Food Chain:

1. Definition: A food chain represents a linear sequence of organisms where each member in the chain feeds on the preceding and is, in turn, consumed by the next.

2. Example: Grass → Rabbit → Fox. Here, grass is eaten by the rabbit, and the rabbit is then preyed upon by the fox.

Food Web:

1. Definition: A food web is a more complex and interconnected system of multiple food chains, illustrating the various relationships between different organisms in an ecosystem.

2. Example: In a forest ecosystem, a food web might involve multiple chains like plants → herbivores (deer, rabbits) → carnivores (foxes, wolves) and so on.

Importance for Environmental Sustainability:

1. **Biodiversity:** Food chains and webs promote biodiversity by showcasing the interdependence of different species within an ecosystem. This diversity contributes to the overall health and resilience of the environment.

2. **Stability:** They contribute to the stability of ecosystems. Disruptions in one part of a food web can have cascading effects, and understanding these relationships is vital for maintaining ecological balance.

3. **Energy Flow:** Food chains and webs illustrate the flow of energy through an ecosystem. Efficient energy transfer is crucial for sustaining life processes and maintaining the ecological pyramid.

4. **Adaptation:** Organisms within food chains and webs often adapt to changes in their environment. Understanding these adaptations is essential for predicting and managing the impact of environmental changes on various species.

5. **Cycles and Nutrient Recycling:** They play a role in nutrient cycling. Decomposers in food webs break down organic matter, releasing nutrients back into the ecosystem, which is vital for the sustainability of plant life.

Overall, these processes are fundamental for maintaining the delicate balance of nature and ensuring the long-term health and sustainability of our environment.