CLASS 10 SCIENCE NOTES: OUR ENVIRONMENT

 TOPICS WE WILL BE COVERING:

• ENVIRONMENT
• ECOSYSTEM
• ABIOTIC AND BIOTIC COMPONENTS
• FOOD CHAIN
• FOOD WEB
• BIOMAGNIFICATION
• OZONE LAYER
• BIODEGRADABLE AND NON- BIODEGRADABLE
• WASTE MANAGEMENT

Environment: Environment is the surrounding where organisms live 

Ecosystem: All living organisms in an area together with the non-living constituents of the environment form an ecosystem.

Thus, an ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil and minerals.

A self-sustaining ecosystem is a system where living (biotic) and non-living (abiotic) components can maintain their own balance and function without needing external inputs or interventions. This means that it can produce and recycle all the necessary resources for its organisms to survive. 

Types of ecosystem:

Natural ecosystem: Ecosystems which operate in nature by themselves without any human interference.

Example: 

Terrestrial ecosystem (Land based ecosystem): desert, forest, mountain. 

Aquatic ecosystem (Water based ecosystem): rivers, ponds, lakes.

Artificial ecosystem: Artificial ecosystems are maintained due to human interference. These are also known as man-made ecosystems.

Example: Agricultural land, parks, aquarium, zoo etc 

Components of ecosystem:

(i) Abiotic Components: All the non-living components such as air, water, land, light, temperature etc. form the abiotic components.

(ii) Biotic Components: All the living components such as plants, animals, bacteria, fungi etc. form the biotic components.

• On the basis of nutrition, biotic components are further divided into:

→ Producers: All green plants and blue-green algae can produce their own food using abiotic components (photosynthesis), hence called producers.

→ 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, cuscuta.

→ Decomposers: Include organisms which decompose the dead plants and animals. Example: bacteria, fungi. These help in the replenishment of natural resources.

Q) We do not clean ponds or lakes but an aquarium needs to be cleaned. Explain.

Ans) Aquarium is an example of an incomplete artificial ecosystem. In aquariums, the uneaten food as well as the waste generated by the fishes mixes with water and is left untreated due to the lack of decomposers. The waste material thus accumulated in the water making it toxic, that's why an aquarium has to be cleaned after regular intervals. 

Food chain 

Food chain is the flow of food energy from one organism to the next and to the next and so on. 

Functioning of ecosystem 

1. The producers in the size complex food with the help of solar energy carbon dioxide sunlight and minerals from soil 

2. The consumers eat up plants and other animals as food so energy is transferred to next organism 

3. When plants and animals die then decomposers feed on dead remains of their body parts and decompose them into simple materials.

Trophic level: It is the position an organism occupies in a food chain. Each link in the food chain represents one trophic level.

10% law of energy transfer:

1. This law was proposed by Reymonds Lindeman in 1942.

2. According to this law only 10% of energy is transferred from level to next successive trophic level. The remaining 90% energy is used in life processes (digestion, growth, reproduction etc.) by present trophic level.

Food web: Food web is a network of interconnected food chains operating in an ecosystem. 

Difference between Food chain and food web 

Food chain	Food web
The sequence of living organisms in which one organism consumes another organism to transfer food energy	The network of interlinked food chains.
Comprised of single chain	Comprised of many food chains
Removal of one group of organism disturbs whole chain	Removal of one group of organism does not cause much disturbance in ecosystem

Bio-magnification: Bio-magnification is the increase of the concentration of toxins or non biodegradable substances in the body tissues of organisms as it moves from one tropic level to the next.

Note 

• Flow of energy in a food chain is always unit directional 

• Generally consist of only four or five steps 

• In a food chain highest energy is the first tropic level lowest energy is a last tropic level 

• Highest concentration of biomagnification biomegnified chemical Las of a level 

• Lowest concentration of biomagnified chemical- first trophic level 

• The green plants in a terrestrial ecosystem capture about one person of the energy of sunlight that falls on their leaves and converted into food energy 

Q) Why do food chains in an ecosystem not have more than 4 to 5 tropic levels?

Ans) According to 10% law, only 10% energy is transferred from one trophic level to another. So during the transfer of energy, the loss of energy at each step of the food chain is such that very little energy remains after 4 to 5 profit levels whereas food chains generally consist of only 4 or 5 profit levels. 

Environmental problems and its management 

1. Ozone layer and its depletion 

2. Managing the garbage we produce 

Causes of ozone layer depletion 

• Chlorofluorocarbon CFC 

• Hydrochloro fluorocarbon hcfc 

• Methyl bromide 

• Methyl chloroform 

Effects of ozone layer depletion 

• Skin cancer 

• cataract 

• DNA damage 

• reduced immunity 

• sunburns 

Steps of depletion of ozone layer:

1. Chlorofluorocarbon (CFCs) emissions reach the Ozone.

2. Cfcs are broken down by the sun's ultraviolet rays releasing the chlorine atoms into the ozone layer 

3. Active chlorine atoms breakdown the ozone molecules causing ozone layer depletion 

4. More ultraviolet rays reach the earth threatening human health

Formation of ozone molecule

(i) The high energy UV radiations break down the O2 molecules into free oxygen (O) atoms.

O →(UV)  O + O (atoms)

(ii) These oxygen atoms then combine with oxygen (O2) molecules to form the ozone molecule.

O2 + O → O3 (ozone)

Difference between biodegradable and non biodegradable wastes:

Methods of waste disposal

(i) Biogas plant: Biodegradable waste can be used in biogas plant to produce biogas and manure.

(ii) Sewage treatment plant: The drain water can be cleaned in sewage treatment plant before adding it to rivers.

(iii) Land fillings: The wastes are buried in low lying areas and are compacted by rolling with bulldozers.

(iv) Composting: Organic wastes are filled in a compost pit and covered with a layer of soil, after about three months garbage changes to manure.

(v) Recycling: Non-biodegradable wastes are recycled to make new items.

(vi) Reuse: It is a conventional technique to use an item again. Example: newspaper for making envelopes.