Question 1

Why are living organisms classified?

Accepted Answer

Living organisms are classified because of the following reasons:(i) Easy identification.(ii)Study of organisms of other places.(iii)Study of fossils(iv)Grouping helps in study of all types of organisms while it is impossible to study individually all of them.(v) It brings out similarities and dissimilarities. They help in knowing relationships among different groups.(vi)Evolution of various taxa can be known.

Question 2

Why are the classification systems changing every now and then?

Accepted Answer

Millions of plants, animals, and microorganisms found on earth, have been identified by the scientists while many new species are still being discovered around the world. Therefore, to classify these newly discovered species, with new characters, new systems of classification have to be devised every now and then. This creates the requirement to change the existing systems of classification.

Question 3

What different criteria would you choose to classify people that you meet often?

Accepted Answer

We can classify people on the basis of their education, profession, hobbies, native place, gender, etc. This is a generalised criteria which when applied to organisms with scientific names needs to meet the criteria of their phyla, order, genus, nature of feeding, etc.

Question 4

What do we learn from identification of individuals and populations?

Accepted Answer

Through the identification of individuals and populations; we can learn about the native place, mother tongue, costumes, food habit, religion, caste, etc.This kind of identification makes easy categorization of them.

Question 5

Given below is the scientific name of Mango. Identify the correctly written name.Mangifera Indica or Mangifera indica?

Accepted Answer

Mangifera indica.When typed, scientific names follows the rules of Bionomial nomenclature. That is, the genus name should start with capital letter and the species name should be completely in small letters. When typed, these should be in italics. If written, they should be underlined separately.

Question 6

Define a taxon. Give some examples of taxa at different hierarchical levels?

Accepted Answer

A particular level of hierarchy in the classification of living beings is called as a taxon. A taxon is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit.For example, the basic level of classification is species, followed by genus, family, order, class, phylum or division, in ascending order. The highest level of classification is known as a kingdom. So each of these categories can be called as a taxon.

Question 7

Can you identify the correct sequence of taxonomical categories?

Accepted Answer

(a) and (c) represent correct sequences of taxonomic categories as the correct hierarchical arrangement of taxonomic categories in ascending order isSpecies → Genus → Family → Order → Class → Phylum → KingdomIn sequence (b), species should have been followed by genus. Therefore, it does not represent the correct sequence.

Question 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.

Accepted Answer

In biological terms, species is the basic unit of taxonomy. It can be defined as a group of similar organisms capable of interbreeding freely among themselves under natural conditions to produce fertile offsprings.Therefore, a group of similar individuals that are reproductively isolated from other groups of individuals forms a species.Species can also be defined as a group of individuals that share the same gene pool.

Question 9

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

Accepted Answer

(i) PhylumThe phylum is second highest unit of classification after Kingdom. It includes one or more related classes of animals. In plants, instead of phylum, the term ‘division’ is used.(ii) ClassThe class is a taxonomic group consisting of one or more related orders. For example, the class, Mammalia, includes many orders like Primata (Man), Carnivora (tiger) etc.(iii) FamilyFamily is a taxonomic group containing one or more related genera, eg., Family hominidae contains apes, monkeys and man. In plants, families are categorized on the basis of vegetative and reproductive features.(iv) OrderOrder is a taxonomic group containing one or more families. For example, the order, carnivora, includes many families.(v) GenusGenus is a taxonomic group including closely related species. For example, the genus, Solanum, includes many species such as nigrum, melongena, tuberosum, etc.

Question 10

How is a key helpful in the identification and classification of an organism?

Accepted Answer

Key is a taxonomical aid that helps in identification of plant and animal species. These keys are based on similarities and dissimilarities in characters, generally in a pair called couplet.Each statement in a taxonomic key is referred to as a lead. For categorizing each taxonomic rank, such as family, genus, species, etc., different keys are used. It is also useful in identification of unknown organisms.Keys are of two types - indented and bracketed keys. Indented key provides a sequence of choices between two or more statements while in bracketed key, a pair of contrasting characters is used.(i) Indented key to identify different species of Rhododendron.1. Leaves evergreen2. leaves densely hairy below, orange or white hair; flowerappears to have separate petals Rhododendron groenlandicum3. Hair absent on leaves, flower has five petals fused in a shallowtube Rhododendron maximus4. Leaves deciduous5. pink flowers with two free petals and three fused petals Rhododendron canadense6. white to pink flowers with all petals fused together(ii) Bracketed key to identify different species of Rhododendron.1. Leaves evergreen - 22. Leaves deciduous - 33. Leaves densely hairy below, orange or white hair; flowerappears to have separate petals Rhododendron groenlandicum4. Hair absent on leaves, flower has five petals fused in shallowtube Rhododendron maximus5. Pink flowers with two free petals and three fused petals Rhododendron canadense6. White to pink flowers with all petals fused together - 4

Question 11

Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.

Accepted Answer

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.Classification of a plant :As an example, let us classify Solanum melongena, (Brinjal).Kingdom – PlantaeDivision – AngiospermaeClass – DicotyledonaeOrder – SolanalesFamily – SolanaceaeGenus – SolanumSpecies – melongenaClassification of an animal : As an example, let us classify man.Kingdom – AnimaliaPhylum – ChordataClass – MammaliaOrder – PrimateFamily – HominidaeGenus – HomoSpecies – Sapiens

Chapter 1 : The Living World