THE LIVING WORLD – Class XI Biology by TEACHING CARE online tuition and coaching classes

THE LIVING WORLD – Class XI Biology by TEACHING CARE online tuition and coaching classes


What is living?

The organisms that show growth, reproduction, ability to sense environment, mount a suitable response metabolism, ability to self-replicate, self-organise, interact and emergence come to living organisms.


Diversity in living organism

Living organisms shows great variation on the basis of mode of nutrition, mode of reproduction, habitats and morphological structure. Both plants and animals have a large number of species distributed at different parts of earth. The number of species that are known and described range between 1.7-1.8 million. This refers to biodiversity or the number and types of organisms present on earth.

We know the plants and animals in our own area by their local names. These local names would vary from place to place, even within a country. So there is need to standardise the species by identifying and naming them.

Nomenclature: The naming of the organism of the organisms such that a particular organism is known by same name throughout world is called nomenclature.

Identification: Correct description of any living organisms that make possible the naming of the organisms.

          Binomial nomenclature

The scientific or technical names were developed by Linnaeus (Philosophica Botanica, 1751). The technical names recognized internationally are the ones given by Linnaeus in the 10th edition of his book Systema Naturae published in 1758. The system developed by Linnaeus is known as Binomial Nomenclature. Binomial nomenclature is the system of

Rules for nomenclature:

The five codes of nomenclature are: International Code of Botanical Nomenclature (ICBN) and International Code of Zoological Nomenclature (ICZN). The names of bacteria and viruses are decided by International Code for Nomenclature of Bacteria (ICNB) and International Code of Viral Nomenclature (ICVN). Similarly, there is a separate International code of Nomenclature for Cultivated Plants (ICNCP). The important rules are :

  • A scientific naming using ‘generic name’ as the first part and ‘specific epithet’ as the second part, e.g., Mangifera indica (mango), Apis mellifera (honey bee), etc.
  • The generic name starts with capital letters and the specific epithet starts with small letters.
  • The biological name always written in Italic form e.g., Mangifera indica, Tamarindus indica.

(iv)     The biological or scientific name is always printed in italics whereas it is underlined while handwritten. This is done to make the scientific name distinct from the text.

          Classification: Grouping or categorizing organisms on the basis of their similarities and dissimilarities for the convenience of study is called as classification.

Classification is not a single step process but involves hierarchy of steps in which each step represents a rank or category. Since the category is a part of overall taxonomic arrangement, it is called the taxonomic category and all categories together constitute the taxonomic hierarchy.  Each category, referred to as a unit of classification, in fact, represents a rank and is commonly termed as taxon (pl.: taxa).

          Taxonomy (A. P. de Candolle): The study which includes identification, nomenclature and classification.

According to some scientists taxonomy and systematic are synonymous terms but according to others, systematic is a wider term.

          Systematics: It includes taxonomy and phylogeny. Thus systematic can be defined as study of diversity of organisms and evolutionary relationship among them.

Taxonomical Hierarchy

          Species : Group of individuals with fundamental similarities and can interbreed.Species occupies a key position in classification

          Genus : It comprises a group of related species which has more characters in common in comparison to species of other genera. We can say that genera are aggregates of closely related species. e.g, potato and brinjal are two different species but both belong to the genus Solanum.


          Family: Family is represented by a group of related genera. All the genera of a family resemble one another in certain correlated characters indicating a common ancestry.

For example, three different genera Solanum, Petunia and Datura are placed in the family Solanaceae. In plants the family ends in the suffix – aceae subfamily in – oidae.

Order:   It is an assemblage of families resembling one another. These characters are less similar as compared to many genera put in a family. An order ends in suffix – ales in plants. Different suffixes are used in case of animals.

          Class: It is a taxonomic category made up of one or more related orders.         It ends in suffixes – phyceae, – opsida and – ae in plants. The suffix is not fixed in case of animals.

          Phylum/Division: Phylum or division consists of one to several related classes having similar correlated characters. The division is given the suffix – phyta and the sub division – phytina.

          Kingdom:    In general it includes all organisms that share a set of distinguishing common characters. This is the highest category of biological classification. Plants are put in plant kingdom and animals are put in animal kingdom.

R.H. Whittaker (1969) has recognized five kingdoms of organisms – Monera, Protista, Fungi, Plantae, and Animalia.

System of classification

Three major systems of classification for different animals and plants in use are

—       Artificial System: Given by Theophrastus, Pliny and Carolous Linneaus

—       Natural System:  G. Bentham and Joseph Dalton Hooker.

—       Modern or Phylogenetic System: Adolf Engler (1884-1930) and Karl Prantl

Taxonomical Aids:

Herbarium: A herbarium is defined as a collection of plants that usually have been dried, pressed and preserved on sheets. The sheets are arranged in accordance with any accepted system of classification.


Museums have collection of preserved plants and animals for study and reference. Only those plants are preserved in museum which can not be kept in herbaria, e.g., algae, fungi, mosses, ferns, parts of Gymnosperms, fruits, underground storage organs, etc. Animals are preserved in chemical solutions (mostly formalin) as well as in stuffed and skeleton forms.

The collected specimens are correctly identified and labelled. They are stored and a catalogue is prepared for future reference.


          Botanical Gardens: These specialised gardens have collections of living plants for reference.

Plant species in these gardens are grown for identification purposes and each plant is labelled indicating its botanical/scientific name and its family. The famous botanical gardens are at Kew (England), Indian Botanical Garden, Howrah (India) and at National Botanical Research Institute, Lucknow, (India).


          Zoological Parks: An enclosed place where live wild animals are kept for public exhibition is called a zoological park. Zoological parks provide more natural environment.

A scientific purpose of the zoo is to breed the animals which otherwise are facing a threat in their natural habitat. Due to development activities, they are facing poaching and habitat destruction.

Information about common name and a scientific name is also displayed in the zoological garden park.

In India, there are about 300 zoological parks. A Central Zoo Authority looks after their management in India.


—       Study of live animal types.

—       Sources of tourist attraction.

—       Ex situ conservation through captive breeding of endangered animals.


A scheme for identification of plants and animals is known as Key. The term key refers to a set of alternate characters arranged in such manner that helps in the identification of an organism by selecting or eliminating the characters according to their presence or absence in the organisms. Thus, taxonomic keys are based on the contrasting characters.

Keys are also used for identification of animals.


Other Taxonomic Aids

Other taxonomic aids are monographs, manuals, publications, etc.

Monographs give comprehensive account of complete compilation of available information of any one family or genus at a given time.

Manuals contain compiled information about area covered, keys, description of families, genus and species.

          Publications like periodicals and dictionaries are brought out to provide information about new additions and updated information.




Pick (Ö) the correct choice :

  1. Name the major categories used in taxonomy and arrange them in hierrachial manner.
  2. Which of the following cover the greater number of organisms.

(a)   Phylum or genus                         (b)   Family or phylum

(c)    Family or order                           (d)   Class or phylum

  1. Give a brief history of zoological parks or museums.
  2. Differentiate between

(a)   Taxonomy and systematics

(b)   Herbarium and museums

(c)    Zoological Park and Botanical Park

  1. What is meant by living? Give any three determining features of living.


  1. Why are living organisms classified?
  2. Why are the classification systems changing every now and then?
  3. What different criteria would you choose to classify people that you meet often?
  4. What do we learn from identification of individuals and populations?
  5. Given below is the scientific name of Mango. Identify the correctly written name.

(a) Mangifera Indica

(b) Mangifera indica

  1. Define a taxon. Give some examples of taxa at different hierarchical levels.
  2. Define and understand the following terms:

(i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus

  1. How is key helpful in identification and classification of an organism?
  2. Illustrate the taxonomical hierarchy with suitable example of plant and animal.
  3. Explain the following terms:

(i) Harbarium (ii) Museum (iii) Monograph (iv) Manuals (v) Botanical gardens




  1. Define systematics.
  2. What is taxonomy?
  3. Define a taxon.
  4. Name the three main system of classification.
  5. Who advised the binomial nomenclature?


  1. Name three international codes of binomial nomenclature.
  2. What is speciation?
  3. Name the three fields of systematics.
  4. What is meant by identification of a species?
  5. Differentiate between botanical garden and herbarium.




  1. Give an account of development of systematics.
  2. List the rules of scientific names.
  3. Distinguish between

          (i)  Systematics and Taxonomy

(ii) Species and Taxon

  1. Give a complete classification of cockroach.
  2. Very briefly explain the following :

(i)  Taxon                                       (ii) Categories

(iii)                                                Artificial classification     (iv)          Zoological Park

(v) Biological classification




Pick (Ö) the correct option :

  1. In Planaria the type of reproduction occurs

(a) Fragmentation                          (b) Asexual

(c) Sexual                                      (d) None of the above

  1. The number of species that are known and described range between

(a) 1.7 – 2.0 million                        (b) 1.7 – 1.8 million

(c) 2.8 – 4.8 million                        (d) 1.6 – 1.7 million

  1. Which one is irrelevant for the nomenclature of the organism :

(a) Group name                              (b) Genetic name

(c) Specific epithet                         (d) Both (b) and (c)

  1. Biological name generally does not follows :

(a) Always written in italics font

(b) Generic name starts with capital letters

(c) Specific epithet always written in small letters

(d) Both the words in common name

  1. The process by which anything is grouped into convenient categories based on some easily observable characters is known as

(a) Taxon                                       (b) Classification

(c) Systematics                              (d) Taxonomy




  1. Define the following terms :

(i)    Aestivation                                  (ii)   Placentation

(iii)  Actinomorphic                             (iv)   Zygomorphic

(v)    Superiorovary                              (vi)   Epipetalous stamen

  1. Differentiate between

          (i)    Recemose and cymose

(ii)   Fibrous root and adventitious Root

(iii)  Apocarpous and Syncarpous ovary

  1. Draw a labelled diagram of

          (i)    Gram seed                                  (ii)   V.S. of mainze seed

  1. Define following terms :

          (i)    Pericarp                                      (ii)   Tesla and tegumen

(iii)  Micropyle                                    (iv)   Parthenocarpic fruit

(v)    Apocarpous and syncarpous

  1. State the different parts of carpel and stamen with labelled diagram.
  2. State placentation with labelled diagram.
  3. Explain the structure of ovule with the diagram showing micropyle and chalazal end.



  1. Explain the following terms with example

(i)    Etario of berry                             (ii)   Pome

(iii)  Drupe                                         (iv)   Amphisaraca

  1. Describe modifications of stem with suitable examples.
  2. Take one flower each of the families fabaceae and solanaceae and write its semi-technical description. Also draw their flora diagram after studying them.
  3. Describe various ty pes of placentation and found in flowering plants.
  4. What is a flower? Describe the parts of a typical angiosperm flower.
  5. How does the various leaf modifications help plants?
  6. Define the term inflorescence. Explain the basis for the different types inflorescence in flowering plants.