Biosphere Summary Notes
Credit and General
Mar-16
BIOSPHERE ........................................................ 1
Biosphere (a) – INVESTIGATING AN ECOSYSTEM ........................................... 1
Sampling organisms ........................................................................................................................ 1
Line Transect .................................................................................................................................. 2
Biosphere (b) – HOW IT WORKS ............................................................................ 5
Energy loss from a food chain/web ................................................................................................. 6
Pyramid of Numbers and Biomass .................................................................................................. 6
Population Growth .......................................................................................................................... 7
Nutrient Cycles ............................................................................................................................... 8
Biosphere (c) - CONTROL AND MANAGEMENT .............................................. 12
Energy Production ........................................................................................................................ 12
Water Pollution ............................................................................................................................. 13
Poor Management of Natural Resources. ...................................................................................... 14
Agricultural Ecosystems ............................................................................................................... 14
Standard Grade Biology
4th Year Revision Notes
03/03/2016
BIOSPHERE
Biosphere (a) – INVESTIGATING AN ECOSYSTEM
Definitions:
Organism
Habitat
Ecosystem
i.e.
Abiotic Factor
a living thing (animal or plant)
the place where an organism lives
all the living and non-living parts within a defined area
ECOSYSTEM = PLANTS + ANIMALS + HABITAT
a physical factor that can affect the organisms living in a
particular habitat e.g. LIGHT, MOISTURE, TEMPERATURE,
OXYGEN OR CARBON DIOXIDE CONCENTRATION, pH.
Ecology is the study of the ways in which organisms interact with each other and
their habitats and how physical factors within their environment affect those
interactions. Ecologists need to measure the populations of organisms and the abiotic
factors within an ecosystem
Sampling organisms
Organisms are sampled to give an estimate of their population size.
Sampling Plants:
A quadrat (a square, often divided into 25 smaller squares – see
opposite) is used to sample plant populations
– the quadrat is placed on the ground.
A quadrat
– Abundance is found by counting the number of squares which
contain the plant (maximum abundance = 25).
– To find the total population in an area, the total number of a plant species within
the whole quadrat is counted. This value is then divided by the area of the
quadrat and multiplied by the total area of the habitat.
To make the results more REPRESENTATIVE or RELIABLE:
The quadrat must be thrown randomly
A number of samples within the area must be taken and the average of
these results calculated.
Sampling Animals:
A Pitfall Trap is a container set flush with ground level.
Animals fall into the trap and cannot escape. To
improve the accuracy of results obtained with the trap:
 it needs to be properly flush with the ground.
 Checked regularly so that the animals don’t eat each
other
 Well camouflaged
 To make the results more REPRESENTATIVE or
RELIABLE – many pitfall traps must be placed in
the habitat.
Credit material is in italics.
GDS
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Standard Grade Biology
4th Year Revision Notes
03/03/2016
Measuring Abiotic Factors
Abiotic factor
Light*
Method for Measuring
Use a light meter
Take care not to shade the meter
Always point to the brightest light source
Use a soil moisture meter
Place the probe firmly and at least 4cm into the ground
Wipe the probe clean between readings
Soil Moisture
* If the light intensity between two different
areas is to be compared, to make a FAIR
comparison readings must be taken:


at the same time of day
under the same weather conditions
Line Transect
A line transect is a method of investigating the distribution of organisms and how it
changes as the habitat changes from one area o another. A line is stretched between
the two areas and at regular intervals measurements are made. Abiotic factors and
also the living organisms will be sampled. By plotting the data in bar charts a picture
of how populations change and the abiotic factors influencing population distribution
can be obtained.
Examples of the influence of abiotic factors
Effect of Abiotic Factor
Green plants are not found in
areas with low light intensity
Woodlice not found in dry
areas
Caddis fly larvae are not
found in polluted rivers
Credit material is in italics.
Reason
Green plants need light for photosynthesis
Woodlice need moisture to allow them to breathe and
so die of they dry out
Caddis fly larvae need a lot of oxygen in the water.
Pollution causes the oxygen level to fall, killing the
larvae.
GDS
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Standard Grade Biology
4th Year Revision Notes
03/03/2016
Learning Intentions
Examples
1- Identify the main
parts of an ecosystem
- Habitat (The place where an animal or a plant lives),
- Animals
- Plants
Quadrats:
Use: estimate the number of plants in an ecosystem.
Technique: square-shaped frame throw randomly at various
places. The number of plants of each type is counted → the total
number of each species can be calculated.
Tree-beating
Use: collect small animals
Technique: the branches of a tree are beaten with a stick and a
tray is used to collect the falling small animals
Pitfall trap
Use: collect crawling animals
Technique: a beaker is inserted into the soil so that the rim is
levelled with surrounding ground.
For all techniques:
The number and types of organisms might not be representative
of the whole ecosystem.
→ an adequate number of samples should be taken
Quadrat
- If too few quadrats have been counted, the number of plants
may not be representative as some species grow in clusters.
→ use large number of quadrats for study
- Some plants may be spreading on either side of the frame. →
overestimation (counting them all) or underestimation numbers
(not counting them).
→ use a rule: e.g. plants going across the top and bottom sides are
counted and these going across the right and left sides are not.
Tree beating
Animals may fall beside the tray
→ use large tray with raised edges, empty the tray regularly
using a large plastic bag
Pitfall trap
Some trapped animals might eat other smaller animals.
→ add 50% ethanol in the trap to kill the animals
non-living factors: light intensity, soil-air-water temperature, soil
moisture, etc…
2- Describe an example
of a technique which
might be used for
sampling organisms and
describe its use
3- (C) Identify a
possible source of error
that might be involved in
a sampling technique and
explain how it might be
reduced.
4- Identify two abiotic
factors
5- Give an example of a
technique which might
be used to measure an
abiotic factor and
describe its use.
Light intensity → Use a light meter
Temperature → use an electronic thermometer(answer valid for
soil, air and water)
Soil moisture → use a soil moisture probe
Credit material is in italics.
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Standard Grade Biology
6-(C) Identify a possible
source of error that might
occur during the
measurement of an abiotic
factor& explain
how it might be reduced
7- State the effect an
abiotic factor has on the
distribution of organism
8- (C) Explain ways in
which abiotic factors can
influence the distribution
of organisms
4th Year Revision Notes
03/03/2016
For all techniques:
→ make sure readings are taken when weather conditions are
similar in all sites
Light intensity:
→ avoid casting a shadow on the light meter
Soil pH/humidity:
→ make sure that the probe is inserted in soil to the same depth
Measurement of temperature:
→ wait until temperature readings stop changing
Measurement of soil moisture
→ make sure that probe is inserted in soil to the same depth
Combination of abiotic factors determines which plants grow in
any one place (e.g. exposure to wind, moisture levels etc…). Types
of plants determine type of animal.
Organism very susceptible to drying out → found in damp and
shaded areas where little water evaporation
E.g. Pleurococcus found on the damper side of a tree trunk (i.e.
exposed to the north) but not on tree trunks which are heavily
shaded.
Credit material is in italics.
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Standard Grade Biology
4th Year Revision Notes
03/03/2016
Biosphere (b) – HOW IT WORKS
More Definitions:
Population
all the organisms of one species (kind) found in an ecosystem e.g. all
the water lilies or rabbits.
Community
all the organisms, of any kind found in an ecosystem i.e. all the
plants and animals. (N.B., Ecosystem= Habitat + Community).
Producer
a green plant that makes its own food by photosynthesis
Consumer
an animal that gets its food by eating plants or animals
Food Chain
a diagram which shows the flow of energy from the producers
through the different levels of consumer
e.g. Grass
(Producer)
Rabbit
(primary consumer)
Fox
(secondary consumer)
(N.B. The sun is the source of Energy for all living things. The arrow shows the
direction in which energy flows, from one organism to another. It points to the
animal which is eating, and from the animal which is eaten.)
Food Web
Herbivore
Carnivore
Omnivore
Predator
Prey
A diagram showing the interconnection of food chains illustrating
that some animals eat and are eaten by a variety of other animals
an animal that eats only plants
an animal that eats only other animals
an animal that eats both plants and animals
an animal that hunts and kills other animals for food
the animal which a predator kills for food
Removing a species from a food web
(e.g. Removing quail from the food web opposite)
The food which the organism ate would now be available
to other species which may INCREASE in number as a
result (i.e. roadrunners would have more insects to eat so
the roadrunners may increase)
The predator that ate it may DECREASE in number as it
has less food (i.e. foxes would have less to eat so they
may decrease in number)
Other animals may DECREASE in number because the
predator now eats more of them (i.e. roadrunners and
mice may decrease in number because the fox eats more
of them).
Credit material is in italics.
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Standard Grade Biology
4th Year Revision Notes
03/03/2016
Energy loss from a food chain/web
Energy passes from one organism to another in a food chain. The body of the animal
contains the energy. When the body of the animal is eaten the energy it contains is
passed to the next organism. Any energy that is not put into the growth of an
organism will therefore not be available for passage along the food chain. i.e. it is lost.
Most energy (~90%) in a food chain is lost from the food chain, ultimately as heat
energy.
ENERGY IS LOST FROM EVERY STEP IN FOOD CHAIN
approx.
10%
eaten by
krill
energy built into organisms body
energy lost
eaten by
whale
100 tons plankton 10 tons krill 1 ton blue whale
(producer)
(herbivore)
(carnivore)
The more links there are in a food chain, the greater the amount of energy which the
producers (plants at the first step) need to provide. Because of this the numbers of
animals at each step in a food chain will tend to decrease.
Pyramid of Numbers and Biomass
A pyramid of numbers is a diagram which is used to
represent the change in numbers of each organism at
each step in a food chain.
As you move along a food chain, the size of an
organism increases, but the numbers of organisms
decreases.
Pyramid of numbers
Credit material is in italics.
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Standard Grade Biology
4th Year Revision Notes
03/03/2016
Occasionally, the food chain does not produce a pyramid. This could be because the
producer is a tree that is consumed by insects. In order that this type of food chain
makes sense, a PYRAMID OF BIOMASS must be used to represent the food chain.
This a diagram which shows the total mass of the population of organisms at each
stage in a food chain.
Pyramid of Numbers
Py
Pyramid of biomass
Pyramid of numbers
The biomass decreases at each stage in a food chain due to the huge energy losses.
Population Growth
The growth of a population depends on the:
 Birth Rate
 Death Rate
Factors which increase the death rate will reduce the population and factors which
increase the birth rate will increase the population. The growth of a population is
limited by:
 Lack of food
 Lack of water
 Lack of space (reduces breeding opportunities e.g. not enough nest sites)
 Increases in the number of predators (increases death rate)
 Build up of poisonous wastes
 Disease
Growth of a population in ideal conditions
A –Lag Phase - Growth starts slowly because
there are few organisms and they also take time
to get ready to reproduce
B- Exponential growth phase – there are no
restrictions on growth (plenty food, space etc.)
growth is at its maximum
C – Declining growth phase - food/ space has
become limited and slows growth. This can
either lead to a constant population size or if
wastes build, the population can be killed off
(e.g. yeast is poisoned by alcohol it produces)
Credit material is in italics.
GDS
C
B
A
7
Standard Grade Biology
4th Year Revision Notes
03/03/2016
Competition
Competition occurs when organisms need the same resources (e.g. food, nest sites
(space) or mates) to survive. As a result of competition, some organisms get a greater
share of resources and survive, others get a smaller share and grow more slowly,
become weak and can die. Competition causes the size of populations to be reduced.
Plants compete for light, water mineral nutrients and space.
Nutrient Cycles
Nutrient cycles are the ways in which minerals essential for life (e.g. nitrogen,
calcium, phosphorous) are released from the bodies of dead animals so that they can
be used to grow new organisms. They are very important because they:
Get rid of the bodies of dead animals and plants
Release chemicals taken up once again by plants through their roots and used for
growth.
The recycling is carried out by decomposers. They feed on dead plants and animals.
Decomposers are bacteria and fungi
The Nitrogen Cycle
The Nitrogen cycle is the process by which nitrogen is moved between the bodies of
plants and animals which use it to make protein. Dead organisms and wastes are
decomposed by bacteria and fungi to release the nitrogen as nitrates in the soil. This
can then be taken up by plants, and used to make more plant protein. Animals eat
plants and make animal protein using the plant protein.
By bacteria
bacteria & fungi
Bacteria only
Bacteria only
Credit material is in italics.
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Standard Grade Biology
4th Year Revision Notes
03/03/2016
Within the cycle:
Ammonification is carried out by bacteria & fungi
Nitrification is only carried out by bacteria
Nitrogen is an important nutrient for the growth of crop plants. Farmers can also
add nitrogen to the soil:
Natural Method:
Dig in manure (dung) or compost
Artificial Method:
Fertilisers.
Nitrogen Cycle Summary
At the core of the cycle, Nitrogen moves from plants to animals, both of which die and
are then decomposed in a 3 step process:
Bacteria & Fungi
Bacteria only
Plant Protein  Animal Protein  Ammonium Compounds  Nitrite  Nitrate
Ammonification
both steps called
nitrification
Nitrate is removed by bacteria in denitrifcation.
Nitrate is added by lightning, which causes it to rain down to the soil (important in
deserts).
Nitrogen Fixation also adds nitrate. In this case, bacteria capture nitrogen from the
air and join it to oxygen. Some plants (legumes e.g. peae, beans, clover) make root
nodules and these bacteria live in the nodules. The bacteria provide the plants with
nitrates (to make protein) and the plants give the bacteria a home and some sugar
food produced from photosynthesis.
These plants are useful to farmers, as growing them in a field
will improve the soil fertility by adding nitrates.
Other ways of adding nitrate to soil and improve fertiltiy are to
add fertilisers.
Natural fertilisers are animal wastes (manure) and plant wastes
(compost = broken down).
Artificial fertilisers are man made chemicals containing nitrates
(as well as phosphates and potassium)
Credit material is in italics.
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Standard Grade Biology
Learning Intentions
1- Describe what is meant by
the words habitat,
population, community and
ecosystem
2- Describe what is meant
by the word producer and
consumer
3- Give an example of a food
chain or a food web
4th Year Revision Notes
03/03/2016
Examples
Habitat : The place where an animal or a plant lives
Population : Organism of the same species living in the same area –
Community: All the populations from different species living in the
same area – Ecosystem: The communities and their interaction with
the physical environment where they
live.
Producer : makes its own food from the energy of sunlight (e.g. green
plants).
Consumer: needs to eat other organisms to feed itself (e.g. all
animals)
See jotters/books
4- State what the arrow in a
food web stands for.
The direction of the flow of energy from one organism to another.
5- (C) Explain how removing
one organism from a food
web could affect the other
organisms
6- State two ways in which
energy can be lost from a
food web
7- (C) Explain what is meant
by the terms pyramid of
numbers (1) and pyramid of
biomass (2) (and pyramid of
energy(3))
Animals which normally feed on this organism will decrease in
numbers. Plants/animals which are consumed by this organism will
increase in number.
8- State what the growth
rate of a population depends
on
9- State three factors
which can limit the growth
of a population
It depends on both:
- the birth rate (number of birth/1000/year)
- the death rate (number of death/1000/year)
For example:
- lack of food, predators, lack of space, disease, lack of water, lack
of light (for plants)
10- Describe and (C) explain
the shape of the growth
curve of a population, under
ideal conditions
A: Flat start: few individuals so population growth is very slow
because there are only few organisms to reproduce.
B: Slow rise: more and more animals are there to reproduce, growth
rate increases.
C: Steep rise: the population is increasingly large so more organisms
can reproduce + no factors are limiting the increase → growth rate
extremely fast
C
Population
size
B
A
Time
12- State when competition
occurs
- heat energy
- movement energy
- undigested part of food, e.g. bones
(1) shows the number of organisms at each level of a food chain.
(2) shows the total mass of organisms at each level of the food
chain.
(3) shows the total energy at each level of the food chain
After C, if conditions are not ideal, curve flattens. This is because
death rate increases due to limiting factors to the point where
death rate = birth rate .
- when resources are limited + organisms compete for the same
resources e.g. food, space, nesting grounds
Credit material is in italics.
GDS
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Standard Grade Biology
13- Describe some effect of
competition
14- Explain why re-cycling of
nutrients is important to the
organisms in an ecosystem
4th Year Revision Notes
03/03/2016
- slower foxes can’t catch enough rabbits to survive→ die
- plants which can’t grow tall enough → not enough light → not
enough energy to reproduce successfully
Nutrients (i.e. minerals such as nitrates) are in limited supply → if no
re-cycling → nutrients would eventually run out.
Credit material is in italics.
GDS
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Standard Grade Biology
4th Year Revision Notes
03/03/2016
Biosphere (c) - CONTROL AND MANAGEMENT
Pollution
A pollutant is any substance which is harmful to plants or animals.
Pollution affects: AIR, SEA, FRESH WATER and LAND
Main Sources of Pollution:
DOMESTIC (from the home) e.g. sewage, household rubbish
AGRICULTURAL e.g. fertilisers, pesticides
INDUSTRIAL e.g. oil, sulphur dioxide, smoke, chemical wastes, nuclear waste.
Energy Production
Energy is vital for all aspects of life. The vast majority of energy comes from the
burning fossil fuels such as coal oil and gas. Burning fossil fuels causes pollution:
ACID RAIN:
the gases, sulphur dioxide &
nitrogen oxides, produced from burning fossil fuels dissolve in
rain water, causing ACID RAIN. This kills fish, and trees and
also causes stonework and metal work to corrode (dissolve).
Power station chimneys are now fitted with chemical
“scrubbers” to remove the sulphur and nitrogen oxides before
releasing the gases into the air.
Cars are also fitted with catalytic converters to change harmful
gases in exhaust fumes into less harmful gases.
GLOBAL WARMING:
Carbon dioxide is also produced by
burning fossil fuels. This acts like a “blanket” in the atmosphere
insulating the earth. As a result the temperature of the planet is
increasing. This may lead to flooding, hurricanes and the extinction
of many species adapted to a cooler climate.
To reduce these problems alternative ways of producing energy are
being developed:
NUCLEAR POWER:
No Acid rain or carbon dioxide is produced by using
nuclear power to generate electricity. However nuclear waste remains dangerous for
a long time and is difficult to store safely.
WIND/WAVE/ SOLAR POWER
These also do not release harmful gases,
however it is unlikely that all our energy needs will be met by these technologies.
Credit material is in italics.
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4th Year Revision Notes
Standard Grade Biology
03/03/2016
Water Pollution
Water is polluted when organic waste (e.g. sewage) is added to it because:
Organic waste acts as a food supply for micro-organisms (e.g. bacteria)
The micro-organisms increase in number and so require more oxygen
Consequently the oxygen in the water decreases
Fewer organisms can survive with these low oxygen levels (fish die)
The addition of phosphates (from detergent or fertilisers – also contain nitrogen) to
water also causes pollution. They cause water plants to grow (algal bloom) and when
the plants die, they provide food for micro-organisms leading to a reduction in oxygen
as above.
Indicator species
The extent to which water is polluted can be determined by using indicator species.
An indicator species is an animal which lives only in a narrow range of oxygen levels.
Pollution affects the level of oxygen and so changes the types of organisms which can
live in the water. Mayfly nymphs and trout are found in high levels of oxygen and so
indicate that there is little pollution present. Conversely, sludge worms and rat tailed
maggots like low levels of oxygen and indicate that pollution is at a higher level.
direction of flow
typical animal of
region
mayfly
sewage added
sludgeworm
water louse
mayfly
level
bacteria
oxygen
downstrream
sewage added
size of population
sludge worm
water louse
mayfly
mayfly
(and other clean water species)
downstrream
**Lichens are indicators of air pollution.
The more lichens there are, the less the air
pollution there is because lichens are killed off by sulphur dioxide in the air.**
Credit material is in italics.
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4th Year Revision Notes
Standard Grade Biology
03/03/2016
Poor Management of Natural Resources.
Humans obtain many important resources from the planet(e.g. oil, timber, food). The
exploitation of natural resources for human needs has lead to habitats being destroyed
or polluted and many species of plants and animals are now endangered or extinct as a
result:
OVERFISHING
cod and other fish species in the North Sea are now very low as
a result of over fishing.
OVER-GRAZING this leads to soil erosion and the formation of deserts. People
become malnourished and prone to diseases as a result.
OVER-USE of FERTILISERS & PESTICIDES this cause rivers and lochs to
become polluted killing fish. Pesticides can accumulate in animals in the food chain
and can cause harm to the final consumer e.g. the eagle in the diagram below.
eagle
high concentration
salmon
stickleback
increasing
concentration
of chemical in
organisms
bodies
water flea
algae
low concentration
of chemical
Accumulation of chemical in food chain
Ways of Protecting Natural resources
Set FISHING QUOTAS to limit the numbers of fish that can be caught
Increase mesh size of fishing nets so small fish can escape, allowing them to breed
and increase the population.
Reduce use of fertilisers/ pesticides, and use more natural methods (manure,
biological controls).
Agricultural Ecosystems
In agricultural, farmers control aspects of the ecosystem to increase the productivity:
FERTILISERS are added to enrich the soil by providing minerals for plant
growth.
WEEDKILLERS reduce competition between weeds and crops for space,
nutrients in the soil and sunlight.
PESTICIDES are chemicals which reduce damage to crops by pests.
LIME is added to soil to reduce the acidity.
Credit material is in italics.
GDS
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Standard Grade Biology
4th Year Revision Notes
03/03/2016
Learning Intention
What is pollution
Examples
It is the addition of a harmful substance to an environment at a rate the
environment cannot cope with it.
1-State which ecosystems
are affected by pollution.
Air, land, fresh water and sea water
2- State the main sources
of pollution (3) and give
examples of a pollutant
from each category.
1- Domestic pollution (land: cans; water: sewage; air: exhaust gases)
2- Agricultural pollution (land and water: chemical pollutant e.g.
fertilisers/pesticides; air: gases produced by animals and rotting food
wastes; water: sewage)
3- Industrial pollution (Water: oil slicks, chemical spills, air: smoke from
factories or power plants)
(a) Burning fossil fuels releases pollutant smokes:
- sulphur dioxide and nitrogen oxides (result in acid rain); -carbon
monoxide (poisonous); carbon dioxide (global warming); lead from gas
exhausts (damages the brain).
(b) Radioactive wastes emitting radiations can persist over thousand
of years (enter the food chain and creates health problems such as
cancers).
- reduce fossil-fuel pollution: use of renewable energies (e.g. solar, wind);
scrubbing the fumes; lead-free petrol.
- reduce domestic pollution: recycle paper, cans, glass, choose showers
over baths
(organic wastes are materials of plants and animals: e.g. sewage, blood
from slaughter houses)
They are food to micro-organisms (bacteria and fungi).
The level of oxygen dissolved in the water decreases due to the activity
of micro-organisms. As a consequence, there is less dissolved oxygen
for other species (e.g. invertebrates, fish).
3- (C) Explain the
undesirable effects of
using (a) fossil fuels and
(b) nuclear power as
energy sources.
4- Give an example of one
way in which pollution
may be controlled.
5- State to which
organisms organic wastes
are food to.
6- Describe the effect of
increased number of
micro-organisms on the
oxygen available to other
organisms
7- (C) Explain how organic
waste pollution can affect
the numbers of microorganisms and hence
oxygen concentration and
numbers of species.
8- (C) State what is
meant by “indicator
species” and explain how
they are affected by
changing oxygen
concentrations
Organic pollution enters water → provides lots of food only for microorganism → micro-organisms reproduce rapidly consuming lots of oxygen
→ less oxygen available for other species → most other species die, only
a few survive → the number of species is reduced
Indicator species: gives an indication of the levels of pollution or some
other abiotic factors.
Water:
May fly → unpolluted
Freshwater shrimp → unpolluted or slight pollution
Blood worm and no may fly or freshwater shrimp → very polluted
Air:
Variety of lichens → very low/no pollution with sulphur dioxide.
Credit material is in italics.
GDS
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Standard Grade Biology
9- Give two examples of
poor management of natural
resources and suggest
possible improvements
10- Describe how the
effect
of poor management of
natural resources can lead
to problems
11- Explain how parts of an
ecosystem are controlled in
either agriculture or
forestry
4th Year Revision Notes
03/03/2016
1- Overgrazing of grassland → top soil is removed by erosion leaving bare
infertile land.
Possible improvement: rotation of the areas to be used for grazing
2- Overfishing → fish stocks are destroyed (e.g. cod) disturbing food
chains.
Possible improvement: Fishing Regulations protecting the endangered
species and encouraging the fishing of other species
1-Growth of crops for cash (e.g. coffee) rather than food in developing
countries → need to buy food → get into debts
2-Destruction of rain forest to sell wood → once forest is destroyed, loss
of species and therefore source of food → top soil rapidly eroded cannot
sustain agriculture → no more natural resources for either food or sales.
1- Agriculture:
a/ Soil fertility → to maintain supply of minerals:
- use of fertilisers, manure
- Crop rotation
b/ Control of plant species growing on land:
- use of herbicides to kill other undesirable species
- species chosen and sown by farmer
- crop rotation to avoid establishment of a single species
c/ Control of disease causing organisms
- use of insecticides (kill insects), fungicides (prevent fungal infections)
and herbicides (kill weeds)
- crop rotation to avoid establishment of a specific disease causing
organism
2- Forestry:
→ protection of vulnerable young plants on exposed forestry sites
- young plants grown in nurseries and transplanted when strong enough to
survive on exposed site
- young plants protected against deer grazing until big enough to survive it.
- fire breakers
Credit material is in italics.
GDS
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