chap 12. ecosystems

• Levels of organisation


  • Individual
  • Population
  • Community
  • Ecosystem
• Organism


  Adapted to the environment it lives in, known as the habitat
• Population


  Organisms of the same kind living in the same environment
• Community


  Different populations of plants and animals living and interacting in a particular environment
• Ecosystem


  The interactions between a community and its physical environment
• We will also learn about the nutrient cycle (not in textbook)
• Balance in an ecosystem


  Different species interact with each other to maintain balance
• The principle of energy conservation states that energy is neither created nor destroyed, but energy may be transformed from one form to another
• The law of conservation of mass states that in a chemical reaction mass is neither created nor destroyed, however, rearrangement of atoms may occur to form new compounds
• Food chains


  1. Feeding relationship between organisms

  2. During feeding, energy and nutrients are transferred from one organism to another
• Food producers


  Green plants that make food through the process of photosynthesis, making use of carbon dioxide and water in the presence of sunlight
• Consumers


  Organisms that obtain energy when they feed on other plants or animals
• Food webs


  Show how one or more food chains are interconnected<|>They show the organisms involved in the transfer of energy and nutrients in an ecosystem
• Energy flow


  • Energy cannot be destroyed, but it will be lost to the environment eventually
  • Energy is lost mainly to heat in the environment
• 10% rule of energy transfer


  Only 10% of the energy is passed on from one trophic level to another
• Roles of organisms


  • Producers - green plants that make food
  • Herbivores - organisms that feed on plants
  • Carnivores - organisms that feed on other animals
  • Omnivores - organisms that feed on both plants and animals
  • Decomposers - organisms that feed on both dead organisms and faeces
• Matter cannot be destroyed but it can be recycled within ecosystems
• Nutrient cycles


  Cyclic
• Energy flow


  Linear, one directional
• Nutrients can be recycled while energy is lost from the ecosystem
• Cyclic processes


  • Water cycle
  • Carbon cycle
  • Nutrient cycle
• Energy cycle is linear (eg cow cannot make food for plant, only take energy from the plant)
• Human activities


  Tend to unbalance ecosystems
• Greenhouse gases


  Gases that have the property of being able to absorb infra-red radiation / heat<|>Eg methane, carbon dioxide, ozone, nitrous oxide, carbon monoxide, chlorofluorocarbon<|>They raise the temperature of the environment and cause global warming
• Infra-red energy is absorbed by greenhouse gases, but come from the sun