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Preliminary Biology Topic 1
A LOCAL ECOSYSTEM
What is this topic about?
To keep it as simple as possible, (K.I.S.S.) this topic involves:
1. DISTRIBUTION & ABUNDANCE OF ORGANISMS
2. BIOTIC & ABIOTIC FACTORS
3. ROLES & RELATIONSHIPS
4. THE FLOW OF ENERGY & MATTER
5. ADAPTATIONS TO ENVIRONMENT
6. HUMAN IMPACTS
but first, some definitions...
Community
Ecology
refers to all the living things within an ecosystem...
all the different types and individual organisms.
is the study of living things and their environment,
and all the inter-relationships between the lifeforms and the factors of the environment itself.
Population
Ecosystem
refers to all the individuals of a particular species
living within the ecosystem. The community within
a complex ecosystem such as a coral reef, or a
tropical rainforest, contains thousands of
populations of different species.
An ecosystem comprises all the living things and
the non-living environment of a particular, defined
area. The size of an ecosystem can vary
enormously...
you might study the ecology
under one rock, or in a lake. You might consider an
entire mountain range as one ecosystem, or an
entire ocean. Ultimately, the entire Earth can be
considered as a single ecosystem.
sun
AN AUSTRALIAN ECOSYSTEM
THE SUN PROVIDES
ALL THE ENERGY FOR
THE ECOSYSTEM
The plants and animals interact
with each other, and with the
non-lliving environment
The temperature, amount of light, the
air, water and the soil are vital nonliving factors of every ecosystem
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CONCEPT DIAGRAM (“Mind Map”) OF TOPIC
Some students find that memorising the OUTLINE of a topic helps them learn and remember
the concepts and important facts. As you proceed through the topic,
come back to this page regularly to see how each bit fits the whole.
At the end of the notes you will find a blank version of this “Mind Map” to practise on.
Abiotic
Factors
Predator
&
Prey
Quadrats
&
CaptureRecapture
Transect
Studies
Parasite
&
Host
Biotic
Factors
Commensalism
Factors of
an Ecosystem
Distribution
&
Abundance
Mutualism
Roles
&
Relationships
Allelopathy
A LOCAL
ECOSYSTEM
Human
Impacts
Competition
Flow of
Energy & Matter
Adaptations
to
Environment
Biomass
Pyramids
Loss of Habitat
Pollution
Eutrophication
Alien Species
Structural
Physiological
Behavioural
Cycling of
matter.
Flow of Energy
Food
Chains
Food
Webs
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1. DISTRIBUTION & ABUNDANCE OF ORGANISMS
The first questions you might ask when beginning to study any ecosystem are:
• which organisms live here?
• where do they live, exactly?
• how many of them are there?
Distribution
Transect Study
In ecology, “distribution” refers to where
within an ecosysytem the individuals of a
species are located.
A “Transect” is like a cross-section
through a study area.
The idea is to define a line which cuts right
across the area being studied. This could
be a string line or a series of marker sticks
hammered into the soil.
Some species might be more or less
evenly distributed throughout the area
being studied, but often the population of
a species is “clumped” together, or found
only in certain parts of the environment.
The study is done by moving along the line
and noting and recording which species
are located at each point.
How a species is distributed gives clues
about how it is interacting with the
environment.
For example:
Often plants are the main subjects of a
Transect Study, because many animals
move around so far and so quickly that
they can’t be studied this way.
An animal that is
usually found in tree
tops may be there to
find its
food, or
may be
escaping
its
enemies.
You may have done a Transect Study as part
of your practical work, or field trip.
For schools near the coast, a common field
trip is to study the rocky seashore
environment.
A plant found mainly along the banks
of creeks or rivers may have a
greater need for water to grow, or
might only be able to reproduce by
spreading its seeds in water.
So, one of the first things to do when
studying an ecosystem is to study the
distribution of the organisms present. One
good way to do this is by carrying out a
Transect Study.
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A Typical Rocky Seashore
The photo shows horizontal “stripes” of living things.
Each stripe is a population of seaweeds, or barnacles, or
tube-w
worms, etc. Why stripes? turn over...
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Distribution at a Rocky Seashore
In sea-shore studies it is quickly
discovered that the different organisms
tend to be found in quite distinct
“zones” which are related to the vertical
heights above and below the tide levels.
Exactly where each species is found is
an indication of the interactions in the
ecosystem between each species and
factors such as:
• Food Supplies they need to be near.
TRANSECT DIAGRAM OF A ROCKY SEASHORE
Blue periwinkles
• Predators they need to avoid.
“Neptune’s necklace” seaweed
High Tide level
Black & striped periwinkles
common here
3 metres
Crabs
common
Brown bubble weed
Low Tide level
Sea Urchins & Starfish
common here
Kelp seaweed only found
at lower levels
30 metres
Note: Vertical scale is exaggerated
• Wave Action. Most of the organisms
along the sea-shore are well adapted to
withstand the pounding of waves, but
some are better adapted than others.
• Exposure to Air
Sea-shore animals are all sea creatures
which can withstand being exposed for
a while at low tide. How well they cope
with this often determines their exact
distribution.
Abundance
Abundance refers to how many individuals are in the population
of a species in the ecosystem.
In some cases it can be easy enough to count
the population directly.
For example, to find the abundance of large
trees in a small forest, simply walk back-andforth in a grid pattern and count as you go.
It would be impractical to
try to count all the
barnacles on a seashore.
“Sampling” the population is
much faster.
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However, small organisms, large areas and animals
that hide or move around a lot make direct counting
impossible. In many cases, abundance of a species
must be done by “sampling”... studying small
samples of the environment, then scaling the data
up to the whole area.
Two commonly used sampling techniques
are described on the next page.
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EXAMPLE OF A QUADRAT STUDY
Quadrat Sampling
KEY:
A “quadrat” is a simple wire/wooden/plastic
frame which is dropped onto the ground at
random throughout the study area.
Quadrat
drops
8 metres
At each quadrat “drop” the number of the
species of interest is counted. After a number
of “drops” (the more, the better) the average
number of organisms per quadrat is
calculated.
Plant
studied
1 m2
Study
Area
= 8x8
= 64 m2
Finally, the estimated population is found by
“scaling-up” from the area of the quadrat to
the total area being studied.
8 metres
In the example shown, the quadrat has been dropped 8 times.
The numbers of plants in each quadrat drop were
2,1,0,3,1,1,1,1
This gives an average of 1.25 plants in each quadrat.
Remember this is an
Estimated = Average count x Study area
estimate only, and
Population
per quadrat
Quadrat area
can be improved by
increasing the
= 80 plants
Estimated = 1.25 x 64
number of “drops”.
Population
1
Capture-Recapture Sampling
The obvious problem with the Quadrat method is
that it does not work with animals that will run, fly,
or swim away from you.
1. Capture a number
of the species being
studied.
For mobile animals, or secretive, hard-to-find
types, the “capture-recapture” technique can be
useful.
For the example shown, 5% (1/20) of the 2nd
capture are “re-captures”. So statistically, the 1st
capture sample of 50 should represent 1/20 of the
total population of the study area.
Therefore, population estimate = 1,000 individuals.
(50 x 20)
Mathematically,
Estimated = 1st capture x 2nd capture
Population
no.marked in 2nd capture
(no. re-captured)
2. Mark or tag
the animals
Example:
1st Capture is
50 individuals
4. Carry out a second
capture program.
.
it..
wa
3. Release animals back
where they were
captured.
5. Count how many of the
2nd capture are marked
from the 1st capture.
Example:
2nd Capture is
60 individuals
(not all shown)
= 50 x 60
3
= 1,000 individuals
Limitations
This technique relies on the tagged individuals mixing randomly
back into the population and being re-caught again at random.
Sometimes this doesn’t happen.
Example:
Out of 60 in the 2nd capture, 3 are marked. So,
5% (1/20) of the 2nd capture are “re-c
captures”.
For example, intelligent mammals learn to avoid the traps or nets, or may even enjoy being caught (for the
food in a trap) and learn to seek out the traps. Either way, this makes the estimate inaccurate.
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Worksheet 1
Distribution & Abundance
At each “drop” you count how many organisms are
in the quadrat. At the end you calculate the
j)............................... per quadrat.
Fill in the blank spaces. Name....................................
Knowing the area of each quadrat, and the area of
k)................................................., the total population
can be estimated. The accuracy will be improved
by l).........................................................
.......................................
“Distribution” in ecology refers to a).....................
a species is located in an area. This gives clues
to how a species is b)............................................
with the environment. For example, an animal
found predominantly in treetops might be there
to find c)........................, or it may be
d)............................ from its enemies.
For animals that move around a lot, the abundance
is best estimated by the m).....................................
.................... method. This involves capturing a
sample of the population, then n).............................
them in some way, and then o).....................................
them again.
A good technique for studying distribution is
carry out a e).......................................... study.
This
is
where
you
work
along
a
f)..................................... across the study area,
noting g)................... ........................ .......................
at each point.
Later, you carry out a second p)...............................,
and count how many of the sample are
q)................................... This allows calculation of an
estimate of the r)..................................... One
limitation of this technique is that it relies on the
captured specimens s).............................................
.............................., which doesn’t always happen.
h)...................................... refers to how many
individuals of a species are in an environment.
One way to estimate this is by dropping
i).................................... at random throughout the
area.
Worksheet 2
Practice Problems Calculating Abundance
Name....................................
Quadrat Study Problems
Capture-Recapture Problems
1.
Abundance of starfish on a rock platform was
studied by the quadrat method. The quadrat was
a plastic frame with an area of 0.25 m2.
The
rock
platform
was
a
rectangle
approximately 20m x 30m.
3.
A capture-recapture study was carried out on
the lizard population on an island. In the first
capture exercise, 230 lizards were captured,
tagged and released.
A week later, 156 lizards were captured. Of these,
18 had tags from the 1st capture.
The numbers of starfish in 10 quadrat “drops”
were: 8, 0, 14, 11, 3, 1, 0, 0, 7, 2.
Calculate an estimate of the lizard population on
the island, to the nearest thousand.
Estimate the starfish population on the rock
platform.
4.
To estimate the possum population in area, 65
possums were captured unharmed, tagged and
released. A week later 48 possums were
captured. Of these, 12 had tags.
2.
A farmer wished to estimate the population
abundance of a noxious weed species in a
paddock measuring 300 x 400 metres. He used a
rectangular wire quadrat frame 1.0 x 0.5 metre.
The number of “target” weeds in 20 quadrat
drops were: 2, 8, 0, 15, 11, 0, 2, 1, 0, 9, 16, 3, 7,
13, 0, 1, 7, 0, 8, 2.
Estimate the possum population.
It was later found that the possums rather
enjoyed being trapped because of the tasty food
used as bait. Does this mean your population
estimate may be too high or too low?
Explain your answer.
What is the approximate population of weeds in
the paddock?
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Worksheet 3
Test Questions (Section 1)
Name....................................
Multiple Choice
Longer Response Questions
1. When studying an ecosystem, a transect study
could be useful for recording the:
Mark values are suggestions only, to give you an idea of
how detailed an answer is appropriate.
Answer on reverse if insufficient space.
A. abundance of species within the study area.
B. distribution of species within the area.
C. special adaptations of species to the habitat.
D. food chains in the area.
5. (4 marks)
The following is a student’s sketch diagram of a
transect done to study the distribution of 4 plant
species J, K, L and M in a certain area.
TRANSECT DIAGRAM OF A ROCKY SEASHORE
2.
Blue periwinkles
Vertical
scale
exaggerated
Pond
“Neptune’s necklace” seaweed
High Tide level
Black & striped periwinkles
common here
Key
Crabs
common
J
Creek
K
L
M
Brown bubble weed
Low Tide level
Sea Urchins & Starfish
common here
Describe the distribution of species K and L.
Kelp seaweed only found
at lower levels
6. (3 marks)
Using a “capture-recapture” method to estimate
the population of trout fish in a lake, the following
results were obtained:
1st capture: 537 trout tagged & released.
2nd capture: 832 captured.
Of these 45 were tagged.
To the nearest 1,000, how many trout are in the
lake?
Show your working or reasoning.
It would be reasonable to infer from this transect study
that:
A. Blue Periwinkles eat kelp plants.
B. blue periwinkles can withstand drying effects
at low tide better than starfish can.
C. Crabs can survive the effects of wave action
better than bubble weed.
D. Kelp has special adaptations to resist drying.
7. (6 marks)
To estimate the population size for a small plant
species living in a field, a quadrat study was
carried out. The field was rectangular, measuring
120m x 85m.
3. The best way to improve the accuracy and reliability
of a “quadrat study” is to:
A. use a bigger quadrat frame.
B. deliberately drop quadrats where the “target
species” is found in larger numbers.
C. measure the size of the study area more
carefully.
D. make more quadrat “drops”.
The quadrat used was a square wired frame
0.50m x 0.50m = 0.25 m2 area.
It was dropped at random 10 times in the field. The
count of the “target species” in each of the “drops”
was:- 8, 14, 2, 5, 9, 22, 3, 0, 12 and 7.
4. When using the “capture-recapture” technique,
which of the following would be most likely to result in
an INACCURATE estimate of population size.
a) Calculate
i) the area of the field.
ii) the average number of plants per quadrat.
A. The marking technique used reduces survival
chances of the animals.
B. Increasing the number captured in the 2nd
capture operation.
C. After release from the first cature, the animals mix
randomly back into the population.
D. Increasing the number captured in the first
capture operation.
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b) Find an estimate of the size of the plant
population in the field. Show working.
c) Suggest one way to improve this study to give a
more accurate estimate.
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2. BIOTIC & ABIOTIC FACTORS OF AN ECOSYSTEM
The distribution and abundance of any species within an ecosystem
depends on a whole host of factors...
Biotic Factors
Abiotic Factors
(“biotic” = living)
examples...
(non-living)
Availability of water
Availability of oxygen
Light intensity
Temperature range
Soil characteristics
...and many more.
Food organisms
Predators
Disease organisms
Competitors
Comparison of Abiotic Characteristics in the
Terrestrial Environment (on land) & Aquatic Environment (in water)
Viscosity
Buoyancy
is a measure of the “stickiness” of a
substance, and how easy or difficult it is
to move through it. On land, plants and
animals are surrounded by air, which
has very low viscosity and is easy to
move through.
is a measure of “flotation” ability. Water
is very buoyant and supports plant and
animal bodies against the pull of gravity.
Aquatic organisms do not need strong
stems or legs to hold themselves up.
Terrestrial plants need strong stems or
trunks of wood to
grow upwards
against gravity. Animals need strong
skeletons.
STREAMLINING
Most of body is muscle
to power the tail
Bony skeleton
supports body
against gravity
Water has a much higher viscosity and is
more difficult to move through. As a
result, many aquatic animals are
streamlined, and equipped with powerful
tails for propulsion.
Strong
trunk to
hold leaves
up to catch
light
Availability of Gases
(oxygen & carbon dioxide)
Since the air is about 20% oxygen, it is readily available in terrestrial environments.
Carbon dioxide (needed by plants for photosynthesis) is only 0.04% of air,
so land plants are limited by this.
These gases do NOT dissolve well in water, so the concentration of gases
in aquatic environments is very low, and gets lower as the water gets warmer.
For this reason, fish’s gills have to be highly efficient to extract the
necessary oxygen, and are far better than our lungs for gas exchange.
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Temperature Variation
Availability of Water
On land the temperature can easily vary
20oC from day to night, and even more from
summer to winter. Living things must be
able to cope with that while maintaining
stable internal body temperatures.
Terrestrial environments are subject to
evaporation, and plants and animals must
have ways to conserve water, by having
water-proof skin, or avoiding losses during
excretion. This problem becomes extreme
in some environments such as deserts.
Terrestrial animals need fur or feathers for
insulation, or have physiological responses
such as sweating or shivering. Some
change their behaviour (sunbaking or
seeking shade) in order to cope.
Conserving water is
critical for survival in
a desert environment
Dogs keep cool by “panting” when they get too hot.
They have few sweat glands, but panting evaporates
water from gums and tongue. This has a cooling effect.
For sea-living plants and animals like
jellyfish and worms, water is never a
problem. They are constantly surrounded
by a liquid exactly the same as their body
fluids. They do not need to have special
mechanisms to collect or conserve water.
Water-living organisms generally do not
need such special adaptations because
aquatic environments have very stable
temperatures.
However, in some cases the organisms are
surrounded by water, but they have water
problems due to osmosis. This will be
studied in the next topic, but in summary:
However, water-living mammals are often
heavily insulated by “blubber” (fat) to
maintain their high body temperature in
cold water.
In salt-water environments fish lose water
by osmosis (mainly from their gills) and
must constantly replace it.
SALTWATER
FISH
This seal looks fat because she is!
Osmosis “sucks”
water from body.
Thick layers of blubber are both food
storage and vital insulation to conserve
body heat in cold water.
Must drink
constantly to
replace water loss
FRESH WATER
FISH
Absorbs water due to
osmosis
Must
excrete
water
constantly
In fresh water, osmosis causes water to
flow into the organism’s body and must
constantly be “pumped out” again. Their
kidneys are mainly used to excrete water,
rather than body wastes.
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Availability of Light
In contrast to air, water does NOT allow light
through so easily. Light can penetrate the
surface layers easily enough, but even just 10
metres deep, much of the light has been
absorbed, and by 100 m down it is totally dark.
Light is essential for plants to carry out
photosynthesis. This process makes all the
food, so the availability of light is a critical factor
in any ecosystem.
Light penetrates through air very easily, so most
terrestrial environments get plenty of light for
the plants. The floor of a rainforest is an
exception... here the dense canopy of trees
means very little light penetrates to reach the
smaller species or seedlings.
Also, water does not absorb all the different
colours (wavelengths) equally. Red and orange
are absorbed rapidly, while green and blue
penetrate deeper into the water.
Different colours
(frequencies)
of light
penetrate water to
different depths.
Rainforest plants have adapted to this in many
ways:
• Epiphytes (e.g. staghorn ferns) germinate and
grow high up in other plants and so avoid the
darkness below.
“Birdnest fern” epiphyte
in a rainforest tree
Red light is
absorbed near
the surface
Blue light penetrates
to greater depth
Many seaweeds
have special
pigments to
efficiently absorb
the available
light.
Most
seaweeds
are not the
familiar
green of land
plants. Many
are brown or
red because
they contain
special
pigments to
absorb the
dominant
blue
wavelength
of light they receive.
• Plants living on the rainforest floor have large,
broad leaves, packed with extra chorophyll, to
absorb what little light is available.
Brown Kelp Seaweed
In deep ocean waters there is no light and
consequently no plants. Deep ecosystems rely
on dead organic remains drifting down from
above for their food supply. On the deep ocean
floor, some ecosystems are based on food made
by chemosynthesis around volcanic vents. This
will be explained in a later topic.
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Worksheet 4
Biotic & Abiotic Factors
Test Questions for this section are in Worksheet 6
Important gases like m)..........................
are abundant in the air Gases do not
n).............................. very well in water,
so aquatic animals need very efficient
o)................................. or other breathing
organs.
Name....................................
Divide these ecosystem “factors” into 2
lists... the “Biotic” and “Abiotic”
factors.
Light, prey, diseases, oxygen, water,
predators, soil, temperature, food
plants, exposure, competitors, acidity.
On land, plants and animals must have
ways to p)...............................................
water and avoid dehydration. This could
involve having q).......................................
skin, or avoiding excessive water loss
during r)....................................
In
aquatic environments there can be
water problems too, due to the process
of s)......................................................
For example, salt-water fish constantly
t)....................................... water, while
fresh-water fish need to constantly
u).............................. water.
Fill in the blanks
In comparing the a)...................................
(on land) environment with the
b)...................................... (in water)
environment, a number of Abiotic
factors are very important;
c).................................. refers to how
easy/difficult it is to move through the
medium. Air has a very d)..............
........................... while water is much
e).......................................... Because of
this, aquatic animals often have a
f).............................. shape.
On land, availability of light is generally
not a problem, except in environments
such v).......................................... To
cope with this, epiphyte plants such as
w)................................, grow up in the
tops of trees. Plants on the floor may
have
leaves
which
are
x)........................................................... to
absorb any light available.
“Buoyancy”
is
a
measure
of
g).................................. ability. Water is
much h)....................... (more/less)
buoyant than air. Terrestrial animals
and
plants
need
strong
i)............................... structures to
withstand gravity, while aquatic
organisms are supported by the water.
In water, light penetration is poor, and
the different y)........................................
of
light
penetrate
differently.
z)........................
wavelengths
are
absorbed
rapidly,
while
aa)............................... penetrates further.
Seaweed plants often have special
ab)................................ (often red/brown
in colour) to better absorb the available
light. In the very deep ocean there is no
light, and no ac)......................................
can survive there. Ecosystems must
rely on ad)................................. drifting
down from above, for food, or on
ae)............................ around volcanic
vents.
Comparing temperature variations, the
terrestrial
environment
shows
j)..................................... variation than
water. That’s why many land animals
have special features such as
k)................................ for insulation, or
the ability to l)...................................
when too hot.
WHEN COMPLETED,
WORKSHEETS BECOME SECTION SUMMARIES
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3. ROLES & RELATIONSHIPS BETWEEN ORGANISMS
Ecology is very much about relationships. This
section looks at some of the ways that different
species within an ecosystem relate to each other.
Predator - Prey
This describes situations where one animal eats
another.
examples...
Predator
Dingo
Lion
Spider
Dolphin
eats
eats
eats
eats
Prey
Wallaby
Zebra
Insect
Fish
Both predator and prey have major impacts on
each other’s distribution and abundance, and each
can cause the other’s population to rise and fall in
a fairly regular pattern.
Commensalism
Commensalism is a relationship in which one
organism benefits while the other is neither harmed
nor helped.
Population Size
(ABUNDANCE)
PREY SPECIES
Population
peaks
A good example is the remora, or “sucker fish”
which attaches itself to a shark with a “suction cup”
structure and hitches a ride. It does the shark no
harm at all. When the shark feeds, the remora feeds
on the debris and scraps from the shark’s meal.
PREDATOR SPECIES
TIME (years)
Notice that
• Predator abundance is always lower than prey.
(Reasons for this are explained later)
• The “peaks” and “troughs” of the predator’s
population always occur after those of the prey.
Shark with remora hitching a ride
A simple example of commensalism is a bird
nesting in a tree. The bird family gain the important
benefit of a relatively safe and secure nest site, while
the tree neither gains nor loses.
What happens:
1. The numbers of the prey species increase
because of its breeding cycle, or seasonal increase
in available food.
2. This provides more food for predators, who
survive in greater numbers and reproduce more
sucessfully.
3. As predator numbers increase, more prey get
eaten and so the prey population decreases.
4. As prey numbers decline, less predators can
survive, so their numbers decline.
Another example, seen commonly in rural areas is
the cattle egret (bird) which follows the cattle
through the pastures, feeding on the insects which
are disturbed by the cows. The cow neither gains
nor loses from the relationship.
In Africa similar birds follow large grazing wild
animals for the same reason. However, the grazers
gain the benefit of an “early warning system” when
the birds react to approaching predators. Since both
species gain some advantage from the association,
this is an example of “mutualism” (next page).
EACH ORGANISM’S ABUNDANCE AFFECTS THE
OTHER’S ABUNDANCE.
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Another example is coral. The coral animal is a
polyp... a soft, hollow animal related to jellyfish.
Inside the polyp’s flesh lives another organism,
an alga (microscopic plant).
Mutualism
In a mutualistic relationship, both species benefit.
Mutualism is much more widespread in nature than is
generally realized.
The classic example are insects (e.g. bee) and many
flowering plants. The insect’s total food supply is
nectar and pollen from the flowers. As it gathers its
food the plants gain the essential service of pollination
of their flowers. Both benefit so profoundly that neither
can survive without the other.
The polyp provides a secure home for the alga,
which pays its way by sharing the food it makes
by photosynthesis. Both organisms gain
tremendous benefits from the relationship.
Many grazing animals (e.g. kangaroos) eat a diet rich
in plant cellulose which is nutritious but difficult to
digest. These animals have a population of mutualistic
microbes living in their gut. The microbes are able to
break the cellulose down and make its nutrition
available to the animal, while the microbes gain a
secure, stable place to live and a permanent food
supply... both benefit.
A mother koala will regurgitate “pap” from her gut to
feed her baby. The pap contains the mutualistic
bacteria that the baby must have to digest the tough
gum leaves.
Parasite - Host
Parasitism is a relationship in which one organism feeds on another
without killing it, or even necessarily harming it significantly.
Allelopathy
is a relationship found particularly among
plants and fungi, in which one organism
directly inhibits the growth and development
of others by releasing toxins. The famous
antibiotic “penicillin” was discovered in the
fungus Penicillium because of its inhibiting
effect on the growth of bacteria.
Some trees and shrubs (including the pest
weed lantana) release inhibiting chemicals
from their roots. These “inhibitors” slow
down or prevent the germination and growth
of the seeds and seedlings of other plants.
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Some parasites, such as tapeworms, live inside their host and
absorb digested food without doing much harm. This way the
host stays healthy and the parasite has a secure
home and guaranteed food supply.
Other parasites, such as leeches and ticks, are “casual”
parasites who attach to a host, take a feed of blood, and then
drop off and live independently until hungry again.
More serious are the many micro-organisms which can cause
infectious diseases. These parasites include bacteria, viruses
and a few protozoans and fungi. They invade the host’s body,
feeding and reproducing so that the host
becomes sick and may even die.
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Competition
Dingo
occurs whenever two different species need to use
exactly the same resource, in the same way. The
resource in question may be a food, or nesting sites
or simply living space, such as when plants like
lantana or bitou bush grow over other plants.
It is known from
fossils that the
Thylacine
(“Tasmanian tiger”)
was once widespread
as one of the main
predators on
mainland Australia.
However, its numbers
rapidly declined after
the introduction of
the dingo from Asia
about 10,000 years
ago.
Competition usually results in a winner and a loser.
One species will be slightly more successful than
the other, and its population will grow, while the less
sucessful competitor will decline in numbers and
may eventually become extinct in the ecosystem.
Sometimes what seems like competition turns out
not to be. For example, the lion and the leopard are
both large African predators, often living in the same
areas and both feeding on the herds of grazing
animals.
Population Size (ABUNDANCE)
A TYPICAL COMPETITION GRAPH
However, careful study
reveals that their hunting
techniques are so different
that they tend to prey on
different species and
different categories
(e.g. young rather than
adults) so they are in
fact NOT competing and
can both survive in the
same habitat.
Thylacine
Extinct
It seems the dingo was a more sucessful predator
and out-competed the Thylacine on the mainland.
The dingo was never introduced to Tasmania, so
there the tigers survived until driven into total
extinction by the impacts of European settlement.
Relationships
A relationship in which one organism gains an
advantage, while the other neither gains nor
loses, is called k)............................................ An
example is the shark and the l)..............................
Fill in the blank spaces.
Name....................................
An animal which kills and eats another animal is
called a a)......................................... The animal it
eats is its b)............................ Each one’s
population abundance affects the other. For
example, if the predator population increases,
the prey population will c).............................
because d)............................................................
On a graph, the peaks & troughs will match
each other, but the predator’s graph will always
be e)............................ and f)...................................
than the prey’s graph.
“Mutualism”
is
when
2
organisms
m).............................................................................
A good example is n).................... and
.....................
Many grazing animals get help to digest the
tough fibres of plant food from mutualistic
relationship with o)....................................... living
in their gut.
Some plants and fungi produce chemical toxins
which p)............................................ the growth of
other organisms. This relationship is called
q)......................................................
A
parasite
is
an
organism
which
g)............................ on its host without
h).................................... A good example is the
i)............................................. which lives in the
gut of its host, eating the digested food. Other
parasites such as j)...................................... and
.................................... feed on the host’s blood.
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Dingo
introduced
TIME (years)
This situation is called
“resource partitioning”.
Worksheet 5
Dingo
Thylacine
Original population
reasonably stable
“Competition” is when 2 organisms both need
to use r)................................................. in an
environment. Usually, the result of competition
is s)..........................................................................
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Worksheet 6
Test Questions Section 2
Multiple Choice
Name....................................
Longer Response Question
1. Which of the following is a “biotic” factor in an
ecosystem?
A. Light intensity.
B. Soil type
C. Diseases
D. Temperature range.
4. (4 marks)
Construct a simple table and fill it in to compare the
terrestrial and aquatic environments with respect
to
viscosity
buoyancy
temperature variation
and
availability of light
2. The streamlined shape of a dolphin is an adaptation
to:
A. the high buoyancy of water.
B. low availablity of gases in the sea.
C. large temperature variations.
D. the high viscosity of water.
3. Many seaweeds have brown or red pigments
because:
A. these absorb the predominately blue light that
penetrates underwater.
B. it camouflages them among the rocks of the sea
floor.
C. red and brown light penetrates water more than
other colours.
D. this helps them control their temperature by
absorbing more heat.
Worksheet 7
Test Questions Section 3
Name....................................
Longer Response Questions
Multiple Choice
1. The following graph shows the changes in
population numbers for a prey species and 4 other
species. Which one (A, B, C or D) is most likely to be
the predator?
3. (5 marks)
a) Define the term “mutualism”.
A
B
ABUNDANCE
Prey
species
b) Give an example of mutualism, naming 2
organisms and outlining how each is affected by
the relationship.
C
D
Time
2. The “cleaner wrasse” is a small fish of the coral reef
which feeds on the parasites clinging to other fish.
Many larger fish will queue up to wait for a cleaner
wrasse to pick off their parasites.
The relationship between the cleaner wrasse and the
larger fish is an example of:
4. (5 marks)
“In nature, allelopathy is a method of beating your
competition”.
Discuss this statement briefly, giving definitions
and examples as appropriate.
A. Mutualism
B. Commensalism
C. Allelopathy
D. Competition
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4. THE FLOW OF ENERGY & MATTER IN AN ECOSYSTEM
Cycling of Matter
How Organisms Use Energy
Within any ecosystem the important chemicals of
life tend to be re-cycled.
Everything that an organism does requires energy.
Organisms:Move
Grow and Repair body tissue
Reproduce
Seek, Eat and Assimilate their food
Respond to happenings around them
Keep their bodies warm
The “water cycle” of nature is well known, and you
should be familiar with the “Oxygen-Carbon” cycle.
CO2
Respiration
Cellular Respiration
Photosynthesis
O2
is the process which releases the energy stored in
food. It takes place in every living cell on the planet and
after photosynthesis (next topic) is the next most
important biological process on Earth.
rgy to
rs ene
transfe
s
s
e
c
o
The pr
PLANTS
ANIMALS
Glucose + Oxygen
(sugar)
Other chemicals that are recycled within
ecosystems include Nitrogen, Calcium and
Phosphorus... in fact ALL the chemicals get used
over and over again.
Major energy
compound in
foods
Unlike the chemicals, energy cannot be recycled.
As it is used it must be replaced from outside the
ecosystem.
energy transfer
INPUT
PLANTS
capture light energy
during
Photosynthesis
ATP
A common misconception is that plants do
PHOTOSYNTHESIS and make food, while
animals do RESPIRATION to use the food.
It’s true that plants do photosynthesis and make
all the food on Earth, but respiration is carried
out by all living things... animals AND plants.
All organisms use the energy
in food to power their life
functions.
The process of Respiration
releases the energy in food.
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6CO2 + 6H2O
Don’t forget that the essential product of
respiration is the energy-carrier “ATP”. The CO2
and H2O are merely waste products to be
recycled in the ecosystem like all chemicals.
produced by plants
waste
heat
energy
Energy-c
carrying
chemical used in
all cells to power
life processes.
Although the process can be written as a simple
chemical reaction, this is very deceptive. Cellular
respiration actually takes place as a sequence of
about 50 chemical steps... the equation above is
merely a summary of the overall process.
Energy is stored in the FOOD
OUTPUT
Waste
products
C6H12O6 + 6O2
The ultimate source of ALL the energy in an
ecosystem is the SUN. The Sun provides the heat
to keep each ecosystem at a livable temperature,
but it is the LIGHT of the Sun which powers all life.
Ligh
t
Carbon + Water
Dioxide
in air
Energy Inputs & Outputs
SUN
ATP
Luckily for us animals, the plants carry out
enough photosynthesis to feed themselves,
AND produce a surplus to feed us as well.
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Food Chains
Plants are food PRODUCERS.
They capture light energy by the process of photosynthesis, and store it as the chemical energy in food.
All other organisms are CONSUMERS of food. They rely on eating the plants or other animals.
So, in any ecosystem there is a chain of feeding, based on the plants... a “food chain”.
is eaten by
Every food chain must
begin with a plant
is eaten by
The arrow shows the direction that food energy flows.
NEVER DRAW THEM BACKWARDS!
GRASS
KANGAROO
DINGO
Plant
Herbivore
Carnivore
Producer
1st order
Consumer
2nd order
Consumer
1st Trophic
2nd Trophic
level
level
(“trophic” refers to “feeding”)
3rd Trophic
level
NOTES:
1. The arrows in a food chain show the direction that the energy flows. The arrows must never be reversed.
2. Note the different ways to describe each organism’s role in the chain. Try not to confuse the different methods...
e.g. a 1st Order Consumer is at the 2nd Trophic Level... etc.
The Role of the Decomposers
All along the food chain organic wastes are produced.
Dead leaves from plants, body wastes and shed skin and fur
from the animals are just a few examples.
Mushrooms and “toadstools” are the
reproductive structures of soil-lliving fungi
This left-over waste material is food for a very important
group of organisms... the decomposers. The main
decomposer organisms are the microscopic bacteria and
the soil fungi. These organisms feed on the scraps and
wastes and in doing so, cause wastes to decay and be
broken down into very simple chemicals such as CO2 and
nitrate and phosphate ions.
THIS IS ESSENTIAL TO THE RECYCLING OF
THE CHEMICALS IN AN ECOSYSTEM.
So the decomposers get rid of all the wastes and clean up
the environment, and they ensure that the vital chemicals
are recycled into air or soil for re-use by the plants... and so the food chains continue.
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Food Webs
Although we can best understand the flow of energy by a food chain,
in fact simple food chains never exist by themselves in nature.
Kangaroos don’t just eat grass, and dingoes don’t just eat wallabies.
The real feeding relationships in an ecosystem can only be described by a food web
which is made up of many inter-connected food chains.
large fish
Example: FOOD WEB IN A ROCK POOL
octopus
starfish
small fish
mussels
limpets
periwinkles
chitons
zooplankton
(microscopic animals)
phytoplankton
green algae
(microscopic plants)
Hints on Constructing a Food Web
To keep it simple and read-able (K.I.S.S.) when constructing a food web:
• always start with the producers (plants) at the bottom and work upwards
• try to keep the members of the same trophic level in-line in the diagram.
(not always possible, because some organisms may be feeding at more than one
trophic level...
look at the mussels in the diagram above.)
A food web diagram allows us to analyse the flow
of energy (stored in food) through the ecosystem
and to make certain predictions...
Question:
If a disease wiped out all the mussels in a
particular area, what effect might this have on
the chiton population?
Answer:
(Chitons are not directly connected to mussels,
so you might think there’d be no effect, but...)
Example Questions and Answers
Question:
List all organisms which are 1st order consumers.
Answer:
Limpets, periwinkles, chitons, mussels &
zooplankton.
If there are no mussels to eat, the octopus might
eat more chitons. Therefore the chiton
population could decrease.
Question:
Which organism is at the highest Trophic Level
above?
OR
Without mussels to eat, the octopus might eat
more starfish. This could mean less chitons
being eaten by starfish so the chiton population
could increase.
Answer:
The large fish, which is at the 5th trophic level.
Question:
What might be the effect on the mussel population
if there was an increase in the octopus population?
Answer:
If there were more octopus they will eat more
mussels, so the mussel population would
decrease.
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This demonstrates the difficulty of
making predictions about natural food
webs... the consequences of change
can be quite unpredictable!
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Biomass
Everything you do requires energy, which you get
from cellular respiration...
“You are what you eat” goes the old saying, and it is
literally true that every molecule of your body is built
from the chemicals that you have eaten as food over
your lifetime. Your body weight is your “Biomass”...
the mass (weight) of living flesh in you.
C6H12O6 + 6O2
6CO2 + 6H2O + ATP
...and as you breathe out you excrete the waste
CO2 (plus some water vapour) and so you lose a
little of the mass of the food you previously ate.
An average person eats at least 250 kg of food per
year and drinks at least 500 litres of liquids. So why
aren’t we all as big as an elephant? Simply because
we all produce roughly the same mass of wastes
and excrete them so that our biomass stays more or
less the same. (Unless still growing, of course).
...and as you use the energy of the ATP molecules,
the energy is converted to “low-grade” heat and
dissipates into your surroundings. This energy is
lost, and cannot be re-used by living things.
In any ecosystem it turns out that about 90% of the
food/energy taken in at any trophic level, is lost as
wastes and low-grade heat. (Thank goodness for
the Decomposers to get rid of all that waste!)
In ecology, we deal with the total biomass of an
entire population, or of the whole community. For
example, if there are 200 starfish living in a particular
rockpool, and each has a mass (on average) of 50
grams, then the biomass of starfish in the rockpool
is 200 x 50 = 10,000 g = 10 kg.
This means that in a food chain, only about 10% of
the biomass and energy at any trophic level is
available to be eaten by the next trophic level
organisms.
It is always found that the biomass of plants is more
than the biomass of herbivores, which is more than
the biomass of carnivores, and so on. Why?
The result is a BIOMASS
PYRAMID.
So, for the food chain
GRASS
PYRAMID OF
BIOMASS
&
ENERGY
DINGO
if there was (say) 100,000 kg of grass in an area, then
this could not support more than about 10,000 kg of
kangaroos, and only about 1,000kg of dingo biomass.
4th
Trophic
Level
3rd
Trophic
Level
KANGAROO
The approximate population numbers would be:
5 million grass plants feeding about 400 kangaroos,
feeding just 50 dingoes... a “pyramid” of numbers too.
10%
90% of Biomass
and Energy lost
Py
ram
id
sh
ap
e
10%
1st
Trophic
Level
2nd
Trophic
Level
Biomass
of
Herbivores
90% of Biomass
and Energy lost
10%
available
Biomass of Producers
(Plants)
90% of Biomass
and Energy lost
This is why very few food chains in nature have more than 5 or 6 trophic levels...
the available food & energy becomes too small to support higher level predators.
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Worksheet 8
Test Questions Section 4 (2 pages)
Multiple Choice
Name....................................
Longer Response Questions
Mark values given are suggestions only, and are to
give you an idea of how detailed an answer is
appropriate. Answer in the spaces provided.
1.
Which of the following statements about ecosystems
is generally true?
A. Energy is re-cycled, while chemicals have to be
constantly supplied.
B. Both matter and energy are re-cycled.
C. Matter is re-cycled, while energy has to be
constantly supplied.
D. Both matter and energy have to be
constantly supplied.
2.
The essential product of cellular respiration is:
A. Glucose
B. Oxygen
C. Carbon Dioxide
D. ATP
6. (8 marks)
a) Write a word equation to summarize the process
of cellular respiration.
b) The process makes energy available to living
cells.
i) What is the original source of this energy?
ii) How does the energy get into an ecosystem?
3.
In the following food chain:
algae > limpet
> octopus >
fish
> shark
iii) In what form is the energy passed from
organism to organism?
the “herbivore” and the organism at the 4th Trophic
level are respectively:
A. limpet and shark
B. limpet and fish
C. algae and fish
D. algae and shark
7. (4 marks)
In a seaside rockpool, the total biomass of all
visible plants, herbivores and carnivores was
estimated as follows: Plants 10 kg
Hebivores 20 kg
Carnivores 2 kg
4.
Soil bacteria usually have the role in ecosystems of:
A. Decomposers
B. Disease causing parasites
C. Producer organisms
D. Epiphytes
a) On these figures alone, could the rockpool be a
viable, stable ecosystem? Explain your answer.
5.
In a certain area, the biomass of species is:
Biomass (kg)
Species
P
10,000
Q
5,000,000
R
100,000
S
500
b) Over time, the rockpool community is studied
and it is found to be very stable and more-or-less
unchanging. Suggest how this might be possible.
If these 4 organisms are involved in the same food
chain, then the order in the food chain is most likely:
A.
S>R>P>Q
B.
P>Q>R>S
C.
Q>S>P>R
D.
Q>R>P>S
Worksheet 9 is a
“Summary Worksheet”
for this section
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Worksheet 8
Continued
Name....................................
8. (5 marks)
The following observations were made about the feeding relationships in an Australian
rural ecosystem. Use the information to construct a food web diagram.
Honey-eater birds feed on the nectar and pollen of native shrubs. These shrubs are also eaten by insects
and wallabies. Grass is eaten by insects, rabbits and wallabies, while mice feed on the grass seeds. Frogs
eat insects, while dingoes prey on rabbits and wallabies. Kookaburras hunt snakes and frogs. The snakes
feed on frogs, mice and take the eggs and babies from honey-eater nests.
9. (8 marks)
From your diagram for Q24 answer the following.
a) Name three 2nd-order consumers.
b) Name an organism which occupies more than one trophic level.
c) Write the longest food chain within this web.
d) Name 2 organisms who could well be competitors.
e) There is a world-wide trend of decline in amphibian populations. If the frog population
in this food web was drastically reduced, what might happen to the:
i) insect population?
ii) mouse population?
f) Comment on a human impact apparent from the food web for this ecosystem.
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5. ADAPTATIONS OF ORGANISMS TO THEIR ENVIRONMENT
A third category is “behavioural” adaptation, which is
where an animal’s instinctive behaviour helps it
survive and thrive in its environment
Adaptations
are “special” characteristics that
help an organism survive in its environment.
For example,
the black bear
of North
America has a
thick coat of fur.
This is a
structural
adaptation to its
environment.
The fur helps
insulate the
body to keep it
warm in the cold climate in which it lives.
This lizard is sunbaking to
warm itself up for active
hunting for insects.
If it becomes
too hot it will
move into the
shade to cool
itself.
Dangers of Inferring Adaptations
You need to be careful when examining any organism
for its adaptations because it may require careful study
to be sure of the real reason for some characteristics.
Other structural adaptations that have already been
mentioned in previous sections include:
• streamlining of many aquatic animals to deal with
the high viscosity of water.
• large, broad, leaves of plants living on the
rainforest floor, to cope with the low light levels.
For example, it is possible that the adaptation you
observe could be inherited from ancestors who lived
in a different environment, and it is not a help to
survival in the current habitat.
• the bony skeleton of most terrestrial animals
needed to support the animal against gravity.
Also, it’s not always easy to decide what survival
advantage a particular characteristic may give.
Another category of adaptation is “physiological”
adaptation. (“Physiological” refers to the way the body
works or functions)
Previously mentioned examples include:
• animals shivering when cold, and sweating when
too hot.
• freshwater fish excreting water constantly to
remove excess water from their bodies. This is
controlled by the functioning of their kidneys.
One of the classic physiological adaptations is the
kidney function of many desert animals. In an
environment where water is scarce, these animals
conserve body water by producing only small
amounts of very concentrated urine.
For example:
is the magpie’s colour scheme an adaptation which
helps it survive because it gives:
or
or
or
In some cases, such as desert mice, their kidneys are
so efficient at retaining water that they do not need to
drink, but can survive on the “metabolic water”
produced by cellular respiration.
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• camouflage?
• temperature control?
• sexual attraction for mating?
• identification, to keep a group together?
Only careful study will reveal the truth
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Worksheet 9
Flow of Energy and Matter
Name....................................
Energy is passed from one organism to
another as food, and the flow of energy
through
an
ecosystem
is
a
l)................................. In any food chain, the
plants are the m)................................, and
animals are n)......................................
Fill in the blank spaces.
In any ecosystem, the chemical resources
tend to be a).........................., but the energy
is used up and must be constantly
b).......................................... The source of all
the energy is the c)................... The energy
is “captured” by the d).......................... in the
process
of
e)...................................................This
converts light energy into the energy
stored in the f)............................. molecules.
The “Decomposers” are vital to get rid of
wastes and dead scraps and to
o)....................................... vital chemicals.
Single food chains rarely exist in nature.
Instead, a number of food chains which
p)........................... with each other, form a
q)..................................... .........................
Organisms need energy for all the life
processes such as moving around,
g).......................... and ...........................
The energy of food is released by the
process of h)....................................
This
requires the gas i)............................ The
products are the chemical wastes
j)........................... and ........................... and
the “energy chemical” known as
k).....................
Worksheet 10
The total body weight of all the individuals
of a species in an ecosystem is known as
the r)................................ There is always
about 10 times more r)............................... of
plants than of s)....................................
because about 90% is always lost as
wastes. Because the biomass decreases
rapidly up through any food chain it is
referred to a “biomass t)............................”
Adaptations
Fill in the blank spaces.
Name....................................
Special characteristics which help an
organism survive in its environment are
called a)........................................
For example, an animal might
f)........................ when too hot, or
g)....................................... if too cold.
Some of these are “structural”: they
involve special structures, such as the
fur of a bear which b)...............................
in a cold climate.
Many desert animals have highly
efficient kidneys so they produce
h)......................... amounts of highly
i).................................... urine, in order to
j)....................................... water.
Another example is how many aquatic
animals are c)...................................... to
allow them to move more easily through
water,
which
has
a
high
d)............................
The third category of adaptations is
k)..................................................
For
example, reptiles cannot regulate their
body temperature physiologically, so
they use behaviours instead. They will
l).................................................. when
too cool, and seek m)...............................
when too hot.
The second category of adaptations are
those that are e)......................................,
or related to the functioning of the body.
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6. HUMAN IMPACTS ON ECOSYSTEMS
Human “culture” is the learned behaviours we have
accumulated over the millenia. Our culture includes
language, art, music, customs and TECHNOLOGY.
Eutrophication
It is our over-population, and our complex, industrial
technology that impacts on natural ecosytems...
Although our sewerage may be thoroughly treated
to make it safe to the environment, the effluent still
contains many minerals which act as a fertiliser.
Typically, the treated effluent from our sewer
systems is discharged into waterways. Similarly,
when farmers use fertiliser on their crops and
fields, some will eventually be washed into creeks
and rivers during rainy weather.
occurs when rivers and streams are over-fertilised
by human sewerage and agricultural run-off.
Loss of Habitat
Very simply, humans clear forests, fill wetlands and
divert streams to make room for our towns and cities
and for our agriculture. For example, only about 3%
of Australian rainforests remain, from those present
200 hundred years ago.
Pollution
The result is that algae living in the waterways are
stimulated to grow in over-abundance, often
choking waterways and blocking light from other
water plants. Later, great masses of algae die off
and their decay uses up all the oxygen in the water,
so that many fish and other organisms suffocate.
Many human activities produce chemicals which
can harm the environment if released.
Introduction of Alien Species
Clearing of natural environments is disaster for
many species. They are specially adapted to their
habitat and cannot survive elsewhere.
The European settlers to Australia brought many
species from other places and released them into
the new environment. The list includes plants such
as prickly pear, lantana and bitou bush, and
animals such as rabbits, foxes, pigs, camels, and
cane toads.
“Acid rain” results from gases such as sulfur dioxide
(SO2) released from burning of fossil fuels,
especially coal. The gas dissolves in rainwater
forming an acid solution that can seriously affect
forests, lakes and wetlands by killing some
organisms so that food chains are disrupted.
Prickly Pear
Cactus
Pesticides and industrial poisons, even in very small
amounts can build up in living communities by
“biological magnification”...
example: the level of toxic chemical in a shrimp
might be quite low, but a fish which eats many
shrimp in a year ends up with a concentration of
toxins 100 times higher... and so on up through the
food chain.
Biological Magnification
All of these species, and many others, have
become major problems in the ecosystems,
because:
Toxin concentration = 10 units
Toxin concentration
= 1000 units
• the “aliens” find themselves in an environment in
which the normal predators and diseases are not
present to keep their population in check
Toxin concentration = 1 unit
• they are often more ruthlessly efficient in using
resources, and so they “out-compete” the
native species.
Scientists are currently alarmed by a world-wide
decline in populations of amphibians (frogs &
toads). It is suspected that various human-made
chemicals are disrupting the reproduction and
development of many species which are vital links in
the food webs in many ecosystems.
Preliminary Biology Topic 1 “Ecosystems”
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Many ecosystems around the world
are being disrupted by “alien” species
introduced by humans.
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Worksheet 11
Test Questions Sections 5 & 6
Multiple Choice
Name....................................
Longer Response Questions
Answer in the spaces provided.
1.
One of the “adaptations” visible in the
North American beaver is a large, broad,
flat tail.
4. (4 marks)
a) Explain what
“adaptation”.
meant
by
an
b) Give an example of an adaptation for
each of the following situations.
i) A structural adaptation (ianimal) to a
cold climate.
This adaptation probably helps the
beaver survive because it:
A.
B.
C.
D.
is
gives it more balance on land.
helps it to carry twigs & branches.
protects against predator attack.
helps it to swim and steer in water.
ii) A plant adaptation to low light levels on
the rain forest floor.
2.
“Eutrophication” is when:
A. polluting chemicals in the
environment become more
concentrated up a food chain.
B. aquatic habitats suffer from “algal
blooms” due to over-fertilization.
C. gases from burning of fossil fuels
cause waterways to become acidic.
D. an introduced species overpopulates an ecosystem.
iii) An adaptation for water conservation in
a desert animal.
5. (3 marks)
Outline a human impact on a named type
of ecosystem.
3.
Many animals seek shade when it
becomes too hot in the Sun. This is an
example of an adaptation which is
probably:
A.
B.
C.
D.
structural.
physiological.
behavioural.
learned.
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CONCEPT DIAGRAM (“Mind Map”) OF TOPIC
Some students find that memorising the OUTLINE of a topic
helps them learn and remember the concepts and important facts.
Practise on this blank version.
A LOCAL
ECOSYSTEM
Preliminary Biology Topic 1 “Ecosystems”
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Answer Section
Worksheet 3
1. B
Worksheet 1
3. D
4. A
5. Species K is not widely distributed, but seems
confined to the hilltop (higher elevation).
Species L seems to occur only near water, on the
banks of ponds and creeks.
a) where
b) interacting
c) food
d) hiding / escaping
e) transect
f) straight line
g) which species are present
h) Abundance
i) quadrats
j) average number
k) study area
l) doing more quadrat drops
m) Capture - Recapture
n) marking/tagging
o) releasing
p) capture
q) marked/tagged
r) total population
s) mixing randomly back into the population
6. Estimated = 1st capture x 2nd capture
Population
no.marked in 2nd capture
= 537 x 832
45
= 9,929
To nearest 1000, Estimate = 10,000 trout.
7.
a) i) Area = length x width = 120 x 85 = 10,200 m2.
ii) Average = (8+14+2+5+9+22+3+0+12+7) / 10
= 82 / 10
= 8.2 plants / quadrat
Worksheet 2
Quadrat Study Problems
1.
Average per quadrat = 46 / 10 = 4.6
Study area = 20 x 30 = 600 m2
b)
Estimated = Average count x Study area
Population
per quadrat
Quadrat area
= 4.6 x 600 / 0.25
= 11,040
Population estimate = 11,000 starfish approx.
Estimated = Average count x Study area
Population per quadrat
Quadrat area
= 8.2 x 10,200/0.25
= 334,560
Estimate = 335,000 plants approximately
(Note: it is NOT appropriate to give an answer of
334,560 since this suggests that the process will
calculate the exact number of plants. It is a
statistical estimate only, and answers should be
rounded off)
2.
Average per quadrat = 105 / 20 = 5.25
Paddock area = 300 x 400 = 120,000 m2
Estimated = Average count x Study area
Population
per quadrat
Quadrat area
= 5.25 x 120,000 / 0.5
= 1,260,000 weeds approx.
c) Make more “drops” of the quadrat.
Worksheet 4
Biotic Factors
prey
diseases
predators
food plants
competitors
Capture - Recapture Problems
3.
Estimated = 1st capture x 2nd capture
Population
no.marked in 2nd capture
= 230 x 156
18
= 1,993
Estimated population ≅ 2,000 lizards
Abiotic Factors
light
oxygen
water
soil
temperature
exposure
acidity
Fill in the blanks
a) terrestrial
b) aquatic
c) Viscosity
d) low viscosity
e) higher viscosity
f) streamlined
g) flotation
h) more
i) support
j) much less
k) fur/fat/feathers
l) sweat
m) oxygen
n) dissolve
o) gills
p) conserve
q) waterproof
r) excretion
s) osmosis
t) lose
u) excrete
v) rainforests
w) staghorns/orchids etc
x) large/broad/packed with chlorophyll
y) colours / wavelengths z) Red/orange
aa) blue
ab) pigments
ac) plants
ad) dead material
ae) chemosynthesis
4.
Estimated = 1st capture x 2nd capture
Population
no.marked in 2nd capture
= 65 x 48
12
= 260 possums
If the possums “enjoy” being trapped then the
recapture sample contains a disproportionately HIGH
number of tagged animals, who have come back to
the traps deliberately. Mathematically, if the number
“12” is too high, then the answer (260) is too low, so
the real population is higher than the estimate.
Preliminary Biology Topic 1 “Ecosystems”
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2. B
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Worksheet 8
Worksheet 5
1. C 2. D 3. B 4. A 5. D
6.
a) Glucose + Oxygen
Carbon + Water + ATP
Dioxide
b) i) The Sun
ii) Energy is captured by plants in photosynthesis.
iii) As food (containing chemical potential energy)
7.
a) No. Stable ecosystems always have about 10
times more biomass of plants than herbivores.
The rockpool has less plant biomass than
herbivores. This is not sustainable.
a) predator
b) prey
c) decrease
d) more prey will be eaten
e) lower
f) later / after
g) feeds
h) killing it
i) tapeworm
j) ticks, mosquitoes, leeches
k) commensalism
l) remora (“sucker fish”)
m) both gain a benefit
n) bee & flowering plants
o) bacteria / protozoa
p) inhibit / slow
q) allelopathy
r) the same resource(s)
s) one survives and thrives, the other declines.
(one wins, one loses)
b) The biomass figures include only visible
plants. There may be a large biomass of
microscopic algae and plankton not accounted
for in the figures.
or,
Perhaps the herbivores in the rockpool are not
just feeding on the plants present, but leave the
pool at high tide to feed elsewhere.
or,
The community might be sustained by extra
biomass which washes into the pool with waves
and tides and feeds the herbivores.
8.
kookaburras
Worksheet 6
1. C
2. D
4.
3. A
Terrestrial
Environment
Aquatic
Environment
Viscosity
low
high
Buoyancy
low
high
Temp.variation high
Light avail.
good
low
gets less with
depth
snakes
frogs
dingoes
Worksheet 7
1. C
honey
eaters
2. A
3.
a) Mutualism is a relationship between 2
different species in which both gain a benefit.
mice
native shrubs
wallabies
rabbits
grass
9.
a) snakes, frogs, dingoes
b) snake or kookaburra
c)nat.shrubs>insects>frogs >snakes >kookaburras
d) wallabies and rabbits (best answer)
(Note: other possible answers are not as good.
e.g. snakes & kookaburras both eat frogs, but
kooks also eat the snake, so they are not just
competing for frogs.
Honey-eaters and insects both eat shrubs, but
different parts of the plant, so not competing.
Same with mice v rabbits... not eating the same
parts of plants.)
b) Honey bee and flowering plant.
Bee gains food supply.
Plant achieves pollination of its flowers.
4.
“Allelopathy” is when one species produces a
chemical or toxin to inhibit the growth and
development of other species.
Allelopathy is a method of dealing with competitors,
such as the lantana plant producing toxins in its roots,
which inhibits other plant species. This allows lantana
to out-compete other plants and gain more soil
minerals and light.
e) i) without predators, the insect population
should increase.
ii) If less frogs, then snakes might eat more
mice.
Therefore mouse population may
decrease.
(Note: this is why lantana is such a noxious
weed... it’s a great competitor when introduced
to a new environment without its natural
diseases and enemies.)
Preliminary Biology Topic 1 “Ecosystems”
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insects
f) The rabbit is an alien species introduced to
Australia from Europe. In the absence of its
natural enemies and diseases, it has overpopulated at the expense of native species.
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Worksheet 9
Worksheet 11
a) re-cycled
b) replaced / input
c) Sun
d) plants
e) photosynthesis
f) food (glucose)
g) growing, reproducing, responding etc
h) cellular respiration
i) oxygen
j) water & carbon dioxide
k) ATP
l) food chain
m) producers
n) consumers
o) re-cycle
p) inter-connect
q) food web
r) biomass
s) herbivores
t) pyramid
1. D
3. C
4.
a) An adaptation is a special feature of an
organism, which helps it to survive in its
environment.
b) i) A thick fur coat, or feathers, or layers of
blubber (fat) all act as heat insulators.
ii) Large, broad leaves capture what light is
present.
iii) Kidneys that produce small amounts of
concentrated urine, so less water is lost by
excretion.
Worksheet 10
a) adaptations
c) streamlined
e) physiological
g) shiver
i) concentrated
k) behavioural
m) shade / shelter
2. B
b) insulates it
d) viscosity
f) sweat
h) small
j) conserve
l) sunbake
5. (many different answers possible)
Humans clear forests, fill and drain wetlands etc
for agriculture and to build towns, roads etc.
This results in loss of habitat for many forest
species which are adapted to particular
environments and cannot live elsewhere.
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but we’re only human
If you notice any errors, please let us know
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