GCSE Biology: Ecology (paper 2)

What is a habitat?

The environment in which an organism lives in that includes both biotic and abiotic factors.

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 is a biotic factor?

Living factors that affect organisms in an ecosystem

E.g plants,animals , microbes

What is an abiotic factor?

Nonliving physical or chemical parts of the environment that affect living organisms and ecosystems

E.g light , water , soil . Temp.

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.

How are camels adaptes. &What are the structural adaptations of camels?

• Adapted to the hot & dry conditions of a desert

  Structural ADAPTATIONS; ( body shape / structure )

• hump on their back :

  • store of fat→ Fat is a thermal insulator → produce very little sweat

  • Water storage → can be broken down into water & energy when food & water are scarce

• thick coat on the upper surface of their body.

  • Thick fur insulates → camels from intense heat & cold nights

  • Tolerate big changes in body temp. → avoiding sweating during heat & saving water

• leathery mouth

  • can chew desert plants which often have thorns. (These plants can be a good source of water).

• Long lashes :

  • keeps dust out of their eyes.

• closable nostrils :

  • Protection from sand storms and dust

• wide , padded feet:

  • prevents camel from sinking into hot dessert sand.

What are the functional (internal) 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?

• nocturnal → active at night & avoid the heat during daytime (in the desert).→ cooler at night & less water loss through sweating / breathing

• burrowing → live in burrows underground → stay cool and protects them from predators.& store seeds to have food available

• Water conservation→ rarely drink water → get moisture from seeds they eat

What are the structural adaptations of an arctic fox?

• thick fur → provides insulation and reduces heat loss to the air.

• fur on the soles of their feet → reduces heat loss to the ice and snow.

• very small ears.→ reduces the surface area of the fox, reducing heat loss.

• 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 → 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.

• have spines → protect them from animals.

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

• store water in their stem → 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.

How do food chains revere sent feeding relationships in the community?

-shows how energy moves through a community by showing who eats whom

• Energy from sunlight flows from producers (plants) →primary consumers (herbivores ) eat producers → secondary consumers (carnivores) eat primary consumers _>tertiary consumers(top predators)eat secondary consumers

• EG:

  algae → water fly → small fish → large fish →

What is the producer in a food chain?

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 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. And cause them to move,die out or thrive

• Temperature: e.g animals move to warmer or cooler areas

• Availability of water: drought may reduce plant and animal life

• Composition of atmospheric gases: in areas where there is more air pollution

• Geographical changes : floods,sea level rise ,deforestation

• Seasonal change : birds migrate or animals hibernate

Describe carbon cycle

-it shows how carbon is recycled innature :

-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