AQA GCSE Single Science Biology: Ecology

When has extinction occurred?

When there are no remaining individuals of a species still alive.

How should the problem of antibiotic resistance be lessened?

• doctors should not prescribe antibiotics inappropriately, such as for treating non-serious or viral infections

• patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains

• the agricultural use of antibiotics should be restricted.

Describe the process of antibiotic resistance

• Mutations of bacterial pathogens produce new strains.

• Some strains might be resistant to antibiotics, and so are not killed.

• They survive and reproduce, so the population of the resistant strain rises.

• The resistant strain will then spread because people are not immune to it and there is no effective treatment.

Define the following terms: ecosystem, community, population

• Ecosystem: the interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment.

• Community: all the populations of different organisms that live together in a habitat

• Population: all the members of a single organism that live in a habitat

For which factors do plants compete?

• Light

• Space

• Water

• Mineral ions

For which factors do animals compete?

• Food

• Mates

• Territory

What do species rely on one another for?

• Seed dispersal

• Food

• Shelter

• Pollination

This is called interdependence

What is a stable community?

One where all the species and environmental factors are in balance so that population sizes remain fairly constant.

List some abiotic factors affecting a community

• light intensity

• temperature

• moisture levels

• soil pH and mineral content

• wind intensity and direction

• carbon dioxide levels for plants

• oxygen levels for aquatic animals.

List some biotic factors affecting a community

• availability of food

• new predators arriving

• new pathogens

• one species outcompeting another so the numbers are no longer sufficient to breed.

Outline a basic food chain.

• A producer (plants or algae that make their own food via photosynthesis) is eaten by a primary consumer

• A primary consumer is a herbivore (plant eater). They are then eaten by a secondary consumer.

• A secondary consumer is a carnivore (meat eater). They are then eaten by a tertiary consumer.

• A tertiary consumer is a carnivore (meat eater). They may be the apex predator, which means they have no predators and are at the top of the food chain.

Required practical: Measure the population size of a common species in a habitat

• Randomly place quadrats and count number of organisms in a quadrat

• Do this many times to calculate a mean- you may use this and the area of the sample area to calculate a mean for the whole sample area.

• You can do this with a transect too- count the number of organisms touching the transect or place quadrats at certain intervals down the line

Explain the carbon cycle

• Carbon enters the atmosphere as carbon dioxide from respiration and combustion.

• Carbon dioxide is absorbed by producers in photosynthesis.

• Animals feed on plants, passing the carbon compounds along the food chain. Most carbon they consume is exhaled as carbon dioxide during respiration. The animals and plants eventually die.

• Dead organisms are eaten by decomposers and carbon in their bodies is returned to the atmosphere as carbon dioxide. In some conditions decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion.

Explain the water cycle

• Energy from the Sun evaporates water

• This cools and condenses, forming clouds

• Water falls as precipitation

• Some of this is absorbed and infiltrated- this is stored in underground rocks

• Some of this runs along the surface of the ground and joins a body of water

• Plants transpire and allow some water to evaporate from leaves

Which factors affect the rate of decay?

• Number of decay organisms

• Temperature

• Presence of oxygen

• Presence of water

Explain the process of generating biogas

• Anaerobic decomposition releases methane

• Methane is burned for cooking or heating

• Carbon dioxide released in burning is used in photosynthesis by animals

Required practical: Investigating effect of temperature on decay of fresh milk

1. Place 20 cm³ of fresh milk into three beakers

2. Decide the three temperatures you will investigate. Write these onto the sides of the beakers. They may be 5, 20 and 35°C.

3. Use universal indicator paper or solution to determine the pH of the milk in the three beakers

4. Cover each beaker in cling film and incubate at the appropriate temperature

5. Use universal indicator paper or solution to determine the pH of the milk in the three beakers after 24, 48 and 72 hours

Which environmental changes affect the distribution of species?

• temperature

• availability of water

• composition of atmospheric gases.

What is biodiversity and why do we need it?

• Biodiversity: the variety of all the different species of organisms on earth, or within an ecosystem

• A great biodiversity ensures the stability of ecosystems by reducing the dependence of one species on another for food, shelter and the maintenance of the physical environment.

Where can pollution occur?

• in water, from sewage, fertiliser or toxic chemicals

• in air, from smoke and acidic gases

• on land, from landfill and from toxic chemicals.

Why are more resources being used and more waste being produced?

• Rapid growth in population

• Higher standard of living

How do humans reduce the amount of land available for organisms?

• Building

• Quarrying

• Farming

• Dumping waste

What are the problems with destroying peat bogs?

• Reduction in biodiversity

• Release of carbon dioxide in the atmosphere

Why has deforestation occurred in tropical areas?

• to provide land for cattle and rice fields

• to grow crops for biofuels

What are some effects of global warming?

• more frequent floods and droughts

• glaciers and polar ice melting

• sea levels rising

• loss of habitats

• temperature and water stress for humans and wildlife

• changes in the distribution of species

• changes in the ability of some regions to produce food

What is the greenhouse effect?

• Short-wave radiation from the Sun is absorbed by the Earth

• Greenhouse gases in the atmospheres absorb the long-wave radiation reflected by the Earth

• The trapping of these gases provides an insulating effect, warming the Earth.

• The increase of greenhouse gases thus increases this effect, causing global warming

What programmes have been put in place to reduce the negative effects of humans and ecosystems and biodiversity?

• breeding programmes for endangered species

• protection and regeneration of rare habitats

• reintroduction of field margins and hedgerows in agricultural areas where farmers grow only one type of crop

• reduction of deforestation and carbon dioxide emissions by some governments

• recycling resources rather than dumping waste in landfill.

Why is biomass lost?

Approximately 10% of the biomass from each trophic level is transferred to the level above it.

• not all the ingested material is absorbed, some is egested as faeces

• some absorbed material is lost as waste, such as carbon dioxide and water in respiration and water and urea in urine.

• large amounts of glucose are used in respiration.

What are some factors affecting food security?

• the increasing birth rate has threatened food security in some countries

• changing diets in developed countries means scarce food resources are transported around the world

• new pests and pathogens that affect farming

• environmental changes that affect food production, such as widespread famine occurring in some countries if rains fail

• the cost of agricultural inputs

• conflicts that have arisen in some parts of the world which affect the availability of water or food.

How can the efficiency of food production be improved?

• By restricting energy transfer from food animals to the environment.

• This can be done by limiting their movement and by controlling the temperature of their surroundings.

• Efficiency can also be improved by feeding animals high protein food

How can fish stocks be preserved?

• Control of net size

• Introduction of fishing quotas

What can GM foods do?

• Improve crop yield

• Improve nutritional value of food

What is Fusarium? How is it used?

• It is a fungus that produces mycoprotein- this is a protein-rich food suitable for vegetarians