NCERT Notes for Class 10 Science Chapter 15 Our Environment

CBSE Class 10 Science notes will assist students in studying the topic thoroughly and clearly.

These CBSE Class 10 Science notes were written by subject experts who made the study material very basic, both in terms of language and format.

Waste Types and Their Effects on Our Environment

Waste substances are those that are left-over, discarded or useless. Improper waste management from numerous activities causes environmental imbalance.

Solid wastes  (farm wastes, industrial wastes, home wastes, etc. ), liquid wastes like chemical wastes, and gaseous wastes (smoke from automobiles and chimneys, etc.) are the three forms of trash.

These waste materials can be split into two categories:

  1. Biodegradable substances
  2. Non – biodegradable substances.

Biodegradable Substances

Biodegradable substances are those that can degrade naturally due to the action of microbes such as fungi and bacteria. These organisms produce enzymes that break down biodegradable materials into simpler ones.

Garbage management plants can also be used to handle biodegradable waste. Sewage,garbage, livestock waste, waste papers,old – tea leaves, left-over food articles, and other materials can be utilised as compost or manure to improve soil fertility.

Effects of Biodegradable Substances

Only when their quantity reaches a certain threshold does it become a pollutant. The following are the impacts of biodegradable substances:

  • The decomposition of biodegradable waste produces an unpleasant odour.
  • Dumping of industrial waste depletes soil fertility, resulting in lower crop yields.
  • The massive breeding of flies on these wastes carries germs and spreads diseases.
  • Water contamination occurs when garbage is dumped into water bodies. As a result, a variety of water-borne diseases are spread.

Non-Biodegradable Substances

Non-biodegradable substances are those that cannot be transformed by microbes into safer and simpler forms. These are damaging, toxic and may be inert, allowing them to build up in the environment.

These are the principal pollution sources in the environment.  The majority of non-biodegradable wastes, such as plastic, radioactive wastes, pesticides, and heavy metals such as arsenic, aluminium and lead  are the result of human activity.

Effects of Non-biodegradable Substances

Non-biodegradable substances have the following effects:

  •  Lead, mercury, radioactive wastes and other toxic substances build up in the environment, causing life-threatening diseases in humans and other living creatures.
  • They damage the environment and endanger aquatic plants and animals.


It is the biosphere’s functional and structural unit. It is a stable ecological unit in which energy is regularly input and matter is circulated.

AG Tansley created the word ecosystem in 1935.

An ecosystem, such as a field, lake or a forest, is made up of all the interacting organisms in a region as well as the nonliving parts (abiotic components) of the environment.

Types of Ecosystem

There are two types of ecosystem. They are :

Natural Ecosystem : The term “natural ecosystem” refers to an ecosystem that exists without the assistance of humans. Natural ecosystems can be terrestrial (grassland, desert  and woodland) or aquatic (lakes, ponds,sea and estuaries) depending on the habitats.

Artificial Ecosystem : Artificial or man-made ecosystems are ecosystems that are built and managed by people. These are dependent on human efforts to survive. It doesn’t have a self-control system. The largest man-made ecosystem is the agro-ecosystem. Aquariums, botanical gardens, parks, field crops, and so forth are some other examples.

Components of Ecosystem – Biotic Components

All living species in the ecosystem, such as animals, plants and bacteria, are considered as biotic components.Living creatures are linked to one another through a variety of ways and are interdependent on each other.

These are divided into distinct groups mostly based on their nutritional relationships.

The different living organisms can be classified into three groups based on the food they consume. They are :

  • Producers
    Producers include all green plants and some blue-green algae that can produce food through photosynthesis.
    Autotrophs are another name for these organisms.
    They absorb the sun’s light energy and generate organic chemicals as a result (i.e.carbohydrates). Autotrophic organisms, such as blue-green algae, and plants transform solar energy into chemical energy.
    These provide nutrition to the rest of the ecosystem. They absorb CO² and release oxygen into the atmosphere, balancing the composition of the air.
  • Consumers
    They eat food prepared by producers and are completely reliant on them for their nutritional needs. As a result, they are known as heterotrophs.
    Consumers can be further classified into the three groups. They are :

    • Herbivores: These are first-order consumers who feed directly on the producers, such as plants. E.g. Grazing animals such as goats, zebras,sheep and  horses, and others.
    • Carnivores : These are the creatures that eat other animals. Second-order consumers are herbivores carnivores that eat herbivores. Some carnivores, such as hawks, lions and wolves, are predators that attack and kill their prey before feeding on their carcasses.
      Some may be scavengers (like jackals who eat dead animals they come upon).
      These people are referred to as third-order consumers.
    • Omnivores : Animals that eat both plants and animals are known as omnivores. Bears and humans are a common example.
  • Decomposers
    Microorganisms that feed on dead and decaying organic matter are known as decomposers. They decompose the remnants of dead plants and animals , releasing a variety of substances that can be used by other members of the ecosystem such as fungi and bacteria.
    They aid in the decomposition of waste in the ecosystem. They assist in the garbage cleanup, recycling of materials and the creation of space for the growth of new species.

Components of Ecosystem – Abiotic Components

The nonliving components of an ecosystem on which living organisms rely are known as abiotic components. Each abiotic factor has an impact on the number and diversity of animals and plants in an ecosystem.

This, in turn, has an impact on an area’s biodiversity. Temperature, light, atmospheric gases, water, wind, and so on are some of these components. They are described in detail below.

  • Temperature : Temperature extremes have a significant impact on the dispersal of animals and plants. The plant’s growth is also influenced by the rain pattern. The general variety of animals that live in that area is determined by plant growth.
  • Light : In practically all ecosystems, light energy (sunlight) is the principal source of energy. Green plants (which contain chlorophyll)  make use of it . Plants produce organic substances by mixing inorganic substances during photosynthesis.
  • Atmospheric gases : Respiration needs oxygen, while photosynthesis needs carbon dioxide. Certain microorganisms, as well as the action of lightning, make nitrogen available to plants.
  • Water : It is required for survival. Animal and plant habitats range from entirely aquatic environments to desert areas.
  • Wind : Some plants benefit from it for pollination and seed dispersal. It has the ability to remove and redistribute top soil, particularly in areas where vegetation has been decreased.

Trophic Levels

Energy and food are transferred through trophic levels, which are channels or levels in the food chain. At the first trophic level, producers (autotrophs) are present. They make solar energy available to consumers (heterotrophs) by fixing it.

At the second trophic level,primary consumers or herbivores, can be found. At the third trophic level,secondary consumers or small carnivores  might be found. The fourth trophic level is made up of tertiary or large consumers.

Food Chain

It is a community’s linear network of living organisms that transfers energy in the form of food. It describes the ‘who eats whom’ connection between organisms.

Types of Food Chains

Food chains are divided into two kinds based on habitat choice:

  • Terrestrial food chain : It is the food chain based on land.
    Eg : Grass -> insect -> snake -> hawk.
  • Aquatic food chain : It is the food chain that exists in various water bodies.
    Eg : Phytoplankton -> Zooplankton -> fish -> shark.

Significance of Food Chain

  • Materials, energy and nutrients are all transferred through the food chain. The food chain’s organisms serve as energy transfer vehicles from one level to the next.
  • Understanding the feeding relationship as well as the interaction between ecosystems and organisms is aided by understanding the food chain.
  • It also aids in understanding the movement of toxic substances and the issues associated with biological magnification in the ecosystem.

Food Web

It is the interconnection of various food chains that function in an ecosystem at various trophic levels.

Two or more types of organisms eat each other. Several other organisms then eat them.

As a result, rather than a single straight line, the relationship is represented by a series of branching lines, forming a food web.

Energy Flow

Primary producers acquire energy, which is then transported to different trophic levels via the food chain. Energy flow is the term for this phenomenon.

It’s one-way and there’s no way to go back to the previous level. Some energy is always lost when energy is transferred from one form or system to another.The following steps can help you understand how energy flows in an ecosystem.

  • In a terrestrial ecosystem, green planes capture around 1% of the energy from the sun (chemical). They use it to create food energy.
  • Primary consumers consume the green planes. As a result, a significant quantity of energy is lost as heat. Some of it is used for digestion and work, while the rest is used for reproduction and growth.
    An organism returns about 10% of the energy it consumes from food to its own body, making it available to the next level of consumers. This is referred to as the 10% law (Lindeman, 1942).
  • As a result, I0 % can be used to represent the average quantity of organic matter present at each step before moving on to the next trophic level.
  • Because there is only a limited amount of energy available for the next level of consumers, food chains are usually three or four steps long. Each process wastes a significant amount of energy. After four trophic levels, there is very little usable energy left.
  • The flow of energy is one-way. The energy collected by autotrophs is not revered in return to the solar input. Furthermore, the energy that goes to herbivores does not return to autotrophs.

Biological Magnification or Biomagnification

It is the gradual increase in the concentration of non-biodegradable toxicants in organisms as they ascend through the trophic levels.

Causes of Biomagnification

To protect crop plants from illnesses and pests, pesticides and harmful chemicals  such as DDT are sprayed on them. These pollutants end up in the water bodies or in the soil.

Plants absorb them from the soil, and aquatic animals and plants take them from water bodies.

This is why pesticide residues are found in various amounts in our dietary grains, such as rice, wheat, vegetables and fruits. Substances infiltrate the food chain in this way.

As these chemicals are non-biodegradable, they accumulate in the bodies of living organisms.

At each trophic level, their concentration continues to rise.

The human body accumulates the highest concentration of these substances. This is due to the fact that they are at the very top of any food chain.

Human Impact on the Natural Environment

Humans play an important role in the environment. Any change in the environment has an impact on us. Human activities damage the environment in a variety of ways, posing major environmental risks.

For example, waste accumulation, ozone layer depletion and so on.

Ozone Depletion

Ozone (0³) is a poisonous molecule made up of three oxygen atoms. It is found in the stratosphere ( 20-30 kilometres above the earth’s surface).

Formation of Ozone in Atmosphere

UV rays acting on the oxygen (0²) molecule produce ozone at higher levels in the atmosphere. Some molecular oxygen (0² ) was split apart by high-energy UV radiations, resulting in free oxygen (0) atoms.

These atoms are extremely reactive, and when they come into contact with molecular oxygen, they generate ozone.


O²—-> O + O            O + O² —-> O³ (Ozone)

Ozone Layer and its Importance

It is the layer of the atmosphere in which most of the ozone is concentrated. It protects the surface of the earth from the sun’s harmful ultraviolet (UV) rays.

These rays are extremely harmful to living things.

They can cause skin cancer in humans, harm eyes (causing cataract disease), disrupt global rainfall, reduce crop productivity and so on.

Depletion of Ozone Layer

The ozone layer began to deplete in the 1980s as a result of pollution. This was because of the increased usage of synthetic compounds such as chlorofluorocarbons (CFCs).

These are used as coolants in refrigerants and in fire extinguishers.

CFCs have a high level of stability. They’ve been discovered to linger in the atmosphere. They do not decay easily and rise high in the atmosphere because they are stable.

UV rays break down CFC molecules in the atmosphere, releasing chlorine atoms. 

When these atoms come into contact with ozone, they break down the ozone molecules into oxygen molecules. As a result, the amount of ozone in the atmosphere decreases and  the ozone layer depletes.

An example of ozone layer depletion can be seen in Antarctica.

The United Nations Environment Programme (UNEP) was successful in reaching an agreement to keep CFCs production frozen at 1986 levels.

Managing the Garbage We Produce

Garbage is the term for household waste. Every household generates a significant amount of garbage on a daily basis. Improvements in our way of life have resulted in increased waste material output.

Methods of Waste Disposal

Garbage management procedures include methods of disposing of garbage that have the least environmental impact.

The term “waste disposal” refers to the act of getting rid of waste.

This procedure should be carried out in a scientific manner.

Firstly, waste should be classified as biodegradable or non-biodegradable, as well as recyclable. This enables for proper disposal treatment. Waste disposal can be done in a variety of ways.

The following are a few of them:

Recycling : It entails the transformation of waste resources into new products. Cans, tins, metallic goods, paper, rags, glass, polythene, and other materials are recyclable.

Composting: Fruit and vegetable peels, leftover food and other biodegradable domestic wastes can be buried in a pit dug into the ground. They are composted and used as animal manure.

Incineration : A material is burned at a high temperature to produce ash. It significantly minimises the volume of waste. It’s a frequent way to get rid of hospital garbage.

Landfills : Solid waste is dumped and covered with soil in a low-lying area. For a long time, a large landfill site can be utilised to dispose of waste materials.

Sewage treatment : Sewage is transported to Sewage Treatment Plants (STPs). The sewage is filtered here. In huge tanks, organic material in sewage is allowed to settle and decay. The water from these tanks is treated before being released into water bodies.

Biogas production : In some regions, sewage is anaerobically digested to produce manure and biogas.

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