ecology

• ecology is the study of the relationship between living organisms and their physical environment.
• the 4 levels of ecological organisation:

  1. individual
  2. organisms
  3. population
  4. whole ecosystem
• individual species of living organisms include every single plant, animal species, bacteria and fungi that can be found on our planet
• population: all the organisms of a particular species that live in that habitat
• habitat: a place where an organism lives
• community: all the populations of different species that live together in a habitat
• ecosystem: the interactions of a community of living organisms with non-living parts of the environment
• 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 and space, and for 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 etc
• interdependence: all species depend on each other, 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.
• biotic factors: living organisms that affect another living organisms in an environment
• biotic factors that can affect a community are:

  • availability of food
  • new predators arriving
  • new pathogens
  • one species outcoming another so the number is no longer sufficient to breed
• abiotic factors: non-living factors that affect the environment and living organisms
• abiotic factors:

  • light intensity
  • temperature
  • moisture levels
  • soil pH and mineral content
  • wind intensity and direction
  • carbon dioxide levels for plants
  • oxygen levels for aquatic animals
• 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.
• structural adaptations: physical features that help an organism survive in its environment
• behavioural adaptations: changes in behaviour that help an organism survive in a particular environment
• functional adaptations: processes inside organisms eg metabolism and reproductive system
• extremophiles: microorganisms that live in extreme environments such as high temperature, pressure or salt concentration. for example bacteria living deep sea vents
• producers: a photosynthetic organism that converts the sun's energy to make biological molecules. biomass.
• Feeding relationships within a community can be represented by food chains
• All food chains begin with a producer which synthesises molecules. This is usually a green plant or alga which makes glucose by photosynthesis
• A range of experimental methods using transects and quadrats are used by ecologists to determine the distribution and abundance of species in an ecosystem.
• 1. producer: a food chain always starts with a producer
  2. primary consumer: producers are eaten by primary consumers
  3. secondary consumers: primary consumers are eaten by secondary consumers
  4. tertiary consumer: secondary consumers are eaten by tertiary consumers
• 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
• most of the energy is lost as you go down the chain
• abundance: refers to how many organisms are in a habitat, or how many individuals are in a population
• distribution: refers to where the organisms are
• sampling: measure a subset of organism and use that to make predictions about the whole population
• quadrats: used to measure abundance
• transets: to measure distribution changes
• quadrats are square frames that are subdivided into lots of smaller spaces
• measure the size of a common species:

  1. uses a tape measure and the field to turn into a large grid
  2. use a random number to generate 10 pairs of random coordinates
  3. place quadrats at those coordinates and count how many plants are found in each
  4. calculate the mean number of plants per m2
  5. estimate the total population using mean and total area
• Consumers that kill and eat other animals are predators, and those eaten are prey. In a stable community the numbers of predators and prey rise and fall in cycles.