Ecology

• Levels of Organisation in an Ecosystem

  • Individual organism
  • Population
  • Community
  • Ecosystem
• Individual organism


  A single member of a species
• Population


  A number of individuals of the same species living in the same area at the same time
• Community


  Multiple populations (of different species) living and interacting in the same area
• Ecosystem


  The interaction between a community (the living, biotic part) and the non-living (abiotic) parts of the environment
• Competition


  If a group of organisms all need the same resource in order to survive and reproduce but there is a limited amount of the resource available, they are said to compete for the resource
• Types of competition


  • Intraspecific competition (between members of the same species)
  • Interspecific competition (between members of different species)
• Adaptation


  If an organism has certain features, behaviours, or other characteristics that help it to survive and reproduce in its habitat, it is said to be adapted to its habitat
• Ecosystem


  The interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment
• Ecosystems can vary greatly in size and scale
• Examples of ecosystems


  • A garden pond
  • A woodland
  • A coral reef
  • A desert
• Interactions within an Ecosystem


  Members of a species will often interact with members of its own species or other species in order to survive and reproduce
• Examples of interactions within an ecosystem

  • Predators (carnivores) eating prey
  • Herbivores eating plants
  • Plant species being pollinated by bees
• Resources competed for by plants

  • Light
  • Water
  • Nutrients
  • Space
• Resources competed for by animals

  • Food
  • Mates
  • Nesting sites
  • Territory
• Interdependence


  Within a community, each species depends on other species for food, shelter, pollination, seed dispersal etc. If one species is removed it can affect the whole.
• Stable community


  A community where all the species and environmental factors are in balance so that population sizes remain fairly constant
• A food web shows the interdependence of organisms
• Questions about interdependence in food webs are common and simple to gain marks on if you answer them fully and correctly
• Abiotic factors that affect a community

  • Light
  • Temperature
  • Water
  • Oxygen
  • Carbon dioxide
  • Nutrients
  • pH
• As CO2 concentration increases


  Average plant height also increases
• When answering questions that refer to a chart, graph or table, remember to reference specific figures from the data to support your answer
• Biotic factors that can affect a community

  • Predators
  • Prey
  • Competitors
  • Pathogens
  • Decomposers
• As the number of grey squirrels increases


  The number of red squirrels decreases
• Types of adaptation to the environment

  • Structural
  • Behavioural
  • Functional
• Organisms that can live in extreme environments are called extremophiles
• Bacteria called chemoautotrophs survive by using inorganic chemicals to obtain energy
• Other species can then use the bacteria as a source of nutrition - the bacteria are producers in these food chains
• Make sure you understand the concept of surface area : volume ratios and why they are important when it comes to how animals are adapted to cold or hot environments
• Photosynthetic organisms are the producers of biomass for life on Earth
• Producers


  • They are at the start of every food chain (the first trophic level, which is always the biggest)
  • They can photosynthesise (producers are normally green plants or algae)
  • They make glucose by photosynthesis
  • They use this glucose to produce other biological molecules, which then make up the producer's biomass (some of the glucose produced is also used in respiration to release energy for the cell)
• In extreme environments (such as underwater volcanic vents) the producers are not photoautotrophs but chemoautotrophs who produce organic molecules without using energy from the Sun
• Food chain


  A simple way to show the feeding interactions between the organisms in a community
• Steps in a food chain

  • Producer
  • Primary consumer
  • Secondary consumer
  • Tertiary consumer
• A food chain shows the transfer of energy from one organism to the next
• The source of all energy in a food chain is light energy from the Sun
• The arrows in a food chain show the transfer of energy from one level of the food chain to the next
• Head to www.savemyexams.com for more awesome resources
• Ecology


  The branch of biology that studies the distribution and abundance of species, the interactions between species, and the interactions between species and their abiotic environment
• Ecologists


  Biologists that study these interactions by investigating ecosystems