Food Chains and Food Webs

A food chain demonstrates a sequence of organisms, with each one being eaten by the next in the chain. It shows the direction of energy flow, from the producers (usually plants) to the top carnivores.
Every food chain starts with a producer. Producers are organisms that can carry out photosynthesis to produce glucose, which is used to create energy.
Primary consumers (or herbivores) eat the producers. Secondary consumers, which are carnivores, consume the primary consumers. Tertiary consumers, also carnivores, then eat the secondary consumers.
Each level of a food chain represents a trophic level. The energy flow between these levels is about 10%, meaning that each level has only around 10% of the energy of the level below. This energy limitation results in most food chains consisting of only three or four trophic levels.
Food webs represent myriad interlinked food chains within an ecosystem. Each organism can play different roles in multiple chains.
Changes in population in one species can affect the entire food web. For instance, if a particular predator population shrinks, it could result in an overpopulation of prey animals which could overrun their food sources.
Detritivores (like earthworms or bacteria) play a significant role in breaking down dead organisms and waste, cycling nutrients back into the soil and making them available for plant uptake.
Decomposition of organic materials is speeded up under moist, warm conditions. This process plays a significant role in nutrient cycles.
Bioaccumulation refers to the process through which certain toxic substances, like pesticides or heavy metals, build up in the food chain, becoming more concentrated at each trophic level.
Biomagnification, a consequence of bioaccumulation, can occur when predators at the top of the food chain eat prey that already has the toxins in their bodies. Therefore, these substances are highly concentrated in top level predators.
The reliability of food chains and webs could be unreliable due to unwarranted human activities such as environmental pollution, logging and overfishing. Efforts to protect biodiversity and conserve environment are essential to maintaining balance in these systems.

Remember, revise these points and make sure you understand the essential principles behind each one of these topics. Draw out some food webs and chains, practise figuring out populations and energy flow, and consider different scenarios that could affect an ecosystem. The more you explore and understand the key concepts, the better prepared you’ll be.