Correct Option
The correct option is Water with dissolved substances and bottom soil deposits.
Explanation
An ecosystem is a functional unit where living organisms interact with each other and their physical environment. The structure of an ecosystem, such as a pond, is defined by the interaction between abiotic (non-living) and biotic (living) components.
Option Analysis
- Water with dissolved substances and bottom soil deposits is Correct: The abiotic components of a pond ecosystem encompass the non-living physical and chemical factors. These include water, dissolved inorganic and organic substances (such as oxygen, carbon dioxide, and nutrients), bottom soil or sediment deposits, solar input, and temperature.
- Phytoplankton, algae, and marginal plants is Incorrect: Phytoplankton, algae, and marginal plants are producers (autotrophs). As living entities that synthesize food using solar energy, they are part of the biotic component.
- Zooplankton and free swimmers is Incorrect: Zooplankton and free swimmers (nekton) are consumers (heterotrophs). These are living organisms that depend on producers for nutrition, classifying them as biotic components.
- Fungi and bacteria in sediments is Incorrect: Fungi and bacteria function as decomposers (saprotrophs). They are living organisms responsible for recycling nutrients by breaking down dead organic matter, making them biotic components.
Key Takeaway: Abiotic components in an aquatic ecosystem refer strictly to the physical environment (water, soil, light) and chemical substances, while all living entities (producers, consumers, decomposers) constitute the biotic components.