Question

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.
Mangifera Indica
Mangifera indica
6. Define a taxon. Give some examples of taxa at different hierarchical levels.
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
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,
9. Define and understand the following terms:
(1) Phylum (ii) Class (iii) Family (iv) Order (v) Genus
10. How is a key helpful in the identification and classification of an organism?
11. Illustrate the taxonomical hierarchy with suitable examples of a plant and an
animal.​

Answer 1

Answer:

1) Living organisms are classified of the following reasons:

• It helps us understand the diversity of living organisms. It helps us to understand the diversity present in them.
• It is necessary to understand the interrelationships among different groups of organisms.
• The science of classification is the base for other sciences such as bio-geography, ecology and ethology.

2) The classifications systems are not changing now. But yes, the classification systems changed a lot in history. This is because the earlier bases for classification were not enough to describe the existing diversity between organisms. For example, Aristotle's classification was on the basis of where the organisms lived. In the 18th century, the classification was made by Carl von Linnaeus in his book, System Nature on the basis of sexual characters of organisms (like: the number and arrangement of stamens and carpels in a flower of a plant). However, this also could not fully explain the underlying diversity. In the 19th century, the basis of classification became natural. They were based on overall similarities and differences between organisms. Charles Darwin further revolutionized classification systems, and changing and changing, it came to its present level. Today, with the help of available resources and technology, diversity has been found at the cellular levels, hence making the current classification the quantum of itself. But, still, as science advances, more and more parameters of diversity might be discovered, paving ways for a broader base of classification.

3) I would classify the people I meet on the following criteria:

• behavior
• geographical location (address)
• family members
• relatives
• friends etc.

4) When we do an identification of individuals and populations, based on suitable characteristics, it helps us to know about their similarities and differences with respect to a similar group (individuals and populations). It also helps us derive relationships.

5) Mangifera indica

6) A unit or a category of classification (taxonomy) is called a taxon.

   The examples of taxa at different hierarchical levels are kingdom, phylum, class, order and family.

7) Species => Order => Phylum => Kingdom

8) 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.

9) Phylum: A Phylum is a taxon that is higher in rank to class, but lower in rank than a kingdom. It's equivalent in botany is Division. It includes many related classes together.

Class: A Class is a taxon that is higher in rank than Order, but below Phylum. It contains many related Orders together.

Family: A Family is a taxon that is above Genus, but below Order. It has many many related genera.

Order: An Order is a taxon (taxonomical unit) that comes after the Family, and below the Class. It consists of many related Families together.

Genus: A genus is a taxon that is above the species, but comes below the Family. A genus contains various related species.

10) (a) Key is a taxonomic aid for identification of unknown organism based on similarities and dissimilarities.

(b) It is based on couplet (pair of contrasting characters).

These are analytical in nature and separate keys are needed for every taxonomic category like genus, order, family, phylum and species.

11) Brinjal (Solanum melongina):

Kingdom – Plantae

Division – Angiospermae

Class – Dicotyledonae

Order – Solanales

Family – Solanaceae

Genus – Solanum

Species – melongena

Human (Homo sapiens):

As an example, let us classify man.

Kingdom – Animalia

Phylum – Chordata

Class – Mammalia

Order – Primate

Family – Hominidae

Genus – Homo

Species – sapiens