Download The biosphere/ 1- Investigating an ecosystem

Standard Grade Biology
TOPIC: Biosphere
The biosphere
1- Investigating and ecosystem
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
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.
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
4- Identify two abiotic
factors
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…
5- Give an example of a
technique which might be
used to measure an abiotic
factor and describe its use.
6-(C) Identify a possible
source of error that might
occur during the measurement
of an abiotic factor& explain
how it might be reduced
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
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
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
The biosphere
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
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.
2- How it works
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)
- 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
10- Describe and (C) explain
the shape of the growth curve
of a population, under ideal
conditions
C
Population
size
B
A
Time
12- State when competition
occurs
13- Describe some effect of
competition
14- Explain why re-cycling of
nutrients is important to the
organisms in an ecosystem
The biosphere
What is pollution
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
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
- 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.
3- Control and management
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 microorganisms on the oxygen
available to other organisms
7- (C) Explain how organic
waste pollution can affect the
numbers of micro-organisms
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
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
Organic pollution enters water → provides lots of food only for
micro-organism → 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.
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