Biology - Ecology

  1. Definitions
    Ecology: study of the interactions between living things & between organisms and their environment

    Biosphere: that part of the planet containing living organisms

    • Ecosystem: a group of clearly distinguished organisms that interact with their environment as a unit
    • Eg. Grassland – mid temperatures, low rainfall – Steppes of Africa

    Population: all members of the same species living in an area

    Community: All different populations in an area
  2. Population Control
    • 1. Competition
    • Occurs when organisms actively struggle for a resource that is in short supply
    • Intra-specific competition: between members of the same species
    • Inter-specific competition: Between members of different species

    • Contest competition: there is an active struggle between two individual organisms
    • Scramble competition: all of competing individuals get some of the resource
    • 2. Predation
    • The catching, killing & eating of another organism
    • Adaptations
    • Birds of prey have excellent sight to detect prey
    • Ladybirds have strong mouths to chew aphids
    • Prey
    • Ladybirds are bright to warn that they are poisonous
    • Frogs are well camouflaged

    • 3. Parasitism
    • Two organisms of different species live in close association and one organism obtains its food from, and to the disadvantage to, the host
    • Endoparasites: Inside host eg. Liver flukes in sheep
    • Exoparasites: Outside host eg. Fleas on a dog
    • 4. Symbiosis
    • Occurs when two organisms of different species live in close association & at least one of them benefits
    • Mutualism: Both benefit from the association
  3. Environmental Factors affecting organisms
    • Abiotic Factors
    • Altitude
    • Aspect
    • Steepness

    • Biotic Factors
    • Food
    • Competition
    • Predation
    • Parasitism

    • Climatic Factors
    • Temperature
    • Rainfall
    • Humidity
    • Wind

    • Edaphic Factors
    • pH
    • Humus
    • Water content
    • Air content

    • Aquatic Factors
    • Light
    • Salt content
    • Wave action
  4. Food Chains
    • Consumers: Organisms that take food form another organism
    • Primary
    • Secondary
    • Tertiary

    • Grazing food chain: A sequence of organisms in which one member is eaten by the next in the chain
    • Eg. Buttercup - Caterpillar - Thrush - Fox

    • Trophic Level: A feeding stage in a food chain
    • 10% of energy in each trophic level is passed on to the next level
  5. Food Webs
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    Food Web: consists of two are more interlinked food chains
  6. Pyramid of Numbers
    Pyramid of Numbers: Represents the number of organisms at each trophies level in a food chain

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    • Limitations:
    • Do not take into account the size of organisms
    • Pyramids cannot be drawn to scale

    Ecological Niche: of an organism is the functional role it plays in the community
  7. Nutrient Recycling
    The way in which elements are exchanged between the living & non-living components of an ecosystem
  8. The Carbon Cycle
    The process by which carbon from the environment is converted to carbon in living things

    • Role of Organisms in the Carbon Cycle
    • Plants – remove carbon from the environment by photosynthesis & return it by respiration
    • Animals – get their carbon by eating plants & release it through respiration
    • Micro-organisms – return carbon to environment when they decompose dead plants & animals
  9. Global Warming
    • Rise in carbon dioxide concentration
    • Sources: Fossil Fuels
    • Deforestation

    • CO2 is a ‘greenhouse gas’
    • It allows heat radiation pass into atmosphere
    • Results: Sea levels may rise
    • Weather patterns may alter
  10. The Nitrogen Cycle
    Function: To take nitrogen from the air & make it available for use by living things

    • Nitrogen Fixation: The conversion of nitrogen gas to ammonia (NH3), ammonium (NH4+) or nitrate (NO3-)
    • Happens in lightening & volcanic eruptions
    • Nitrogen-fixing bacteria – legumes eg. Clover, soya beans, peas & beans

    Nitrification: The conversion of ammonia & ammonium (NH4+) compounds to nitrite then nitrate

    Denitrification: The conversion of nitrates to nitrogen gas
  11. Role of Organisms in the Nitrogen Cycle
    • Bacteria: 4 types
    • Nitrogen-Fixing Bacteria – Convert nitrogen to nitrates
    • Bacteria of decay – Decaying nitrogen to Ammonia
    • Nitrifying bacteria – Ammonia to Nitrates
    • Denitrifying bacteria – Nitrates to Nitrogen Gas

    Fungi: Convert dead plants/animals to ammonia

    Plants: Absorb nitrates & use them to form proteins

    Animals: Consume plants & use their nitrogen to form animal protein
  12. Human Impact on Ecosystems
    Pollution: any harmful addition to the environment

    Pollutants: substances that cause pollution

    Ozone Depletion – an example of air pollution

    • Caused by manufactured chemical pollutants:
    • · CFCs ( Chlorofluorocarbons)
    • · Freon Gas
    • · Styrofoam

    • Effects:
    • Increased numbers of skin cancers, cataracts & weakened immunity
    • Damage to crop & plants
    • Concern that plankton will be depleted

    • Control of Ozone Depletion:
    • Reduction & replacement of CFCs with HCFs
    • Do not use sprays or foams containing CFCs
    • Fridge’s shouldn’t be dumped in landfill sites
  13. Conservation: the wise management of our existing natural resources, in order to maintain a wide range of habitats and prevent the death & extinction of organisms
    • Benefits of Conservation:
    • Prevents extinction
    • Maintains balance of nature
    • Maintains biodiversity
    • Organisms may be found to be useful in the future

    • Conservation in Fisheries
    • Fishing with large-mesh nets does not remove the young, small fish. This allows the fish numbers to be maintained
  14. Waste Management
    • In agriculture slurry enters rivers or lakes & minerals in it cause increased algal growth. The algae die & are decomposed by bacteria, depleting the water of oxygen. Aquatic plants & animals die. This is called eutrophication.
    • This can be controlled by
    • 1. Storing slurry in leak-proof pits
    • 2. Spreading slurry on dry land
  15. Problems associated with waste disposal
    • Micro-organisms carry diseases, easily spread through water
    • Toxic chemicals washed into water
    • Nutrients cause eutrophication
    • Landfills unsightly
    • Poisonous gases
Card Set
Biology - Ecology