The Living World-NCERT Limits-PART 1

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Hi guys.Let's start with THE LIVING WORLD. In this article,I will share some important concepts in Living world within NCERT Limits.

What is LIVING?

When we try to define ‘living’, we conventionally look for distinctive characteristics exhibited by living organisms. Growth, reproduction, ability to sense environment and mount a suitable response come to our mind immediately as unique features of living organisms

  • All living organisms grow. Increase in mass and increase in number of individuals are twin characteristics of growth.
In plants,this growth occurs continuously where as it is limited by certain checks in animals.However, cell division occurs in certain tissues to replace lost cells.But,unicellular organisms multiply by cell division. Even non-living things like sand mounds,mountains and boulders grow.So,it cannot be considered as a defining character for living

  • Reproduction refers to the production of progeny possessing features more or less similar to those of parents which invariably and implicitly refer to sexual reproduction. However,asexual reproduction also occurs in some organisms
  1. Fungi-Asexual and sexual spores
  2. Yeast and Hydra-Budding
  3. Planaria-True regeneration
  4. Fungi,filamentous algae,protonema of mosses-Fragmentation
When it comes to unicellular organisms like bacteria, unicellular algae or Amoeba, reproduction is synonymous with growth, i.e., increase in number of cells.But it cannot be considered as a defining character since some married infertile couples,mules and worker bees don't reproduce.

  • Another characteristic of life is metabolism.The conversion of one bio-molecule into other is termed as metabolic reactions. All plants, animals, fungi and microbes exhibit metabolism. The sum total of all the chemical reactions occurring in our body is metabolism. No non-living object exhibits metabolism.So metabolism is one of the defining features of all living organisms
Note: Isolated metabolic reaction in test tubes are not living things but living reactions
  • Cellular organisation is also a defining feature
  • The most obvious and technically complicated feature of all living organisms is this ability to sense their surroundings or environment which is known as Consciousness.All organisms are aware of their surroundings yet human being is aware of himself i.e self consciousness.Consciousness is also one of the defining property of life
  •  Properties of tissues are not present in the constituent cells but arise as a result of interactions among the constituent cells.These interactions result in emergent properties at a higher level of organisation

Diversity in the Living world:

Number of species described so far is between 1.7-1.8 million which is known as bio-diversity.Hence there is a need for nomenclature.This can be done clearly only when the organism is correctly identified and described.
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Some points to ponder:

Organizations involved in Nomenclature of organisms:
  1. ICBN-International Code for Botanical Nomenclature
  2. ICZN-International Code for Zoological Nomenclature
  3. ICVN-International Code of Viral Nomenclature
  4. ICNCP-International Code of Nomenclature of Cultivated Plants
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Biological names are universal where it has two components:
1.The first one represents the Generic name
2.The second one is Specific epithet
It was introduced by Gaspard Bauhin and made into use properly by Carolus Linnaeus

The rules followed during nomenclature are

1. Biological names are generally in Latin and written in italics or underlined separately when handwritten. They are Latinised or derived from Latin irrespective of their origin. 
2. The first word in a biological name represents the genus while the second component denotes the specific epithet.
3. Both the words in a biological name, when handwritten, are separately underlined, or printed in italics to indicate their Latin origin. 
4. The first word denoting the genus starts with a capital letter while the specific epithet starts with a small letter. 
5.The name of author may appear at the end in an abbreviated form.It can be illustrated with an example 
Eg:Mangifera indica Linn. or Mangifera indica Linn.

  • Whether it is a 'Cat' or 'Mammals' or 'Plants', the scientific term used is taxa. Here you must recognize that taxa can indicate categories at very different levels
  • Characterisation, identification, classification and nomenclature are the processes that are basic to taxonomy.
The earliest classification were based on the uses of various organisms but later the classifications were based on floral characters which don't change with time
  • Systematics-(Latin) 
Systema-systematic arrangement of organisms introduced by Linnaeus in his book 'Systema Naturae'


Inspiring individuals:

Ernst Mayr(1904-2004)
  • ‘The Darwin of the 20th century’
  • Gave biological concept of species
  •  also pioneered the currently accepted definition of a biological species
To see biology NCERT BOOK, click here to view



Location: Coimbatore, Tamil Nadu, India

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