Ecology GCSE

Competition

• Key Definitions:
• Habitat - Where an organism lives
• Population - all the organisms of one species living in a habitat
• Community - the population of different species living in a habitat
• Abiotic factors - non living factors of the environment
• Biotic factors - living factors of the environment
• Ecosystem - the interaction of a community of living organisms with non living parts of their environment
• Organisms need things from their environment and other organisms to survive and reproduce, and they often have to compete with other species for these resources.
• In a community, each species depend on other species for things such as food, shelter, polllination and seed dispersal - this is called interdependence.
• The interdependence of all living things in an ecosystem means that if there are any changes such as the extinction of species, there can be several impacts.
• In some commmunities, all the environmental factors are in balance so that the population sizes are rougly constant, and tis is called a stable community, and these include places such as tropical rainforests and ancient oak woodland.

Abiotic and Biotic Factors

• Abiotic factors are non living factors, for example:
• Moisture level
• Light intensity
• Temperature
• CO2 level
• Wind intensity and direction
• O2 levels
• Soil pH and mineral contents
• A change in the environment could decrease or increase abiotic factors, and these changes can impact the size of populations within a community.
• For example, if there is a decrease in light intensity, CO2 levels and temperature, plants will struggle to photosynthesise, and the population size would decrease
• Biotic factors are living factors, for example:
• Predators
• Competition
• New pathogens
• Availability of food
• A change in the environment could decrease or increase biotic factors, and these changes can impact the size of populations within a community.
• For example, an increase in predators would lead to a decrease in the population size of the prey.
• For example, if there are two types of squirrels who eat the same food, one may increase in size as it is able to reach food more efficiently, whereas the other would decrease in size.

Adaptation

• Adaptations can be:
• Structural adaptation is where the features of an organisms body structure change, for example, arctic foxes have white fur so theyre camouflaged against the snow, which is useful for avoiding predators.
• Behavioural adaptation is the way an organism behaves, for example, birds migrate to warmer climates during the winter.
• Functional adaptation are the processes that go on inside an organisms body that can be related to processes like reproduction and metabolism. For example, desert animals conserve water by producing little sweat and small amounts of concentrated urine.
• Some microorganisms are labelled as extremophiles, because they live in such extreme conditions, such as very high or low temperatures. They have adapted greatly to survive in such extreme conditions.

Food Chains

• Food chains always start with a producer, which are organisms which make their own food using energy from the sun. They are normally plants which make glucose through photosynthesis. When a green plant produces glucose, some of it is used to make other biological molecules in the plant. These biological molecules are the plants biomass i.e. the mass of the living material. Biomass can be thought of as energy stored in the plant. The energy is transferred through living organisms in an ecosystem when the producer is consumed, and this carries on. Producers are eaten by a primary consumer and then the organism that eats the primary consumer is the secondary consumer etc.
• In a stable community containing predators and prey:
• The population of the species is usually limited by the amount of food available
• If the population of the prey increases, so does the population of the predator
• As the population of the predator increases, the population of the prey decreases.
• The predator-prey cycles are always out of phase with each other, because it takes a while for one to respond to changes in the other population.

The Water Cycle

• The water on Earth is constantly recycled:
• Energy from the sun evaporates water from the land and sea, forming water vapour
• Water also evaporates from plants which is called transpiration
• The warm water vapor is carried upwards as warm air rises, and when it gets higher, it cools and condenses to form clouds
• Water falls from the clouds as precipitation, onto land where it provides fresh water for organisms
• Some of the water is absorbed by soil, which provides plants with fresh water for photosynthesis. Some of the plant water is taken up by plants and forms plant tissue
• Animals return water to the atmosphere through excretion
• Water that isnt absorbed runs off into streams , and is drained back into the sea where it is absorbed.

The Carbon Cycle

• Living things are made up of materials they take from the world around them. They take elements and form complex compounds that make up living organisms. These get passed up the food chain. These materials are returned to the Earth through waste products or when the organisms die and decay.
• Materials decay because theyre broken down by microorganisms. This happens faster in the aerobic conditions (oxygen rich), as microorganisms work fastest in these conditions.
• Decay puts the things the plants need to grow back in the soil, such as mineral ions. In a stable community, the materials that are taken out of the soil and are used by the plant are balanced by those that are put back in. There is a constant cycle.
• The Carbon Cycle:
• CO2 is taken from the atmosphere by green plants during photosynthesis, and is used to produce glucose which can be turned into carbohydrases, fats and proteins that make up the body of the plant
• When the plants respire, some carbon is returned to the atmosphere in the form of CO2
• When plants are consumed, some carbon becomes part of the fats and proteins in their bodies. The carbon then makes its way through the food chain
• When animals respire, some of the carbon is released as CO2
• When the above organisms die (plants and animals), microorganisms and other animals feed on their remains. When these organisms respire, CO2 is released back into the atmosphere
• The combustion of wood also releases CO2
• So the carbon is constantly being recycled

Biodiversity and Waste Management

• Biodiversity - The variety of different species of organisms on Earth or in an ecosystem
• High biodiversity is very important to build interdependence in ecosystems, which leads to more stable communities.
• Lots of human actions such as deforestation, global warming and waste production are reducing biodiversity, however measures are being taken to stop this.
• The human population is rising due to the use of modern medicine and farming methods, however this also means that we are having a bigger impact on the environment:
• We need more resources
• People demand a higher standard of living, so the energy used in manufacturing and getting resources are increased
• Many resources are being used up quicker than they can be replaced
• As we produce more and more things, we waste more and more products, which needs to be carefully disposed of, otherwise:
• Sewage and toxic chemicals from industry can pollute lakes, rivers and oceans, where they affect species and break down the ecosystem they live in
• We bury nuclear waste underground and our use of landfill sites is growing
• Smoke and acidic gases can pollute the atmosphere

Global Warming

• The temperature of the Earth is a balance between the energy we get from the sun, and the energy we radiate out into space. Gases in the atmosphere act as an insulating layer. They absorb most of the energy that would normally be radiated out into space, and re-radiate it in all directions (on Earth). This increases the temperature of Earth. If this process didnt happen, little energy would be kept in, and temperatures would be very low.
• However, people are becomingly increasingly worried about the rise in some of these "greenhouse gases" such as CO2 and methane, as they are rising very sharply. This causes the Earths temperature to rise, and is called Global Warming, which is a type of climate change which causes other types of climate change such as changing rainfall patterns.
• There are several consequences of Global Warming:
• Higher temperatures cause seawater to expand and ice to melt, causing the sea level to rise. If it rises too much, places with low lying land risk flooding, resulting in the loss of habitats
• Species distribution across regions will change, as the conditions will change in certain places. For example, certain species may spread over a wder area as the conditions needed are now more widely available
• There could be changes in migration patterns
• Biodiversity could decrease, leading to less interdependence, and more instability within communities

Deforestation and Land Use

• Humans use land for many things, such as urbanisation, farming and dumping waste. This means that there is less land for organisms, especially when it involves deforestation, which leads to increased destruction of habitats.
• Deforestation is cutting down of forests. This causes problems when done on a large scale. It is mostly done to clear land to provide food and to grow crops.
• Deforestation causes problems:
• Trees reduce the amount of CO2 in the atmosphere, as they take CO2 in during photosynthesis, and some of it remains "locked up".
• CO2 is released when trees are burnt to clear land, and when microorganisms feed on dead bits of wood, they respire and release more CO2
• Habitats are destroyed, which leads to less biodiveristy
• Plants in bogs dont fully decay, as there isn't enough oxygen. The plant rot builds up to form peat, hence the word peat bogs. As a result of the plant not rotting, CO2 is stored in them, and is not released into the atmosphere.
• However peat bogs are often drained so that the area can be used as farmland, or the peat is cut up and used for dried fuel. When the peat is brought into contact with air, the microorganisms begin to decompose it. This uses oxygen in the air and releases CO2 into the atmosphere, increasing global warming.
• CO2 is also released when the peat is burned.
• In addition to all this, burning the peat bogs destroys the habitats, which reduces biodiversity.

Maintaining Ecosystems and Biodiversity

• It is important that biodiversity is maintained to help build more stable ecosystems, and human measures are being put into place to help:
• Animals in danger of becoming extinct are bred in captivity to ensure the survival of the species
• Programmes to defend and regenerate rare habitats such as the coral reefs are being put into place to protect the species that live there
• Field margins are areas of land around the edges of a field where wild flowers and grasses are left to grow, so a wider range of organisms can survve
• Government legislation regulates deforestation
• People are encouraged to recycle
• However, there are some pressures of doing this:
• It can be very expensive to monitor the programmes, and pay people to regulate the actions being put into place
• People may lose jobs. With regards to deforestation , although reducing it is great, workers may be made redundant, which is damaging to the economy and livelihood of people
• Ceryain organisms are seen as pests by farmers, and attempts to increase biodiversity provides habitats for the pests near crops, which can impact the yield
• Although we try out best, the population is rising, and sometimes land just has to be used up to provide for people.