KA4

• Biodiversity is the variety of different organisms in an ecosystem.
• An ecosystem is the habitat and the community together.
• A habitat is the place where an organism lives.
• The community is all the organisms present.
• Habitat + Community ———— Ecosystem

  (Non-living) (Living) (Biological unit)
• A population is a group of organisms of the same species.
• A species is a group of organisms that can breed to produce fertile offspring.
• Ecosystem = forest

  Habitat = tree

  Community = squirrels, deer, fox

  Population = fox

  Species = deer (offspring/young in picture is fertile and can reproduce)
• Pitfall trap

   samples organisms in the soil

   hole dug and cup put in

   cup must be level with the soil

  – so organisms fall in

   cover the top of the cup

  – so birds don’t see trapped organisms and eat them

   several traps are set

  – to increase reliability

   traps are checked regularly

  – so animals don’t have time to eat each other
• Quadrat

   samples abundance (amount) of plants

   quadrat is thrown at random and the number of squares

  with a plant in it are counted

   several quadrats thrown

  – increases reliability

   rule for deciding which plants to count as “IN”

  – to ensure consistency

   quadrat thrown at random

  – to get a representative result
• Keys are used to identify organisms – branching key and paired statement key.
• Biotic factors are living factors that can affect the distribution of living things.
•  Predation – predators eat prey

   Disease

   Food availability

   Grazing – levels need to be not too high or too low

   Competition – two types

  o Interspecific: competition between members of different species for similar

  resources eg. fox and owl

  o Intraspecific: competition between member of the same species for the same

  resources; more intense eg. two lion
• Abiotic factors are non-living factors that can affect the distribution of living things.

   Light intensity – use a light meter; don’t cast a shadow over the meter

   Moisture content – use a moisture meter; wipe the probe between readings

   pH – use a pH meter; wait for the needle on the meter to stop moving before taking a

  reading

   Temperature – use a thermometer; make sure the thermometer is far enough into

  the ground
• A line transect is used to take readings from one area over to another to see how varying

  conditions affect the distribution of organisms eg. measuring abundance of daises from

  under a tree into an open area.
• An indicator species indicates the level of pollution in an area due to their presence or

  absence. Eg. lichen