Quick review CH – 15 Our Environment

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CH – 15   Our Environment

Class X

Syllabus of Our environment: Eco-system, Environmental problems, Ozone depletion, waste production, and their solutions. Biodegradable and non-biodegradable substances.

1. Substances that break down from biological processes are called biodegradable.
2. Substances that do not break down from biological processes are called non-biodegradable.
3. There is a loss of energy from one trophic level to the next trophic level and this limits the number of trophic levels in a food chain.
4. The use of chemicals such as CFCs (chlorofluorocarbons) that are used as fire extinguishers and refrigerants reduces the ozone layer. The ozone layer protects the Earth's surface from ultraviolet radiation from the Sun, which can harm the environment.  
5. An ecosystem includes living organisms such as flowers, trees, grasses, animals such as insects, frogs, tigers, deer, and birds, etc. and abiotic components that include physical factors such as minerals, soil, temperature, lakes, wind forests, ponds, and rainfall.
6. All green plants and certain blue-green algae that can produce food by photosynthesis in the presence of sunlight, water, and carbon dioxide are called the producers.
7. Consumers - Organisms that consume food produced by producers, either directly from producers or indirectly by feeding to another are called consumers.
8. Decomposers - Microorganisms that break down complex organic materials into simple inorganic materials, which lead to natural replenishment of the soil, are called decomposers.
9. Each level of the food chain forms a trophic level. Producers (autotrophs) form the first trophic level. They trap solar energy and make it available to consumers. Primary consumers (vegetarian or herbivores) make up the second level, Secondary consumers (small carnivores) make up the third and large carnivores make up the fourth trophic level.
10. Autotrophs capture the energy present in sunlight and convert it into chemical energy. This energy helps in all activities of the living world. Energy moves from autotrophs to heterotrophs and decomposers.
11. In a terrestrial ecosystem, green plants consume about 1% of the energy of sunlight that falls on their leaves and converts it into food energy.
12. When primary consumers eat green plants a large amount of energy is lost in the environment as heat, some energy is used in digestion and some in working. The rest leads to reproduction and development.
13. The flow of energy captured by the autotroph is unidirectional and does not return to the solar and the energy going from the autotroph to the herbivores.
14. Harmful chemicals enter our body through the food chain - the main reason is the use of many pesticides and chemicals to protect our crops from diseases and pests. These chemicals are washed either in soil or in water bodies. These chemicals are absorbed from the soil by plants with water and minerals and are taken from water bodies by these aquatic plants and aquatic animals. This is the way they enter the food chain.
15. Biological magnification - The chemicals present in the food in the form of pesticides are not degraded and accumulate slowly at each trophic level. When humans are at the top level in the food chain, large amounts of these chemicals accumulate in our bodies. This phenomenon is known as biological magnification.
16. O₃ ozone is a molecule of three atoms of oxygen, it is a poison. Ozone performs an essential function. It is present at high levels of the atmosphere. It protects the Earth's surface from the sun's ultraviolet radiation. This radiation is very harmful to organisms, it can cause skin cancer in humans.
17. In the 1980s, synthetic chemicals such as chlorofluorocarbons (CFCs) started decreasing the amount of ozone in the atmosphere, which is used as refrigerants and fire extinguishers.