Ecosystems (answers)
Instructions to students
Marks
•
You have 50 minutes to complete the test.
Section I: Multiple-choice questions:
10 marks
•
Please answer all questions in the spaces
provided.
Section II: Short-answer questions:
26 marks
Section III: Extended-response questions:
14 marks
•
There is to be no talking during the test.
Total:
50 marks
Name: ________________________________________________________
Score:
/50
Class: _________________________________________________________
Grade:
%
Comments:
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Section I: Multiple-choice questions
For each question, circle or highlight the correct answer.
1
A quadrat would be best suited to sample:
A
small Australian mammals
B
birds and flying insects.
C
stationary animals.
D
any land-based animals.
2
When different populations interact with each other it is called:
A
an ecosystem.
B
a biosphere.
C
a habitat.
D
a community.
3
Which species interactions are examples of symbiosis?
A
predator-prey, competition, commensalism
B
competition, parasitism, inhibition
C
commensalism, parasitism, mutualism
D
commensalism, mutualism, inhibition
4
Which of the following statements about ecosystems is true?
A
Energy flows through an ecosystem in one direction but matter is recycled.
B
Both energy and matter flow through an ecosystem in one direction.
C
Both energy and matter are recycled.
D
Matter flows through an ecosystem in one direction but energy is recycled.
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5
Use the following statements to answer question below.
Cellular respiration:
I
happens in living plant cells, day and night.
II
requires a constant supply of glucose.
III
produces oxygen as a waste product.
IV happens in the mitochondria in organisms.
V
happens in the mitochondria in animals and in the chloroplasts of plants.
Which of these statements are correct about cellular respiration?
A
I, III and V
B
I, II and IV
C
I, II and V
D
II, III and IV
6
Organisms like bacteria and fungi that break down dead matter into simple compounds are called:
A
decomposers.
B
herbivores.
C
producers.
D
secondary consumers.
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7
Use the following statements to answer the question below.
Photosynthesis:
I
requires carbon dioxide and water.
II
requires glucose and oxygen.
III
produces carbon dioxide and water.
IV produces glucose and oxygen.
Which of these statements are correct about photosynthesis?
A
II and IV
B
II and III
C
I and III
D
I and IV
8
Guard cells:
A
trap light energy within the chloroplast of a plant.
B
open and close the stomata of a plant.
C
break down glucose in the process of glycolysis.
D
allow decomposers to feed off of dead organic matter.
9
Which of the following is a biotic factor?
A
water temperature
B
wind speed
C
competition for food
D
soil composition
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10 Which one of the following food chains is correct with reference to the food web shown?
A
grass  grasshopper  praying mantis  bird  lizard
B
grass  grasshopper  praying mantis  frog  bird
C
grass  grasshopper  praying mantis  lizard
D
grass  grasshopper  frog  praying mantis
Section I
Total marks:
/10 marks
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Section II: Short-answer questions
11 You are asked to estimate the number of ring-tailed possums in a national park. Name the
technique you would use and briefly describe how you would carry out this method.
Mark–recapture / capture–recapture technique (1 mark)
(Up to 2 marks for accurate description of marking and capturing over two nights.)
For example:

set out traps to capture possums on night one.

record number of possums caught, mark them and release.

set out traps to capture possums on night two.

record number of possums caught and the number of these with marks.
/3 marks
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12 After two nights the following information is gathered about the ring-tailed possums in question 11:

Night 1: 22 possums caught

Night 2: 30 possums caught (three of these were caught on night one)
Use this data to calculate the estimated number of ring-tailed possums in the national park.
Total number = N1  N2  M2 or 22  30  3 (1 mark)
= 220 ring-tailed possums (1 mark)
/2 marks
13 Provide three reasons why producers are so important to ecosystems.
Students’ answers will vary. Accept any three of the following, for 1 mark each.
Producers photosynthesise and photosynthesis is the only natural method of removing carbon dioxide
from the atmosphere and so regulates the greenhouse effect and climate of ecosystems (1 mark).
Photosynthesis is the source of energy for all other organisms within an ecosystem that gain their
energy from producers either directly (e.g. herbivore) or indirectly (feeding on a herbivore) (1 mark).
Photosynthesis transforms solar energy into chemical potential energy, which can then be passed up
food chains (1 mark).
Plants also absorb other nutrients from the soil and make them available to other organisms that could
not obtain them directly from the soil themselves (1 mark).
Any other reasonable response is acceptable.
/3 marks
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14 Explain why every food chain and food web should start with a producer.
Food chains and webs show how energy flows through an ecosystem (1 mark). Producers are
responsible for converting sunlight energy into chemical energy, which is a form that can flow through
the ecosystem / This energy is transferred from one organism to another when they feed (1 mark).
/2 marks
15 List three ways that the carbon cycle would be affected by logging trees in an ecosystem.
Any three suitable ways (1 mark each), such as:

decreased photosynthesis

decreased removal of atmospheric carbon dioxide

decreased soil organic matter if trees removed

decreased input of atmospheric carbon dioxide from respiration..
/3 marks
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16 If rabbits could successfully be removed from the ecosystem represented by the food web, suggest
two possible benefits to other organisms in the ecosystem.
Any two of the following (1 mark each):

less competition with kangaroos / wombats / termites / grasshoppers for grass and so native
herbivore populations will increase

less food for dingos so dingo populations will reduce

fewer dingos will reduce predation on kangaroos / wombats / echidnas / frill-necked lizards so
native numbers will increase

less pressure on grass so grass will recover and there will be less soil erosion.
/2 marks
17 Outline the importance of decomposers in an ecosystem.
Decomposers feed off dead organic matter that would otherwise build up in the environment (1 mark).
The nutrients within a dead organism are recycled to be reused by other organisms within the
ecosystem (1 mark). These nutrients would otherwise remain trapped an unavailable for essential plant
growth that in turn provides energy for other organisms (1 mark).
/3 marks
18 The graph below is of a predator–prey relationship. Identify which is the predator and which is the
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9
prey by labelling the graph below. Justify your choice.
Award 1 mark for A and B correct
A: predator
B: prey
Suitable reason (award 1 mark for suitable reason such as the examples below):
If the food source (prey) decreases it will result in a decrease in the number of predators, therefore the
predators will decline after their food source / prey has declined.
If there were more predator animals than prey animals, there would not be enough food for the
predators and they would either die or move to a new ecosystem.
/2 marks
19 Describe each of the following two species relationships. Provide an example for each.

Competition

Mutualism
Description (1 mark) Suitable example (1 mark)
Competition – when two species use the same limited resource (1 mark) e.g. seedlings competing for
light at forest floor.
Mutualism – when two species both benefit from interacting (1 mark) e.g. sea anemone is cleaned and
clown fish is protected from predators.
/4 marks
20 Only 10% of the energy is passed from one organism to the next in an ecosystem, making it a very
inefficient process. Provide two reasons for this.
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Any two (1 mark each) of the following:

energy is used to build molecules that build tissue

energy is used to do the work of cells, such as maintenance and metabolic processes

energy is used in respiration, with much ‘lost’ as heat.
/2 marks
Section II
Total marks:
/26 marks
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Section III: Extended-response questions
21 Compare and contrast the processes of photosynthesis and respiration. In your answer you may
consider:

the reactants and products of each reaction

how each process is involved in the flow of energy through an ecosystem

where each process takes place.
Students’ answers will vary. Award 1 mark for each comparison or contrast to a total of 5 marks.
Both processes provide energy for other organisms in an ecosystem.
Photosynthesis provides the first source of energy by producing glucose. Respiration converts this
glucose into useable energy to be passed from one organism to another in a food chain.
Many of the molecules in the two reactions are the same, e.g. glucose is produced in photosynthesis
and as a reactant in respiration.
Photosynthesis uses carbon dioxide and water to produce glucose and oxygen using light energy.
Respiration uses glucose and oxygen to produce carbon dioxide, water and ATP (or equations).
Photosynthesis occurs in chloroplasts of plants while respiration occurs in all organisms.
Photosynthesis traps energy from the Sun into chemical bonds, such as those of glucose. Respiration
moves the energy out of glucose and into the bonds of ATP, which can then be used by cells.
/5 marks
22 Identify one way in which human activities impact negatively on the environment. Provide an
example of a species that is directly affected by the activity, as well as how it is affected. Suggest
an alternative activity to reduce or avoid further environmental impact.
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Students’ answers will vary.
Award 1 mark for an appropriate human activity; 1 mark for an appropriate example of affected species;
1 mark for an explanation of how the species is affected; 1 mark for an alternative activity.
Example of an acceptable response:

human activity: mining

species directly affected: endemic species such as the orangutan in Malaysia

how the species is affected: mining destroys their habitat

alternative activity: mining in a different (less sensitive) area or importing the materials required.
/4 marks
23 Using a specific example of an ecosystem, identify two abiotic and two biotic factors.
Students’ examples will vary. Award 1 mark for identifying an ecosystem, 1 mark each for two
appropriate abiotic factors and 1 mark each for two biotic factors.
Sample answer:
Antarctic ecosystem (1 mark)
Abiotic factors: very low air and water temperatures (1 mark); high wind speeds (1 mark); no daylight
hours during winter (1 mark)
Biotic factors: predator–prey relationship between penguins and leopard seals (1 mark); cooperative
breeding of emperor penguins (1 mark)
/5 marks
Section III
Total marks:
/14 marks
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