Our Environment Class 10 Notes Science Chapter 13

Introduction

Our environment is the intricate and dynamic system that supports and sustains all living organisms. 

It comprises a blend of:

1. Physical Factors: The natural elements of our surroundings, including landforms, climate, and weather patterns.
2. Chemical Factors: The substances present in the environment, such as air, water, and soil, and their chemical interactions.
3. Biotic Factors: The living organisms within an ecosystem, including plants, animals, and microorganisms, and their interactions with one another.

In this chapter, we will explore the various components of the environment in detail and understand how they interact to form a balanced ecosystem. 
By examining these factors, we aim to highlight the importance of environmental conservation and sustainable practices to maintain the health and stability of our ecosystems.

Ecosystem- What are its Components?

• An ecosystem is formed by the interaction between all living organisms—plants, animals, microorganisms, and humans—and their physical surroundings.
• This interaction maintains a balance in nature.
• The ecosystem includes both the living organisms and the non-living components of their environment, working together as a unified system.
• This interconnected system is known as an ecosystem, which consists of biotic components (living organisms) and abiotic components (physical factors like temperature, rainfall, wind, soil, and minerals).

Types of Ecosystem
It is of two types:
1. Natural ecosystem: The ecosystem which exists in nature on its own.
Example: forest, lake, ocean.
2. Artificial ecosystem: Man-made ecosystems are called artificial ecosystems.
Example: crop field, aquarium, garden.

Components of Ecosystem

Components of Ecosystem1. Abiotic Components: All the non-living components such as air, water, land, light, temperature etc. form the abiotic components.
2. Biotic Components: All the living components such as plants, animals, bacteria, fungi etc. form the biotic components.

Organisms can be categorized as producers, consumers, and decomposers based on how they obtain sustenance from the environment.
1. Producers: All green plants and blue-green algae can produce their own food using abiotic components (photosynthesis), hence called producers.
2. Consumers: Include all animals which depend on producers directly or indirectly for their food. Division of Consumers(i) Herbivores: Plant eaters. Example:  goat, deer.
(ii) Carnivores: Flash eaters. Example: tiger, crocodile.
(iii) Omnivores: Eats both plants and animals. Example: human.
(iv) Parasites: Live on the body of the host and take food from it. Example: lice, cascuta.
3. Decomposers: Include organisms which decompose the dead plants and animals. Example: bacteria, fungi. These help in the replenishment of natural resources.

Food Chains and Webs

• Food chain is a series of organisms in which one organism eats another organism as food. For example: Grass → Deer → Lion
  
• In a food chain, various steps where transfer of energy takes place is called a trophic level.
• The first trophic level is occupied by autotrophs or producers, which capture solar energy and make it available for heterotrophs or consumers.
• The second trophic level consists of herbivores or primary consumers, while the third trophic level consists of small carnivores or secondary consumers.
• The fourth trophic level is occupied by larger carnivores or tertiary consumers.

• The interactions among the components of the environment involve the transfer of energy from one component to another.
• Autotrophs capture solar energy and convert it into chemical energy, which supports all living activities.
• Energy flows from autotrophs to heterotrophs and decomposers.

• Some energy is lost to the environment when one form of energy is converted to another.
• Green plants in a land environment take in around 1% of the sunlight that hits their leaves and change it into food.
• When green plants are consumed by animals that eat plants, a lot of energy is lost as heat to the surroundings.
• Only about 10% of the food that plant-eating animals consume becomes part of their own bodies and is accessible to the animals that eat them.
• As a result, roughly 10% of the material from living things goes on to the next group of animals in the food chain at each level.

• Due to the significant energy loss at each step, food chains generally consist of only three or four trophic levels.
• There are typically more individuals at the lower trophic levels of an ecosystem, with the greatest number being the producers.
• Food chains can vary in length and complexity, and each organism is usually eaten by multiple other organisms.
• This relationship can be represented as a food web, which consists of branching lines instead of a straight-line food chain.

Energy Flow in Ecosystems

Energy Flow in Ecosystems

From the energy flow diagram, two key observations can be made:

1. Unidirectional Flow: 

• Energy flows in a one-way direction. 
• Energy captured by autotrophs (producers) does not return to the solar input, and energy transferred to herbivores does not revert to autotrophs.
• As energy progresses through different trophic levels, it becomes unavailable to previous levels.

2. Progressive Diminishment: 

• The amount of energy available at each trophic level decreases progressively. 
• This reduction occurs due to energy loss at each level, typically as heat and metabolic waste.

Harmful chemicals from pesticides and crop protection products enter our bodies through the food chain. They are absorbed by plants and animals, ultimately accumulating in humans at the top of the food chain. This is why pesticide residues can be found in food grains, vegetables, fruits, and meat, and they are not always removable through washing or other methods.

How Do Our Activities Affect the Environment?

Changes in the environment affect us and our activities change the environment around us. Human activities leads to pollution, deforestation etc.

Ozone Layer and How it is Getting Depleted?

• The ozone layer is a protective blanket around the earth that absorbs most of the harmful UV (ultraviolet) radiations of the sunlight, thus protecting living beings from many health hazards such as skin cancer, cataracts, destruction of plants etc.

Ozone Layer Depletion

• Ozone is a molecule made up of three oxygen atoms, while oxygen (O₂) is essential for aerobic life.
• Ozone is a deadly poison, but it plays a crucial role in shielding the Earth's surface from harmful UV radiation from the Sun.
• UV radiation in the higher levels of the atmosphere causes molecular oxygen (O₂) to split into free oxygen (O) atoms, which then combine with more molecular oxygen to form ozone.
  O →(UV)  O + O (atoms)
  O₂ + O → O₃ (ozone)

Ozone Depletion and International Response

• Sharp Decline: The amount of ozone in the atmosphere began to decrease significantly in the 1980s.
• Cause: This decline has been linked to synthetic chemicals such as chlorofluorocarbons (CFCs), which are used in refrigerants and fire extinguishers.
• International Agreement: In 1987, the United Nations Environment Programme (UNEP) established an agreement to freeze CFC production at 1986 levels.
• Current Mandates: It is now mandatory for all manufacturing companies worldwide to produce CFC-free refrigerators.

Managing the Garbage we Produce

• Enzyme Specificity: 
  Enzymes in our body are specialized and can only break down specific substances.
  This is why we cannot derive energy from non-digestible materials like coal.
• Persistence of Human-Made Materials: 
  Many synthetic materials, such as plastics, are not decomposed by bacteria or other organisms.
  As a result, these materials can remain in the environment for extended periods.

Types of materials in Garbage

(i) Biodegradable: Substances which can be decomposed by the action of micro-organisms are called biodegradable wastes.
Example:  fruit and vegetable peels, cotton, jute, dung, paper, etc.
(ii) Non-biodegradable wastes: Substances which cannot be decomposed by the action of micro-organisms are called non-biodegradable wastes.
Example: plastic, polythenes, metals, synthetic fibres, radioactive wastes, pesticides etc.

• Garbage and litter can be found in towns, cities, and tourist areas.
• Changes in lifestyle and attitudes have led to increased waste generation.
• Disposable products and non-biodegradable packaging contribute to the problem.
• The impact of these factors on the environment is a concern.