Ecology

• Ecosystem organisation

  • Individual organisms
  • Population
  • Community
  • Ecosystem
• Population

  The total number of organisms of the same species that live in one specific geographical area
• Community

  Group of two or more populations of different species living in one specific geographical area
• Ecosystem

  The interaction of a community of living organisms with the non-living parts of their environment
• Competition


  • To survive and reproduce, organisms require a supply of resources from their surroundings and from the other living organisms there
  • This can create competition, where organisms within a community compete for resources
• Types of competition


  • Interspecific competition (between organisms of different species)
  • Intraspecific competition (between organisms of the same species)
• Things animals often compete for

  • Food
  • Mates
  • Territory
• Things plants often compete for

  • Light
  • Space
  • Water and mineral ions from the soil
• Interdependence


  Within a community each species interacts with many others and may depend on other species for things like food, shelter, pollination, and seed dispersal
• If one species is removed it can affect the whole community- this is called interdependence
• Abiotic factors


  Non-living factors in the ecosystem that can affect a community
• Abiotic factors that can negatively affect a community

  • Carbon dioxide levels for plants
  • Light intensity
  • Moisture levels
  • Oxygen levels for animals that live in water
  • Soil pH and mineral content
  • Temperature
  • Wind intensity and direction
• Biotic factors


  Living factors in the ecosystem that can affect a community
• Biotic factors that can negatively affect a community

  • Decreased availability of food
  • New predators arriving
  • New pathogens
  • Competition between species, for example, one species outcompeting another for food or shelter, causing a decline in the other species population
• Adaptations of organisms


  • Features that enable them to survive in the conditions in which they live
  • The adaptations of an organism may allow it to outcompete others, and provide it with an evolutionary advantage
• Types of adaptations


  • Structural adaptations (physical features)
  • Behavioural adaptations (behaviour of the organism)
  • Functional adaptations (adaptations related to processes that allow an organism to survive)
• Structural adaptations


  • Sharp teeth to hunt prey
  • Camouflage to hide from predators or to hunt prey
  • Large or small body surface-area-to-volume ratio
• Behavioural adaptations


  • Making nests to shelter offspring or attract a mate
  • Courtship dances to attract a mate
  • Use of tools to obtain food
  • Working together in packs
• Functional adaptations


  • Photosynthesis in plants
  • Production of poisons or venom to deter predators or kill prey
  • Changes in reproduction timings
• Extremophiles


  Organisms that live in environments that are very extreme where most other organisms could not survive
• Environments extremophiles can live in

  • Very high or low temperatures
  • Extreme pressures
  • High salt concentrations
  • Highly acidic or alkaline conditions
  • Low levels of oxygen or water
• Bacteria that live in deep sea vents are extremophiles
• Food chain


  Feeding relationships within a community can be represented by food chains
• All food chains begin with a producer, for example, a green plant or alga producing glucose through photosynthesis
• Consumers in a food chain

  • Primary consumers (herbivores that eat producers)
  • Secondary consumers (carnivores that eat primary consumers)
  • Tertiary consumers (carnivores that eat secondary consumers)
  • Apex predators (carnivores with no predators)
• Organisms usually have more complex feeding relationships, with more than one predator or more than one food source. These can be shown in a food web
• Carbon cycle


  All materials in the living world are recycled, which provides the building materials for future organisms
• The carbon cycle


  1. Photosynthesis removes CO2 from the air and dissolves in water, particularly oceans

  2. Respiration releases CO2 back into the air

  3. Combustion of fossil fuels releases CO2 into the air

  4. Decomposition by microorganisms releases CO2
• Global warming


  The gradual increase in the average temperature of the Earth
• Levels of carbon dioxide and methane in the atmosphere are increasing due to human activity, contributing to global warming and climate change
• Effects of global warming

  • Large-scale habitat change and reduction, causing decrease in biodiversity
  • Extreme weather and sea-level changes
  • Migration of species to different parts of the world, affecting ecosystems
  • Threats to the security and availability of food
• Biodiversity


  The variety of all the different species of organisms (plant, animal, and organ) on Earth, or within a specific ecosystem
• High biodiversity ensures the stability of an ecosystem because it reduces the dependence of one species on another for food or habitat maintenance
• The future of the human species depends on us maintaining a good level of biodiversity
• Ways to maintain biodiversity

  • Breeding programmes in zoos for endangered species
  • Protection and regeneration of rare habitats (e.g. national parks)
  • Reintroduction of hedgerows in agricultural areas where single crop species are grown, as hedges provide habitat for many organisms
  • Government policies to reduce deforestation and carbon dioxide emissions
  • Recycling resources rather than dumping waste in landfill
• Rapid population growth has led to humans using much more land for building, quarrying, farming, and dumping waste, reducing the area in which animals can live and further destroying habitats through pollution
• Large-scale deforestation in tropical areas has been carried out to provide land for cattle and rice fields, and to grow crops for biofuels, resulting in large amounts of carbon dioxide being released into the atmosphere, extinctions and reductions in biodiversity as habitats are destroyed, and climate change as trees absorb carbon dioxide and release water vapour
• Pollution can occur in water, from sewage, fertiliser run-off, or toxic chemicals, in air, from smoke and acidic gases, and on land, from landfill and toxic chemicals
• Waste and chemical materials need to be properly handled in order to reduce the amount of pollution they cause, as pollution kills plants and animals, and can accumulate in food chains, reducing biodiversity