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  • Diversity in The Living World
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The Living World

What is Living World?

Living beings are called organisms. Living, organisms are similar to non-living objects in being -formed of similar elements which combine in similar way to form similar molecules (called biomoleouls-, in living organisms) and follow similar physical and chemical laws like gravitation, magnetism, action and reaction etc. All living organisms grow.

Living organisms show a great biodiversity and are classified into different kingdoms-Monera, Protista, Fungi, Plantae and Animalia.


All of these share the following properties:

  • They have definite organisation.

  • They always have cellular nature so are either unicellular (e.g. Amoeba, Paramecium etc.) or multicellular (e.g., Hydra, man etc.).

  • They show co-ordination between different parts of body to maintain homeostasis (constant internal 'environment) inside the body.

  • They have the ability of movements and locomotion.

  • They show metabolic functions in the presence of energy.

  • These have the ability of intussusceptional (internal) growth and development.

  • These have regulatory mechanisms (e.g., nerves and hormonal in animals, and only hormonalin plants) to maintain homeostasis inside the body.

  • These show adaptations to their environment to increase their chances of survival.

  • These show variations which help in speciation and evolution.

  • These have reproductive powers for continuity of their race.

  • These have definite life span (period from birth to death).        

  • These undergo ageing after adulthood and then natural death.

Diversity in the Living World (Biodiversity)

Diversity in the living world or biodiversity is the occurrence of a wide variety of life from differing in morphology, size, colour, anatomy, habitats and habits. Each different kind of plant, animal or microorganism represents a species.

The past organisms have also left their impressions or remains in the rocks. They are called fossils. The term microfossil is used for impressions and remains of microorganisms as well as microscopic remains of larger organisms. It is believed that the extinct species may outnumber the living ones by 50-100 times. With such a large number of living and extinct organisms, it is essential to have a proper universal system of nomenclature, identification and classification that can bring out their true relationships. They are all domains of systematics.

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Watch this Video for more clarity on “The Living World”

Building blocks of life and their function:

Living organism is formed of many types of inorganic as well as organic biomolecules.· Inorganic compounds include water, minerals etc. and are always micro-biomolecules (small sized, low. molecular weight, readily soluble in water and diffusible) while organic molecules may be micro (e.g. monosugars, amino acids etc.) or macro­biomolecules (large sized, high molecular weight, insoluble or slightly soluble and non-diffusible e.g., proteins, fats, nucleic acids, etc.).

These both types of biornolecules play important roles in metabolism:

a) Role of Water: Water forms 70-90% of the cellular pool. It forms 65% (about two-thirds) of human body. It is formed of H and O in the ratio of 2:1. 95% of water is found in free state and 5% in combined form in the cell. Water helps in sustaining the life processes. So water is called elixir or cradle of lip as life is not possible in the absence of water.

b) Role of Oxygen: Oxygen is mainly utilized in aerobic cell respiration of the nutrients inside the mitochondria to produce energy-rich ATP molecules so is essential for life. In the absence of oxygen, only 5% of energy available is released.

c) Role of Sodium chloride (common salt): Sodium chloride plays an important role in metabolic functions of body especially when in ionic form.

d) Role of Carbohydrates: Carbohydrates are organic compounds formed of C, H and O generally in the ratio of 1:2:1. These are commonly called saccharides (Gk. saccharon = sugar) Carbohydrates are the main storage molecules and most organisms use carbohydrates as an important fuel, breaking these bonds and releasing energy to sustain life.

e) Role of Proteins: Proteins are polymeric compounds formed by interlinking of amino acids (monomers) by peptide bonds. Out of about 100 types of amino acids, only 20 types of amino acids are of biological importance, so are called Magic 20. Proteins play a vital role in the formation of structures in living organisms. Like carbohydrate and fat protein can be broken down with the release of energy. Protein is not stored as such in the body and it is normally only used as a substantial source of energy in conditions of starvation.

f) Role of lipids: Lipids comprise a major group of insoluble hydrocarbons having many functions. These are polymers of alcohols (e.g. glycerol) and fatty acids interlinked by ester bonds. Complex lipids such as true fats are important organic molecules that are used to provide energy. Fats in animals also provide protection from heat loss.

g) Role of Nucleic Acid: These are polymers of nucleotides interlinked by phosphodiester bonds, so called polynucleotides. Each nucleotide is formed of 3 components: a pentose sugar (e.g. ribose in RNA and deoxyribose in DNA), a phosphate group and an inorganic nitrogen-base (a purine or a pyrimidine).

“DNA acts as genetic material in most organisms and controls the synthesis of structural and. functional proteins. RNA also act as genetic material in all plant viruses e.g. TMV and helps in protein synthesis.

To read more, Buy study materials of The Living World comprising study notes, revision notes, video lectures, previous year solved questions etc. Also browse for more study materials on Biolgoy here.

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