What is an ecosystem?
Ecology – the science that examines the interactions between organisms and their living (biotic) and non-living (abiotic) environment. Groups of organisms and their biophysical environment interact and exchange matter and energy. Ecosystem – the dynamic complex of plant, animal and micro-organism communities and their non-living environment as a functional unit. Ecosystems are dynamic; constantly changing and adapting.
Ecosystems are systems through which incoming solar energy is captured (photosynthesis) and channelled through a hierarchy of life forms. Each ecosystem has its own characteristic plant and animal community. The quest for food is the central organising principle with in ecosystems. Important feature is the set of processes by which nutrients are retained and recycled. Living things recycle nutrients obtained from air, soil, water and other organisms, using solar energy to build and maintain themselves. Variations in Ecosystems
Components of any ecosystem can vary naturally or due to human intervention. Variations will affect other components and processes which may be magnified. There have been substantial fluctuations in environmental conditions over the past 18,000 years. E.g. Climate change and rising sea level.
Classified according to their dominant features.
Land based ecosystems = terrestrial ecosystems or biomes. (Forests, deserts, grasslands). Differences between terrestrial ecosystems primarily arise from variations in average temperature and precipitation. Water based ecosystems = aquatic ecosystems. (Ponds, lakes, rivers, oceans, wetlands, coral reefs). Differences between aquatic ecosystems primarily arise from variations in the amount of nutrients dissolved, salinity, depth of sunlight penetration (turbidity) and average temperature. Ecosystems rarely have distinct boundaries.
Zone of transition = ecotone.
An ecotone contains organisms common to both ecosystems and organisms unique to the transition area. Ecotones often have a greater biodiversity than surrounding ecosystems. The Ecosphere
Ecosphere – collection of living and dead organisms (biosphere), interacting with one another and their non-living environment. (Represents the aggregate of the world’s ecosystems). Study of ecology is primarily concerned with interactions that occur at the five levels of organisation; organisms, populations, communities, ecosystems and the ecosphere. Simplest distinction between organisms is between producers, consumers, and decomposers. Plants range from single-celled phytoplankton to the giant sequoia trees of North America. Animals range from microscopic zooplankton to 30m long blue whales. Decomposers range from microscopic bacteria to large fungi.
Population – a group of organisms of the same species living together in an area. Are said to be dynamic; constantly adapting to environmental conditions by changing their size, distribution, age structure and genetic make-up. Species – a single type of organism able to reproduce its own kind. Estimated 5m – 30m species around the world.
Habitat – the area in which an organism or population lives. Interactions between the abiotic features and the soil allows life forms to develop. Community – several populations interacting with each other in a particular habitat. Therefore, ecosystems can be referred to as – the combination of a community and its non-living environment: an ever changing (dynamic) network of biological, chemical and physical interactions that sustains a community and allows it to respond to changes in environmental conditions.