6.3.2 - populations and sustainability

• Carrying capacity is the maximum population size that a habitat can support, defined by the presence of limiting factors.
• Factors that limit the maximum size of a population are:

  • Food
  • water
  • light
  • oxygen
  • predators
• In a predator prey relationship:

  prey is eaten by predator, resulting in increased predator population and decreased prey population

  fewer prey means increased competition for food, so predator population decreases

  fewer predators means more prey survives and the cycle begins again
• Intraspecific competition: competition between individuals of the same species
• interspecific competition: competition between individuals of different species
• Conservation: maintains biodiversity of a habitat by allowing sustainable use of the resources.
• preservation: maintains biodiversity of a habitat by minimising human impact
• We conserve and preserve habitats for:

  • economic - food source, ecotourism, drug development
  • social - activities with others eg, hiking
  • ethical - maintain habitats for future generations
• sustainability - using resources in a way that maintains them for future generations
• sustainable methods for timber production include

  coppicing

  replacing felled trees

  selective cutting
• sustainable methods for fishing include:

  fishing quotas

  mesh sizes

  species restrictions

  trawler sizes
• Human effects are controlled in sensitive ecosystems like the Galápagos Islands. Many endangered species due to hunting and tourism. New species introduced but caused damage to native species. So now we try to find a balance.
• Population growth curve shows number of organisms against time
• first phase of population growth, is a very slow population growth where the birth rate is higher than the death rate.
• second phase of population growth is very rapid growth of population size where there is few limits on the population growth. There is a much higher birth rate than death rate
• Third phase ( stable phase) is where further growth is very limited due to external factors, the population fluctuates around the carrying capacity.
• Carrying capacity is not subject to anymore succession
• If all resources were available in plentiful supply the population would grow exponentially. Limiting factors can be categorised into abiotic or biotic factors. Other variables that can affect population growth include immigration ( movement of organisms into the area) and emigration ( movement of organisms out of the area).
• Predation is a biotic factor which can influence population size.
• Conservation is management of nature to protect species and habitats.
• preservation leaves the environment and leaves ecosystem untouched.
• Aims of sustainability are:

  • preserve the environment
  • ensure resources are available for future generations
  • allow humans in all societies to live comfortably
  • enable less economically developed countries to develop through exploiting their natural resources
  • create a more even balance in the consumption of these resources in more economically developed countries and less economically developed countries.
• Coppicing is where the tree is cut Close to the ground so new shoots will grow and process is repeated after certain times.
• Advantages of coppicing:

  new stems grow more rapidly than saplings

  lifespan of tree extended

  provides variety of light levels

  fewer large trees mean more light for smaller plants

  provides variety of habitats.

  Maintains biodiversity

  roots prevent soil erosion
• Selective felling is cutting down of selected mature trees in a forest. This allows other trees to grow to maturity and leaves enough for habitats for animals.
• Rotational felling consists of planting a site and then felling the trees when they are mature and repeating this every 8 to 20 years
• strip felling is cutting down of selected mature trees in a forest in a strip
• after you have felled a tree, if appropriate you must replant the tree
• Introducing fishing quotas limits the number of certain species of fish that can be caught.
• certain hole size in nets allows smaller fish to escape to reach maturity and breeding age.
• fishing is only allowed at certain times of the year allowing population reach a sustainable level.
• Galápagos Islands have lots of endemic species - found no where else in the world.
• Effects of human activity on Galápagos Islands are:

  • Habitat destruction for buildings
  • deforestation of land
  • increase in boats
  • more pollution, sewage in the sea and oil spills
  • overfishing
  • competition from introduced species
  • introduction of new pathogens and diseases
• Controlling human impact in islands includes:

  introduction of park rangers

  limiting human access to particular islands

  stricter control on migration
• Effects of human activity on Antarctica:

  Whale and fish populations have been impacted through overfishing and whaling.

  There are now bans and restrictions on whaling and fishing

  waste must be taken with when you leave

  boats cant dump their waste into the sea