Ecosystems and material cycles

• Levels of organisation in ecosystems

  Individual- a single organism

  Population- all the organisms of one species in a habitat

  Community- all the organisms of different species living in a habitat

  Ecosystem- a community of organisms along with all the non living conditions.
• How does abiotic factors affect communities?

  1. Temperature- higher temperatures can cause distribution of species
  2. Amount of water- if the conditions of water change the population will decrease (especially plants)
  3. Light intensity- if the light intensity changes other species may thrive more in the conditions and others may not
  4. Levels of pollutants- air pollutants may cause plants to die out if they are too high
• How do biotic factors impact communities?

  1. Competition- organisms compete with other species for the same resources, meaning there will be a decrease in population for one of the species
  2. Predation- If the number of predators decreases then the number of their prey will increase
• Interdependence in a community

  Interdependence is when organisms depend on each other for food and shelter in order to survive and reproduce. This means the change in the population of one species will have a large knock on effect for other species in the same community.
• Mutualism


  A relationship between two organisms in which both benefit from one another. e.g bees and flowering plants both benefit from the exchange of pollen.
• Parasites


  Parasites live very closely with a host species. It will take what it needs to survive, however the host does not benefit from it, and it damages the host mostly.
• Investigating the relationship between organisms and their environment- Quadrats

  A quadrat is a square frame enclosing a known area.

  1. Pick two sample areas. In the first area, place a 1m^3 quadrat at a random point on the ground.
  2. Count the organisms within the quadrat area you are interested in
  3. Repeat this 10 times and calculate the mean number of organisms per quadrat
  4. Repeat this with the second sample area and then compare the means.
• Investigating the relationship between organisms and their environment- Belt transacts

  Abiotic factors may cause a gradient to occur in a habitat. We use quadrats laid out along a line to see this:

  1. Mark out a line in an area you want to study
  2. Collect data using quadrats placed next to each other and also record abiotic factors in each quadrat like light intensity
  3. Repeat this several times and then find the mean number of organisms
  4. Plot on graphs to see if the changing abiotic factor is correlated with a change in the distribution of the species.
• Fertiliser impact on biodiversity

  Nitrates are put onto fields as fertilisers and if too much is applied and it rains afterwards nitrates can get into rivers and lakes causing eutrophication:

  1. Fertilisers enter water adding excess nitrate
  2. This causes algae to grow fast and block out light
  3. Plants cant photosynthesise and decompose and die
  4. Microorganisms that feed on decomposing plants increase and take all the oxygen
  5. Organisms that need oxygen such as fish die.
• Fish farms impact on biodiversity

  It can cause a lack of biodiversity:

  1. Food added to nets to feed fish produces huge amounts of waste which can leak into water causing eutrophication
  2. Fish farms are a breeding ground for parasites which can get out of the farm and infect wild animals
  3. Predators can become trapped in the nets and die
  4. Farmed fish can escape causing problems for indigenous species
• Introduction of non indigenous species impact on biodiversity

  A non-indigenous species is one that doesnt naturally occur in an area. They may be introduced intentionally or unintentionally. It may cause:

  1. Competition for resources and winning against the indigenous species
  2. New diseases which will infect and kill lots of indigenous species
• Reforestation


  Forests that are replanted have a high biodiversity because they contain a wide variety of habitats that provide food and shelter. Reforestation progammes need to be carefully planned to maximise positive effects, for example replanting a variety of tree species to maxmise biodiversity
• Conservation of animals

  Conservation helps protect biodiversity by:

  • Protecting a species natural habitat
  • Protecting species in a safe area outside of their natural habitat and including captive breeding programmes to increase numbers
  • The use of seed banks to store and redistribute seeds of endangered plants
• Benefits of maintaining biodiversity

  1. Protecting human food supply
  2. Ensuring minimal damage to food chains
  3. Providing future medicines from plants
  4. Cultural aspects
  5. Ecotourism
  6. Providing new jobs
• Material cycle


  Materials are recycled through both biotic and abiotic components of ecosystems:

  1. Living things are made of elements they take from the environment
  2. They turn these elements into complex compounds that make up living organisms. Elements are passed along food chains.
  3. The elements are recycled- waste products and dead organisms are broken down by decomposers and returned to soil or air.
• Why is the carbon cycle important?

  Carbon is an important element in the materials living things are made from however there is a limited amount of carbon so it must be constantly recycled
• Carbon cycle

  1. Green plants use the carbon from CO2 to make carbohydrates, fats, and proteins
  2. Eating passes the carbon compounds in the plant along to the animal
  3. Their respiration releases CO2 back into the air
  4. They eventually die/ decompose and are broken down by micro organisms that release CO2 back into the air by respiration
  5. Some useful products like wood are burned and produce CO2
  6. Decomposition of materials means habitats are maintained because nutrients are returned to soils.
• Water cycle

  1. Energy from the sun makes water evaporate from the land and sea turning it to water vapour
  2. The warm water vapour is carried upwards and when it gets higher it cools and condenses to form clouds
  3. Water falls from the clouds as precipitation onto land providing fresh water for plants and animals
  4. It then drains into the sea and the cycle begins again
• Why is the water cycle important?

  We would quickly run out of water if it wasnt recycled and all living things on earth need water to survive
• Desalination


  In areas of drought, desalination can be used to produce potable water from salt water by taking salts out of sea waters in ways like:

  • Distillation- boiling water so that the steam evaporates up into a pipe where it can condense into fresh water and the salt is left at the bottom
  • Reverse osmosis- Salt water is treated to remove solids and fed through a partially permeable membrane at high pressure where it causes water molecules to move in the opposite direction to osmosis to a low salt concentration and through the membrane while the salt is left behind.
• Nitrogen cycle (p1)

  1. Nitrogen in the air has to be turned into mineral ions like nitrates before use. Plants absorb these mineral ions from the soil and use the nitrogen in them as protein. It is then passed along the food chain
  2. Decomposers break down proteins in rotting plants animals and urea. This returns nitrogen to the soil and recycles it
• Nitrogen cycle (p2)


  3. Nitrogen fixation is the process of turning N2 from the air into nitrogen containing ions in the soil. This happens by lightning (energy from a lightning bolt making oxygen and nitrogen react to make nitrates) or nitrogen fixing bacteria in roots and soil (atmospheric N2 made into ammonia and then ammonium ions)
• Bacteria involved in the nitrogen cycle

  1. Decomposers- decompose proteins and urea into ammonia and then into ammonium ions plants can use
  2. Nitrifying bacteria- turn ammonia in decaying matter into nitrites and then nitrates
  3. Nitrogen fixing bacteria- turns atmospheric N2 gas into ammonia which forms ammonium ions
  4. Denitrifying bacteria- turns nitrates into N2 gas.
• Crop rotation and nitrogen

  Instead of growing the same crop in a field year after year, different crops are grown in a cycle which usually includes a nitrogen fixing crop helping put nitrates back into the soil for another crop to use
• Fertilisers and nitrogen


  Spreading animal manure or composts on fields recycles the nutrients left in plant and animal waste and returns them to the soil by decomposition. Artificial fertilisers containing nitrates can also be used however are expensive