Ecosystem: All living organisms and all the non-living components in a specific habitat, and their interactions. Ecology is the study of the interactions between organsims and their environment.
Ecosystems are dynamic systems.
Biotic factor: How living organisms affect each other, food supply, predation, diease.
Abiotic factor: The effect of non-living components on the ecosystem, pH, temperature, soil type.
Producer: An organism that converts simple inorganic compounds into complex organic compounds.
Consumer: An organism that gains energy from complex organic matter.
Decomposer: An organism that feeds on waste from other organisms, or dead organisms.
Trophic level: Each feeding level in a food chain.
Energy is transferred by organisms consuming each other. This is shown in a food web, with the arrows representing the flow of energy between organisms.
Energy transfers between trophic levels can be measured.
Each sample is dried in an oven. The samples are weighed, and then burned in a bomb calorimeter in oxygen. The energy produced passes to a known mass of water and the temperature rise of the water is measured. How much energy is released per gram is calculated to kJ.
Energy is lost between trophic levels because animals never eat all of the available food and canot digest all of the food they eat. They also use energy to respire, lose heat energy to the surroundings and lose energy in urine and faeces.
Net primary productivity is different in different ecosystems because tropical ecosystems compared to temperate ones have higher temperatures and more sunlight (days are longer) so they photosynthesise faster and form more biomass and therefore energy. Woodland or rainforest ecosystems compared to grassland have a greater complexity with greater biodiversty so more niches. This means competition for space is less limiting.
Human activities can manipulate the flow of energy through ecosystems.
Increasing productivity of producers through:
- Soil improvment
- Removal of competing weeds, damaging pathogens and pests
Increasing productivity of producers and consumers through selective breeding or genetic engineering.
Sheltering organisms from damaging environmental factors.
Primary succession resulting in a climax community:
A sand dune.
Pioneer plants such as sea rocket colonise the sand just above the high water mark. These plants can tolerate salt water spray, lack of fresh water and unstable sand.