GCSE Biology Topic 7

Define 'community'.

A group of interdependent organisms that are made of different species

Define 'ecosystem'.

The interaction of a community with the abiotic parts of the environment

What are abiotic factors? State two examples.

Non-living factors in an environment (eg. light intensity, soil pH, wind, humidity, temperature)

What are biotic factors? State two examples.

Living factors in an environment (eg. predators, competitors, pathogens/microorganisms)

Define 'population'.

A group of organisms of one species that interbreed and live in the same place at the same time

What is interdependence?

A relationship that describes how all species within a community depend on each other to survive

What is meant by a stable community?

Where all the species and environmental factors are in balance, hence population sizes remain fairly constant

A disease causes large areas of trees to die. Is their death cause by an abiotic or biotic factor?

Biotic (as diseases are caused by pathogens, which are living beings)

Briefly explain why low light intensity may decrease animal populations.

Less light, less photosynthesis by plants --> poor plant growth --> less plant availble for animals to eat --> less herbivores grow and survive --> further affects higher levels in the food chain

Sort the following into abiotic and biotic factors: soil pH, availability of food, oxygen availability, wind intensity, new competitors, carbon dioxide levels

Ab: soil pH, CO2 levels, O2 availability, wind intensity; Bio: food availability, new competitors

State three biotic factors.

New pathogens, new predators, new competitors, food availability

State an equipment that is commonly used to investigate a population of plants in a particular area.

Quadrat

What is quantitative sampling?

A technique to record and estimate the number of organisms in a particular area

How can the distribution of a species be measured?

Sampling along a transect

State a difference between quantitative sampling and transect sampling.

Quantitative sampling takes samples at random coordinates; Transect sampling takes samples at specific intervals along the line (not random)

What are the three things that animals compete for?

Food, mates, territory

Give one characteristic of a lion that makes it a good competitor.

Sharp teeth/claws

Give one charactersitic of a deer that makes it a good competitor.

Horns/Antlers

Give one charactersitc of a peacock that makes it a good competitor, and state what it is competing for using this trait.

Behaviour (eg. mating dance)/Attractive, colourful feathers to attract mate

Tigers urinating on trees is a behaviour adaptation to compete for...?

Territory

Wasps building nests is a behaviour adaptation to compete for...?

Shelter/Habitat

Owls' sharp hearing is an adaptation to compete for...?

Food

What are the four things that plants compete for?

Light, space, water, mineral ions

Some small plants in woodlands grow only in winter and dies before spring comes. Suggest why this occurs.

To avoid competiton for sunlight when large trees grow leaves and block out sunlight in spring/summer

Suggest why plants may have different root depths.

To avoid competition for water and/or minerial ions at the same soil depth

Suggest why seed dispersal is considered an adaptation to avoid competition.

Seed is carried far away instead of landing right next to parent plant, so offspring plant doesn't compete with parent plant

Catcus' long roots is a feature to help compete for...?

Water

Large flowers are a feature to help compete for...?

(attract) Pollinators

Weeds' rapid growth in height is a feature to help compete for...?

Light

What are extremophiles?

(micro)organisms that live in environments that are very extreme (eg. high temp, pressure, salt conc)

Which domain tends to include most extremophiles?

Archaea

State the specific name given to extremophiles that are adapted to live in high temperatures.

Thermophiles

Suggest one adaptation that thermophiles have to help them live in high temperatures.

Special enzymes with higher optimal temp (don't denature at high temp)/Specially structured cell membrane and/or cell wall

Suggest one adaptation that halophiles have to help them survive in salty areas.

Special cytoplasm to prevent water loss by osmosis/Special cell membrane/cell wall

For animals that living in cold climates, would they have adaptations to increase or decrease their surface area to volume ratio?

Decrease

Why do animals that live in hot climates adapt to have a high SA:V ratio?

Increase heat loss

State an adaptation that polar bears have to survive in cold climates.

More insulation (thick fat layer + fur)

Give a behavioural adaptation of penguins.

Huddling

What is stored in camels' humps and what is it for?

Fat store --> can be metabolised to make water

Apart from their humps, give one other adaptation of camels to help them reduce water loss.

Specially adapted kidneys / Very little sweating

Arctic foxes' fur coat changes from grey to white during winter. Suggest two reasons why.

Reduce heat loss by radiation + Better camouflage in the snow

What is the major way in which plants lose water in hot, dry conditions?

Transpiration

Why do plants in dry and hot conditions have curled leaves?

Traps moist air --> reduce water vapour conc gradient --> Reduce transpiration

Why do some plants have thorns?

Prevent predation by herbivores

Why do some plants have long roots?

Increase water uptake

Why do cacti have swollen stems?

Store water

Why do cacti have spine-like leaves?

Reduce SA --> reduce water loss

Define 'biomass'.

Amount of biological material in an organism (without water)

What are producers?

Organisms that can make food/biomass from raw materials such as CO2 and water (eg. plants, algae)

How do producers make biomass?

By doing photosynthesis

What are primary consumers? Give an example.

Animals that eat producers + Any herbivores (eg. cows, sheep, rabbits)

What are secondary consumers? Give an example.

Animals that eat primary consumers + Any carnivores (eg. lions, foxes, eagles)

Secondary consumers may be eaten by...?

Tertiary consumers

Describe and explain how prey population changes as predator population increases.

Prey population decreases as more predator eats more prey

Describe and explain how predator population changes as prey population decreases.

Predator population decreases, as less prey/food available, more predators die

Describe and explain how prey population changes as predator population decreases.

Prey population increases, as less predators hunting them, more prey can survive and reproduce

Describe and explain how predator population changes as prey population increases.

Predator population increases, as more food/prey available, more predator and eat to survive and reproduce

What are decomposers?

Microorganisms that break down waste products and dead bodies

Name the type of organism that decomposes dead material.

Microorganisms

As decomposers break down organic material, what is released into the air? How does it return to organisms?

Carbon dioxide --> taken into producers for photosynthesis

As decomposers break down organic material, what is released into the soil? How does it return to organisms?

Mineral ions (eg. nitrates) --> taken into producers through roots to build biomass (eg. proteins)

Name two ways in which organic material is returned to the soil for decomposers to break down.

Death + Excretion

Name two ways in which water gets released from plants to the environment.

Transpiration + Respiration

Name the process where water escapes into the ocean through gaps between soil and rocks.

Percolation

Name the process where water is rained down from the clouds.

Precipitation

Name the process(es) where water escapes from the oceans and into the clouds.

Evaporation and condensation

How does carbon get from the air into plants?

Photosynthesis

How does carbon from plants get into animals?

Feeding/Eating

How does carbon from animals get into the atmosphere?

Respiration/Decay (or decomposition)

How does carbon from plants and animals get formed into rocks?

Fossilisation

How does carbon from fossil fuels get into the air?

Combustion

In what form is carbon in the air?

Carbon dioxide

State three abiotic conditions for decay.

Temperature, moisture levels, oxygen availability

Explain why decay slows down or stops if the temperature is too hot or cold.

Enzymes in decomposers denatured if too hot/inactive if too cold

Explain why decay occurs in moist conditions, but not dry conditions.

Moisture helps microorganisms digest food easier and prevents them from drying out

Explain why oxygen is needed for faster decay.

Most decomposers respire aerobically to break down organic material

How are compost made?

Allowing kitchen and garden waste and manure (animal feaces) to decompose

What are composts used for?

Natural fertilisers

What does anaerobic decay produce?

Methane

How may anaerobic decay be useful?

Produce methane (biogas) to use as fuel

What machine is needed to make methane from decaying material?

Biogas generators

Define 'biodiversity'.

A measure of the variety of all the different species of organisms within an ecosystem

Why is having a high biodiversity important to form stable ecosystems?

Each species becomes less dependent on specific species for food/shelter --> less pressure on certain species which could've lead to extinction --> all species populations are balanced

What are two major problems from the exponential increase in human population?

More natural resources are used up + Produce more wastes --> decrease biodiversity

State four sources of land pollution.

Human sewage + Household wastes + Industrial wastes + Pesticides and herbicides in farming

How does land pollution affect our biodiversity?

Less (clean) food available / Loss of habitat / Global warming leading to migration

How does human sewage contribute towards land pollution?

Harmful microbes and bad chemicals lead to spread of diseases on land

Explain how household and industrial wastes pollute land.

Take up space in landfills + Toxic/radioactive chemicals --> poison soils + destorys habtitats

State four sources of water pollution.

Untreated sewage + Fertilisers + Industrial wastes + Pesticides and herbicides

Name the situation where a body of water has low oxygen levels, leading to marine organisms' death.

Eutrophication

What causes eutrophication?

Fertilisers leaked into lakes, excess nutrients causes excessive plant growth, leading to an increase in competition/algae covering water surface (less light allowed into lake for water plants)

What is bioaccumulation?

Accumulation of chemicals in an organism

Name a chemical that gets built up in organisms in bioaccumulation.

Heavy metals/Fertiliers/Pesticides/Herbicides

Why is bioaccumulation bad?

Chemical conc increases each trophic levels --> may reach fatal levels when get to the top consumer

Name a source of air pollution.

Combustion of fossil fuels

How is acid rain formed?

Acidic gases released from burning fossil fuels are dissolved in rain water

Name three acidic gases released from burning fossil fuels.

Carbon dioxide + sulphur dioxide + Nitric oxides

Give 3 effects of acid rain.

Kills plants; Destroys roots in soil; Acidifies bodies of water, killing marine organisms; Affects neighbouring countries; Acid snow kills young plants

What is global dimming?

Particulates made from combustion covers the atmosphere, reflecting sunlight so less light reaches the surface

What causes global dimming?

Particulates