ECOLOGY

• describe the different levels of organization in an ecosystem.


  individuals → populations → communities
• what is a habitat?


  the place where an organism lives
• what is a community?


  the populations of different species living in a habitat
• what are abiotic factors?


  non-living factors of the environment
• what are biotic factors?


  living factors of the environment
• what is an ecosystem?


  the interaction of a community of biotic organisms with the abiotic parts in their environment
• what do plants compete for in their community?


  - light

  - space

  - water

  - mineral ions from the soil
• what do animals compete for in their community?


  - territory

  - food

  - water

  - mates
• why is competition important?


  because animals and plants need resources to survive and reproduce
• what does each species depend on each other for within a community?


  - food

  - shelter

  - pollination

  - seed dispersal
• what does interdependence mean?


  when any major change in an ecosystem can have far-reaching effects
• why is interdependence important?


  because everything relies on each other so serious effects can occur if anything is changed
• what is a stable community?


  one where all the species and environmental factors are in balance so that population sizes remain fairly constant
• what are examples of abiotic factors which can affect a community?


  - light intensity

  - temperature

  - moisture levels

  - soil pH and mineral content

  - wind intensity and direction

  - CO₂ levels for plants

  - O₂ levels for aquatic animals
• what are examples of biotic factors which can affect a community?

  - availability of food

  - new predators arriving

  - new pathogens

  - one species outcompeting another
• what are adaptations?

  features that enable organisms to survive in the conditions which they normally live
• what are structural adaptations?

  body structure, appearance
• what are behavioral adaptations?


  the way an animal behaves, e.g. migration
• what are functional adaptations?


  the internal workings e.g. metabolism, respiration
• what are extremophiles?


  organisms that live in extreme conditions such as high temperature, pressure, or salt concentration
• what happens when prey levels in a stable community increase?

  predators increase

  
• what happens when predator levels in a stable community increase?

  prey decrease
• why are quadrats used?

  to measure and compare the distribution of species in two sample areas
• PRACTICAL: how are quadrats used?


  1 - place a 1 m² on the ground at a random point

  2 - count all the organisms within the quadrat

  3 - repeat 1-2 as many times as you can

  4 - work out the mean number of organisms per quadrat within the first sample area

  5 - repeat 1-4 in the second sample area

  6 - compare the two means
• why are transects used?


  to study how distribution changes across by placing quadrats along a transect
• PRACTICAL: how are transects used?

  1 - mark out a line in the area you want to study and collect the data

  2 - this can be done by just counting the organisms that touch the line or by using quadrats along the line
• what is the water cycle?

  evaporation + transpiration → condensation → precipitation
• what is the carbon cycle?

  - CO₂ is removed from the air during photosynthesis, C is used to make glucose

  - C is moved through the food chain by primary consumers

  - respiration by plants and animals returns some C to the atmosphere as CO₂

  - in decay, decomposers feed and respire CO₂; C is released into the groun

  - combustion of wood and fuels releases CO₂
• what is the rate of decay affected by?


  - temperature

  - oxygen availability

  - water availability

  - number of decay organisms
• what is biogas?


  mainly made up of methane, produced in anaerobic decay and can be burned as a fuel
• what are examples of environmental changes?


  - temperature

  - availability of water

  - composition of atmospheric gases
• what kinds of environmental changes are there?


  - seasonal

  - geographic

  - caused by human interaction
• what is biodiversity?


  the variety of all the different species of organisms on earth, or within an ecosystem
• how does a great biodiversity ensure the stability of ecosystems?


  by reducing the dependence of one species on another for food, shelter, and the maintenance of the physical environment
• what has caused more waste to be produced?

  the rapid growth in human population and an increase in the standard of living, causing more resources to be used
• how can pollution occur in water?


  from sewage, fertilizer or toxic chemicals
• how can pollution occur in air?

  from smoke, acidic gases
• how can pollution occur on land?

  from landfill, toxic chemicals
• how have humans reduced the amount of land available for other animals?

  by building, quarrying, farming and dumping waste
• why has large-scale deforestation occurred in tropical areas?


  to provide land for cattle and rice fields, to grow crops for biofuels