Unit 8 - Ecology

• A habitat is a place where an organism lives e.g: a field
• A population means all the organism of one species in a habitat
• A community is all the different species in a habitat
• An ecosystem is where all the organisms living in a particular area and all the non-living (abiotic) conditions e.g. temp, climate, soil-type.
• Abiotic factors affect communities through environmental conditions and toxic chemicals.
• Environmental conditions affect communities such as temperature, light intensity (plants only), moisture level and soil pH.
• Biotic factors also affect communities such as availability of food, number of predators and competition
• Toxic chemicals such as pesticides and fertilizers. Pesticides can build up the food chain through bioaccumulation.
• Bioaccumulation is where at each stage of the food chain, the concentration of pesticides increases so that the top of the chain receives a toxic dose.
• Excess fertilisers are released into lakes and ponds causing eutrophication which leads to death of organisms like fish.
• What is a quadrat used for?

  It is a square frame enclosing a known area e.g: 1m². It is used for ecological sampling.
• Eutrophication is the enrichment of a body of water with nutrients, especially nitrogen and phosphorus.
• Hypoxia/anoxia kills off aquatic animals and algae, reducing the biomass of the ecosystem.
• The main cause of eutrophication is agricultural runoff from farms containing excess amounts of fertilisers.
• Place 1m² on the ground a t a random point within the first sample area.
• How to get results that are representative of the whole sample area?

  Do this by dividing sample area into a grid then using a random number generator to pick coordinates to place your quadrats at.
• After step 1, count all the organisms you're interested in within the qudrat. Repeat step 1 and 2 lots of time
• After steps 1, 2, and 3 work out the mean number of organisms per quadrat within the first sample area, then repeat step 1 to 4 in the second sample area.
• Mean for quadrat = total number of organisms/number of quadrats.
• After that, compare the two means for example you might find a mean of 2 daisies per m² in one area, and 22 daisies per m² in another.
• Abiotic factors that affect plants

  • sunlight - photosynthesis
  • water - growth
  • temperature - photosynthesis
  • minerals - mppn
  • carbon dioxide
  • pH - enzymes
• Light is absorbed by chloroplasts which is used in photosynthesis. The chemical energy created helps to open the stomata to let more carbon dioxide in.
• Why is not all the energy absorbed by food chains?

  • Excreted as waste
  • Energy used to stay alive - respiration, heat output
  • Not all organisms eaten - bone
• Only 10% of the total energy in food chains becomes biomass for example it is stored or used for growth
• You can estimate a population size by using quadrats. You multioly the mean by the total area of the habitat.
• Each bar on a pyramid of NUMBERS represents the number of organisms at that stage of the food chain.
• Each bar on a pyramid of BIOMASS represents the mass of living material at that stage of the food chain (how much each organism would weigh)
• In a TYPICAL pyramid of numbers when you go up a trophic level, the number of organisms goes down. This is because it takes lots of food from the level below to keep one animal alive.
• Biomass and energy pyramids are always the right shape.
• Pyramids of energy represent the energy transferred to each trophic level in a food chain.
• Plants use carbon dioxide for photosynthesis which helps them to make carbohydrates, lipids and proteins.
• When plants and animals decompose they're broken down by decomposers. They release enzymes to catalyse the breakdown of dead material into smaller molecules.
• Decomposers, animals and living plants release Carbon Dioxide into the air by respiration
• Combustion releases carbon dioxide back into the air
• Fossil fuels are made of decayed plant and animal matter.
• Decomposition of materials means that habitats can be maintained for the organisms that live there.
• Carbon monoxide and sulfur dioxide are poisonous gases
• Carbon monoxides can be produced by incomplete combustion of fuels.
• Carbon monoxide attaches itself to the haemoglobin red blood cells and prevents it from carrying oxygen around the body.
• Modern cars are fitted with catalytic converters that turn the carbon monoxide into carbon dioxide which decreases the amount of CO that's released into the atmosphere.