Communities

• Define an ecosystem

  • the interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment.
• What do organisms require in order to survive and reproduce?

  Supply of materials :

  • from surroundings
  • other living organisms
• What did animals in a community or habitat compete for?

  • food
  • mates
  • territory
• Define the term interdependence


  • Within a community each species depends on other species.
  • If one species is removed it can affect the whole community
• Examples of what organisms depend on each other for

  • Food
  • Shelter
  • Pollination
  • Seed dispersal
• Define a stable community and effect on the population 


  • where all the species and environmental factors are in balance.
  • population sizes remain fairly constant.
• What do plants in a community or habitat often compete with each other for?

  • Light
  • Space
  • Water
  • Mineral ions
• What are 'abiotic factors'?

  • non-living factors
• What are 'biotic factors'?

  • Living factors
• 7 examples of abiotic factors

  • Light intensity
  • Temperature
  • Moisture levels
  • Soil pH & Mineral Content
  • Wind intensity & Direction
  • Carbon dioxide levels for plants
  • Oxygen levels for aquatic plants
• 4 examples of biotic factors that affect communities :

  • Food availability
  • New predators arriving
  • New pathogens
  • one species outcompeting another so the numbers are no longer sufficient to breed.
• 3 types of adaptations in communities :

  • Structural
  • Behavioural
  • Functional
• Define what is meant by an adaptation


  • Features that enable organisms to survive in conditions in which they normally live in.
• What are extremophiles? 


  • Organisms that live in environments that are very extreme.
• Example of extreme conditions : 


  • High temperature, pressure, salt concentration
• Examples of extremophiles 


  • Bacteria that live in deep sea vents
• Abiotic : Light intensity

  • light is required for photosynthesis
  • rate of photosynthesis affects growth of plant
  • plants can be food sources or shelters for other organisms
• Abiotic : Temperature 


  • temperature affects rate of photosynthesis as there are enzymes controlling photosynthesis
• Moisture levels


  • animals and plants need water to survive
• Soil pH and mineral content

  • soil pH affects rate of decay and how rate of mineral ions return to soil, then absorbed by plants.
  • different species of plants thrive in different nutrient concentration levels
• Wind intensity and direction

  • wind affects the rate of transpiration
  • transpiration affects temperature of plant, rate of photosynthesis since it transports water and mineral ions to the leaves
• carbon dioxide levels


  • carbon dioxide affects the rate of photosynthesis
  • affects the distribution of organisms as some thrive in higher carbon dioxide concentrations
• oxygen levels in aquatic animals

  • levels of oxygen water vary
  • most fish need high concentration of oxygen to survive
• Increase in food availability

  • organisms can breed more successfully and therefore populations increase
• New pathogens


  • When a new pathogen arises in a population that has no resistance, so is wiped out rapidly
• Competition


  • If one species is better adapted to the environment than another, then it will outcompete it until the numbers of lesser adapted species insufficient to breed