ECOLOGY

• Habitat = the place where organisms lives
• Population = all the organisms of one species living in a habitat
• Community = the population of different species living in a habitat
• Ecosystem = the interaction of a community of living organisms with non-living parts of the environment 

Organisms compete for resources to survive:

• Plants need light, space, water and nutrients from soil
• Animals need territory, food, water and mates

Any change in any environment can have knock-on effects.

Abiotic factors (non-living factors of the environment) : 

• moisture level
• light intensity
• temperature
• carbon dioxide level
• wind intensity/direction
• oxygen level
• soil PH

Biotic factors (living factors of the environment) :

• new predators arriving
• competiton 
• new pathogens
• availibility of food

Adaptations allow organisms to survive.

• Structural - features of an organism's body structure e.g. arctic foxes have white fur so they're camouflaged against snow to avoid predators & sneak up on prey.
• Behavioural - ways that organisms behave e.g. swallows migrate in warmer climates during the winter avoid the problems of living in cold conditions.
• Functional - things that go inside an organisms body that can be related to processes like reproduction and metabolism e.g. desert animals conserve water by producing little sweat and small amounts of concentrated urine.

Microorganisms adapt aswell. Some microorganisms (e.g. bacteria) are known as extremophiles - they're adapted to live in extreme conditions.

• Producers - produce their own food
• Biomass is the mass of living material
• Energy is transferred when organisms eat other organisms 

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• Stable communities - In some communities all species and environmental factors are in balance so the population size is roughly constant.
• Predator-prey cycles are always out of phase with                                                                  each other because it takes a while for one                                                                            population to respond to changes in the other                                                                    population. 

• Availability of water e.g.each year in Africa, lots of giant wildebeest migrate,, moving north and then back south as the rainfall patterns change.
• Temperature e.g. the European bee-eater, a Mediterranean bird, is now present in Germany.
• Atmospheric gases e.g. some species of lichen can't grow in areas where sulfur dioxide is given out by certain industrial processes.

The water cycle - water is endlessly recycled.

Elements are cycled back to the start of the food chain by decay.

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Biodiversity = the variety of different species of organisms on Earth, or within an eosystem.

Waste : water - sewage/chemicals from industry, land - landfill sites/chemicals, air - smoke/acidic gases

Microorganisms break down plant and animal material and waste to get energy. 

The rate of decay is affected by:

• Temperature
• Oxygen availability
• Water availability
• Number of microorganisms

Biogas (mainly made up of methane)  is made by anaerobic decay of waste material. It is made in a simple fermenter called a digester/generator.

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Consequences:

• ice melts - sea level rises
• distribution of wild animal & plant species may change
• changes in migration patterns 
• biodiversity could be reduced (extinction could occur)

Land use by humans:

• building
• quarrying 
• farming
• dumping waste

Reasons for deforestation include clearing land for farming & to grow crops.

Problems caused by deforestation:

• less CO2 taken in (by the trees), less is locked up/absorbed 
• more CO2 in the atmosphere - released when trees are burnt & microorganisms feeding on dead wood release CO2 (through respiration)
• less biodiversity e.g. forests are habitats for many species of animal & plant

Destroying peat bogs (land that is acidic & waterlogged) adds CO2 to the atmosphere. This is because plants dont fully decay in bogs due to lack of oxygen so they don't release CO2 until the bogs are drained (to clear more land).

Programmes that protect ecosystems and biodiversity:

• breeding programmes
• programmes to protect and regenerate rare habitats e.g. mangroves, coral reefs
• programmes to reintroduce hedgerows and field margins (provide habitats for wild varieties)
• governments introduce regulations to reduce deforestation and CO2 produced by businesses
• people are enncouraged to reduce, reuse & recycle

conflicting pressures that limit biodiversity maintainance:

• cost money
• cost people's livelihood e.g. tree-felling industry left unemployed
• protecting biodiversity vs protecting food security
• development e.g. housing demand

• level 1 - producers
• level 2 - primary consumers
• level 3 - secondary consumers
• level 4 - tertiary consumers
• decomposers - break down uneaten remains and waste (by releasing enzymes that break dead stuff down into small soluble food molecules that then diffuse into the microorganism)

Pyramids of biomass show the relative mass of each trophic level. (always pyramid shaped)

Biomass is lost between each trophic level.

Only a small amount (about 1%) of the energy transferred from the sun to the producers is transferred for photosynthesis.

About 10% of biomass is passed on to the next trophic level.

How biomass is lost: 

• Not all of the organism is consumed e.g. bones
• Organisms don't absorb everything they injest, some is released as faeces
• A lot of the energy transferred is used for warmth, respiration and movement...

efficiency of biomass transfer = (biomass transferred to the next level / biomass available at the next level) x 100

Factors affecting food security:

• population increase
• demand for certain foods to be imported due to change in diets 
• maintaining food production is too expensive for some
• new pests and pathogens - loss of crops/livestock
• conflict

Overfishing is decreasing fish stock.

Fishing quotas - limits on the number of fish that can be caught in certain areas

Net size - limits on the mesh size of the net, depending on what's being fished

Food production can be made more efficient:

• factory farming livestock, including fish!
• feeding animals high-protein food to increase growth

Mycoprotein - food from fungi e.g. quorn

Bacteria can be engineered to produce human insulin:

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Crops can be genetically modified to be:

• pest resistant
• more nutritional