Food Chain, Food Web and Trophic Levels - SS1 Biology Lesson Note

Food Chain: A food chain is a linear representation of the transfer of energy and nutrients between different organisms in an ecosystem. It shows the flow of energy from one organism to another as they consume and are consumed by each other. A typical food chain starts with a primary producer (autotroph) that converts sunlight or inorganic compounds into energy-rich organic compounds. The primary producer is then consumed by a primary consumer (herbivore), which in turn may be consumed by a secondary consumer (carnivore or omnivore), and so on. Each organism in the chain is called a trophic level, and energy is transferred from one trophic level to the next.

Food Web: A food web is a more complex and interconnected representation of feeding relationships within an ecosystem. It consists of multiple interconnected food chains, illustrating the various pathways of energy flow and interactions between different species. In a food web, organisms can occupy multiple trophic levels and have multiple feeding relationships. This interconnectedness reflects the complex nature of ecosystems, where multiple species interact with each other through various feeding relationships.

Figure 82 image from istockphoto.com

Trophic Levels: Trophic levels refer to the different positions or levels in a food chain or food web, based on an organism's source of energy and its feeding relationship with other organisms. The trophic level of an organism indicates its position in the energy transfer hierarchy. The primary producers (autotrophs) occupy the first trophic level, as they directly convert energy from the sun or inorganic compounds into organic matter. Primary consumers (herbivores) occupy the second trophic level, as they feed directly on the primary producers. Secondary consumers (carnivores or omnivores) occupy the third trophic level, as they consume the primary consumers, and so on. Each trophic level represents a transfer of energy and nutrients, with energy decreasing as it moves up the trophic levels due to energy loss as heat and metabolic processes. The concept of trophic levels helps us understand the flow of energy, nutrient cycling, and the interconnectedness of organisms within an ecosystem. It also highlights the importance of maintaining a balanced and diverse community of organisms to ensure a stable and functioning ecosystem.

Biomass: Biomass represents the total mass of living organisms within an ecosystem and serves as a measure of its productivity and energy storage. It encompasses all the organic matter present, including plants, animals, and microorganisms. Biomass is an essential component of the Earth's ecosystems, as it drives energy flow and nutrient cycling. It plays a vital role in supporting food webs, regulating carbon dioxide levels, and sustaining the overall functioning and stability of ecosystems. Changes in biomass can reflect shifts in ecosystem health, such as changes in primary productivity, population dynamics, or responses to environmental disturbances. Therefore, studying biomass provides valuable insights into the structure, functioning, and dynamics of ecosystems.