class 10th

What is Consumers

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They are heterotrophic organisms which consume the food produced by the producers. They derive their nutrition by feeding on other living organisms. A consumer which derives nutrition by eating plants is called primary consumer or herbivore. The secondary consumer or carnivore is an animal that gets its nutrition by eating the flesh of herbivores or other animals’. The organisms which can feed on both plants and animals is called an omnivore.

Herbivores: these are called primary consumers or first order consumers which obtain their food directly from plants.

  • Terrestrial herbivores- Deer, rabbit, mouse, goat cattle etc
  • Aquatic herbivores- Crustaceans, protozoan.

Carnivores: Carnivores feed upon other animals. They have been classified as

  • Secondary Consumers: They prey upon primary consumers or herbivores.  E.g. frog, birds, fishes, jackal, fox, snakes.
  • Tertiary consumers:  Carnivores e.g. owl, peacock, lion, tiger etc. Carnivores like lion, tiger etc. which cannot be preyed upon further are called top carnivores and their number is generally low compared to the lower biotic levels of an ecosystem.

Ocean thermal energy

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Solar energy stored in the oceans in the form of heat is called ocean thermal energy (OTE).

  • Sun warms the ocean water at the surface and the wave motion mixes the warmed water to the depth of about 100m. This mixed warm layer is separated from the deep cold water layer and the temperature difference b/w these layers ranges from 10 to 300C.  
  • World’s first OTEC plant with a capacity of 100MW is proposed off the coast of Tamil Nadu.
  • Pressurised ammonia is vaporised in an evaporator. Through which sea water (240c to 300c) flows.
  • Resulted becomes expanded through a turbine to generate electricity with the help of a generator.
  • Cold ocean water (at 40c to 80c) is transported to the surface from depth (from 800m to 1000m) and is used to condense ammonia vapour through a condenser.
  • NH3 condensate & pumped back to the evaporator through a pump.   

Since ammonia circulates in closed loop. This OTEC power plant is called closed cycle OTEC system.

The sun warms the water surface of ocean and wave motion mixes the warmed water downwards to the depth of 100m. This mixed warm layer is separated from the deep cold water layer and the temperature difference b/w these layer ranges from 100C to 300C.

The process of harnessing thermal energy of sea called OTEC.


  • It is pollution free and renewable sources of energy.
  • OTEC system does not have daily or seasonal variations in their output as is the case with other solar energy devices.
  • OTEC is the one of the most clean power production technology.


  • OTEC system requires a lot of capital investment.
  • Due to small temperature difference conversion efficiency is low.

Nuclear energy

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The energy obtained from the nucleus of an atom is called nuclear energy. The source of energy is same in both types of nuclear reaction is same. Certain mass is disappearing in this type of reaction mainly in the form of energy.

The difference in the mass of reactant and product is called mass defect, which appear in the form of nuclear energy according to Einstein by equation: E = mc2 . This equation was derived by Albert Einstein in 1905.

  1. Nuclear fusion

It is the phenomenon of combining of two or more lighter nuclei to form a more stable heavy nucleus with the liberation of vast amounts of energy.

Such nuclear reactions are the source of energy in the sun other than stars. These reactions are called Thermo nuclear reaction.

  • It is used in formation of Hydrogen Bomb. There is extremely high temperature near about 107degree. It is quite more powerful than hydrogen bomb.
  • Two deuterons can join to form triton and a proton with release of 4.03Mev energy. The nuclear reaction is

 2H1 + 2H1                                              3H1 + 1H1 + 4.03Mev

  • Two deuteron can join together to form a helium nucleus and a neutron and it is represented as:

2H1 + 2H1                                               3He2 + 1n0 + 3.27Mev

  • Nuclear fission

The phenomenon of splitting of an unstable nucleus of a heavy atom into two lighter nuclei with the liberation of an enormous amount of energy. This occurs when it bombarded with neutron.

  • This phenomenon was discovered by Otto Hahn and Fritz Strassman in the year 1939.
  • 235U92 + 1n0                                      139Ba56 + 94kr36 + 31n0 + E
  • Energy produced by burning of one kilogram of uranium is equal to the energy produced by burning of 2500 tons of coal.
  • Nuclear power plant in India, Tarapur in Maharashtra, Kalpakkam in Tamil Nadu, etc. Nuclear Bomb or Atomic Bomb based on the phenomenon of nuclear fission.

1Mev = 1.602 × 10-13J

1U = 1.492 × 10-10J


  • It produce large amount of energy from small amount of nuclear fuel.
  • Once the nuclear fuel loaded into the reactor, nuclear power plant can on producing electricity for two to three years.


  • Leakage of nuclear radiation from reactor.
  • Disposal of nuclear wastes.

Sources of Energy (part – 2)

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Fossil fuels

These are the remains of prehistoric plants and animals which got buried deep inside the earth millions of years ago due to some natural processes. Fossil fuel is the major source of energy for generating the electricity in power plants.

Coal: It is the most abundant fossil fuel on the earth. It is mainly used as combustion fuel. It is the complex mixture of carbon, hydrogen and oxygen and some free carbon. Small amount of sulphur and nitrogen compound.

Coal formation

Coal is the product of plants which died millions year ago. The action of certain bacteria causes release of oxygen and hydrogen and its residue rich in carbon. As more material accumulated water squeeze out. Due to high temperature and pressure material becomes condensed and gases expelled out. The proportion of carbon continued to increase till it slowly changed into coal over a period of millions of years. This layer of carbon is called PEAT and show 27% of carbon.

  • Apart from peat, there is three another type of coal: lignite (28% – 30%), bituminous (78% – 87%) and anthracite (94% – 98%).
  • When coal is burnt, carbon is present in it react with oxygen to produce carbon-di-oxide and lots of heat.   

Coke is produced when coal is heating strongly in absence of air. Coke has high energy value and produce less smoke.

India has about 7% of world’s known coal reserves and these are mainly found in Bihar, Orissa and Madhya Pradesh. Coal supplies 50% of the country’s total energy requirement.  

Uses of coal

  • It is used as fuel in industries
  • It is used to produce electricity.
  • It is used to manufacture of fuel gases like coal gas.
  • When coal is heating strongly in the absence of air it changes into coke.
  • It is better quality fuel than coal because it produces more heat.

What is Biodiversity and its types

Biodiversity Introduction by Science World

‘Biodiversity’ is a term frequently used. It is short for ‘biological diversity’. A concise definition of biodiversity is “the variety of life on earth”. Biodiversity is an over-arching concept which includes wildlife, habitats and conservation. Biodiversity is important to us for aesthetic and even spiritual reasons but also for practical and utilitarian ones. There is a widespread and deep concern for our countryside, wildlife and habitats as shown by the huge membership of wildlife and conservation organisations.

As we know that biology is the study of living organisms or living things. It is a combination of two words ‘bios’ which means life and ‘logos’ means happening. It deals with all aspects of life in which different types of species involved. As environmental science is a vast field which deals with all types of living things such as plants, animals or insects etc. There are different branches of environmental science one of them is biodiversity. The study of variation of different living organisms such as plants and animals in a specific area for the sake of food, living, and shelter is called as biodiversity.

Biological diversity or biodiversity refers to the variety of life forms: the different plants, animals and microorganisms, the genes they contain, and the ecosystems they form. This living wealth is the product of hundreds of millions of years of evolutionary history. The process of evolution means that the pool of living diversity is dynamic: it increases when new genetic variation is produced, a new species is created or a novel ecosystem formed; it decreases when the genetic variation within a species decreases, a species becomes extinct or an ecosystem complex is lost. The concept emphasizes the interrelated nature of the living world and its processes.

Biological diversity is usually considered at three different levels: genetic diversity, species diversity and ecosystem diversity.

Genetic diversity refers to the variety of genetic information contained in all of the individual plants, animals and microorganisms. Genetic diversity occurs within and between populations of species as well as between species. Species diversity refers to the variety of living species.

Ecosystem diversity relates to the variety of habitats, biotic communities, and ecological processes, as well as the tremendous diversity present within ecosystems in terms of habitat differences and the variety of ecological processes.

At the ecosystem level, biodiversity provides the conditions and drives the processes that sustain the global economy – and our very survival as a species. The benefits and services provided by ecosystems include:

The activities of microbial and animal species – including bacteria, algae, fungi, mites, millipedes and worms – condition soils, break down organic matter, and release essential nutrients to plants. These processes play a key role in the cycling of such crucial elements as nitrogen, carbon and phosphorous between the living and non-living parts of the biosphere.

Plant species purify the air and regulate the composition of the atmosphere, recycling vital oxygen and filtering harmful particles resulting from industrial activities.