Ecosystem: patterns and components
An ecosystem is a functional unit of nature where living organisms interact with each other and with their physical surroundings. A pond shows all its components and functions.
What is an ecosystem?
An ecosystem is a functional unit of nature. In it, living organisms interact among themselves and with their physical environment. Ecosystems range in size from a small pond to a large forest or a sea. Many ecologists treat the whole biosphere as one global ecosystem, made of all the local ecosystems on Earth. The biosphere is too big to study at once, so it is divided into two basic types: terrestrial and aquatic. Forests, grasslands and deserts are terrestrial. Ponds, lakes, wetlands, rivers and estuaries are aquatic. Crop fields and aquaria are man-made ecosystems.
Components of an ecosystem, with a pond as the example
| Component | What it includes | In a pond |
|---|---|---|
| Abiotic (non-living) | Water, soil, minerals, dissolved substances, sunlight, temperature, day-length | Water with dissolved inorganic and organic substances; the rich soil deposit at the bottom; the solar input, temperature cycle and day-length |
| Producers (autotrophs) | Make food from inorganic materials using sunlight | Phytoplankton, some algae, and floating, submerged and marginal plants at the edges |
| Consumers (heterotrophs) | Feed on producers or on other consumers | Zooplankton, free-swimming animals such as fish, and bottom-dwellers such as snails |
| Decomposers | Break dead organic matter into inorganic substances | Fungi, bacteria and flagellates, most abundant at the bottom of the pond |
Structure: species composition and stratification
The interaction of the biotic and abiotic components gives each ecosystem its own physical structure. Listing the plant and animal species of an ecosystem gives its species composition. The vertical distribution of species at different levels is called stratification. In a forest, trees occupy the top layer, shrubs the second, and herbs and grasses the bottom layers.
How a pond works as an ecosystem
- back to Inorganic nutrients in water and mud
Nutrients go round and round, but energy moves one way to higher trophic levels and is lost as heat.
The four functional aspects of an ecosystem
- Productivity: the rate at which producers make new organic matter.
- Decomposition: the breakdown of dead matter into inorganic substances.
- Energy flow: the one-way movement of energy from the Sun through producers to consumers.
- Nutrient cycling: the repeated movement of nutrients between the living and non-living parts. Your textbook names it, but its details (such as the carbon and phosphorus cycles) are not in the current syllabus.
A village tank or temple pond is a complete ecosystem: lotus and algae make food, fish and frogs eat, and bacteria in the mud recycle wastes. A paddy field is a man-made ecosystem that farmers manage for one crop.
1 marks: “Give one example each of a terrestrial ecosystem and a man-made ecosystem.” Terrestrial: a forest, grassland or desert. Man-made: a crop field or an aquarium.
2 marks: “What is stratification? Give an example.” The vertical distribution of species at different levels in an ecosystem. In a forest, trees occupy the top layer, shrubs the second, and herbs and grasses the bottom layers.
3 marks: “Describe a pond as an ecosystem, naming its abiotic and biotic components.” Abiotic: water with dissolved substances, bottom soil, sunlight, temperature. Producers: phytoplankton, algae, floating, submerged and marginal plants. Consumers: zooplankton, free-swimming and bottom-dwelling animals. Decomposers: fungi, bacteria and flagellates at the bottom. It fixes energy, consumes, decomposes and recycles nutrients.
Ecosystem functions spell PEND: Productivity, Energy flow, Nutrient cycling, Decomposition.