B7 - Ecology

• What are the different levels of an ecosystem?

  Individual, population, community, ecosystem.
• Describe the importance of interdependence within a community.


  Within a community, each species depends on other species for food, shelter, pollination, seed dispersal etc. This means that a change in the population of one species can have significant knock-on effects for other species in the same community. If one species is removed it can also affect the whole community. This is called interdependence.
• Describe the importance of competition within a community.

  Animals in an ecosystem compete for food, mates and their territory. Organisms which have more of these resources tend to grow more healthily and are more likely to have offspring. Competition can be interspecific or intraspecific depending on whether organisms from different species or the same species are competing for resources.
• What do organisms require to survive and reproduce?


  A supply of materials from their surroundings and from the other living organisms there.
• What do plants compete for within a community or habitat?

  • Light
  • Space
  • Water
  • Mineral ions
• What do animals compete for within a community or habitat?

  • Food
  • Mates
  • Territory
• What is a stable community?


  A community where all the species and environmental factors are in balance so that population sizes remain fairly constant.
• What is an abiotic factor?


  Non-living factor in an ecosystem.
• Name some abiotic factors that can affect a community.


  • Light intensity
  • Temperature
  • Moisture levels
  • Soil pH and mineral content
  • Wind intensity and direction
  • Carbon dioxide levels for plants
  • Oxygen levels for aquatic animals
• What is a biotic factor?


  A living factor in an ecoystem
• Name some biotic factors that can affect a community.


  • Availability of food
  • New predators arriving
  • New pathogens
  • One species outcompeting another so the numbers are no longer sufficient to breed
• How are organisms adapted to live in their natural environment?


  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.
• What are extremophiles?


  Microorganisms that thrive in extreme environments, such as high temperature, pressure, or salt concentration. Bacteria living in deep sea vents are extremophiles.
• What are the producers of biomass for life on Earth?

  Photosynthetic organisms
• How can feeding relationships within a community be represented?


  Food chains.
• Where do all food chains begin?

  A producer which synthesises molecules. This is usually a green plant or algae which makes glucose by photosynthesis.
• How do ecologists determine the distribution and abundance of species in an ecosystem?


  A range of experimental methods using transects and quadrats.
• What is the relationship between producers, primary consumers, secondary consumers, and tertiary consumers?


  Producers are eaten by primary consumers, which in turn may be eaten by secondary consumers and then tertiary consumers.
• Consumers and Predators


  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.
• How are materials cycled?

  Many different materials cycle through the abiotic and biotic components of an ecosystem.
• Explain the importance of the carbon cycle to living organisms


  The carbon cycle returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis.
• Explain the importance of the water cycle to living organisms.


  The water cycle provides fresh water for plants and animals on land before draining into the seas. Water is continuously evaporated and precipitated.
• Explain the role of microorganisms in cycling materials through an ecosystem.


  They help decompose dead matter and release minerals and nutrients back to the environment, which can then be used by other organisms. As the bacteria and fungi decompose dead matter, they also respire and so release carbon dioxide to the environment, contributing to the carbon cycle.
• How does temperature affect rate of decay of biological material?

  Decomposers become more active and the rate of decay increases as temperature increases. When decomposers break compost down, the compost heap becomes warmer due to the respiration of the bacteria and fungi generating heat. At extremely high temperatures decomposers will be killed and decomposition will stop.
• How does water affect rate of decay of biological matter?

  As the volume of available water increases, the rate of decomposition also increases. Many decomposers secrete enzymes onto decaying matter and then absorb any dissolved molecules. Without water these reactions cannot occur.
• How does availability of oxygen affect the rate of decay of biological matter?

  As the volume of available oxygen increases, the rate of decomposition also increases. Some decomposers can survive without oxygen. These are used in biogas generators.
• Optimum Conditions for Decomposition

  Gardeners and farmers try to provide optimum conditions for rapid decay of waste biological material. The compost produced is used as a natural fertiliser for growing garden plants or crops.
• How is methane gas produced?


  Anaerobic decay produces methane gas. Biogas generators can be used to produce methane gas as a fuel.
• How can environmental change be caused?

  Seasonal causes, geographic causes, human interaction
• What do environmental changes affect?


  The distribution of species in an ecosystem.
• Impact of temperature

  As you climb up a mountain the temperature reduces. This reduction, together with other abiotic and biotic factors, determines what species of plant are found at different elevations.
• Impact of water

  All life on Earth needs water. Too much and some species will drown or rot. Too little and all species die.
• Impact of atmospheric gases


  Gases dissolve in liquids, thus oxygen in the air dissolves in water. It is this dissolved oxygen, together with that produced by plants and algae, that support aquatic life. When levels of pollution increase the levels of dissolved oxygen reduce.
• What is biodiversity?


  The variety of all the different species of organisms on earth or within an ecosystem.
• What does a great biodiversity ensure?


  • 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 actions are reducing biodiversity and only recently have measures been taken to try stop this reduction.
• Waste management and pollution

  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.
• How can pollution occur?

  • In water, from sewage, fertiliser, or toxic chemicals
  • In air, from smoke and acidic gases
  • On land, from landfill and toxic chemicals

  Pollution kills plants and animals, which can reduce biodiversity.
• How do humans reduce the land available for habitats?

  Building, quarrying, farming, and dumping waste
• The destruction of habitats - 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.
• Why has large scale deforestation occured?


  • Provide land for cattle and rice field
  • Grow crops for biofuels