Standard Grade Biology
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TOPIC: Biosphere
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The biosphere
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1- Investigating and ecosystem
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1- Identify the main parts of an ecosystem
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- Habitat (The place where an animal or a plant lives),
- Animals
- Plants
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2- Describe an example of a technique which might be used for sampling organisms and describe its use
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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.
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3- (C) Identify a possible source of error that might be involved in a sampling technique and explain how it might be reduced.
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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
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4- Identify two abiotic factors
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non-living factors: light intensity, soil-air-water temperature, soil moisture, etc…
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5- Give an example of a technique which might be used to measure an abiotic factor and describe its use.
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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
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6-(C) Identify a possible source of error that might occur during the measurement of an abiotic factor& explain
how it might be reduced
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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
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7- State the effect an abiotic factor has on the distribution of organism
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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.
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8- (C) Explain ways in which abiotic factors can influence the distribution of organisms
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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.
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The biosphere
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2- How it works
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1- Describe what is meant by the words habitat, population, community and ecosystem
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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.
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2- Describe what is meant by the word producer and consumer
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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)
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3- Give an example of a food chain or a food web
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See jotters/books
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4- State what the arrow in a food web stands for.
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The direction of the flow of energy from one organism to another.
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5- (C) Explain how removing one organism from a food web could affect the other organisms
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Animals which normally feed on this organism will decrease in numbers. Plants/animals which are consumed by this organism will increase in number.
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6- State two ways in which energy can be lost from a food web
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- heat energy
- movement energy
- undigested part of food, e.g. bones
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7- (C) Explain what is meant by the terms pyramid of numbers (1) and pyramid of biomass (2) (and pyramid of energy(3))
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(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
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8- State what the growth rate of a population depends on
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It depends on both:
- the birth rate (number of birth/1000/year)
- the death rate (number of death/1000/year)
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9- State three factors which can limit the growth of a population
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For example:
- lack of food, predators, lack of space, disease, lack of water, lack of light (for plants)
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10- Describe and (C) explain the shape of the growth curve of a population, under ideal conditions
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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 .
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12- State when competition occurs
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- when resources are limited + organisms compete for the same resources e.g. food, space, nesting grounds
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13- Describe some effect of competition
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- 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
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14- Explain why re-cycling of nutrients is important to the organisms in an ecosystem
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Nutrients (i.e. minerals such as nitrates) are in limited supply → if no re-cycling → nutrients would eventually run out.
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The biosphere
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3- Control and management
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What is pollution
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It is the addition of a harmful substance to an environment at a rate the environment cannot cope with it.
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1-State which ecosystems are affected by pollution.
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Air, land, fresh water and sea water
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2- State the main sources of pollution (3) and give examples of a pollutant from each category.
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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)
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3- (C) Explain the undesirable effects of using (a) fossil fuels and (b) nuclear power as energy sources.
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(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).
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4- Give an example of one way in which pollution may be controlled.
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- 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
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5- State to which organisms organic wastes are food to.
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(organic wastes are materials of plants and animals: e.g. sewage, blood from slaughter houses)
They are food to micro-organisms (bacteria and fungi).
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6- Describe the effect of increased number of micro-organisms on the oxygen available to other organisms
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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).
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7- (C) Explain how organic waste pollution can affect the numbers of micro-organisms and hence oxygen concentration and numbers of species.
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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
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8- (C) State what is meant by “indicator species” and explain how they are affected by changing oxygen concentrations
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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.
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9- Give two examples of poor management of natural resources and suggest possible improvements
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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
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10- Describe how the effect
of poor management of natural resources can lead to problems
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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.
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11- Explain how parts of an ecosystem are controlled in either agriculture or forestry
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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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