Download The Living World

The Living World
Question: 1 - Why are living organisms classified?
Answer: The diversity of living beings makes it a challenge to systematically study them.
Classification is a helpful tool to categorize them based on certain common characteristics.
This enables scientists to study them in a more systematic way. The study of living beings
is essential for the benefit of humankind. Discovery of new medicines, and better yielding
crop varieties can be made possible only by systematic study of living beings. Moreover,
environmental protection also makes it necessary for us to study the living beings in a
systematic way.
Question 2 - Why are the classification systems changing every now and then?
Answer: In any branch of science nothing is written in concrete. Theories keep on
changing as more relevant and correct theory are being discovered. In case of living beings
certain species become extinct and some new species is being formed in every era. This
process of addition and deletion of species necessitates the continuous change of the
classification system.
Question 3. What different criteria would you choose to classify people that you meet
often?
Answer: In our day to day life we categorize people based on following criteria:
1. Level of education
2. Profession
3. Height and skin colour
4. Native Place
5. Sex
6. Hobbies
7. Nature
Question 4. What do we learn from identification of individuals and populations?
Answer: In a diverse country like India we can learn following things from identification of
individuals and population:
1. Native Place.
2. Mother Tongue
3. Costumes
4. Cuisine
3. Religion
4. Caste
5. Socio-economic Background
Question 5. Given below is the scientific name of Mango. Identify the correctly
written name.
Mangifera Indica
Mangifera indica
Answer: Mangifera indica
Question 6. Define a taxon. Give some examples of taxa at different hierarchical
levels.
Answer: A taxon is a particular level of hierarchy in the system of classification of living
beings. The following figure gives taxa at different hierarchical levels:
Question 7. Can you specify the correct sequence of taxonomic categories?
(a) Species , Order, Phylum, Kingdom
(b) Genus, Species, Order, Kingdom
(c) Species, Genus, Order, Phylum
Answer: As clear from the table in previous answer (a) and (c) is showing the correct order.
Question 8. Define the following terms:
(a) Phylum (b) Class (c) Family (d) Order (e) Genus
Answer: (a) Phylum: Phylum comes next to Kingdom in the taxonomical hierarchy. All
broad characteristics of an animal or plant are defined in a phylum. For example all
chordates have a notochord and gill at some stage of life cycle. Similarly all arthopods have
jointed legs made of chitin.
(b) Class: A class includes related orders. Class defines more detailed characters other
than broad architecture. For example all mammals have mammary glands to secrete milk,
have hairy body. All birds or aves have pneumatic bones to assist in flying. The common
character among them is the presence of notochord thereby making them members of the
same phylum.
(c) Family: Family, has a group of related genera with still less number of similarities as
compared to genus and species. Families are characterised on the basis of both vegetative
and reproductive features of plant species. Among plants for example, three different
genera Solanum, Petunia and Datura are placed in the family Solanaceae. Among animals
for example, genus Panthera, comprising lion, tiger, leopard is put along with genus, Felis
(cats) in the family Felidae. Similarly, if you observe the features of a cat and a dog, you will
find some similarities and some differences as well. They are separated into two different
families – Felidae and Cancidae, respectively.
(d) Order: Order further zeroes down on characteristics and includes related genus. For
example humans and monkeys belong to the order primates. Both humans and monkeys
can use their hands to manipulate objects and can walk on their hind legs.
(e) Genus: 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. For example, potato, tomato and brinjal are three different species but all
belong to the genus Solanum. Lion (Panthera leo), leopard (P. pardus) and tiger (P. tigris)
with several common features, are all species of the genus Panthera. This genus differs
from another genus Felis which includes cats.
Question 9. How is a key helpful in the identification and classification of an
organism?
Answer: Keys are pairs of two contrasting characters. Selection of one character leads to
rejection of another character while identifying a particular species or genera or family and
so on. For example presence or absence of hair on body can give aclue if an animal
belongs to mammalian or not.
Question 10. Illustrate the taxonomical hierarchy with suitable examples of a plant
and an animal.
Answer: Taxonomical Hierarchy
1. Man
Phylum: Chordata
Class: Mammalia
Order: Primata
Family: Hominidae
Genus: Homo
Species: Homo sapiens
2. Mango
Phylum: Angiosperm
Class: Dicotyledons
Order: Sapindales
Family: Anacardiaceae
Genus: Mangifera
Species: Mangifera indica