Ecosystems
- An ecosystem can be defined as:
A group of organisms interacting with each other and with the non-living parts of the environment
- There are both biotic components and abiotic components within an ecosystem
- Ecosystems vary greatly in size and scale
- Both a small pond in a back garden and the open ocean could be described as ecosystems
- Ecosystems vary in complexity:
- A desert is a relatively simple ecosystem
- A tropical rainforest is a very complex ecosystem
Ecosystem example
- An ocean is an example of a complex ecosystem
- There is a large community of organisms, including fish, crustaceans, corals, algae, plants and microorganisms
- The abiotic components of the ecosystem include the salinity, pH, temperature, light intensity, and mineral availability
- The abiotic components of the ecosystem influence the community of organisms, e.g. by providing habitat, nutrients and other resources organisms need in order to survive and reproduce
Ecosystems include communities and their interactions with the abiotic environment
Ecosystems as open systems
- Ecosystems are open systems, meaning that both energy and matter can enter and exit the system
- Energy can enter and exit as follows:
- Energy enters in the form of sunlight, and flows through an ecosystem in the form of stored chemical energy
- Energy can also enter an ecosystem stored in the tissues of any organisms that migrate into the system
- When energy is stored in the molecules of an organism and that individual leaves the ecosystem, that stored energy is removed
- Matter can enter and exit as follows:
- Matter enters an ecosystem when an organism arrives, in the form of all of the molecules of its cells and tissues, e.g. when a bird migrates into an ecosystem
- Matter is removed when an organism leaves an ecosystem, e.g. dead plant matter could be washed away by the waves on a beach and carried to a new ecosystem, or trees are cut down and the timber removed
- It is worth noting that most of the organisms in an ecosystem remain inside the system throughout their lives, and the matter and energy stored in their tissues is recycled within the ecosystem when an individual dies
- While ecosystems are open, they are considered to be largely self-contained
- Open systems are different to closed systems
- In a closed system:
- Matter can only be recycled within the system and cannot enter or leave
- Energy can enter and leave
- Earth is an example of a closed system; energy enters and leaves but matter is recycled
- In a closed system: