Review of TOPIC 2: The Ecosystem (UNIT 1: 2.1 – 2.3)
2.1 Structure
Assessment Criteria with Practice Questions
2.1.1 Distinguish between biotic and abiotic (physical) components of an ecosystem.
Which list includes three abiotic factors that affect phytoplankton?
A.
number of decomposers, pH of water, day length
B.
water temperature, oxygen concentration, light intensity
C.
carbon dioxide concentration, number of primary consumers, wavelength of light
D.
water temperature, number of secondary consumers, carbon dioxide concentration
snakes
2.1.2 Define the term trophic level.
Below is a diagram of part of a food web.
frogs
spiders
insects
snails
green plants
 How many trophic levels are represented in this food web? _________
2.1.3 Identify and explain trophic levels in food chains and food webs selected from the local environment.
Apply relevant terms to local, named examples and other food chains and food webs.

A.
B.
C.
D.
Food chains seldom have more than four members because
the total biodiversity of any area is limited.
energy is lost as it moves along a food chain and little remains at the top carnivore level.
in many parts of the world, species have become extinct and complex ecosystems are rare.
in most ecosystems competition for food is great.
2.1.4 Explain the principles of pyramids of numbers, pyramids of biomass, and pyramids of productivity,
and construct such pyramids from given data.
 The diagram below shows a pyramid of biomass for an ecosystem (not drawn to scale).
BIOMASS (g m–2 )
TROPHIC LEVEL
Unknown
Carnivores
X
Y
1 200
Producers
1. What is the value of X? _______________ 2. What type of organism is Y? _______________________
2.1.5 Discuss how the pyramid structure affects the functioning of an ecosystem.
 What is primary productivity?
 The diagram below represents the pyramid of biomass for a certain ecosystem.

A.
B.
C.
D.
trophic level 3
carnivores
trophic level 2
herbivores
trophic level 1
producers
The most likely explanation for the biomass of trophic level 2 being greater than that of trophic
level 1 is that the
system shows seasonal fluctuations and the plants have died off before the herbivores.
number of plants is greater than the number of herbivores.
number of herbivores is greater than the number of plants.
productivity of the herbivores is greater than the productivity of the plants.
2.1.6 Define the terms species, population, habitat, niche, community and ecosystem with reference to local
examples.
 Describe the population, habitat, niche, community and ecosystem of the barn owl in its environment.
2.1.7 Describe and explain population interactions using examples of named species.
The graph below shows the number of pairs of penguins breeding on an island in the Southern Ocean.
12500
10000
Breeding pairs
7500
5000
2500
0
1940
1950
1960
1970
1980
1990
2000
Year
 Penguins are a part of a complex oceanic ecosystem that also includes organisms above them in the
food-chain (carnivores such as leopard seals) and below them (fish). What changes in the population of
fish would you expect as the result of the changes in penguin numbers shown in the graph?
2.2 Measuring abiotic components of the system
2.2.1 List the significant abiotic (physical) factors of an ecosystem.
Terrestrial
EX.s
Marine
EX.s
Abiotic factors
Freshwater
EX.s
Abiotic factors
Abiotic factors
2.2.2 Describe and evaluate methods for measuring at least three abiotic (physical) factors within an ecosystem.
Choose one of the environments above (2.2.1) and STATE any three significant abiotic factors in the environment and
STATE how these may vary in a given ecosystem with depth, time or distance. NOT ON THIS TEST
ENVIRONMENT: __________________________________________
1.
__________________________________
Effects of depth:
Time:
Distance:
2.
__________________________________
Effects of depth:
Time:
Distance:
3.
__________________________________
Effects of Depth:
Time:
Distance:
2.3 Measuring biotic components of the system
2.3.1 Construct simple keys and use published keys for the identification of organisms.

What is a dichotomous key? Construct a dichotomous key for these three organisms: bee, butterfly and worm
2.3.2 Describe and evaluate methods for estimating abundance of organisms.
Methods should include capture–mark–release–recapture (Lincoln index) and quadrats for measuring population density,
percentage frequency and percentage cover. (See practice ppt if needed, for review)
2.3.3 Describe and evaluate methods for estimating the biomass of trophic levels in a community.
(2.3.3 IS NOT ON THIS TEST)
2.3.4 Define the term diversity.
(Two components: the number of different species and the relative numbers of individuals of each species.)
State what a low diversity index indicates about a habitat and suggest how a low value may occur.
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Distinguish between the terms diversity and abundance.
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2.3.5 Apply Simpson’s diversity index and outline its significance. . (See practice ppt if needed, for review)
D = N(N – 1)
Σ n(n – 1)
CLASSIFICATION:

Scientific Naming

Levels of Classification

Characteristics of the three Domains

Characteristics of the Eukaryotic Kingdoms
Other Important Review SOURCES

Quizzes: Vocabulary Quiz, Classification Quiz, Symbiosis Practice Quiz

NOTES: Biotic-biotic interactions

Look through your notes and activities and make a VOCABULARY LIST
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