CBSE Class 10 Science Our Environment Notes Set 03

Content- Eco-system, Environmental problems, Ozone depletion, wastes production and their solutions, Biodegradable and non-biodegradable substances.

ECOSYSTEM

An ecosystem is a system consisting of biotic and abiotic components that function together as a unit.

• Biotic components- all the living things
• Abiotic components - non-living things like water, light, wind, soil etc.

Ecosystem maintains a balance in the nature.

• Natural ecosystem – forest, pond, lake
• Man-made (artificial ecosystem)- crop fields, garden

Producer: autotrophic, perform photosynthesis e.g. green plants, blue green algae

Consumer: consume the food produced either directly from producer or indirectly by feeding on other consumers
types of consumers:-
i- Herbivores – deer
ii- Carnivores – lion
iii- Omnivores – cat
iv- Parasites – bacteria

Decomposers: feed on dead and decomposed products. E.g. fungi, bacteria

Importance of Decomposers –

• Break down dead remains and waste products of organisms.
• Break down the complex organic substance into simple inorganic substances.
• Release minerals into the soil. Thus helps in maintaining the fertility of soil.
• Clean the environment
• Help in recycling the materials in the biosphere.

FOOD CHAIN

The sequence of living organisms in a ecosystem in which one organism consumes another organism to transfer food energy, is called a food chain.

For example
i- Grass---- Goat…Tiger
ii- Grass---- insects…..frog……snake.........eagle
iii- Planktons…..insects……fish……crane

TROPHIC LEVELS:

The various steps in the food chain at which the transfer of food (or energy) takes place is called trophic levels.

The different trophic levels are – Producers (T1), Primary consumers (herbivores-T2), Secondary consumers (primary carnivores -T2), Tertiary consumers(Sec carnivores -T3), Decomposers

Significance of Food Chains

• The food chain transfer energy from one trophic level to another.
• Autotrophs----------------- heterotrophs….................decomposers
• Only 10 % of energy is transferred from one trophic level to another. Rest of energy is lost as heat, into doing work, in digestion, growth, reproduction. It is called 10 % law.
• Help in study of food relationships and interactions among the various organisms in an ecosystem.

FOOD WEB

It is inter-connected food chains in an ecosystem.
It forms a network of relationship between various species.
In a food web, one organism may occupy a position in more than one food chain.
More stable food chain / food web means more stable ecosystem.

FOOD PYRAMID

It is graphic representation of food chain.
It may be formed as, depicted as a pyramid having a broad base formed by producers and tapering to a point formed by end consumers.

BIOMAGNIFICATION

Accumulation of toxic pollutants at successive higher trophic level is called as bio magnification.

OZONE LAYER

• Ozone \( (\text{O}_3) \) is a molecule formed by three atoms of oxygen.
• Ozone shields the surface of the earth from ultraviolet (UV) radiation from the Sun.
• UV radiation is highly damaging to organisms. It may cause even skin cancer in human beings.
• Ozone at the higher levels of the atmosphere is a product of UV radiation acting on oxygen \( (\text{O}_2) \) molecule.
• The higher energy UV radiations split apart some molecular oxygen \( (\text{O}_2) \) into free oxygen \( (\text{O}) \) atoms. These atoms then combine with the molecular oxygen to form ozone as shown—
• The ozone layer depletion takes place at higher rate. The major cause is chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers.

BIODEGRADABLE AND NON BIODEGRADABLE WATSES

i- Biodegradable Wastes: These can be broken down by the biological processes.
E.g. Food waste, plant parts, animal wastes, agricultural residue, paper etc.
Decomposers can decompose these without harming ecosystem. Food waste, trees leaves, urine and fecal matter, sewage agricultural residue, paper, wood, cloth, cow-dung etc.

ii- Non-biodegradable waste- these can‘t be broken down by biological processes.
E.g. - Chemical pesticides, DDT, mercury, lead, plastics, polythene bags etc.
These wastes are major pollutants of the environment.

MAINTAININMG THE GARBAGE WE PRODUE

• Change in attitudes toward using only biodegradable items.
• Proper disposal of wastes
• Follow Sewage treatment norms
• 3 'R' principle- reduce , recycle, reuse