13. Our Environment

We have heard the word ‘environment’ often being used on the television, in newspapers and by people around us. Our elders tell us that the ‘environment’ is not what it used to be earlier; others say that we should work in a healthy ‘environment’; and global summits involving the developed and developing countries are regularly held to discuss ‘environmental’ issues. In this chapter, we shall be studying how various components in the environment interact with each other and how we impact the environment.

The term 'environment' refers to everything that surrounds us, including living organisms, natural resources, and various ecosystems. The environment has changed over time, often in ways that are not favorable to human life. As such, it is crucial to understand these changes and their effects on our health and the planet. This chapter will explore the interactions between different components of the environment and how our actions impact these relationships.

Think of the environment like a large interconnected web. If one part of the web is damaged or cut, it can affect every other part. Just as a spider's web is delicate and needs to stay intact for the spider to thrive, our environment requires careful balance and maintenance for all living creatures, including us, to survive.

All organisms such as plants, animals, microorganisms and human beings as well as the physical surroundings interact with each other and maintain a balance in nature. All the interacting organisms in an area together with the non-living constituents of the environment form an ecosystem. Thus, an ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil and minerals.

An ecosystem is a community where living organisms (biotic components) like plants, animals, and humans coexist with non-living elements (abiotic components) such as water, soil, and air. These elements work together to create a balanced environment. For instance, plants absorb sunlight and provide food for animals, while animals contribute to the nutrient cycle when they die and decompose.

Imagine a small pond. In this ecosystem, you have fish, frogs, water lilies, and insects coexisting. The fish (biotic component) rely on plants for oxygen and food, while the water and soil (abiotic components) provide the necessary habitat. If one part of this system were to change significantly, it would impact all the others, much like removing a piece from a puzzle can cause the whole image to break down.

For example, if you visit a garden you will find different plants, such as grasses, trees; flower bearing plants like rose, jasmine, sunflower; and animals like frogs, insects and birds. All these living organisms interact with each other and their growth, reproduction and other activities are affected by the abiotic components of the ecosystem. So a garden is an ecosystem. Other types of ecosystems are forests, ponds and lakes. These are natural ecosystems while gardens and crop-fields are human-made (artificial) ecosystems.

Ecosystems can be classified into natural and artificial categories. Natural ecosystems, like forests and lakes, have developed without human intervention and showcase the natural interactions of various species. In contrast, artificial ecosystems, like gardens, are created and maintained by humans and often include specific plants and animals chosen for their aesthetic or agricultural value. Understanding both types helps us learn how to manage them sustainably.

Consider a forest versus a city park. The forest, teeming with diverse species and complex interactions, represents a natural ecosystem, whereas the city park, which features designed landscapes, typically includes selected trees and flowers. While both are vital, managing the park efficiently is essential to ensure its health, just as we would protect the integrity of a natural forest.

We have seen in earlier classes that organisms can be grouped as producers, consumers and decomposers according to the manner in which they obtain their sustenance from the environment.

Ecosystems consist of three primary types of organisms based on their roles: producers, consumers, and decomposers. Producers, like plants, create their own food through photosynthesis. Consumers, including animals, rely on other organisms for food. Decomposers, such as bacteria and fungi, break down dead organic materials, returning nutrients to the soil and completing the nutrient cycle. Each group plays a crucial role in maintaining the ecosystem's health and balance.

Think of a pizza. The dough and toppings represent producers because they provide the base for the meal. The person who eats the pizza is the consumer, gaining energy and nutrients from what was once alive. Finally, if there are leftovers, composting them involves decomposers that break down the food scraps, enriching the soil for future crops—connecting all parts of the meal back to the earth.

Each step or level of the food chain forms a trophic level. The autotrophs or the producers are at the first trophic level. They fix up the solar energy and make it available for heterotrophs or the consumers. The herbivores or the primary consumers come at the second, small carnivores or the secondary consumers at the third and larger carnivores or the tertiary consumers form the fourth trophic level.

A food chain represents the flow of energy in an ecosystem through various trophic levels. At the first level are producers (autotrophs) that make energy from sunlight. The next levels consist of herbivores (primary consumers), followed by small carnivores (secondary consumers), and then larger carnivores (tertiary consumers). Each level depends on the level below it for energy, illustrating a direct relationship of energy transfer that sustains life in that ecosystem.

Consider a food chain starting with grass (producer). A rabbit eats the grass (primary consumer), and then a fox eats the rabbit (secondary consumer). If a hawk catches the fox, it serves as the tertiary consumer. Each step represents a transfer of energy, just like a relay race where the baton (energy) is passed from one runner to the next.

We know that the food we eat acts as a fuel to provide us energy to do work. Thus the interactions among various components of the environment involves flow of energy from one component of the system to another. As we have studied, the autotrophs capture the energy present in sunlight and convert it into chemical energy.

Energy flow in an ecosystem starts with producers that capture sunlight and convert it into chemical energy through photosynthesis. This energy is then transferred to consumers as they feed, creating a continuous cycle of energy movement. It's essential to understand this flow to appreciate how ecosystems function and how energy loss occurs at each trophic level, limiting the total number of levels possible in a food chain.

Think of energy flow like a water slide at a amusement park. At the top, water represents energy stored in producers. As it flows down the slide (feeding through various levels), energy is diminished at each step due to splashes (energy loss). Ultimately, there's only so much water left at the bottom—demonstrating how energy decreases at every level of consumption.

Another interesting aspect of food chain is how unknowingly some harmful chemicals enter our bodies through the food chain. These chemicals are either washed down into the soil or into the water bodies. From the soil, these are absorbed by the plants along with water and minerals, and from the water bodies these are taken up by aquatic plants and animals.

Biological magnification refers to the process where harmful substances, such as pesticides, accumulate in organisms and increase in concentration at higher trophic levels. As plants absorb these chemicals, herbivores consume them, and then carnivores eat the herbivores, the toxins build up, impacting health notably in top predators, including humans, who ingest the highest concentrations.

It's like a game of telephone where a harmful message is passed along. Initially, the message (toxin) is small, but as it gets passed along through the game (food chain), it grows and distorts, until the last person hears a drastically altered or harmful version. This is how pollutants can become a significant threat to health as they travel up the food chain.

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