Topic 2 The Ecosystem
Notes Ch. 2 – Part 1
2.1 Structure pp. 14 - 23
1. Biotic - Abiotic / Trophic levels – Food Chains –
Food Webs
Definitions – keep simple
a) biotic
b) abiotic
c) producer
d) consumer
e) primary consumer
f) secondary consumer
g) trophic level
h) decomposer
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Read abiotic and biotic definitions and answer the following questions.
IB1. Which list contains only abiotic components of an ecosystem?
A.
air, water, rock
B.
air, producers, climate
C.
soil, consumers, water
D.
carnivores, herbivores, decomposers
IB2. Which list includes three abiotic factors that affect aquatic plants?
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
Explain , in general, why the other answers are wrong:
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Read Trophic Levels, food chains and food webs
1. Explain which way the arrows point in a food chain.
2. Explain the sequence of why you have primary, secondary etc. consumers
and only 1 producer.
DIAGRAM
IB3. Most food chains seldom have more than four trophic levels because
A.
in most ecosystems, competition for food is very great.
B.
the total biodiversity in any ecosystem is limited.
C.
energy is lost as it moves along a food chain and little remains at the level
of the top carnivore.
D.
in many parts of the world, many species have become extinct and
complex ecosystems are rare.
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IB4.
The diagram below represents the pyramid of biomass for a certain ecosystem.
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
A.
system shows seasonal fluctuations and the plants have died off before the
herbivores.
B.
number of plants is greater than the number of herbivores.
C.
number of herbivores is greater than the number of plants.
D.
productivity of the herbivores is greater than the productivity of the plants.
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2. Pyramids , biomass, productivity
Definitions – keep simple
a)
b)
c)
d)
e)
f)
Pyramids of numbers
Pyramid of biomass
Pyramids of productivity
Biomass
Productivity
Bioaccumulation
1. a) In general, how much energy ( biomass) is passed from one level to
the next in a pyramid?
b) How does this relate to thermodynamics? Explain the difference
between pyramid a and b p. 17 fig. 2.4 ( see above)
2. How is biomass measured?
3. Explain pyramids of productivity and how they are fundamentally
different than pyramids of biomass. Explain units involved.
.
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Pyramid structure and ecosystem functioning
Explain the risk to top carnivores using DDT as an example :
3. Species, populations, habitats and niches
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Definitions – keep simple
a)
b)
c)
d)
e)
f)
Species –
Population –
Habitat –
Niche –
Community –
Ecosystem –
Write one sentence that clearly illustrates the words species, population and
habitat. Use a specific organism. :
Write one sentence that clearly illustrates the words niche, community and
ecosystem. Use a specific organisms and a specific ecosystem. :
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IB6. An ecological niche is
A.
where a species lives.
B.
all the populations of an ecosystem.
C.
what a species eats.
D.
the role a species has in an ecosystem.
IB7. A community is composed of
A.
several habitats.
B.
several populations.
C.
several abiotic factors.
D.
biotic and abiotic factors
Population Interactions
Briefly explain each type of population interaction
Competition –
Predation –
Parasitism –
Mutualism –
Make sure you understand fig. 2.7 and 2.8
Fig. 2.7
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Fig. 2.8
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IB8. Which interaction would benefit both organisms in a relationship?
A.
Predation
B.
Commensalism
C.
Mutualism
D.
Competition
IB9. Spiders mainly use a web and poisonous fangs to trap and eat insects such
as flies. What type of interaction is this?
A.
Parasitism
B.
Competition
C.
Mutualism
D.
Predation
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2.2 Measuring abiotic components pp. 24 – 28
1. Measuring
A. List the basic types of ecosystems and 1 example of each
B. Compare the abiotic factors of marine ecosystems and terrestrial systems.
By looking at the lists, how can you tell by common sense that some of the
terrestrial abiotic factors are not marine abiotic factors?
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IB10. Which list contains only abiotic factors in a marine environment?
A.
algae, temperature and nitrogen level
B.
salinity, turbidity and plankton
C.
decomposers, carbon dioxide and calcium level
D.
pH, dissolved oxygen and light intensity
In the question above , even if you didn’t know the abiotic list of a marine
ecosystem, how could you still get the right answer?
Use this strategy to answer the following question:
IB11. Which of the following is a list of abiotic factors that affect the distribution of
organisms?
A.
Sunlight, decomposers and soil pH
B.
Temperature, sunlight and soil pH
C.
Water, sunlight and competition
D.
Disease, pH and dissolved oxygen
2. Evaluating abiotic factors
Make sure you know the basic aspects of each type of measurement
Light meter - sun light
Temperature – indicates DO
pH – indicates DO
Wind - direction
Particle size – indicates drainage and water – holding capacity ( sand vs. pebbles
vs clay)
Slope – indicates surface runoff
Soil moisture- heat soils before and after to measure amount of moisture it can
hold
Mineral content - N, S, K etc.
Flow velocity – water flow in rivers indicate rain fall , how much water is being
released by dams for farming etc. Also affect DO by generating bubbles.
Salinity – indicates DO .
DO – most important :
as salinity, temp. increases, DO decreases. Salt “ dehydrates “ water and
removes DO. Higher temp. increases kinetic energy and causes O2 to move
around more and may evaporate so overall conc. of DO goes down.
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Atmospheric pressure above water affects DO. As press. Above water increases
it “ pushes O2 into water and increases DO. At higher elevations there is less
atm press. so less DO in general.
pH – decreases or increase of pH away from neutral 7.0 generally lowers DO
due to acid base reactions.
Photosynthesis by plants etc. increases DO and respiration by organisms in
water decreases DO.
Eutrophication ( know this term) – due to increase of N or P in water causes
increase of nutrients in water especially for plants. This causes too much plant
growth than normal causing algae blooms ( large masses of plant and alga
growth). Although plants will produce O2 during the day via photosynthesis
plants also “ RESPIRE” – absorb O2 at night via photorespiration. This will
decrease overall DO. Too much plant growth on surface of lakes etc. will also
block sunlight getting to bottom of lakes reducing photosynthesis.
IB 12 : Below is a diagram of part of a food web.
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snakes
frogs
spiders
insects
snails
green plants
Which of the following is an abiotic factor that might affect this food web?
A.
Presence of parasites
B.
Spread of diseases in frogs
C.
Increase in temperature
D.
Introduction of new plant species
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2.3 Measuring biotic components pp. 29 – 35
1. Key for species identification – Dichotomous key : Make sure you
know how it works.
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16
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2. Describe and evaluate methods for estimating abundance of
organisms. Make sure you understand the following examples:
Lincoln Index – allows you to estimate the total population size of an animal in
your study area. Called a “ capture – mark – release – recapture” technique.
Basically you capture some animals ,mark them and release them back into the
population. Then on another day, you capture animals from the population again
and count how many of the marked animals you have . ONE SPECIES ONLY
3. Quadrats
Used for non mobile organisms ( plants, trees, fungi etc. ) and basically measure
number of species per m2.
4. Simpson’s diversity index
Takes into account the total number of all species ( N) and the number of a
particular species ( n)
D = N ( N-1)
Σ n ( n-1)
D = diversity index
N = total number of organisms of all species found
n = number of individuals of a particular species
Σ = sum of
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SEE FOLLOWING EXAMPLE
IB 13 :The table below gives the number of individuals of four species of trees in
two small patches of Australian forest.
Tree species
(b)
(i)
Area A
Area B
Allocasurina huegelina
4
1
Banksia grandis
5
8
Eucalyptus calophylla
7
9
Acacia saligna
4
2
Using the formula for Simpson’s diversity index
D=
N(N  1)
n(n  1)
calculate which of area A or area B has the higher diversity index.
A has been done for you . Try to do B:
A = 5=4+7+4 = N = 20
N (N-1)
= 20(20-1) = 380
Area A n ( n-1)
4 ( 4-1) = 12
5( 5-1) = 20
7(7-1) = 42
4( 4-1) = 12
____________________
Σ n ( n-1) = 86
D=
380
86
N(N  1)
=
n(n  1)
= 4.4 FINAL ANSWER
NOW TRY B
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IB14. Define the term species
IB 15 . The 4 species shown in Fig. 1 below can be found in wetland ecosystems
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IB 15. ( Cont. )
IB 16. Describe a method to estimate the size of an avocet population .
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