(IGP) GS Paper 1 – General Science – “Diversity in Living Organisms”

Integrated Guidance Programme of General Studies for IAS
(Pre) – 2013

Subject – General Science
Chapter : Diversity in Living Organisms

Diversity in Living Organisms

Biologists such as Ernst Haeckel, Robert Whittaker and Carl
woese have tried to classify all living organism into broad categories called
kingdom. The classification which Whittaker proposed has five kingdoms: monera,
protista, fungi, plantae and animals.

  • Monera : These organisms do not have a defined
    nucleus nor do any of them show multi- cellular body designs. This group
    includes bacteria, blue green algae, or cyanobacteria and mycoplasma.

  • Protista : These groups include many kinds of
    unicellular eukaryotic organisms some of these organisms use appendages,
    such as hair like cilia or whip like flagella for moving around. e.g. :
    unicellular algae, diatoms, protozoans.

  • Fungi : there are heterotrophic eukaryotic
    organisms. They are decaying organic materials as food and are therefore
    called saprophytes. They have a cell wall made up of a tough complex sugar
    called chitin.
    Examples are are yeast and mushrooms
    Some fungal species live in permanent mutually dependent relationships with
    blue green algae such relationship is called symbiotic.
    These symbiotic life form are called lichens. We have all seen lichens as
    the slow growing large columned pitches on the bark of trees.

Differentiation in Plants


  • Plants that do not have well differentiated body design
    fall in this group.

  • The plants in this group are commonly called algae. These
    plants are predominantly aquatic.

  • E.g. : Spirogyra, cladophora and chara.


  • These are called the amphibians of the plant kingdom.
    There is no specialized tissue for the conduction of water and other
    substances from one past of the plant body to another.E.g. : moss (fumaria)
    and marchantia


  • In this group plant body is differentiated into roots,
    stem and leaves and has specialized tissue for the conduction of water and
    other substances from one plant of the plant body to another. Eg- marsilea,
    ferns, and horse tails.


  • The plant of this group bear naked seeds and one usually
    perennial and evergreen and woody. E.g.- pines such as deodar.


  • The seeds develop inside an organ which is modified to
    become a fruit. These are also called flowering plants.

  • Plant embryos in seeds have structures called cotyledons.
    Cotyledons are called seed leaves because in many instances they emerge and
    become green the seed germinates.

  • The angiosperms are divided into two groups on the basis
    of the number of cotyledons present in the seed.


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Differentiation of Animals


  • These are non mobile animals attached to some solid
    support. There are holes or pores all over the body. These lead to a canal
    system that helps in circulating water throughout the body to bring in food
    and O2. They are commonly called sponges mainly found in marine habitats.


  • These are animals living in water. The body is made up of
    two layers of cells. One makes up cells on the outside of the body and the
    other makes the inner living of the body.

  • Some of these species live in colonies while others have
    a solitary life e.g. span (Hydra) jellyfish are common example.


  • There are three layers of cells from which different
    tissues can be made. This allow outside and inside body linings as well as
    some organs to be made.

  • Thus there is some degree of tissues formation.

  • They are either free living or parasitic. e.g.
    Planarians, liver flukes.


  • These are very familiar as parasitic worms causing
    diseases such as the worms causing elephantiasis (filaria worms) or the
    worms in the intestine (round or pin worms)


  • They have true body cavity. This allows true organs to be
    packaged in the body structure. There is thus an extensive organ different
    ion. This differentiation occurs in a segmental fashion with the segment
    lined up one after the other from head to tail. Eg- Earthworms, leeches.


  • There is an open circulatory system and so the blood does
    not flow in well defined blood vessels. They have joint legs. Eg- prawns,
    butterflies, houseflies, spiders, scorpions and crabs.


  • They have an open circulatory system and kidney like
    organs for excretion. There is a little segmentation. There is a foot that
    is used for moving around. Eg- snails, and mussels, octopus.


  • There are spiny skinned organisms. These are exclusively
    free living marine animals. They have peculiar water driven tube system that
    they use for moving around.

  • They have hard calcium carbonate structure that they use
    as skeleton. Eg- starfish, sea cucumber.


  • They are marine animals. balanoglossus, hardemania and


  • These animals have a true vertebral column & internal
    skeleton. These are grouped into five classes.


  • These are fish. They are cold blooded and their hearts
    have only two chambers unlike the four that human have.

  • Some with skeletons made entirely of cartilage, such as

  • Some with skeleton made of both bones and cartilages such
    as tuna or rohu.


  • They have mucus glands in the skin and a three chambered
    heart. Respiration is through either gills or lungs. Eg- frogs, toades, and


  • These animals are cold blooded have scales and breathe
    through lungs. While most of them have a three chamber heart while crocodile
    have four heart chambers. Eg- snakes, turtles, lizards and crocodiles.


  • These are warm blooded animals and have a four chambered
    heart. They lay eggs. They breathe through lungs. All birds fall in this


  • They are warm blooded animals with four chambered hearts.

  • They have mammary glands for the production of milk to
    nourish their young. They produce live young ones.

  • However a few of them like platypus and the echidna lay

Micro Organisms

Facts from NCERT

Micro organisms are classified into four major groups. These
groups are bacteria, fungi, protozoa and algae.

Viruses :

  • They reproduce only inside the cells of the host
    organisms which may be bacterium, plants or animal.

  • Common cold, influnenza and most coughs are caused by

  • Serious diseases like polio and chicken pox are also
    caused by viruses.

  • Micro organisms may be single celled like bacteria, Some
    algae and protozoa. Multicellular such as algae and fungi.

  • Micro organisms like amoeba can live alone, while fungi
    and bacteria may live in colonies.

Friendly Micro Organisms

  • Making of curd and breed:-milk is turned into curd by
    bacteria. The bacterium lacto bacillus promotes the formation of curd.

  • Yeast reproduces rapidly and produces CO2 during
    respiration. Bubbles of the gas fill the dough and increase its volume; this
    is the basis of the use of yeast in the booking industry for making breads,
    pastries and cakes.

Medicinal Use of Micro Organisms:

  • The medicine which kills or stops the growth of diseases
    causing microorga-nism is called antibiotics.

  • Streptomycin, tetracycline and erythromycin are some of
    the commonly known antibiotics. Which are made from fungi and bacteria.


  • When a disease carrying microbe enters our body, the body
    produces antibodies to fight the invader.

  • The antibodies remain in the body and we are protected
    from the disease causing microbes. This is how a vaccine work.

  • Several diseases including cholera, TB, small pox and
    hepatitis can be prevented by vaccination.

Harmful Microorganisms

  • Microbial diseases that can spread from an infected
    person to a healthy person through air water, food, or physical contact are
    called communicable diseases. i.e.- cholera, common cold, chicken pox and

  • There are some insects and animals which act as carrier
    of disease causing microbes like house fly. Another is female anopheles
    mosquito which caries the parasite of malaria

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