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CBSE Class 11 Biology Notes

The Living World

Biology is the science of life forms and non-living processes. The living world comprises an amazing diversity of living organisms.  In order to facilitate the study of kinds and diversity of organisms, biologists have evolved certain rules and principles for identification, nomenclature and classification of organisms.  The branch of biology dealing with these aspects is referred to as Taxonomy.

Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased (death), or else because they lack such functions and are classified as inanimate.  Biology is the science concerned with the study of life.

Characteristics features of Living things / Differences between living and non-living things:

  • Growth
  • Reproduction
  • Metabolism
  • Response to stimuli

Biodiversity:  Range of organisms present on earth (1.7 – 1.8 million)

Identification: Comparing similarities and differences with already known ones.

Nomenclature: Naming of organisms. The names are unique and universal.

Rules for nomenclature are provided by

  • ICBN – International Code for  Botanical Nomenclature
  • ICZN – International Code for Zoological Nomenclature

Binomial Nomenclature:

Carolous Linnaeus – Father of Taxonomy
Name with two parts: - Generic name (Genus) & Specific epithet (Species)

Guidelines and Principles for Nomenclature:

  • It should be in Latin / derived from Latin.
  • If it is written in Italics when types and underlined when handwritten.
  • It contains two parts, first word is Genus ; second word is Species.
  • Genus name starts with Capital while species name starts with small letters.
  • Name should be short, precise & easy to pronounce.
  • Name of the author is written is an abbreviated form after the species name.  Ex. Mangifera indica Linn.

Example:
Mangifera indica ( Mango)
Homo sapiens ( Human)
Panthera pardus (Leopard)
Felis domestica (Cat)

Classification – Grouping of organisms in to categories based on observable characters. (category –taxa )

Taxonomy  - Characterization, identification , classification and nomenclature are the process of taxonomy.

Systematics  -  Different kinds of organisms and their relationships Linnaeus – Systema Naturae (evaolutionary relationships among organisms).

Taxonomical Hierarchy – Similarities decreases/ Differences increases

Species à Genus à Family à Order àClass àPhylum àDivisions àKingdom

  1. Species -Panthera leo, Panthera pardus, Panthera tigris.
  2. Genus-   Panthera (Lion, Leopad,Tiger )
  3. Family-  Panthera and Felis together into Felidae
  4. Order -   Felidae (cat family) , Canidae (dog family)  - Carnivora
  5. Class -     Carnivora (tiger, cat, dog), Primates  (monkeys )-  Mammalian
  6. Phylum – Pisces,  Amphibian, Reptilian, Aves & Mammals
  7. Kingdom – Plantae, Animalia.

Taxonomical Aids :

  1. Herbarium
  2. Botanical garden- NBRI (Lucknow ) & IBG (Howrah )
  3. Museum
  4. Zoological parks.
  5. Key (analytical  in nature)
  6. Monograph ( 1 family / genera at a time. )
  7. Manuals (particular area , family/ genus/ species )
  8. Flora (habitat & description of plants in a given area )

Taxonomical aids

  • These are the procedures and techniques used to store and preserve information as well as specimens of various plants and animals.
  •  These help in identification, naming, and classification of organisms.

Herbarium

  •  It is the storehouse of collected plant specimens.
  •  Collected plant specimens are dried, pressed, and preserved on sheets and then arranged systematically according to the universally accepted system of classification.
  •  Herbarium sheet contains label regarding date, place of the collection, scientific name, family, collector's name, etc. of the specimen.

Botanical gardens

  • It has the collection of living plant species that are grown for identification and reference.
  • Each plant contains labels indicating their scientific name and family.
  • Some famous botanical gardens are Indian Botanical Garden, Calcutta (largest in India), Royal Botanical Garden, Kew (largest in world till date) and National Botanical Research Institute.

Museum

  • It is the repository that has a collection of various plant and animal specimens that are preserved for study and reference.
  • The organisms are preserved either in preservative solution or in the form of dry specimen
  • It often has a collection of skeletons of animals also.

Zoological parks

  •  Wild animals are kept in protected environments.
  •   Provides opportunity for studying the behaviour and food habits of the animals

Key

  • Keys are used for identification of plants and animals based on similarities and dissimilarities.
  • Manuals, monographs, and catalogues are other means of recording descriptions.
  • Manuals help in the identification of names of various species of organisms in a given area.
  • Monograph is a detailed and well-documented work on any particular taxon.

Organisms with their Taxonomic categories:

Man : Homo sapiens – Homo – Hominidae – Primate – Chordate - Mammalia

Housefly : Musca domestica  - Musca  – Muscidae – Diptera -  Insecta -Arthropoda

Mango : Mangifera indica –  Mangifera  -  Anacardiaceae -  Sapindales- Dicotyledonae - Angiospermae

Wheat : Triticum aestivum – Triticum – Poaceae – Poales - Monocotyledonae - Angiospermae
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