leaves/roots; acidify lakes, killing aquatic organisms;
limestone rocks / buildings; dissolve toxic heavy metals eg aluminium
(a)
2
14 marks
2
2
2
2
8 marks
2
2
erode
2
6 marks
secondary consumers
primary consumers
5.
6.
oak trees
2
(b) 44000 / 4600000 * 100 = 0.96% (1%)
2
(c) not absorbed by leaves/chloroplasts; wrong wavelength/green; lost as heat.
2
(d) lost as heat in primary consumers;
used for work/movement by primary consumers;
lost as waste from primary consumers; lost as dead primary consumers that are not eaten;
3
lost in decay
(e) because so little energy is passed on that there would not be enough in higher levels.
1
10 marks
(a) too dark; too cold
2
(b) proteins
1
(c) The plants grow; so they absorb more nitrate
2
(d) The dead plants are decomposed by decomposing microbes
which turn the nitrogen / proteins into ammonia
nitrifying bacteria turn the ammonia into nitrate
3
(e) fertilisers cause nitrate in lake to increase
This causes more plant / algal growth
This causes an increase in aerobic decomposers when plants die
Decomposers use up oxygen in lake by respiration, so fish suffocate
4
12 marks
(a) It decomposes / decays / rots
1
(b) To provide microbes, which are needed for decay
2
(c) To let air / oxygen in (or CO2 out) for the microbes to respire
1
(d) The carbon compounds in the plants are digested and respired by the microbes;
2
releasing CO2 into the atmosphere.
6 marks
Total
56 Marks
HGS Biology (NCM/9/99)
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1. This table shows what some living things in a wood do at different times of the
year.
Organism
Oak
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Hazel
Primrose
Bluebell
Squirrel
Owl
Key:
In leaf
In flower
Mating season
Rearing young
Use the information from the table to answer the following questions.
(a) For how many months do oak trees have leaves?
(1)
(b) In which season do the oak trees have no leaves?
(1)
(c) Suggest one physical change in the environment that might make oak trees
loose their leaves.
(1)
(d) Bluebells are small plants that grow on the forest floor. Suggest why they start (2)
to grow leaves as early as February.
(e) Owls only mate in one month of the year. Which month is it?
(1)
(f) Suggest one reason why it is better for owls to raise their young in summer (1)
rather than in winter.
(g) Squirrels mate and raise young twice a year. Suggest one advantage in (1)
raising young in the winter.
8 marks
4. Frogs were common in
Britain 40 years ago, but are
now very rare in many areas.
They live mainly near ponds
and marshes. This map
shows how the population of
frogs has changed between
1950 and 1990.
(a) Describe, as fully as you can, how the population of frogs has changed in
different parts of Britain over the 40 years.
(3)
(b) Explain the difference in the frog population in the areas marked X and Y.
(2)
(c) State three human activities that reduce the amount of land available for
(3)
other living organisms.
8 marks
HGS Biology (NCM/9/99)
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9. A farmer installs a biogas
generator on his large dairy
farm. This will dispose of the
waste products from the cows
and produce a useful fuel gas
for the farm.
biogas out
effluent out
waste products in
(a)
(b)
(c)
(d)
10. (a)
(b)
(c)
(d)
(e)
(f)
(g)
Name the fuel gas present in biogas.
(1)
What process is taking place in the generator to produce this biogas?
(1)
Suggest one use for biogas on the farm.
(1)
Liquid biofuels can also be produced in a similar way. Choose one example
of a liquid biofuel and describe briefly how it is made and what it is used for.
(3)
6 marks
9
winter
Cold temperature, short days, less light
So they can photosynthesise before the oak leaves shade the light.
April
warmer, more food, longer days
less competition in winter
4.
(a) Frog population has decreased everywhere, but most in populated areas, and least in unpopulated
areas.
(b) X has large human population / industry / buildings / etc, so there is less space / ponds / marshes
for frogs to live. Y has small human population, so more space for frogs to live.
(c) building / quarrying / farming / dumping waste
9.
(a)
(b)
(c)
(d)
methane
anaerobic fermentation
to provide heat / energy / etc
ethanol is made by fermentation of sugar cane juices or maize starch and used as motor fuel.
HGS Biology (NCM/9/99)
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