Ecosystems contain two categories of components. Biotic components are living things and abiotic components are non-living things. Scientists study the interaction between biotic elements; the interaction between abiotic elements and the interrelation of biotic and abiotic components of an ecosystem.
An ecosystem is a system containing living organisms in a location. They are supported and interact with the physical environment in that location. Although human environments, like cities fit into this definition, the term is usually only used by those studying nature and specific areas with unusual animal and plant life.
The biotic components in an ecosystem are the living things. These are the animals, the insects, the birds, fish, crustaceans and the bacteria found in an area. All forms of vegetable life fall into this category as well, including trees, weeds, crops, fungi, shrubs flowers and grasses.
Abiotic components are the things that don’t classify as living. This category includes soil, sand, salt, rocks, mountains; landscape features, such as valleys and ravines; bodies of water, like streams, rivers, icebergs and ice flows, ponds, lakes, seas and oceans. Non-tangible factors are included as abiotic components. These include the meteorological factors of temperature, rainfall, humidity and winds.
The abiotic components in an ecosystem support the biotic components. The nature of the environment dictates the forms of animals that live in the area. Hence, monkeys have the abilities and form they have because they live in the trees. Cows eat grass, and so do not live in the desert. The biotic sphere forms a chain of support and nourishment within itself, but would not exist without the underlying support of the abiotic sphere -- there would be no grass without soil and rain.
An ecosystem does not have to be a large area of countryside or forest. Micro-organisms exist in their own ecosystems within the broader ecosystem. For example, conditions inside a rotting log create idea conditions for certain life forms, because the moisture caused by rainfall and humidity interacts with the biological material of the log. In this environment, once more, abiotic components support biotic components to form an ecosystem. That ecosystem is itself, part of a wider ecosystem, existing in a forest, a wood, or a back garden.