UNIT 1
DIVERSITY IN THE LIVING WORLD
Chapter 1 Biology is the science of life forms and living processes. The living world
The Living World comprises an amazing diversity of living organisms. Early man could
easily perceive the difference between inanimate matter and living
Chapter 2 organisms. Early man deified some of the inanimate matter (wind, sea,
Biological Classification fire etc.) and some among the animals and plants. A common feature of
all such forms of inanimate and animate objects was the sense of awe
Chapter 3 or fear that they evoked. The description of living organisms including
Plant Kingdom human beings began much later in human history. Societies which
indulged in anthropocentric view of biology could register limited
Chapter 4 progress in biological knowledge. Systematic and monumental
Animal Kingdom description of life forms brought in, out of necessity, detailed systems
of identification, nomenclature and classification. The biggest spin off
of such studies was the recognition of the sharing of similarities among
living organisms both horizontally and vertically. That all present day
living organisms are related to each other and also to all organisms
that ever lived on this earth, was a revelation which humbled man and
led to cultural movements for conservation of biodiversity. In the
following chapters of this unit, you will get a description, including
classification, of animals and plants from a taxonomist’s perspective.
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THE LIVING WORLD 9
S UMMARY
The living world is rich in variety. Millions of plants and animals have been
identified and described but a large number still remains unknown. The
very range of organisms in terms of size, colour, habitat, physiological and
morphological features make us seek the defining characteristics of living
organisms. In order to facilitate the study of kinds and diversity of organisms,
biologists have evolved certain rules and principles for identification,
nomenclature and classification of organisms. The branch of knowledge
dealing with these aspects is referred to as taxonomy. The taxonomic studies
of various species of plants and animals are useful in agriculture, forestry,
industry and in general for knowing our bio-resources and their diversity.
The basics of taxonomy like identification, naming and classification of
organisms are universally evolved under international codes. Based on the
resemblances and distinct differences, each organism is identified and
assigned a correct scientific/biological name comprising two words as per
the binomial system of nomenclature. An organism represents/occupies a
place or position in the system of classification. There are many categories/
ranks and are generally referred to as taxonomic categories or taxa. All the
categories constitute a taxonomic hierarchy.
E XERCISES
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:
(i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus
10. Illustrate the taxonomical hierarchy with suitable examples of a plant
and an animal.
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