Standard Grade Biology topic: Biosphere

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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

2- Describe an example of a technique which might be used for sampling organisms and describe its use


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.


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.

3- (C) Identify a possible source of error that might be involved in a sampling technique and explain how it might be reduced.

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


- 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

4- Identify two abiotic factors

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.

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

6-(C) Identify a possible source of error that might occur during the measurement of an abiotic factor& explain

how it might be reduced

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

7- State the effect an abiotic factor has on the distribution of organism

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.

8- (C) Explain ways in which abiotic factors can influence the distribution of organisms

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.

The biosphere

2- How it works

1- Describe what is meant by the words habitat, population, community and ecosystem

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


2- Describe what is meant by the word producer and consumer

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)

3- Give an example of a food chain or a food web

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

Animals which normally feed on this organism will decrease in numbers. Plants/animals which are consumed by this organism will increase in number.

6- State two ways in which energy can be lost from a food web

- heat energy

- movement energy

- undigested part of food, e.g. bones

7- (C) Explain what is meant by the terms pyramid of numbers (1) and pyramid of biomass (2) (and pyramid of energy(3))

(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

8- State what the growth rate of a population depends on

It depends on both:

- the birth rate (number of birth/1000/year)

- the death rate (number of death/1000/year)

9- State three factors which can limit the growth of a population

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
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 .

12- State when competition occurs

- when resources are limited + organisms compete for the same resources e.g. food, space, nesting grounds

13- Describe some effect of competition

- 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

14- Explain why re-cycling of nutrients is important to the organisms in an ecosystem

Nutrients (i.e. minerals such as nitrates) are in limited supply → if no re-cycling → nutrients would eventually run out.

The biosphere

3- Control and management

What is pollution

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)

3- (C) Explain the undesirable effects of using (a) fossil fuels and (b) nuclear power as energy sources.

(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).

4- Give an example of one way in which pollution may be controlled.

- 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

5- State to which organisms organic wastes are food to.

(organic wastes are materials of plants and animals: e.g. sewage, blood from slaughter houses)

They are food to micro-organisms (bacteria and fungi).

6- Describe the effect of increased number of micro-organisms on the oxygen available to other organisms

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).

7- (C) Explain how organic waste pollution can affect the numbers of micro-organisms and hence oxygen concentration and numbers of species.

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

8- (C) State what is meant by “indicator species” and explain how they are affected by changing oxygen concentrations

Indicator species: gives an indication of the levels of pollution or some other abiotic factors.


May fly → unpolluted

Freshwater shrimp → unpolluted or slight pollution

Blood worm and no may fly or freshwater shrimp → very polluted


Variety of lichens → very low/no pollution with sulphur dioxide.

9- Give two examples of poor management of natural resources and suggest possible improvements

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

10- Describe how the effect

of poor management of natural resources can lead to problems

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.

11- Explain how parts of an ecosystem are controlled in either agriculture or forestry

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

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