Ecology

• Ecosystems 


  An ecosystem is made up of living (biotic) things and non-living (abiotic) parts.

  Individuals - smallest part of an ecosystem

  Populations - made up of individuals and make up a single specie

  Communities - made up of populations of different species
• Competition for resources in an ecosystem

  Organisms need resources from both abiotic and biotic parts of an ecosystem to survive and reproduce. But resources are not infinite. Different species and individuals compete for resources

  Competition between plants - often compete for water and mineral ions from the soil as well as for light and space

  Competition between animals - animals often compete for food, mates and territory
• Species interdependence 


  Species may rely on other species for different things such as:

  Food

  Shelter

  Pollination

  Seed dispersal
• A stable community is when all the species and environmental factors are balanced and population sizes stay more or less constant
• Food chains 


  Food chains nearly always begin with a producer that makes its own food. This is usually a green plant or algae that can photosynthesise

  Producers are eaten by animals called primary consumers

  Primary consumers are eaten by secondary consumers

  Secondary consumers are eaten by tertiary consumers

  An apex predator is at the top of the food chain
• Predator-prey graphs


  Predator-prey graphs show the cyclical nature of predator and prey populations in stable communities

  An increase in prey means more food is available for predators therefor predator numbers increase

  The increase in predators means the prey have more predators so prey decrease

  Then predators have less food so numbers decrease

  A decreasing predator numbers allows prey to increase again so the cycle repeats
• Assessing ecosystems 


  Quadrats - square frames that can be used to estimate population sizes

  Transects - transects can be used to investigate the effect of a factor on the distribution of a species

  Transect line is a piece of tape spread across habitat of interest

  Quadrats are place at regular intervals along the transect line
• The recycling of materials is essential as they provide the building blocks for future organisms. Two cycles that are particularly important are : the carbon cycle and the water cycle
• The carbon cycle

  • CO2 is REMOVED from the air in photosynthesis by green plants and algae - they use the carbon to make carbohydrates, proteins and fats. They are eaten and the carbon moves up the food chain
  • CO2 is RETURNED to the air when plants, algae and animals respire. Decomposers respire while they return mineral ions to the soil
  • CO" is returned to the air when wood and fossil fuels are burnt as they contain carbon from photosynthesis
• Compost 


  When biological material decays it produces this

  It is used by gardeners and farmers as a natural fertiliser

  To do this they have to provide optimum conditions for decay

  If more oxygen is available then respire aerobically, producing heat

  The increase temperature increases the rate of decay so the compost is made quicker
• Methane gas 


  Microorganisms decompose waste anaerobically to produce methane gas

  This can be burnt as fuel

  Biogas generators are used to produce methane

  Require a constant temperature (30 degrees) so the microorganisms keep respiring

  It cannot be stored as a liquid so needs to be used immediately
• The water cycle 


  The sun's energy causes water to evaporate from the sea and lakes, forming water vapour

  Water vapour is also formed as a result of transpiration in plants

  Water vapour rises and then condenses to form clouds

  Water is returned to the land by precipitation and this runs into lakes to provide water for plants and animals

  This then runs into seas and the cycle begins again

  In areas of drought we can harness the water cycle to produce potable water
• Biodiversity 


  The variety of different species of organisms on Earth or within an ecosystem
• The effect of human activities on biodiversity

  More land is being used for housing, farming, shops, roads and factories which destroys habitats

  Pollution kills plants and animals

  Sewage, fertilisers and toxic chemicals pollute the water

  Smoke and acidic gases pollute the air

  Landfill and toxic chemicals can result in the pollution of the land

  We are using up raw materials quicker than they are being produced
• Peat bogs 


  Peat is a material that forms when plant material has not fully decayed as there is not enough oxygen

  It accumulates in bogs that are acidic and waterlogged

  These bogs are a habitat for many species, in particular migrating birds

  Peat bogs are being destroyed - they are being drained in order to create space for farming, peat is used as compost , or dried to use as fuel as it contains carbon

  It is being used up quicker than it is being formed, the formation process is slow
• polluting the water 


  Use of nitrate fertiliser that washes from soil into waterways

  Release of untreated sewage eg farm slurry

  Both cause eutrophication - when waterways are enriched with minerals and too many algae and plants grow

  Pesticides and herbicides are washed into waterways
• Eutrophication 


  This means rich in nutrients

  Natural but humans speed t up

  Bad as it makes algae and plants grow too much leading to an increase in bacteria and fungi and therefore a decrease in oxygen

  High nitrate levels from fertilizers or farm slurry increase growth of aquatic plants and algae

  Rapid algae growth makes water murky preventing light reaching plants further down so they die

  Dead algae decomposed by aerobic bacteria therefore removing oxygen from water

  Organism need oxygen to live
• Extremophiles 


  Organisms - often micro-organisms that are adapted to live in extreme conditions
• Structural adaptations 


  Sharp teeth of a carnivore to tear meat apart

  Camouflage e.g. tan/brown lioness

  Species in cold environments may have blubber
• Behavioural adaptations 


  Individuals may play dead to avoid predators

  Basking in the sun to absorb heat

  Courting behaviour to attract a mate
• Functional adaptations 


  Late implantation of embryos

  Conservation of water through producing little sweat
• Adaptations for cold climates

  Smaller SA:V ratio to reduce heat loss

  Lots of insulation e.g. Blubber, fur coat
• Adaptations for dry climates

  Adaptions to kidneys so they can retain lots of water producing very concentrated urine

  Being active early in the morning and evenings when it is cooler

  resting in shady areas

  Large SA:V ratio to increase heat loss
• Plant adaptations 


  Curled leaves to reduce water loss

  Extensive root systems to take in as much water as possible

  Waxy cuticle to stop water evaporating

  Water storing tissue in stem
• Abiotic factors 


  Light intensity

  Temperature

  Moisture levels

  Soil pH and mineral content

  Wind intensity and direction

  CO2 levels

  Oxygen levels for aquatic animals
• Biotic factors 


  Food availability

  New predators

  New pathogens

  Competition
• Deforestation 


  Cutting down of a large number of trees in the same area in order to use the land for somethign else
• It happens in tropical areas to

  Provide lands for cattle and rice fields

  To grow crops for biofuels which are used to produce energy
• The problems caused by deforestation

  As trees contain carbon, burning them results in more CO2 being released into the environment which contributes to global warming. Following deforestation, microorganisms decompose the dead vegetation producing CO2 as they respire

  Trees take in CO" when they photosynthesise so less trees = more CO2

  The number of habitats are reduced, decreasing biodiversity
• Global warming 


  The term global warming refers to the fact that the temperature around the world is increasing. This is because we are producing more greenhouse gases, resulting in more heat being absorbed and reflected back to the earth, heating it up
• The consequences of the temp increasing from global warming is

  Melting of the ice caps, reducing habitats

  Rising sea levels, reducing habitats as low-lying areas will be flooded with salty water

  Temperature and rainfall levels will affect migration and therefore the distribution of different species as they may no longer be able to survive where they live

  Organisms will become extinct as their habitats are lost, reducing biodiversity
• Positive human interactions with ecosystems

  Maintaining rainforests, ensuring habitats here are not destroyed

  Reducing water pollution and monitoring the changes over time

  Preserving areas of scientific interest by stopping humans from going there

  Replanting hedgerows and woodlands to provide habitats which were previously destroyed
• Negative human interactions with ecosystems

  Production of greenhouse gases leading to global warming

  Producing sulfur dioxide in factories which leads to acid rain - affects habitats

  Chemicals used in farming leak into the environment

  Clearing land in order to build on, reducing the number of habitats
• To reduce our negative impact programmes have been put in place:

  Breeding programmes: to stop endangered species becoming extinct

  Protection of rare habitats

  Reintroduction of hedgerows and field margins around land where only one type of crop is grown

  Reduction of deforestation and CO2 production

  Recycling