Biology Class 9 Notes- Chapter 3

CLASSIFICATION OF LIVING ORGANISMS

BIODIVERSITY

Biodiversity comprises all the millions of different species that live on our planet, as well as the genetic differences within species. It also refers to the multitude of different ecosystems in which species form unique communities, interacting with one another and the air, water and soil.

QNo.1: What is taxonomy?

Ans. Taxonomy (Taxis= arrangement, Nomos= law) can be defined as branch of biology which deals with the description, identification, classification and naming of living organisms according to structural similarities and differences.

QNo.2:  What are the bases of classification?

Ans. Following are the bases of classification of living organisms:

1.      Homologous structures: These are those structures that are similar because of their common origin.

2.      Biochemistry: Particularly bacteria are classified on the basis of chemical substances which they contain.

3.      Cytology: Organisms are also classified on the basis of cytological structures. For example chromosome number.

4.      Genetics: Relevant base sequence in DNA is an important tool for classifying organisms.

QNo.3: What are the units of classification?

Ans. There are seven units of classification of living organisms:

1.      Species: It is the basic unit of classification. Species is defined as a group of common individuals which can inter breed with each other and can produce fertile offspring.

2.      Genera (Singular Genus): Closely related species are called genus.

3.      Family: Closely related genera are called family.

4.      Order: Closely related families are called order.

5.      Class: Closely related orders are called class.

6.      Division/ Phylum: Closely related classes are called division/ phylum.

7.      Kingdom: Closely related divisions/ phylums are called kingdom.

QNo.4: What is binomial nomenclature?

Ans. Carl Linnaeus (1707- 1778) adopted the binomial nomenclature system for naming organisms. The rules for giving a scientific name are:

1.      Each species is given a scientific name consisting of two words.

2.      First word refers to genus and begins with capital letter

3.      Second word refers to specific name and begins with small letter.

4.      Scientific name is always written in italic or underlined.

For Example scientific name of Mustard plant is Brassica campestris.

QNo.5: Write classification of some common organisms.

Ans. Classification of some common organisms:

1.      Mustard Plant

Common name	Mustard
Kingdom	Plantae
Division	Tracheophyta
Class	Dicotyledonae
Order	Capparales
Family	Brassicaceae
Genus	Brassica
Species	Campestris
Scientific name	Brassica campestris

2.      Man

Common name	Man
Kingdom	Animalia
Phylum	Chordata
Class	Mammalia
Order	Primat
Family	Hominidae
Genus	Homo
Species	Sapiens
Scientific name	Homo sapiens

3.      Frog

Common name	Man
Kingdom	Animalia
Phylum	Chordata
Class	Amphibia
Order	Salientia (Anura)
Family	Ranidae
Genus	Rana
Species	Tigrina
Scientific name	Rana tigrina

QNo.6: Describe major groups of living organisms.

Ans.

v  Previously living things were classified into two kingdoms namely Plant Kingdom and Animal Kingdom on the basis of absence and presence of cell wall and chlorophyll.

v  But a larger number of living organisms did not fit into categories under plant and animal kingdoms.

v  To solve this problem, H. Whittaker suggested a five kingdom system in 1969.

QNo.7: Describe the H. Whittaker’s five kingdom system.

Ans. H. Whittaker (1969) suggested a five kingdom system.

1.      Kingdom Monera: Prokaryotes which feed by varieties of different methods.

2.      Kingdom Protista: Unicellular eukaryotes feed by varieties of different methods.

3.      Kingdom Fungi: Multicellular eukaryotes which feed heterotrophically by absorption.

4.      Kingdom Plantae: Multicellular eukaryotes which feed photosynthetically.

5.      Kingdom Animalia: Multicellular eukaryotes which feed heterotrophically by ingestion.

QNo.8: What were the draw backs in Whittaker’s scheme?

 Ans. Following are the draw backs in Whittaker’s scheme:

1.      Kingdom Protista contains all unicellular organisms, including protozoan which were formerly regarded as animals and unicellular algae which was formerly regarded as plants.

2.      Algae was present into two separate kingdoms, the kingdom  protista and the plant kingdom.

QNo.9: Describe the five kingdom system proposed by Margulis and Schwartz in 1989.

Ans. Two biologists Margulis and Schwartz put forward a modification of Whittaker’s scheme in 1989.

1.      Kingdom Prokaryotae: It includes all the prokaryotes e.g. bacteria and cyanobacteria etc.

2.       Kingdom Protoctista: It includes all the eukaryotic organisms which are no longer classified as animals, plants or fungi. E.g. euglena paramecium, chlamydomonas, yeast etc.

3.      Kingdom Fungi: It includes non-chlorophyllous, multicellular, eukaryotic organisms having cell-wall, e.g. Agaricus (Mushroom) etc.

4.      Kingdom Plantae: It includes chlorophylous, multicellular, eukaryotic organisms having and embryonic development, e.g. Apple, Sunflower etc.

5.      Kingdom Animalia: It includes non-chlorophyllous, multicellular, eukaryotic organisms, having no cell-wall, e.g. hydra, earthworm, man etc.