Organisms in the environment and feeding relationships.

• Community

  All the populations of different species that live in the ecosystem.

  Eg: many species of fish, insects and pondweed living in a lake.
• Ecology


  The study of living organisms in their environment
• Physical

  Factors

  (Abiotic)

  Non-living factors that affect the abundance and distribution of organisms.

  Eg: Temperature, nutrients, light, water, O 2 and CO 2
• Biological

  Factors

  (Biotic )


  Living organisms that affect the abundance and distribution of organisms

  Eg: Competition for food or space
• Environment


  The physical and biological factors that affect a species
• Population


  All the organisms of one species living in the same habitat.

  Eg: A population of perch living in the lake
• Distribution


  How organisms are spread out in an area
• Ecosystem


  All the living organisms in a large unit of the environment along with all the physical factors that influence them.

  Eg: The lake and all its organisms and physical factors
• Abundance

  The number of organisms of a particular species in an area related to the population size
• Habitat


  A small part of an ecosystem where a species lives.

  Eg: Open water or mud at the bottom or weed near the side of the lake.
• Biodiversity


  As wide a range of different species as possible.
• Equation for estimated total population size

  Estimated total population size = mean number in a quadrat x (total area/area of quadrat)
• Producer


  A green plant that produces its own food via photosynthesis. E.g. Rose bush
• Tertiary

  Consumer

  An animal that eats secondary consumers

  Eg: Black bird
• Trophic level


  A position in a food chain or pyramid occupied by a group of organisms.
• Primary

  Consumer


  An animal that eats plants.

  Eg: Green fly
• Secondary

  Consumer


  An animal that eats primary consumers.

  Eg: Lady bird (lady bug)
• Omnivore


  An animal that eats both plants and animals

  Eg: Black bird
• Decomposer


  An organism that causes decay of dead material.

  (Eg: Bacteria and Fungi)
• Herbivore


  An animal that eats plants.

  Eg: Green fly
• Carnivore


  An animal that eats meat.

  Eg: Lady bird
• Scavenger


  An animal that eats dead plants and animals.

  (Eg: Vulture or Hyena)
• Predator


  An animal that feeds by killing and eating other animals.

  Eg: Lady Bird
• Prey


  An animal that is hunted or killed by another animal for food.

  Eg: Green fly
• Food chains and food webs

  Food chains describe the feeding relationships in a habitat - they show the transfer of energy and biomass from organism to organism. The arrow shows the direction of the energy flow from one trophic level to the next. A food web is a better description of the feeding

  relationship in a habitat since it reveals how different food chains are interlinked.
• Transfer of energy between trophic levels


  Only around 10% of the biomass consumed by an organism is turned into new biomass

  and made available for the next stage of the food chain. The rest is lost to the

  environment either as chemical energy or heat energy. That means there is always

  less energy transferred to the next trophic level than was taken in. This explains

  why the pyramid of energy is always pyramid shaped.