B7 Ecology

• Ecosystem


  An ecosystem is the interaction of a community of living organisms with the non-living (abiotic) parts of their environment
• Organisms require materials from their surroundings and other living organisms to survive and reproduce
• Interdependence


  Within a community, each species depends on other species for food, shelter, pollination, seed dispersal. If one species is removed it can affect the whole community
• A stable community is one where all the species and environmental factors are in balance so that population sizes remain fairly constant
• Population

  Population is a group of species
• Community


  Made up of different populations of species of animals and plants
• An ecosystem is made up of a community of organisms interacting with the non-living or abiotic elements of their environment
• Abiotic

  The non-living factors of an environment
• Biotic

  The living factors of an evironment
• Community


  A Community is made up of populations of different species of animals and plants, protists, fungi, bacteria and archaea that are interdependent in a habitat
• Ecological niche

  • An ecological niche is the role and position a species has in its environment, how it meets its needs for food and shelter, how it survives, and how it reproduces
• Species’ niche

  • A species’ niche includes all of its interactions with the biotic and abiotic factors of its environment
• Extremophiles


  Extremophiles are organisms that have adaptations enabling them to live in extreme conditions of salt, temperature or pressure e.g. organisms living in very cold waters have chemicals in their cells which act like antifreeze
• Thermophiles 


  Thermophiles live at high temperatures. e.g. Bacteria living in volcanic sulphur vents have special enzymes that don’t denature and so work at high temperatures
• How can plants survive very hot dry conditions?

  • Make sure more water is taken in: Large deep root system to collect lots of water
  • Reduced water loss from the leaves: Having leaves with very small surface area (low surface area to volume ratio), Waxy leaves (prevent water loss), Leaves that curl over to reduce SA & to trap a layer of moist air
  • Water can be stored in the stem or in fleshy leaves
• Interdependent

  • Plants make food (using abiotic elements of the environment)
  • Animals rely on plants/other animals for food, shelter/nesting materials
  • Plants rely on animals to pollinate, disperse seeds and they use the nutrients from animal droppings and decay
• How communities can be stable in arctic conditions

  • Arctic conditions - very cold and lower light levels
  • The plant leaves are smaller because they don’t have the temperature to be any bigger (risk of freezing)
  • This means the populations of animals living on them are smaller - don't have lots to eat
  • So there are low numbers of carnivores
  • If new animals are introduced, the community would be unstable and would be competition for limited plants and the most successful competitor would survive. But if they’re overgrazed then all the herbivores might die
• Difference between interdependence and competition

  • To survive and reproduce, organisms require a supply of materials from their surroundings and from the other living organisms there
  • Plants in a community or habitat often compete with each other for light, space, water and mineral ions from the soil
  • Animals often compete with each other for food, mates and territory
  • Within a community each species depends on other species for food, shelter, pollination, seed dispersal
  • If one species is removed it can affect the whole community - interdependence
• Detritivores

  An animal which feeds on dead organic material, especially plant detritus
• Decomposers


  Group of microorganisms that feed on waste droppings and dead organisms
• Abiotic (non-living) factors which can affect a community are:

  • light intensity
  • temperature
  • moisture levels
  • soil pH and mineral content
  • wind intensity and direction
  • carbon dioxide levels for plants
  • oxygen levels for aquatic animals
• Biotic (living) factors which can affect a community are:

  • availability of food
  • new predators arriving
  • new pathogens
  • one species outcompeting another so the numbers are no longer sufficient to breed
• Adaptations


  Organisms have features (adaptations) that enable them to survive in the conditions in which they normally live. These adaptations may be structural, behavioural or functional.
• Water Cycle

  1. Water from lakes, rivers, oceans and the soil evaporates into water vapour and rises into the atmosphere
  2. Water can also evaporate from plants via transpiration
  3. As the water vapour rises, it cools and condenses to form clouds
  4. The water will fall as rain which we call precipitation
  5. The water can seep into the soil (percolation), flow into rivers or lakes and be taken up by plants
  6. The whole cycle then repeats over and over
• The Carbon Cycle

  1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion
  2. Carbon dioxide is absorbed by producers to make glucose in photosynthesis
  3. Animals feed on plants and use glucose to build up fats, carbohydrate, proteins. Most carbon is exhales as carbon dioxide during respiration
  4. The animals & plants eventually die and are eaten by decomposers and carbon in their bodies is returned to the atmosphere as carbon dioxide
  5. The plant & animal material may be available as fossil fuel for combustion which produces carbon dioxide
• Biodiversity

  Biodiversity is the variety of all the different species of organisms on earth, or within an ecosystem.
• Importance of biodiversity

  • A great biodiversity ensures the stability of ecosystems by reducing the dependence of one species on another for food, shelter and the maintenance of the physical environment.
• • The future of the human species on Earth relies on us maintaining a good level of biodiversity.
  • Many human activities are reducing biodiversity and only recently have measures been taken to try to stop this reduction.
• Rapid growth in the human population and an increase in the standard of living mean that increasingly more resources are used and more waste is produced. Unless waste and chemical materials are properly handled, more pollution will be caused.
• Pollution can occur:

  • in water, from sewage, fertiliser or toxic chemicals
  • in air, from smoke and acidic gases
  • on land, from landfill and from toxic chemicals.

  Pollution kills plants and animals which can reduce biodiversity.
• Maintaining biodiversity

  • breeding programmes for endangered species
  • protection and regeneration of rare habitats
  • reintroduction of field margins and hedgerows in agricultural areas where farmers grow only one type of crop
  • reduction of deforestation and carbon dioxide emissions by some governments
  • recycling resources rather than dumping waste in landfill.
• Negatives of maintaining biodiversity

  • Protecting Biodiversity is expensive
  • To maintain our high standard of living we have to use fertilisers and pesticides for enough food
  • We have to dig huge mines for rare metals for phones and computers
  • In developing countries, they rely on the environment for their livelihood e.g. building homes, firewood for cooking, growing crops
• Greenhouse effect

  1. Solar radiation from the sun passes through the atmosphere and hits the earth
  2. Some of this energy is reflected straight back towards space, while some is absorbed by the earth and them reemitted towards space
  3. Some of the reemitted energy makes it all the way to space, but much is absorbed by small molecules called greenhouse gases
  4. These molecules then reemit the energy and the whole process of absorption and emission can happen over and over again
  5. This trapped energy keeps the atmosphere warmer and more stable than it would otherwise be
• Effects of global warming

  • Melting of ice caps, increases volume of water in the ocean and could lead to seasonal flooding or submersion of entire islands.
  • This is made worse as water expands when heated so it will also increase in volume
• Land Use

  • Humans reduce the amount of land available for other animals and plants by building, quarrying, farming and dumping waste.
• Deforestation

  Large-scale deforestation in tropical areas has occurred to:

  • provide land for cattle and rice fields
  • grow crops for biofuels
  • Logging to build or for fuel
• Effects of Deforestation

  1. Less photosynthesis so trees won’t be taking in Carbon Dioxide in the atmosphere - Global Warming
  2. Burning forests release carbon dioxide which can suffocate animals and pollute towns - contributes to Global Warming
  3. Destroys high biodiversity habitats, entire species become extinct
• Peat Bogs

  • The destruction of peat bogs, and other areas of peat to produce garden compost, reduces the area of this habitat and thus the variety of different plant, animal and microorganism species that live there (biodiversity).
  • The decay or burning of the peat releases carbon dioxide into the atmosphere.
• How draining peat bogs contributes to global warming

  • The draining of water allows air and oxygen to return to the soil
  • This allows microorganisms to carry out aerobic respiration and decay the organic matter
  • This releases carbon dioxide which acts as a greenhouse gas and contributes to global warming
• Ways to increase global food production

  • Clearing of forests and other natural lands for agriculture
  • Application of fertilisers, pesticides, herbicides, and other chemicals
  • Selective breeding
  • Genetic modification