bio paper 2

• Habitat


  The place where an organism lives
• Population


  All the organisms of one species living in a habitat
• Community


  The populations of different species living in a habitat
• Abiotic factors


  Non-living factors of the environment, e.g. temperature
• Biotic factors


  Living factors of the environment, e.g. food
• Ecosystem


  The interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment
• Organisms need things from their environment and from other organisms in order to survive and reproduce
• Things plants need


  • Light
  • Space
  • Water
  • Mineral ions (nutrients) from the soil
• Things animals need


  • Space (territory)
  • Food
  • Water
  • Mates
• Organisms compete with other species (and members of their own species) for the same resources
• In a community, each species depends on other species for things such as food, shelter, pollination and seed dispersal - this is called interdependence
• Any major change in the ecosystem (such as one species being removed) can have far-reaching effects due to the interdependence of all the living things
• Part of a food web from a stream

  • Stonefly larvae
  • Blackfly larvae
  • Water spider
  • Sticklebacks
• Stonefly larvae are particularly sensitive to pollution
• Loss of stonefly larvae

  • Less competition for algae
  • More likely to be eaten by predators
  • Less food for water spider or mayfly larvae (numbers decrease)
• Food webs are very complex and these effects are hard to predict accurately
• Stable communities


  Communities where all the species and environmental factors are in balance so that the population sizes are roughly constant
• Stable communities


  • Tropical rainforests
  • Ancient oak woodlands
• Abiotic factors


  Non-living factors that can vary in an ecosystem, e.g. light intensity, temperature, water, carbon dioxide level, wind intensity and direction, oxygen level, mineral content
• Changes in abiotic factors can affect the size of populations in a community, which can have knock-on effects due to interdependence
• Decrease in light intensity, temperature or carbon dioxide level


  Decrease the rate of photosynthesis in plants
• Decrease in mineral content of soil

  Cause nutrient deficiencies that affect plant growth and population size
• Biotic factors


  Living factors that can vary in an ecosystem, e.g. new predators, competition, new pathogens, changes in food availability
• Introduction of a new predator

  Cause a decrease in the prey population
• Competition between grey and red squirrels

  Grey squirrels outcompete red squirrels, causing a decrease in the red squirrel population
• Effect of a new pathogen on Species A

  • Population size increased until 1985, then decreased rapidly until 1990, then started to rise again after 1990
• Adaptations


  Features or characteristics that allow organisms to survive in different environments
• Types of adaptations


  • Structural
  • Behavioural
  • Functional
• Structural adaptations


  • Thick fur of Arctic animals
  • Thick blubber layer of animals in cold places
  • Thin layer of fat and large surface area to volume ratio of animals in hot places
• Behavioural adaptations


  • Migration of some species to warmer climates in winter
• Functional adaptations


  • Desert animals conserving water by producing little waste and concentrated urine
  • Brown bears hibernating over winter to conserve energy
• Microorganisms have a huge variety of adaptations that allow them to live in very extreme conditions
• Extremophiles - microorganisms adapted to live in extreme conditions


  • High temperatures (e.g. volcanic vents)
  • High salt concentration (e.g. very salty lakes)
  • High pressure (e.g. deep sea vents)
• Food Chains


  Show what's eaten by what in an ecosystem
• Food Chains


  1. Producers produce food using energy from the Sun

  2. Producers are usually green plants or algae - they make glucose by photosynthesis

  3. Plants produce biomass, some of which is used to make other biological molecules

  4. Biomass can be thought of as energy stored in a plant

  5. Energy flows through living organisms in an ecosystem

  6. Producers are eaten by primary consumers

  7. Primary consumers are then eaten by secondary consumers

  8. Secondary consumers are then eaten by tertiary consumers
• Food Chain


  • 5000 dandelions -> 100 rabbits -> 1 fox
• Populations of prey and predators


  Go in cycles
• The population of any species is usually limited by the amount of food available
• If the population of the prey increases


  The population of the predators will also increase
• As the population of predators increases


  The number of prey will decrease