Class 10 Science • Chapter 15 • Complete Notes
The environment includes the living organisms and the physical conditions surrounding them. Living organisms interact continuously with their surroundings.
Biotic components are the living components of an ecosystem, such as plants, animals, microorganisms and decomposers.
Abiotic components include non-living factors such as air, water, soil, light, temperature and minerals.
An ecosystem is a functional unit in which living organisms interact with one another and with the non-living components of their surroundings.
Producers are organisms that prepare their own food, usually through photosynthesis.
Green plants are the primary producers in most terrestrial ecosystems.
Consumers obtain food by feeding on producers or other organisms.
Decomposers such as bacteria and fungi break down dead organic matter into simpler substances.
They play an important role in nutrient recycling and help return materials to the environment.
A food chain represents a sequence in which food and energy are transferred from one organism to another.
The arrows represent the direction of energy transfer from the food organism to the organism that consumes it.
A food web consists of interconnected food chains. In natural ecosystems, organisms often have multiple food sources and may be consumed by several organisms.
The different positions occupied by organisms in a food chain are called trophic levels.
| Level | Position |
|---|---|
| 1st | Producers |
| 2nd | Primary consumers |
| 3rd | Secondary consumers |
| 4th | Higher consumers |
Energy enters most ecosystems through sunlight. Producers convert solar energy into chemical energy stored in food.
This energy is then transferred through successive trophic levels.
A commonly taught ecological approximation is that only about 10% of the energy available at one trophic level is transferred to the next trophic level.
For example, if producers contain 10,000 units of available energy, approximately 1,000 units may be available to primary consumers, 100 units to secondary consumers and 10 units to the next level.
Decomposition is the breakdown of dead organic matter into simpler substances.
Biodegradable substances can be broken down into simpler materials by biological processes, especially through the activity of microorganisms.
Examples include:
Non-biodegradable substances are not easily broken down by natural biological processes and may remain in the environment for long periods.
Examples include many:
Biological magnification, or biomagnification, refers to the increasing concentration of certain persistent pollutants in organisms at successively higher trophic levels.
Persistent substances that are not easily degraded can enter food chains and become more concentrated in higher-level consumers.
Ozone is a form of oxygen containing three oxygen atoms. A region of the atmosphere with relatively higher ozone concentration is commonly referred to as the ozone layer.
Stratospheric ozone absorbs much of the Sun's harmful ultraviolet radiation.
Certain human-made chemicals can contribute to depletion of stratospheric ozone.
Reduction of the protective ozone layer can allow more harmful ultraviolet radiation to reach Earth's surface.
Ecosystems depend on interactions among organisms and their physical environment. Changes in one component can affect other components.
Human activities such as excessive waste generation, pollution, habitat destruction and overuse of resources can disturb ecosystems.
Avoid unnecessary consumption and waste generation.
Use products repeatedly whenever possible.
Recover useful materials from waste and convert them into reusable products.
Separate different types of waste so that suitable processing and disposal methods can be used.
| Concept | Meaning |
|---|---|
| Food Chain | A single pathway of feeding relationships. |
| Food Web | Interconnected feeding pathways. |
| Biodegradable | Can be broken down biologically. |
| Non-Biodegradable | Not easily broken down biologically. |
| Biomagnification | Increasing concentration of persistent pollutants at higher trophic levels. |