Key Points

An ecosystem consists of all interacting organisms (biotic components) in an area together with the non-living constituents (abiotic components) of the environment, such as temperature, soil, and water.

Ecosystems can be natural, like forests and lakes, or human-made (artificial), such as gardens, crop-fields, and aquariums.

Organisms are grouped as producers (autotrophs like plants), consumers (heterotrophs like animals), and decomposers (microorganisms like bacteria and fungi) based on how they obtain sustenance.

A food chain is a series of organisms where each depends on the next as a source of food. Each step in the food chain is called a trophic level, starting with producers at the first level.

A simple food chain could be: Grass (Producer) $\rightarrow$ Goat (Primary Consumer) $\rightarrow$ Human (Secondary Consumer).

A food web is a network of interconnected food chains, representing the complex feeding relationships within an ecosystem, as most organisms are eaten by more than one other organism.

The flow of energy in an ecosystem is unidirectional. It is captured by producers from the sun, transferred to consumers, and does not revert back to the previous trophic level.

On average, only 10% of the energy available at one trophic level is transferred to the next. The remaining energy is lost to the environment as heat or used for metabolic activities.

Biological magnification is the increasing concentration of harmful, non-biodegradable chemicals like pesticides at successive trophic levels in a food chain. The highest concentration is found in the top-level consumers.

The ozone ($\text{O}_3$) layer in the upper atmosphere shields the Earth from harmful ultraviolet (UV) radiation from the Sun, which can cause diseases like skin cancer.

Ozone is formed when high-energy UV radiation splits oxygen molecules ($O_2 \xrightarrow{\text{UV}} O + O$), and the resulting free oxygen atoms combine with other oxygen molecules ($O + O_2 \rightarrow O_3$).

The ozone layer is being depleted by synthetic chemicals, primarily chlorofluorocarbons (CFCs), which were widely used as refrigerants and in fire extinguishers.

Substances that can be broken down by biological processes, such as the action of bacteria or fungi, are called biodegradable. Examples include kitchen waste, paper, and wood.

Substances that cannot be broken down by biological processes are called non-biodegradable. These materials, like plastics and glass, persist in the environment for a long time and can cause pollution.

Proper waste disposal involves segregating biodegradable and non-biodegradable waste. Methods include recycling, composting, incineration, and landfilling to reduce environmental impact.