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Diversity In Living World

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Diversity in Living World PDF Notes, Important Questions and Formulas

Diversity in Living World


Taxonomy is the branch of science which deals the study of nomenclature, classification and principles of classification. Taxonomy word was given by "Candolle" (Taxis -arrangements. Nomos -Law) Aristotle: - He is known as the "father of zoology". He is also known as the father of ancient taxonomy. He classified animals into two groups on the basis of the colour of blood.

  1. Anaima - Those animals which don't have red blood or in which RBC are absent in invertebrates like Sponges, Cnidaria, Mollusca, Arthropoda. Echinodermata.
  2. Enaima: - These animals have red blood. This group includes all vertebrates and it has been further divided into two sub groups.

(a)  Vivipara: - It includes animals which give birth to young-ones. E.g. Mammals.

(b)  Ovipara: - It includes animals which lay eggs. E.g. Pisces, Amphibians, Reptiles, Aves etc.

  1. Basis of Classification
  1. Level of body organization




Protozoa (included in kingdom – Protista


e.g. Amoeba, Paramoecium etc


Porifera (Kingon – Animalia)






Hydra,Jellyfish etc.


Ctenophora (minor phylum)






Flat worm (e.g Tape worm)




Round worm (eg:Ascaris)




Earthworm Leech etc




Insects,Scorpian,Fly etc




Snail, Pita, Octopus etc




Star fishes








Fish snake, Birds, Monkey etc.


  1. Asymmetry:-When any plane that passes through the centre does not divide the body of animals into two equal halves e .g: most of the sponges are asymmetrical.
  2. Radial symmetry: When any plane passing through the central axis of the body divide the animal into two identical halves E.g. Coelenterates, Ctenophores and Echinoderms (adult)
  3. Bilateral symmetry: When the body can be divided into identical left & right halves in only one plane. E.g. Platyhelminthes to Chordates


Germinal layers

  1. Diploblastic - Animals in which the cells are arranged in two embryonic layers ectoderm and endoderm with an interveining undifferentiated mesoglea e.g. Sponges, Coelenterates and Ctenophores.
  2. Triploblastic - Those animals in which the developing embryo has a third germinal layers-Mesoderm in between the ectoderm and endoderm e.g. Platyhelminthes to Chordates.



Biology is the science of life forms and living processes. The living world comprises an amazing diversity of living organisms. Early man could easily perceive the difference between inanimate matter and living organisms. Early man deified some of the inanimate matter (wind, sea, fire etc.) and some among the animals and plants. A common feature of all such forms of inanimate and animate objects was the sense of awe or fear that they evoked. The description of living organisms including human beings began much later in human history.

Societies which indulged in anthropocentric view of biology could register limited progress in biological knowledge.

Systematic and monumental description of life forms brought in, out of necessity, detailed systems of identification, nomenclature and classification. The biggest spin off of such studies was the recognition of the sharing of similarities among living organisms both horizontally and vertically. That all present day living organisms are related to each other and also to all organisms that ever lived on this earth, was a revelation which humbled man and led to cultural movements for conservation of biodiversity.



What is Living: - Following are the main characters of “living” –

Characteristics of living


The character which has no exception is called as defining property of life.

I.  Growth

  • Increase in masses or overall size of a tissue or organism or its parts is called growth.
  • Increase in mass and increase in number of individuals are twin characters of growth.
  • Growth is an irreversible permanent increase in size of an organ or its parts or even of an individual cell.
  • Growth is the result of metabolism, when the synthetic reactions or anabolism is more than that of the destructive processes or catabolism, growth occurs.
  • In the reverse situation (Anabolism & Catabolism) there will be 'Degrowth' or negative growth.

Growth is of two types:-

  1. Intrinsic growth: - This growth is from inside of the body of living organisms.
  2. Extrinsic growth: - This growth is from outside i.e. accumulation of material on anybody surface Nonliving exhibits this type of growth.

Growth is of two types _

  1. Indeterminate growth = Unlimited growth:
    Growth which occurs continuously throughout their life span is indeterminate growth or unlimited growth. It occurs in plants and not in animals.
  2. Determinate growth = Limited growth:
    Growth which occurs only up to a certain age is determinate growth or Limited growth it occurs in animals.

However, cell division occurs in certain tissues to replace lost cells.

  • In majority of higher plants and animals, growth and reproduction are mutually exclusive events.
  • Because both living and non-living exhibit growth so it cannot be taken as defining property.
  • Growth from inside (intrinsic growth) can be taken as defining property.


Production of new individual or progeny is called as reproduction.

  • Reproduction in case of multicellular organisms is production of progeny possessing features more or less similar to those of parents.
  • Reproduction in case of unicellular organisms like bacteria, unicellular algae or Amoeba is increase in number of cells. Means in unicellular organisms the growth and reproduction are synonyms or same.
  • Reproduction is not found in any non-living object.
  • There are many living organisms which can/do not reproduce like mules, sterile human couples, worker bees.
  • So the reproduction also cannot be taken as defining characteristic of living organisms.

Reproduction is of two types.

  1. Asexual Reproduction: - Reproduction in which gametic fusion or fertilisation and meiosis are not involved is Asexual Reproduction. Many methods of asexual reproduction are there.

(a)  By Asexual spores: - In algae and fungi

(b)  By Budding: - In Yeast and Hydra

(c)  By Fragmentation: - In Filamentous algae, fungi and the protonema of moss plants

(d) True Regeneration: - Fragmented organisms regenerate the lost part of its body and become a new organism, e.g. Planaria

Note: Regeneration is a process in which only the lost part of the body is repaired or regained e.g., Star fish, Lizard.

(B) Sexual Reproduction: - Reproduction in which gametes are formed by meiosis and fertilisation also takes place to form progeny is called as sexual reproduction.


  • The sum total of all the chemical reactions occurring in our body is metabolism.
  • All living organisms, both unicellular and multicellular exhibit metabolism.
  • No non-living object shows metabolism.
  • In this way metabolism is a -defining character of living organisms because it has no exceptions.
  • Now we have known most of the chemical or metabolic reactions occurring in our body so we can demonstrate many of them in a cell free medium or in a test tube in lab.
  • The isolated metabolic reaction outside the body of an organism, performed in a test tube (in-vitro) is neither living nor non-living.
  • These isolated reactions cannot be regarded as living things, but they are definitely living reactions because they are similar to the reactions performing in our body.
  • Here we should not forget the fact that metabolism is the total sum of all the chemical reactions performing in our body, it is not the sum of few or more living reactions.
  • All organisms are made of small or big chemicals. These chemicals perform thousands of reactions and form some other chemicals also in the bodies of living organisms.
  • All plants, animals, fungi and microbes exhibit metabolism.

Cellular Organization:

  • Cell is the basic unit of life.
  • All living organisms are composed of cells. Some are composed of a single cell and are called as Unicellular Organisms while other like us composed of many cells, are called multicellular organisms.
  • Unicellular organisms are capable of independent existence and performing essential functions of life
  • Anything less than a complete structure of a cell, does not ensure independent living. Hence, cell is the fundamental structural and functional unit of all living organisms.
  • In this way the cellular organisation is proved to be defining property of all living organisms.


Ability to sense the surrounding environments and respond to these environmental stimuli is called as consciousness.



All the multicellular eukaryotic plants are placed in Kingdom-Plantae.They are autotrophic i.e. they manufacture their food by photosynthesis.

(1)   The term "Thallophyta" was given by "Endlicher". According to two kingdom classification, all the algae, fungi and bacteria were placed in thallophyta, because their plant body is thallus.
(2)   All the thallophytes are non-vascular.
(3)   In thallophyta plant is haploid i.e. gametophyte
Eg. Green algae, red algae, yellow green algae, dinoflagellate, cellular slime mold.

Note: Exceptionally in some thallophytes, plant is diploid i.e. sporophyte

(4)  In thallophyta the male sex organs are called as Antheridia and female sex organs are called as Oogonia. Sex organs are unicellular & Jacket less [Jacket - layer of sterile cells]

(5)  The sexual reproduction in thallophyta is isogamous, anisogamous and oogamous.

(6)  In thallophyta, sexual reproduction takes place through zygotic meiosis, therefore embryo is not formed.


  1. Algae
  2. Bryophyta
  3. Pteridophyta
  4. Gymnosperm
  5. Angiosperm


Introduction to GROUP -ALGAE

  • Term "Algae" was given by Linnaeus.
  • Phycology - Study of algae.
  • Father of Phycology - Fristch  Book "Structure & Reproduction of algae"
  • Father of Indian phycology - M.O.P. Iyengar

General Characteristrics                                         

  1. Algae are found in both fresh and marine water.
  2. Algae are found in many forms like filamentous, colonial.
  3. Algae are surrounded by mucilagenous sheath and below the sheath cell wall is present which is made up of cellulose and pectin but mainly made up of cellulose, galactans, mannans and mineral like calcium carbonate.
  4. On the basis of structure, algae are thalloid i.e. plant body is not differentiated into root, stem and leaves.Tissue system is also absent in algae.
  5. On the basis of nutrition, algae are photoautotrophic.
  6. They have chloroplast in which photosynthetic pigments are present. Classification of algae is mainly based on pigments.
  7. Chl-a and carotene are universal pigment of algae.

Classification of Alage

The classification of algae is mainly based on the photosynthetic pigments. In addition to this, cell wall composition and stored food are also the base of classification.

Algae is divided into following divisions

  1. Chlorophyceae - Green Algae
  2. Phaeophyceae - Brown Algae
  3. Rhodophyceae - Red Algae


It hard to believe that there are more than 20,000 species of ants , 3,00,000 species of beetles, 28,000 species of fishes and nearly 20,000 species of orchids.


Biodiversity is the term popularised by the sociobiologist Edward Wilson to describe the combined diversity at all the levels of biological organisation. The most important of them are-

Genetic diversity: A single species might show high diversity at the genetic level over its distributional range. The genetic variation shown by the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges might be in terms of the potency and concentration of the active chemical (reserpine) that the plant produces. India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango.

Species diversity: The diversity at the species level. For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.

Ecological diversity: At the ecosystem level, India, for instance, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows has greater ecosystem diversity than a Scandinavian country like Norway.

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