topic 7- ecology

• Ecology


  The study of organisms and the environment they live in, and how the two interact
• Terms to understand ecology

  • Habitat - the place where an organism lives
  • Population - all the organisms of one species living in a habitat
  • Community - the populations of different species living in a habitat
  • Abiotic factors - non-living factors of the environment, e.g. temperature
  • Biotic factors - living factors of the environment, e.g. food
  • Ecosystem - the interaction of a community of living organisms with the non-living (abiotic) parts of their environment
• Organisms compete for resources to survive
• Resources organisms need to survive

  • Light and space (for plants)
  • Water and mineral ions (nutrients) from the soil (for plants)
  • Space (territory), food, water and mates (for animals)
• Organisms compete with other species (and members of their own species) for the same resources
• Any change in any environment can have knock-on effects
• Interdependence


  In a community, each species depends on other species for things such as food, shelter, pollination and seed dispersal
• The interdependence of all the living things in an ecosystem means that any major change in the ecosystem (such as one species being removed) can have far-reaching effects
• Stable communities include tropical rainforests and ancient oak woodlands
• Abiotic factors that can vary in an ecosystem

  • Moisture level
  • Light intensity
  • Temperature
  • Carbon dioxide level (for plants)
  • Wind intensity and direction
  • Oxygen level (for aquatic animals)
  • Soil and mineral content
• Changes in abiotic factors can affect the size of populations in a community
• Biotic factors

  • New predators arriving
  • Competition - one species may outcompete another
  • New pathogens
  • Lack of food
• Changes in biotic factors can also affect the size of populations in a community
• A pathogen caused the population of Species A to decrease rapidly until 1990, then start to rise again
• Adaptation


  Features or characteristics that allow organisms to survive in different environments
• Types of adaptations

  • Structural - features of an organism's body structure
  • Behavioural - ways that organisms behave
  • Functional - things that go on inside an organism's body
• Some microorganisms (e.g. bacteria) are known as extremophiles and are adapted to live in very extreme conditions
• Food chain


  Shows what's eaten by what in an ecosystem, starting with producers (green plants or algae) and going through primary, secondary and tertiary consumers
• Populations of prey and predators go in cycles
• Quadrat


  A square frame enclosing a known area, used to study the distribution of small organisms
• Using quadrats to study distribution


  1. Place 1m² quadrat at random point

  2. Count all organisms within quadrat

  3. Repeat in multiple locations

  4. Calculate mean number of organisms per quadrat
• Population size

  The total number of a particular organism in a given area
• Transect


  A line along which the distribution of organisms is studied
• Using transects to study distribution


  1. Mark out a line in the area

  2. Collect data by counting organisms along the line or using quadrats placed at intervals along the line
• Percentage cover


  Estimating the percentage area of a quadrat covered by a particular type of organism
• Quadrats can be placed next to each other along the line or at intervals, for example, every 2 m
• Estimating the Percentage Cover of a Quadrat

  1. Count the number of squares covered by organism A

  2. Make this into a percentage-divide the number of squares covered by the organism by the total number of squares in the quadrat (100), then multiply the result by 100

  3. Do the same for organism B
• • In the example, for organism A, 42 squares were covered, which is 42% of the quadrat
  • For organism B, 47 squares were covered, which is 47% of the quadrat
• Environmental changes can cause the distribution of organisms to change
• Environmental changes that can affect organisms

  • Change in the availability of water
  • Change in temperature
  • Change in the composition of atmospheric gases
• Environmental changes can be caused by seasonal factors, geographic factors or human interaction
• Water cycle

  Water is constantly recycled on Earth
• The water cycle

  1. Energy from the Sun makes water evaporate from the land and sea, turning it into water vapour

  2. The warm water vapour is carried upwards and condenses to form clouds

  3. Water falls from the clouds as precipitation onto the land and sea

  4. The water then drains into the sea, before the whole process starts again
• Materials are returned to the environment in waste products, or when organisms die and decay
• The carbon cycle

  1. CO2 is removed from the atmosphere by green plants and algae during photosynthesis

  2. When plants and algae respire, some carbon is returned to the atmosphere as CO2

  3. Carbon moves through the food chain as animals consume plants and other animals

  4. When plants, algae and animals die, detritus feeders and microorganisms break down their remains, returning CO2 to the atmosphere

  5. The combustion of wood and fossil fuels also releases CO2 back into the atmosphere
• Decay


  The process where microorganisms break down plant and animal material and waste to get energy
• Factors affecting the rate of decay

  • Temperature - warmer temperatures increase the rate of decay
  • Oxygen availability - many organisms need oxygen to respire and decay
  • Water availability - decay takes place faster in moist environments
  • Number of decay organisms - more microorganisms and detritus feeders increase the rate of decay
• Biogas

  Methane-rich gas produced by the anaerobic decay of plant and animal waste
• Producing biogas

  1. Microorganisms are used to decay plant and animal waste anaerobically (without oxygen)

  2. The methane gas produced is collected and can be used for heating, cooking, lighting or generating electricity
• Types of biogas generators

  • Batch generators - waste is loaded in, left to digest, and the by-products are cleared away
  • Continuous generators - waste is continuously fed in, producing biogas at a steady rate