An ecosystem is all the living and non-living parts of a habitat. these exist of individual organisims, populations (groups of he same species) and communities. In order to survive and reproduce organisms require certian things from the ecosystem. they may have to compete to get these. Eg plants compete for; light, space, water and ions in the soil. Animals compete for; food, mates, teratory. 

species depend on each other as food, sheter, pollination, seed distribution within an ecosystem. the way these sepecies depend on each other is called interdependance. meaning the loss of one specie from the habitat affects the whole community. in stable communities the species and environment are in balence so the population remains the same. 

Factors affecting a comunity are abiotic (light intensity, tempurature, moisure, soil pH and minerals, wind, co2 levels for plants, oxygen levels for aquatic animals) or biotic (food, new predetors, pathogens or desieses, outcompeting species). 

Adaptations allow species to survive in the conditions they live in. they can be structural, behavioural or functional. Organisms living in extreme conditions eg. bacteria in deep sea vents are extremophiles. 

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Studying Ecosystems

Population sizes can be estimated using quadrats which is a method of sampling. 

Transects can be used to measure the distriuion of plants in a habitat. 

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dead organisms are broken down by decomposers which are certian types of bacteria or fungi. these need oxygen, moisture and a suitable temp and pH in order to work. They work by secreting enzymes to partly digest the waste and then take up the small souluable food molecules. 

In compost heaps gardners try to provide the optimum conditions, and the compost is used as a natural fertiliser. in anearobic conditions methane gas is produced, this shows how biogas generators work, producing biogas from waste to be used as a fuel. To slow dow decay of food we rwmove a condition of decay eg cool food down in fridges. 

Decomposers are needed in the carbon cycle to return co2 to the atmosphere. 

the carbon cycle and the water cycle show how components of the living world are recycled to be used in future organisims. 

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Feeding relationships

feeding relationships in a comunity are shown in food chains, these all begin with a producer which synsthesises makes) molecules, eg plants make glucose molecules from photosynthesis. producers being eaten by primary consumers being eaten by secondary consumers ect shows the ffeeing levels (trophic levels) represented by numbers. top consumers are apex predators with no predators. the numbers of predators and prey rise and fall in cycles. 

Pyramids of biomass are used to compare the amount ofbiomass in each stage of the food chain. this shows the energy flow through food chains. plants trap 1% of light energy which hits them by photosynthesis. only about 10% of the biomass from one trophic level is transferred to the level above it. this is due to food passing out of the body as faeces, glucose being used in respiration, material lost through exretion eg co2 and water in respiration. loss of biomas and reduction of energy means there are less organisms in higher trophic levels . 

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is the variety of different species on earth. High biodiversity helps ecosystems become more stable as they depend on each other for food and shelter. many human activities are reducing bipdiversity. factors effecting biodiversity are; availability of water, temp, atmospheric gas. these changes may be due to: changes in seasons, geographical activity eg volcanos, human interaction. 

pollution kills plants and animals, reducing biodiversity. as population increases and a higher standard of living more resources are used and waste is produced. pollution can occur in water (sewage, fertalisers, chemicals) in air (gases like sulpur dioxide which disolves in moisure to for acid rain) on land (from landfill and toxic chemicals like pesticides) 

overexploitation is where humans put bidversity at risk by taking too many resources out of the environment. eg building, quarring, and landfill reduces space for habitats. garden compost destroys peat bogs, reducing the habitiat and the organisms in it. burning peat releases co2 into the atmosphere. deforestation for cattle and farming reduces habitats. global warming from deforestation and pollution of gases in the atmosphere causes loss of habitat from flooding, changes in migration, changes in distribution of species where temp or rainfall has changed. 

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conserving biodiversity

Pollution and over-exploitation can be reduced to minimise loss of biodiversity. Eg;

- Setting up breeeding programs to increase numbers of endangered species

- protecting rare habitats

- encouraging farmers to maintain hedgerows to fields 

- reducing deforestation 

- recyling rather then using landfill

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food security is where everyone has enough food to be healthy, this is tricky due to: increasing population, changing diets (more food transported to meet demand), new pests and patogens impacting farms, changes in weather (famine from drought) cost of agricultural supplies, conflicts. sustainable methods of food production increase food production now but leave enough reserves for the future. 

Food can be made more sustainable by reducing energy transfer from animals to the environment by limiting movement of animals, controlling there tempurature. factory farming uses these ideas to make farming more efficient. high protien foods may also be fed to animals to increase growth. 

Fish stocks are declining, to stop this ishing quotas can be set so only a set number are caught, net sizes can be controled so only old ish are caught. 

Biotechnolgy is the growth of microrganisms in large quantites for food. this is done in fermeters where conditions are controled Eg the fungus fusarium is used to produce mycoprotien which is protien rich, high in fibre, low in fat, vegetarian. this is grown in glucose syrup aerobically, harvested and purified. GM crops can be grown to producemore sustainable food. Eg golden rice with improved nutritional value, or drought resistant crops to increase supply. 

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