b7

• population - all the organisms of one species living in a particular area at the same time
• community - the population of different species living in a habitat
• abiotic - non living factors of the environment
• ecosystem - the interaction of a community of living organisms with the abiotic parts of their environment
• plants need

  • light
  • space
  • water
  • mineral ions
• animals need

  • space (territory)
  • water
  • food
  • mating partners
• stable communities - species and environmental factors are balanced so sizes are constant

  eg. tropical rainforests, ancient oak woodlands
• biomass - the total mass of living material in an ecosystem
• environmental changes caused by

  • seasonal factors
  • geographical factors
  • human interaction

  can change

  • temperature
  • availability of water
  • composition of atmospheric gases
• composition of atmospheric gases

  • some species of lichen cant grow where sulfur dioxide is given out by certain industrial processes
• rate of decay is affected by

  • temperature
  • water availability
  • oxygen availability
  • number of decay organisms
• compost is decomposed organic matter that is used as a natural fertiliser for plants, farmers try provide ideal conditions for quick decay to make compost
• 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.
  • CO2 is RETURNED to the air when wood and fossil fuels are burnt (called combustion) as they contain carbon from photosynthesis.
• 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 (rain, snow or hail), and this runs into lakes to provide water for plants and animals.
  • This then runs into seas and the cycle begins again.
• Decomposers break down dead plant and animal matter.

  • They do this by secreting enzymes
  • The matter is broken down into small soluble food molecules and they move into the microorganism by diffusion.
• global warming

  consequences:

  • 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
• trophic levels

  Level 1

  • Organisms at the first level are called producers such as plants and algae.
  • They make their own food by photosynthesis.

  Level 2

  • Organisms at the second level are called primary consumers.
  • These are herbivores that only eat plants.

  Level 3

  • Organisms at the third level are called secondary consumers.
  • These are carnivores and they eat herbivores.

  Level 4

  • Organisms at the fourth level are called tertiary consumers.
  • These are carnivores that eat other carnivores.
  • they have no predators and are at the top of the food chain – called apex predators
• Detritus feeders - small animals like worms and woodlice that feed on dead organic matter.
• 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 for 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 contain carbon (releasing CO2 into the atmosphere)
  • It is being used up quicker than it is being formed
• 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
• water pollution

  Fertiliser from agriculture 

  Sewage from cities 
•  air pollution

  Acidic gases from burning fossil fuels 

  Smoke from combustion 
• land pollution

  Nuclear waste 

  Landfill
• problems caused by deforestation:

  1. 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.
  2. Trees take in CO2 when they photosynthesise, so less trees means less CO2 is taken in
  3. The number of habitats are reduced, decreasing 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.
• maintaining biodiversity

  1. Breeding programs: stops endangered species from going extinct
  2. Protection of rare habitats: stops species from going extinct
  3. Reintroduction of hedgerows and field margins - maintains biodiversity as they provide a habitat for lots of organisms
  4. Reduction of deforestation and carbon dioxide production: reduces the rate of global warming, slowing down the rate that habitats are destroyed
  5. Recycling rather than dumping waste in landfill: reduces the amount of land taken up for landfills, and slows the rate we are using up natural resources.
• factors effecting food security

  1. Increasing birth rate means more food is required.
  2. Changing diets in developed countries means food resources which are already in low amounts become even more scarce as the demand for them increases.
  3. New pests and pathogens can destroy crops.
  4. Climate change affects food production (such as no rain resulting in crops failing).
  5. Conflicts in some countries can affect the availability of water and food.
• The number of fish in the oceans is decreasing:

  • This is because humans are fishing at a faster rate than the populations can regenerate.
  • To avoid species disappearing in some areas, the populations need stay above a certain level so breeding can continue.
  • Some restrictions have been put in place: There are limits of net sizes (making them bigger) so smaller fish are not caught and can reach breeding age and produce more fish, Fishing quotas mean only a certain number of a species of fish can be caught (in an area and over a time period) to prevent overfishing
• Only approximately 10% of the biomass of each trophic level is transferred to the next.

  Not all biomass can be eaten.

  • Carnivores cannot generally eat bone, hooves, claws and teeth.

  not all the biomass eaten is converted into biomass of the animal eating it

  • Lots of glucose is used in respiration, which produces the waste product carbon dioxide
  • Urea is a waste substance which is released in urine
  • Biomass consumed can be lost as faeces