· Consist…of all the living organisms and all the non-living components in a specific habitat, and their interactions.
· Are constantly changing – are dynamic.
· Populations of individuals rise and fall, nutrient levels change.
· Is…the place where an organism lives, including the non-living factors as well as the other species that live there.
· Is occupied by a range of species which can be described as the community.
· The species are adapted to live in a particular habitat e.g. earthworms in soil.
· Is…all of the populations of different species who live in the same place at the same time and can interact with each other.
· Is…the role an organism plays in a habitat.
· Is…all of the organisms of one species that live in the same place at the same time and that can breed together.
· Are…the living components of the environment e.g. competition, disease, predation.
· Are…the non-living components of the environment e.g. temperature, pH, light intensity.
Energy flow through an ecosystem
· Energy enters an ecosystem in the form of sunlight – via photosynthesis.
· Some of this energy is trapped in the form of organic carbon-based compounds e.g. glucose.
· This energy is then transferred through via different trophic levels and food chains.
· Are…organism that carry out photosynthesis.
· Are…organisms that consume other organisms.
· Primary consumers are usually herbivores, secondary/tertiary consumers are usually omnivores or carnivores.
· Are…organisms that consume dead tissue and waste.
Productivity of ecosystems
· Only a small percentage (less than 1%) of the solar energy falling on a plant becomes trapped in the biomass.
· Gross Primary Productivity (GPP) is the energy trapped by producers in photosynthesis. This is the rate at which plants convert light energy into chemical energy (i.e. photosynthesis).
· Net Primary Productivity (NPP) is the remainder of energy stored within the tissues of the plant as it grows.
GPP = NPP + Respiration
Why not all energy is used in photosynthesis
· Some light is reflected from the surface of the leaf.
· Only certain wavelengths of light are absorbed by chlorophyll.
· Light may not strike a chloroplast.
· Other limiting factor e.g. CO2.
Why consumers only trap a small proportion of their intake
· Not all energy is absorbed – some remains in gut, some is lost in faeces e.g. cellulose cell walls.
· Animals have a high level of activity (have high energy requirement for movement and physiology) so therefore respiration rate is high.
· Mammals and bird are homiotherms so have to maintain a constant body temperature, so therefore respiration rate is high.
· All of these processes need energy so a low % of energy is passed on to the next trophic level.