NCERT Solutions - The Living World NEET Notes | EduRev

NCERT Textbooks (Class 6 to Class 12)

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UPSC : NCERT Solutions - The Living World NEET Notes | EduRev

The document NCERT Solutions - The Living World NEET Notes | EduRev is a part of the UPSC Course NCERT Textbooks (Class 6 to Class 12).
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Ques 1: Why are living organisms classified?
Ans: Organisms are classified because of following reasons:

  • There are millions of organisms on Earth. Classification on the basis of similarities and dissimilarities makes the study of the organisms easier.Characteristics of a model organism of a taxon are similar to that of other organisms placed in the same taxon. Therefore, it eliminates the need to study all the organisms.
  • Classification helps in the identification of organisms
  • It helps to establish phylogenetic or ancestral relationship among organisms
  • Classification helps in comparing organisms of same or different taxa.
    NCERT Solutions - The Living World NEET Notes | EduRev

Ques 2: Why are the classification systems changing every now and then?
Ans: Evolution is the major factor responsible for the change in classification systems. Since, evolution still continues, so many different species of plants and animals are added in the already existed biodiversity. These newly discovered plant and animal specimens are then identified, classified and named according to the already existing classification systems. 
Due to evolution, animal and plant species keep on changing, so necessary changes in the already existed classification systems are necessary to place every newly discovered plant and animal in their respective ranks. 

Although the organisms belonging to a particular group have similarities, they also have dissimilarities. Scientists are always reluctant to find new methods of classification that ensures organisms with most similar characteristics are placed in a particular taxon.


Ques 3:  What different criteria would you choose to classify people that you meet often?
Ans: The people we come across in our daily life can be classified on the basis of their gender (male or female), morphological characteristics such as height, weight, colour of their eyes or hair, areas they live in or states they belong to, level of education or favourite subjects or sport etc.
 
Ques 4: What do we learn from identification of individuals and populations?
Ans: The identification of individuals based on their characteristics helps us to know how an individual differs from the other members of the population and in what points it is similar to the population. It also helps us in deriving relationships between individuals of different population. Such relationships help in classifying organisms in their right groups.
Learning the characteristics of the populations aid in the study of that population as well as how it can be related to the other populations. Through this practice, one can establish evolutionary relationships between different populations.

Ques 5: Given below is the scientific name of Mango. Identify the correctly written name.
(i) Mangifera Indica
(ii) Mangifera indica

Ans: In binomial system of nomenclature, the generic name of a species always starts with a capital letter whereas the specific name starts with a small letter.
Both the names

are typed or printed in italics or underlined separately when hand-written.

Therefore, the correct scientific name of Mango is Mangifera indica.
NCERT Solutions - The Living World NEET Notes | EduRev
Fig: Mangifera Indica

Ques 6: Define a taxon. Give some examples of taxa at different hierarchical levels.
Ans: Taxon is a group of organisms of any level in the hierarchical classification, which is based on some common characteristics. 
Example insects represent a class of phylum-Arthropoda. 
All the insects possess common characters of three pairs of jointed legs. 
Examples of taxa are kingdom, phylum or division, class, order, family, genus and species. These taxa form taxonomic hierarchy. 
Example of taxa for human: Phylum — Chordata Class — Mammalia Order — Primata Family — Hominidae Genus — Homo Species — sapiens  

Ques 7:  Can you identify the correct sequence of taxonomical categories?
(a) Species → Order → Phylum → Kingdom
(b) Genus → Species → Order → Kingdom
(c) Species → Genus → Order → Phylum

Ans: The correct hierarchical arrangement of taxonomic categories in ascending order is:
Species → Genus → Family → Order → Class → Phylum → Kingdom 

Therefore, both (a) and (c) represent correct sequences of taxonomic categories. In sequence (b), species should be followed by genus. Therefore, it does not represent the correct sequence.

Ques 8: Try to collect all the currently accepted meanings for the word ‘species’. Discuss with your teacher the meaning of species in case of higher plants and animals on one hand and bacteria on the other hand.
Ans: In biological terms, species is the basic taxonomical rank. It can be defined as a group of similar organisms that are capable of interbreeding under natural conditions to produce fertile offspring.
NCERT Solutions - The Living World NEET Notes | EduRev

Fig: Lion Species

Therefore, a group of similar individuals that are respectively isolated form a species. Species can also be defined as a group of individuals that share the same gene pool.


Ques 9:  Define and understand the following terms:
(i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus

Ans: 
(i) Phylum: It is a principal taxonomic category that comes above class and below kingdom. It is a group or taxon of one or several related classes. In botany, the term Division is used for phylum instead of phylum.
For example, Chordata is a phylum. It contains all those organisms that have or at some point during their development had a notochord.

(ii) Class: It is a taxonomical rank that ranks above Order and below phylum. Class is a group or taxon of one or more related orders.
For example, Mammalia is a class. It contains all those chordate organisms that have characteristic features of mammals like fur, mammary glands, glands, and warm- bloodedness.

(iii) Family: This taxonomical rank contains a group of related genera. It is classified between order and genus.
For example, cat belongs to the family, felidae. This means that all animals that are chordates, mammals and carnivorous having characteristic cat like features would belong to this family. So cats, lions, tigers, leopard all belong to the family felidae.

(iv) Order: It is a taxonomic rank used for classifying organisms below the rank class, and is made up of families sharing a set of similar nature or characters.
For example, Primata is an order which contains all the primates.

(v) Genus: A genus is a taxonomic rank that ranks above species and below family, and is denoted by a capitalized Latin name, e.g. Mangifera. Genus is also known as generic name. It is a group or taxon of one or several related species.


Ques 10: How is a key helpful in the identification and classification of an organism?
Ans: Keys are based on similarities and dissimilarities in characters, generally in a pair called couplet. For example, animals with or without organs. It represents the choice made between two opposite options. This results in acceptance of only one and rejection of the other. 

Each statement in the key is called a lead. Separate taxonomic keys are required for each taxonomic category such as family, genus and species for identification purposes. Keys are generally analytical in nature. 

Flora, manuals, monographs and catalogues are some other means of recording descriptions. They also help in correct identification. Flora contains the actual account of habitat and distribution of plants of a given area. 

These provide the index to the plant species found in a particular area. Manuals are useful in providing information for identification of names of species found in an area. Monographs contain information on any one taxon.

Ques 11: Illustrate the Taxonomical hierarchy with suitable examples of a plant and an animal.
Ans: The arrangement of various taxa in a hierarchical order is called taxonomic hierarchy.
In this hierarchy, species is present at the lowest level whereas kingdom is present at the highest level. 

NCERT Solutions - The Living World NEET Notes | EduRev

A Taxonomic hierarchy

Classification of a plant:
As an example, let us classify Solanum melongena (Brinjal).
1. Kingdom – Plantae
2. Division – Angiospermae
3. Class – Dicotyledonae
4. Order – Solanales
5. Family – Solanaceae
6. Genus – Solanum
7. Species – Melongena

Classification of an animal:
As an example, let us classify Columba livia (Blue rock Dove).
1. Kingdom – Animalia
2. Phylum – Chordata
3. Class – Aves
4. Order – Columbiformes
5. Family – Columbidae
6.Genus – Columba
7. Species – Livia

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