Ecology and Environment

• Habitat: The specific place where an organism lives in the ecosystem
• Population: the number of individuals of one species within an ecosystem
• Community: All of the plant and animal populations in an ecosystem
• Ecosystem: all the biotic and abiotic factors of an area
• Biodiversity: The variety of different species of organisms within an ecosystem or on earth.
• Abiotic factors affect communities. Such as light intensity limiting plant growth, toxic chemicals like pesticides building up in food chains.
• Biotic factors affect communities. Such as predators limiting populations, competition limiting resources, availability of food and water limiting/increasing populations
• Producer: A living organism that makes its own food by photosynthesis. They start the food chain.
• Primary consumers: eat producers and are eaten by secondary consumers
• Secondary consumers: eat primary consumers and are eaten by tertiary consumers
• Decomposers: Organisms that break down dead organic matter and return it to the soil.
• The sun is the original source of all energy in food chains. Plants absorb sunlight and its energy for photosynthesis
• Only 10% of energy is transferred between trophic levels in a food chain
• Energy in organisms is lost as some parts of the organism isn't eaten, not all is digested, excretion, heat from respiration, movement
• As energy is lost between trophic levels, higher trophic levels receive less energy so must eat in larger quantities which means they expend more energy when hunting. This means the number of trophic levels is limited as there is not enough energy.
• 3 types of pyramid: number, biomass and energy
• Pyramids of energy and biomass are always pyramid-shaped whereas pyramids of number can be any shape
• The processes that transfer carbon around an ecosystem are respiration, decomposition, photosynthesis, combustion, feeding
• 1. Photosynthesis

  
• 2. Respiration

  
• 3. Feeding

  
• 4. Death and waste

  
• 6. Decomposition

  
• 7. No decomposition

  
• 8. Combustion
• Decomposers break down dead organic matter and release nutrients back into the soil. They respire which releases CO2 back into the atmosphere
• The atmosphere contains 78% nitrogen gas. It is very unreactive so it cannot be used directly used by plants and animals, hence the nitrogen cycle.
• Nitrogen is needed for amino acids and proteins as their make-up is C, H, O, N. Proteins are needed for growth and repair.
• The 4 types of bacteria in the Nitrogen Cycle are nitrifying, denitrifying, nitrogen fixing and decomposers
• Sources of Nitrogen are the air, the soil and proteins in animals and plants
• 1. Nitrogen Fixation by bacteria or lightning

  
• 2. Nitrification to convert ammonia to nitrites to nitrates

  
• 3. Assimilation to form proteins in plant

  
• 4. Feeding

  
• 5. Death and Waste

  
• 6. Ammonification converting proteins into ammonia

  
• 7. Denitrification by bacteria

  
• Nitrogen fixing bacteria live freely in the soil or in the root nodules of legumes.
• Using a quadrat: Place quadrat at a random point to get a random sample. Use a number generator to determine random co-ordinates of quadrat. Count all plants/animals in quadrat and repeat in other sample areas to get mean and scale up for whole population.
• The two main gases that contribute to air pollution are carbon monoxide and sulphur dioxide.