ecology

• An ecosystem is the interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment.
• 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.
• If one species is removed it can affect the whole community, this is called interdependence.
• A stable community is one where all the species and environmental factors are in balance so that population sizes remain fairly constant.
• Abiotic (non-living) factors that can affect a community are light intensity, temperature, moisture levels, soil pH and mineral content, wind intensity and direction, carbon dioxide levels for plants, and oxygen levels for aquatic animals.
• Biotic (living) factors that 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
• Organisms have features (adaptations) that enable them to survive in the conditions in which they normally live. These adaptations may be structural, behavioral or functional. Some organisms live in very extreme environments, such as at high temperatures, pressure, or salt concentrations. These organisms are called extremophiles. Bacteria living in deep sea vents are extremophiles.
• 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
• Producers are eaten by primary consumers, which in turn may be eaten by secondary consumers and then tertiary consumers. 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.
• All materials in the living world are recycled to provide the building blocks for future organisms. The carbon cycle returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis. The water cycle provides fresh water for plants and animals on land before draining into the seas. Water is continuously evaporated and precipitated.
• Biodiversity is the variety of all the different species of organisms on earth, or within an ecosystem. 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, fertilizer, or toxic chemicals, in air, from smoke and acidic gases, on land, from landfills, and toxic chemicals. Pollution kills plants and animals which can reduce biodiversity.
• Humans reduce the amount of land available for other animals and plants by building, quarrying, farming, and dumping waste. 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.
• Large-scale deforestation in tropical areas has occurred to: provide land for cattle and rice fields or grow crops for biofuels
• Levels of carbon dioxide and methane in the atmosphere are increasing, and contribute to ‘global warming’.
• Scientists and concerned citizens have put in place programs to reduce the negative effects of humans on ecosystems and biodiversity. These include 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, and recycling resources rather than dumping waste in landfill.
• Life processes depend on molecules whose structure is related to their function.
• The fundamental units of living organisms are cells, which may be part of highly adapted structures including tissues, organs and organ systems, enabling living processes to be performed effectively.
• Living organisms may form populations of single species, communities of many species and ecosystems, interacting with each other, with the environment and with humans in many different ways.
• Living organisms are interdependent and show adaptations to their environment.
• Life on Earth is dependent on photosynthesis in which green plants and algae trap light from the Sun to fix carbon dioxide and combine it with hydrogen from water to make organic compounds and oxygen.
• The chemicals in ecosystems are continually cycling through the natural world.
• The characteristics of a living organism are influenced by its genome and its interaction with the environment.
• Evolution occurs by a process of natural selection and accounts both for biodiversity and how organisms are all related to varying degrees.
• 1. choose a starting point on the school field in an area where the grass is often cut
  2. use random numbers to generate a set of coordinates to place your first quadrat
  3. count the number of different plant species within this quadrat (the species richness)
  4. return to your starting position and repeat steps two and three a further 14 times using different random numbers
  5. repeat steps one to four for a part of the school field which the grass is infrequently cut
  6. compare your results by calculating a mean for each location
• Quadrats- random sampling

  1. Use a random number generator to obtain 2 numbers, which are to be used as coordinates to find a location on the 2 tape measures set up. 2. Set down the quadrat at the coordinates.
  2. 3. Count and record the number of the required plant species in the quadrat.
  3. 4. Repeat steps 1-3 to take 9 more samples.
  4. 5. Estimate the population size using this formula:
  5. area sampled / total area x number of plant species counted
• Teansects- continious sampling

  1.Write down a hypothesis of the effect of a change in an abiotic factor on the distribution of the plant species. 2. Lay down a tape measure from the base of a tree to an open area of ground/ along a location with an ecological gradient. 3. Place the quadrat along the ‘0’ end of the tape measure, with one corner touching the ‘0’ mark. 4. Count the number of plants 5. Place the quadrat 5 m up the tape measure and repeat step 3. 6. Repeat step 4 at 5 m intervals until you reach the end of the transect line.