GCSE Biology: Ecology

What is a habitat?

The environment in which an organism lives in.

What is a population?

The total number of organisms of the same species living in the same geographical area.

What is a community?

The populations of all the different species that live in the same habitat.

What word is used to describe the living part of the environment?

Biotic

What word is used to describe the non-living part of the environment?

Abiotic- These include the amount of water and minerals in the soil.

What is an ecosystem?

Both the biotic and abiotic parts of an environment and how they interact.

What do plants compete with each other for?

• Light

• Space

• Water

• Mineral ions in the soil

What do animals compete with each other for?

• Food

• Water

• Mating partners

• Territory

What is interdependence?

Where, in a community, each species depends on other species for things such as food, shelter, pollination and seed dispersal.

What is a stable community?

A community where all the species and environmental factors are in balance, so that the population sizes are roughly constant.

What are the 4 different biotic factors that might affect organisms in an ecosystem?

• Availability of food

• Arrival of new predator

• Competition

• New pathogens

What are the 7 different abiotic factors?

• Light intensity

• Temperature

• Water/moisture levels

• pH and mineral content of the soil

• Wind intensity and direction

• Carbon dioxide levels (for plants)

• Oxygen levels (for aquatic animals)

Significance of availability of food

If the availability of food falls, then the number of organisms in that community will also fall.

Significance of the arrival of a new predator

• Can cause the population of a prey species to fall

• Can also affect existing predators e.g. if they’re competing for the same prey

Significance of competition (between species)

If a species is outcompeted then it’s population can fall so much that numbers are no longer sufficient to breed and the species may become extinct.

Significance of new pathogens

If an infectious disease emerges and then spreads, it can wipe out a population of a species.

Significance of light intensity

• All plants need light to carry out photosynthesis; if the light intensity is too low then the rate of photosynthesis falls and the plants will grow more slowly.

• This is significance because if plants grow more slowly, then animals that eat plants may not have enough food

Significance of temperature

• If the temperature of an environment changes then this could cause the distribution of species to change

• E.g. animals could migrate and plant species might disappear from that area.

Significance of water/ moisture levels

It’s a significance abiotic factor as without water, both plants and animals can’t survive.

Significance of pH and mineral content of the soil

• Many plants cannot grown on soil which is too acidic or too alkaline

• Plants also require certain minerals in the soil e.g. nitrate which is used to make amino acids for proteins

Significance of wind intensity and direction

• Strong winds blowing inland from the sea can cause plants to lose water

Significance of carbon dioxide levels (for plants)

• Plants need carbon dioxide to photosynthesise and if carbon dioxide levels fall then the rate of photosynthesis can also decrease, meaning that the plant grows more slowly. If plants grow slower, then animals that feed on plants may not have enough food.

Significance of oxygen (for aquatic animals)

• Oxygen is needed for aerobic respiration

• The level of dissolved oxygen in water can decrease e.g. on hot days. This is harmful to aquatic organisms such as fish.

What are the structural adaptations of camels?

• Camels have a hump on their back which is a store of fat. Fat is a thermal insulator. By storing the fat in one place, this allows heat loss from the other parts of the camel’s body. This reduces water loss from sweating.

• Camels have a thick coat on the upper surface of their body. This insulates the top of the camels from the heat of the sun; this reduces water loss from sweating.

• The inside of a camels mouth is leathery. This means that they can chew desert plants which often have thorns. (These plants can be a good source of water).

• Camels have long eyelashes to keep dust out of their eyes.

• Camels can close their nostrils to keep dust out of their nose.

• Camels have wide feet which prevents the camel from sinking into the sand.

What are the functional adaptations of camels?

• Camels produce concentrated urine which reduces water loss.

• Camels produce dry faeces which reduces water loss.

• Camels can tolerate very large changes in their body temperature. This helps them to cope with intense heat of the desert.

• Can break down fat in hump to release water

What are the behavioural adaptations of a kangaroo rat?

• They’re nocturnal which means that they avoid the heat of the daytime (in the desert).

• During the day, kangaroo rats live in burrows underground. This keeps them cool and protects them from predators.

What are the structural adaptations of an arctic fox?

• Arctic foxes have very thick fur. This provides insulation and reduces heat loss to the air.

• Arctic foxes also have fur on the soles of their feet which reduces heat loss to the ice and snow.

• Artic foxes also have very small ears. This reduces the surface area of the fox, reducing heat loss.

• The coat of arctic foxes provide effective camouflage which helps them to hunt their prey.

What are the adaptations of cacti?

• Some cacti have very small leaves which reduces water loss (which is a huge problem for plants in dry conditions).

• Other cacti have no leaves at all, only spines so they don’t lose water.

• Cacti have spines which also protect them from animals.

• Cacti have extensive and shallow roots (as deserts are dry and it doesn’t rain very often) which allows them to catch as much water as possible after rainfall, before the water evaporates or sinks into the ground.

• Cacti can also store water in their stem meaning that they can survive many moths without rain.

What is an extremophile?

An organism which is adapted to live in very extreme conditions, such as high temperature, pressure or salt concentrations.

Give an example of an extremophile.

Bacteria living in deep sea vents.

What is the producer in a food chain?

A producer is an organism that makes its own food using energy from the sun. All food chains begin with a producer.

• In most food chains, the producer is a green plants or algae as they make their own food (which is glucose) by photosynthesis.

Why are producers extremely important in food chains?

Because they’re the source of all the biomass/energy in a food chain.

What is biomass?

The total mass of the living material that is found in an organism, multiplied by the number of organisms that can be found

What are primary consumers?

Organisms that eat the producers.

What are secondary consumers?

Organisms that eat primary consumers

What are tertiary consumers?

Organisms that eat secondary consumers.

What are predators?

Consumers that kill and eat other animals

What are prey?

The animals that are eaten by predators.

Describe the practical for studying the distribution of organisms using quadrats

You can use quadrats to compare how common an organism is in 2 sample area or to work the population size of an organism in 1 area (estimates).

• Place 2 (20m) tape measures at right angles and divide the area into a grid

• Randomly select 2 numbers to the the coordinates for your first quadrat and then count all the organisms within the quadrat.

• Repeat step 2 as many times as you can to increase the validity of your experiment.

• Use formula to estimate the total population size of the organism of that species counted in sample

What is the formula for total population size (abundance) of an organism?

total area/area sampled × number of organisms of that species counted in sample

Describe the practical for studying the distribution of organisms using transects.

You can use lines called transects to study how organisms are distributed across an area.

• Mark out a line in the area you want to study using a tape measure (the transect is the tape measure).

• Then collect data along the line, using a quadrat to count the number of organisms at intervals on the transect.

• Move the tape measure along and repeat step 2 a number of times to get valid results.

Environmental changes that affect the distribution of organisms

These environmental changes can be caused by seasonal factors, geographic factors or human interaction.

• Temperature: The distribution of bird species in Germany is changing because of a rise in average temperature e.g. the European bee-eater is a Mediterranean species but it’s now present in parts of Germany.

• Availability of water: The distribution of some animals and plant species in the tropics change between the wet and dry seasons e.g. each year in Africa, large numbers of giant wildebeest migrate, moving North and then back South as the rainfall patterns change.

• Composition of atmospheric gases: The distribution of some species changes in areas where there is more air pollution e.g. some species of lichen can’t grown in areas where sulfur dioxide is given out by certain industrial processes.

Describe carbon cycle

The carbon cycle starts with carbon dioxide in the atmosphere

Photosynthesis brings carbon into the cycle (only way)

Carbon dioxide returns back to the atmosphere by respiration (every single living organisms carries out respiration).

• Carbon dioxide in atmosphere

• Plants and algae take in carbon dioxide in the atmosphere in photosynthesis

• The carbon is used to make glucose, which can be turned into carbohydrates, fats and proteins that make up the bodies of the plants and algae.

• Plants and algae respire so some of the carbon is released back to the atmosphere as carbon dioxide

• Plants and algae can be eaten by animals, carbon becomes part of the carbohydrates, fats and proteins in their bodies.

• The carbon then moves through the food chain.

• Animals (like plants) respire so some of the carbon is released back to the atmosphere as carbon dioxide.

• Animals release waste products such as faeces and eventually all plants and animals die. Now we have carbon is waste products and dead remains This is broken down by other animals (called detritus feeders) and decomposing microorganisms (e.g. bacteria and fungi).

• When decomposers carry out respiration, the carbon in the waste and dead remains is returned to the atmosphere as carbon dioxide.

• However, under certain conditions, decomposers cannot function effectively. If this happens, then the carbon is dead remains can slowly be converted to fossil fuels.

• When these fossil fuels are combusted, large amount of carbon are released back into the atmosphere as carbon dioxide.

Why are decomposers extremely important?

Because they cycle materials through an ecosystem.

What do decomposers do?

• Release carbon back into the atmosphere as carbon dioxide

• Release mineral ions to the soil

Describe the water cycle

Key points:

All forms of precipitation contain fresh water (no salt).

• Energy from the sun causes the water to evaporate from the surface of the sea

• The water vapour now travels into the air and cools down. When it cools down it condenses to form clouds.

• The water in clouds then falls to the ground as precipitation (usually rain, but sometimes snow, hail and sleet).

• Once the water hits the ground: some of the fresh water is provided for the plants and animals, some of it simply evaporates back into the atmosphere as water vapour, some of it passes through rocks and forms aquifers and a lot of the water forms rivers or streams. The water in plants leave by transpiration. The water in animals is released in their urine, faeces and when they exhale. The water in rivers and streams eventually drains back into the sea, before the whole process starts again.

What is decay?

The process through which microorganisms break down plant and animal waste to get energy. This process allows the material contained within the organisms to be released, so that it can cycle through the ecosystem.

What does decomposition produce?

Compost- a dead decomposed organic matter (e.g. food waste) that is used as a natural fertiliser for crops and garden plants

Farmers and gardeners try to provide the ideal conditions for quick decay in order to make compost.

What are the optimal conditions for decay?

• Temperature

• Water availability

• Oxygen availability

Why are compost heaps quite warm?

Because decomposers release energy when they carry out aerobic respiration.

How does temperature affect the rate of decay?

Decay takes place faster at warmer temperatures as decomposers use enzymes to break down plant material and these enzymes work faster in warm conditions. However, it’s important that the compost doesn’t get too hot. This slows down or stops the rate of decay as the enzymes could denature and the decomposers can die. Really cold temperatures slow down the rate of decay too.

How does water availability affect the rate of decay?

Decomposing microorganisms work faster in moist environments as they need water to carry out biological processes.

How does oxygen availability affect the rate or decay?

Many decomposers carry out aerobic respiration, which requires a good supply of oxygen, in order to survive.

What do decomposing microorganisms do in the absence of oxygen?

Carry out anaerobic decay

What does anaerobic decay produce?

Biogas

What is biogas?

• A mixture of gases, mainly methane

• Biogas generators can be used to produce biogas as a fuel.

• Biogas generators need to be kept at a constant temperature to keep the microorganisms respiring away.

• Biogas can’t be kept as a liquid (it needs too high a pressure), so it has to be used straight away.

• Biogas can be used for: heating, cooking, lighting, or to power a turbine to generate electricity.

What are the 2 main types of biogas generators?

Key points:

Both generators requires:

1) An inlet for waste material to be put in

2) An outlet for digested material (to be used as fertiliser) to be removed through.

3) An outlet so that the biogas can be piped to where it is needed.

• Batch generators- Batch generators make biogas in small batches. They’re manually loaded up with waste, which is left to digest, and the by-products are cleared away at the end of each session.

• Continuous generators- Continuous generators make biogas all the time. Waste is continuously fed in, and biogas is produced at a steady rate.

What is biodiversity?

The variety of all of the different species of organisms on Earth or in an ecosystem.

Why are human activities increasing pollution and reducing biodiversity?

• Rapid growth in the human population and an increase in the standard of living mean that increasingly more resources are used and more waste is produced

• Unless waste and chemical materials are properly handled, more pollution will be caused.

• Pollution affects water, land and air and kills plants and animals, reducing biodiversity.

What does biodiversity do?

• It makes an ecosystem more stable, the higher the rate of biodiversity the more stable the ecosystem. This is because there are more species so the ecosystem is less dependent on one species for food, shelter and the maintenance of the physical environment.

Describe how water pollution is caused and how it reduces biodiversity in aquatic ecosystems.

• Sewage: Untreated sewage is accidentally released into rivers or streams. This causes dissolved oxygen levels in the rivers or streams to fall, which can kill aquatic organisms.

• Toxic chemicals from industry: Sometimes toxic chemicals are released into rivers from factories, which can kill aquatic organisms.

• Chemicals used on land (e.g. fertilisers, pesticides and herbicides): They can be washed away into water, causing dissolved oxygen levels in rivers and streams to decrease, which can kill aquatic organisms.

Describe how air pollution is caused and how it reduces biodiversity.

• Burning coal:

  • This releases smoke and acidic gases into the atmosphere which can pollute the air, e.g. sulfur dioxide can cause acid rain.

  • Air pollution like this can kill plants and animals, reducing biodiversity.

Describe how land pollution is caused and how it reduces biodiversity.

• Landfills:

  • Millions of tons of waste are dumped in landfills. Landfills destroy habitats for plants and animals, which can kill off living organisms, reducing biodiversity

• Toxic chemicals:

  • Toxic chemicals can also leach out of landfills and pollute the soil. These chemicals can kill living organisms, reducing biodiversity.

What are structural adaptations?

These are features of an organisms body structure- such as shape or colour.

What are behavioural adaptations?

These are the way that organisms behave which help them survive. Many species migrate to warmer climates during the winter to avoid the problems of living in cold conditions.

What are functional adaptations?

These are the things that go on inside an organism’s body that can be related to processes.

One example of how humans are having a negative effect on biodiversity is deforestation . Explain why?

• Tropical forests contain a very rich biodiversity.

• However, large areas of these forests are being destroyed to provide land.

• The land is used for: rice fields, grazing cattle and to grow crops which are then used to make biofuels.

• Deforestation means that many species have a reducing habitat, thus reducing biodiversity.

Why do humans need land?

For buildings, quarrying, farming and dumping waste

• All of this means that there’s less land available for animals and plants.

• Due to the reduction in habitats, this reduces biodiversity.

What is peat used for?

• Fuel

• Garden compost

What are problems with peat extraction?

• Draining peat bogs reduces biodiversity because they are a unique environment and some species can only live there.

• Using peat for energy releases CO2 into the atmosphere

• (Garden compost) When peat is exposed to the air it starts to decay- microorganisms respire while they do this, releasing CO2 into the atmosphere.

• Destroying peat bogs increases risk of flooding as they help absorb water.

What two groups carry out decomposition?

• Detritus feeders

• Decomposers

What are detritus feeders and what do they do?

They’re small animals like worms and woodlice. They feed on dead organic matter.

Why could the rate of decomposition fall if soil becomes waterlogged?

Water fills the air gaps within soil, decreasing the oxygen levels. This decreases the aerobic respiration carried out by decomposers, thus slowing down the rate of decomposition.

• e.g. in peat bogs

Give 3 reasons why maintaining a high biodiversity is important

• It increases the stability of the ecosystem, so that changes are less likely to have adverse affects

• Many species provide specific services, such as pollination

• Many of our medicinal drugs come from wild species

Effects of deforestation

• Tree cutting- There will be fewer trees carrying out photosynthesis and absorbing carbon dioxide from the atmosphere. This means there is more carbon dioxide contributing to global warming. 

• Deforestation often involves burning the trees, which releases carbon dioxide into the atmosphere.

• It destroys animals' habitats, meaning that fewer species can survive. This reduces biodiversity . 

What are peat bogs?

Areas of land where the soil is acidic and waterlogged. This means that the microorganisms that carry out decay can’t function because the conditions are too acidic, but also because the peat bogs are waterlogged. This stops the air from getting into the soil so there’s not enough oxygen for aerobic respiration.

Why are materials cycled?

All materials in the living world are recycled to provide the building blocks for future organisms.

Describe the effects of global warming

Levels of carbon dioxide and methane in the atmosphere are increasing, and contribute to ‘global warming’

Effects:

• Loss of habitats e.g. ice levels reducing in the Arctic which will cause populations of Arctic organisms such as polar bears to fall as their habitat is reduced.

• Migration of species- As global temperatures rise, animals such as insects and birds may gradually extend their range northwards towards cooler regions e.g. mosquitos cannot survive in cold conditions such as the UK. However if global temperatures rise, it’s possible that mosquitos will spread to the UK and spread malaria too.

• Migration patterns of species may change

• Plants- e.g. spring plants in the UK are flowering earlier due to warmer conditions. In the future, as temperature increases, it might be possible to grow crops such as grapes in the parts of the UK where we can’t today. However in other parts of the world it might be too hot to grow the crops that they need.

What is climate change?

The effects of global warming

What is the atmosphere?

The atmosphere is a layer of gases surrounding the Earth that is held in place by gravity.

What is the difference between climate and weather?

Weather refers to short term atmospheric conditions, like whether it's raining or sunny on a particular day

Climate describes the typical weather conditions in an entire region for a very long time

How to reduce the loss of biodiversity?

• breeding programmes for endangered species

• protection and regeneration of rare habitats

• reintroduction of field margins and hedgerows (where wild plants and animals can live) 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

Trophic levels

Trophic level 1- producer

Trophic level 2- primary consumer

Trophic level 3- secondary consumer

Trophic level 4- tertiary consumer

What are apex predators?

Carnivores with no predators

How do decomposers break down dead plant and animal matter as well as waste product?

• Decomposers secrete/release enzymes into the environment.

• The enzymes digest the dead materials and the small soluble food molecules then diffuse back into the decomposer.

What do the arrows in a food chain show?

The transfer of energy & biomass

What are pyramids of biomass?

Pyramids which represent the total biomass of all organisms in each trophic level.

How much of the light energy that falls on producers is actually absorbed and used for photosynthesis?

1%

Explain how biomass is lost between the different trophic levels

• Only approximately 10% of the biomass from each trophic level is transferred to the level above it

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

  • Some of the ingested material which is absorbed is converted into waste products of metabolism and is released.

  • Some of the ingested material which is absorbed is lost as waste, such as carbon dioxide and water in respiration and water and urea in urine

What is biomass???

A living tissue of an organism including proteins, lipids and carbohydrates.

Give an example of waste products in humans

urea

What is the energy released from respiration used for?

• In movement

• To maintain a constant body temperature (mammals and birds)

Why are there very few food chains with a large number of different trophic levels?

Because in most food chains the biomass at each trophic level tends to decrease by 90%.

Formula for efficiency of biomass transfer

Efficiency= Gain in biomass/total biomass intake

What is food security?

Having enough food to feed a population.

What are the 6 biological threats to food security?

• The increasing birth rate in some countries- As the population grows, the amount of food available will have to increase to feed the whole population.

• Changing diets in developed countries-changing diets in developed countries means scarce food resources are transported around the world from different countries, which can threaten their food security.

• New pests and pathogens that affect farming- Pests eat food crops and pathogens cause infectious diseases. Both of these reduce the amount of food crops available to eat.

• Environmental changes that affect food production- Unpredictable weather is an effect of global warming. This could change rainfall patterns which threatens the food security of many countries as they might not be able to grow enough crops to feed their populations, which could lead to widespread famine.

• The cost of agricultural inputs-Many farming methods require a great deal of resources e.g. many farmers rely on fertilisers and pesticides to increase their crop yields and farmers producing livestock need to buy food for their animals. As the population of the world increases, these resources may become more expensive. In certain countries, this increased cost may be more than they can afford which threatens their food security.

• Conflicts-Conflicts that have arisen in some parts of the world which affect the availability of water or food as imports of food and water may not be possible.

Sustainable methods must be found to feed all people on Earth

How can the efficiency of food production in farming be improved?

Through intensive farming

• Food animals are raised inside a temperature-controlled shed.

• This means that less biomass is wasted through the animals trying to maintain a constant body temperature.

• The space in these sheds is limited which restricts the animals’ movement.

• This means that less biomass is wasted through respiration required for animals’ movement.

This means that less biomass is wasted compared to free-range animals.

• Some animals are also fed a high protein diet to increase growth.

• The food the animals eat is controlled so it contains all the nutrients they need and less food is wasted.

What are free-range chickens?

Chickens that can move as much as they want to. They’re provided with food, but they can also find their own food e.g. insects.

• Problems:

  • A lot of the biomass that these chickens eat is being used in respiration, providing energy for movement.

  • Also because these chickens are outdoors where it can be cold, energy is needed to keep their body temperature constant.

• This means that there’s less biomass for the chickens to grow and also produce eggs.

What are disadvantages of intensive farming?

• In crowded conditions, infectious diseases can spread more easily. To prevent this animals in factory farms are often treated with antibiotics which could increase the risk of antibiotic-resistant bacteria.

• In crowded conditions, the animals are more likely to be stressed and to fight.

Ethical objections to some modern intensive farming techniques

• People believe that animals should be raised in natural conditions and able to engage in normal behaviour e.g. foraging for their own food. People believe that this will increase the animals’ welfare e.g. reducing stress.