Diversity In Living Organisms Basis Of Classification Essay

Class 9 Science Notes pdf Chapter 7 DIVERSITY IN LIVING ORGANISMS

1. Each organism is different from all other organisms.

2. In this activity, we decide which characteristics (we can run, but the Banyan tree can’t run is a characteristic) are important in forming the desired category.

3. Greek thinker Aristotle classified animals according to whether they lived on land, in water or in air. This classification is a landmark in ideology, but has limitations. For example, animals that live in the sea include Corals, Whales, Octopus, Starfish, and Shark. In fact they are different from each other.

4. Classification and Evolution: organisms are classified based on body design, hierarchy in developing, relation to evolution. Charles Darwin first described the idea of evolution in 1859 in his book “ The Origin of Species”

5. The Biologists, such as Haeckel, Whittaker & Carl Woese tried to classify all living organisms into broad Kingdoms. The Whittaker proposed five kingdoms: Monera, Protista, Fungi, Plantae and Animalia. Carl Woese introduced by dividing Monera into Archaebacteria and Eubacteria.

6. Hierarchy of Classification :

7. Monera: They have unicellular, Prokaryotic organisms (do not have defined nucleus or organelles). The cell wall may or may not present. The mode of nutrition is autotrophic (synthesizing food on their own) (or)heterotrophic (getting food from environment). Ex. Bacteria, Anabaena. ( (Please refer to Fig. 7.1 Monera NCERT Book Page-83)

8. Protista: They have unicellular eukaryotic organisms (do have well defined nucleus or organelles). The body is covered by cilia, flagella for locomotion. The mode of nutrition is autotrophicorheterotrophic. Ex. Diatoms, protozoans.(Please refer to Fig. 7.2 NCERT Book Page-84)

9. Fungi: These are multi-cellular eukaryotic organisms with cell wall, made up of Chitin. They do not perform Photosynthesis (heterotrophic), Saprophytic (derive nutrition from decaying material). Ex. Aspergillus, Penicillium, Mushroom, Rhizopus. The fungi living with algae forms Lichen (Symbiotic Association) .(Please refer to Fig. 7.3 NCERT Book Page-84).

10. Plantae: These are multi-cellular eukaryotic organisms with cell wall, made up of Cellulose. Able to perform photosynthesis (autotrophic). Ex. Rice, wheat.

11. Animalia: These are multi-cellular eukaryotic organisms without cell wall. They are not able to perform photosynthesis (heterotrophic).

Ex Human beings, Peacock.(Please refer to Fig. 7.4 NCERT Book Page-85).


1. The kingdom Plantae is further classified as Thallophyta, Bryophyta, Pteridophyta, Gymnosperms, Angiosperms .

2.Thallophyta: The plants do not have well defined body design, commonly called as” Algae”, mostly aquatic. Ex. Spirogyra, Ulothrix. (Please refer to Fig. 7.5 NCERT Book Page-86).

These are commonly called as the “Amphibians of Kingdom”. The plant body is differentiated into roots like, stem like and leaf like structures. No specialized tissues for the conduction of water and food.Ex. Marchantia, Funaria. (Please refer to Fig. 7.6 NCERT Book Page-86).

4.Pteridophyta: These are commonly called as the “First vascular land plants ”. The plant body is differentiated into root, stem and leaf. Specialized tissues for the conduction of water and food are developed in these plants. The reproductive organs are inconspicuous. Ex. Marsilea, Fern. (Please refer to Fig. 7.7 NCERT Book Page-87).

Special Note: The reproductive organs are inconspicuous in Thallophyta, Bryophyta, Pteridophyta are can’t develop seeds. They are together called as” Cryptogamae (Non- Flowering Plants)”. The plants with well differentiated reproductive organs and that ultimately make seeds are called” Phanerogams (Flowering Plants)”. This group is further classified Gymnosperms (Bear naked Seeds) &Angiosperms (Bears seeds inside Fruit).

5. Gymnosperms: These are commonly called as “Naked seed bearing plants”. They areusually perennial, evergreen and woody. Ex. Pinus, Cycas (Please refer to Fig. 7.8 NCERT Book Page-87).

6. Angiosperms: These are commonly called as “Enclosed seed bearing plants”. Plants with seeds having a single cotyledon are called as” Monocotyledons or Monocots”. Plants with seeds having two cotyledons are called as “Dicots”. Ex. Ipomoea, Paphiopedium.

(Please refer to Fig 7.9 &. 7.10 NCERT Book Page-87 ;Fig. 7.11 Page-88).

These are Eukaryote, multicultural and hetero-tropic

They are further classified as Non- Chordates( Porifera, Coelenterata, Platyhelminthes , Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata) and Chordates { Protochordata, Vertebrata ( Pisces, Amphibians, Reptilia, Aves, Mammalia)} .

I.Non- Chordates

1. Porifera: The word Porifera” means organisms with holes”. The canal system helps in circulating water, food, oxygen. They are non-motile with cellular level of organization and mainly marine organisms with hard outer coat called as Skeleton. They are commonly called as Sponges. Ex. Spongilla, Sycon

( Please refer Fig. 7.12, NCERT Text Book Page-

2. Coelenterata: The wordCoelenterata” means organisms with body cavity calledCoelenteron” . They are radially symmetrical, Diploblastic ( two layers of cells), commonly called as Cnidarians ( Stinging cells for protection are present in the body). Ex. Hydra, Sea Anemone

(Please refer Fig. 7.13, NCERT Text Book Page- 89).

3. Platyhelminthes: The word Platyhelminthes means organisms with flatworms ( dorsocentrally flattened)”.They are bilaterally symmetrical Triploblastic ( three layers ofcells ), either free-living or parasitic. No true Coelom is present - Acoelomates. Ex. Planaria( Free living) , Tape worm( Parasitic)

( Please refer Fig. 7.14, NCERT Text Book Page- 90).

4. Nematoda: The word Nematoda“means organisms with roundworms”. They are bilaterally symmetrical Triploblastic ( three layers of cells ), familiar with parasitic worms. The false Coelom is called as Pseudocoelome. Ex. Ascaris, Wuchereria (Filarial worm causes elephantiasis).

( Please refer Fig. 7.15, NCERT Text Book Page- 90).

The word Annelida “ means organisms with metameric-segmented”. They are bilaterally symmetrical Triploblastic(three layers of cells) with closed circulatory system, familiar with earth worms. The Coelom is called as true Coelom. Ex. Neris, Earth worm, Leech

(Please refer Fig. 7.16, NCERT Text Book Page- 90).

6. Arthropoda: The word Arthropoda “means organisms with jointed legs” They are bilaterally symmetrical Triploblastic(three layers of cells ), familiar with cockroaches. The Coelom is blood filled called as Haemo Coelom. Ex. Prawn, Scorpion, Housefly

(Please refer Fig. 7.17, NCERT Text Book Page- 91)

7.Mollusca: The word Mollusca “means organisms with soft body” They are bilaterally symmetrical, Triploblastic(three layers of cells), familiar with Octopus, Pila. Foot is for moving, kidney like organ for excretion, with open circulatory system. Ex. Unio, chiton

( Please refer Fig. 7.18, NCERT Text Book Page- 91)

8. Echinodermata: The word Echinodermata “means organisms with spiny skinned”. Exoskeleton is with calcium carbonate. They are radially symmetrical Triploblastic ( three layers of cells ) with coelomic cavity, familiar with Star fish. They are exclusively free-living marine animals. Ex. Sea Cucumber, Feather Star

(Please refer Fig. 7.19, NCERT Text Book Page- 91).

They are further classified as two major groups such as Protochordata& Vertebrata

Notochord present in at least larval forms, but very rudimentary. It is a rod like supporting structure, runs along with nervous tissue from the gut of animal. They
are bilaterally symmetrical, triploblastc(three layers of cells) with a Coelom, familiar with Amphioxus. Ex. Balanoglossus

(Please refer Fig. 7.20, NCERT Text Book Page- 92).

Notochord is replaced by vertebral column and internal skeleton. They are bilaterally symmetrical, triploblastic, coelomic and segmented having paired gill pouches. Vertebrates are grouped into five classes.

1. Pisces: These are commonly called as “fishes”, exclusively aquatic. Body is streamlined and a tail for locomotion. Gills for respiration, heart is two chambered, cold blooded, skin is covered with scales, plates. They are cold-blooded animals. Skeleton of bone ( Rohu) / cartilage( Shark). They lay eggs. Ex. Lion Fish, Dog Fish(Please refer Fig. 7.21, NCERT Text Book Page- 92).

2. Amphibians:
These are commonly called as “Amphibians” because they can live on land and in water”. Body is streamlined and a webbed foot/ foot for locomotion. Gills or lungs or skin for respiration, heart is three chambered, cold blooded, skin is lack of scales, plates. They are cold-blooded animals. They lay eggs. Ex. Rana, Hyla

(Please refer Fig. 7.22, NCERT Text Book Page- 93).

3. Reptilia:
These are commonly called as “Reptilians”. A lung for respiration, heart is three chambered (Crocodile heart is four chambered), skin have scales. They are cold-blooded animals. They lay eggs. Ex. Snakes, Turtles

(Please refer Fig. 7.23, NCERT Text Book Page- 93).

4. Aves :These are commonly called as “Birds”. A lung for respiration, heart is four chambered, fore limbs are modified for flight, skin has feathers. They are warm-blooded animals. They lay eggs. Ex. Ostrich (Flightless Bird), Pigeon, Sparrow

(Please refer Fig. 7.24, NCERT Text Book Page- 94).

5. Mammalia:
These are commonly called as “animals with mammary glands for producing milk to nourish their young ones”. A lung for respiration, heart is four chambered, skin has hairs, sweat or oil glands. They are warm-blooded animals. They lay eggs (Platypus, Echidna), give birth to young ones poorly developed (Kangaroo) & give birth to developed young ones (Human beings). Ex. Lion, Whale, Bat

(Please refer Fig. 7.25, NCERT Text Book Page- 94& Fig.7.26, classification of Animals, Page- 95).


NOMENCLATURE: The system of scientific naming or nomenclature was introduced by Carolus Linnaeus. It is unique to identify in the world. We limit ourselves to writing the names of the Genus and Species of that particular organism. The world over, it has been agreed that both these names will be used in Latin forms.When printed is given in italics and when written by hand, the Genus and Species name have to be underlined separately.

Ex. Ostrich (Common name): Struthiocamelus(scientific name with two parts namely the Genus and Species).


1. What is the book written by Charles Darwin?...................... (The Origin of Species)
2. Who proposed the five kingdoms such as, Monera, Protista, Fungi, Plantae and Animalia? (Whittaker)
3.Monera members areunicellular, Prokaryotic organisms, mention TRUE/ FALSE ….. (TRUE)
4. The Diatoms belongs to the kingdom................. ( Protista)
5. TheAnabaena belongs to the kingdom …………………(Monera)
6……………………. are commonly called as the“Amphibians of Plant Kingdom”.( Bryophyta)
7. The warm-blooded animals with fore limbs modified for flight, skin has feathers are called as………………….. (Aves/Birds)
8. Write the four salient features of Reptiles.
9.Compare the Pisces and Amphibians.
10..Write the five salient features of Mammalia, give two examples.


1. Questions 1-5 (1 Mark each)

2. Questions 6-10 ( 2 Mark each)

3. Questions 11-15 (3Mark each)

4.. Questions 16-17 (5Mark each)

Q.1 Anabaena is member of the Phylum…………………………………
Q.2 Aspergillum is a member of the Phylum……………………………..
Q.3 Define the term Autotrophic mode of nutrition………………….
Q.4 The fungus living with algae is called as ……………………………..
Q.5 Name the scientist who has divided the Monera into two sub-groups…………………..
Q.6 Draw and label Paramecium.
Q.7 Distinguish the meaning of terms Gymnosperms and Angiosperms.
Q.8 What is Pseudocoelome? Give one example of it.
Q.9 What is Haemocoelome? Give one example of it.
Q.10 Write two salient features of mammalian group.
Q.11 What is the basis of nomenclature of organisms, give the scientific name of Ostrich.
Q.12 Give three salient features of Amphibia.
Q.13 Mention three features of Chordates.
Q.14. Draw and label Balanoglossus.
Q.15 Give two salient features of Aves and mention one example of a flightless bird.
Q.16 Write about the Hierarchy of Classification- Groups and mention basic unit of
classification.Q.17 Give the salient features of Bryophytes and draw the diagram of Funaria.

In this tutorial you will be learning about the Linnaean system of classification used in the biological sciences to describe and categorize all living things.  The focus is on finding out how humans fit within this system.  In addition, you will discover part of the great diversity of life forms and come to understand why some animals are considered to be close to us in their evolutionary history.

How many species are there?

This is not an easy question to answer.  About 1.8 million have been given scientific names.  Thousands more are added to the list every year.  Over the last half century, scientific estimates of the total number of living specieshave ranged from 3 to 100 million.  The most recent methodical survey indicates that it is likely to beclose to 9 million, with 6.5 million of them living on the land and 2.2 million in the oceans.  Tropical forests and deep ocean areas very likely hold the highest number of still unknown species.  However, we may never know how many there are because it is probable thatmost will become extinct before being discovered and described.

The tremendous diversity in life today is not new to our planet.  The noted paleontologist Stephen Jay Gould estimated that 99% of all plant and animal species that have existed have already become extinct with most leaving no fossils.  It is also humbling to realize that humans and other large animals are freakishly rare life forms, given that 99% of all known animal species are smaller than bumble bees.

Why should we be interested in
learning about the diversity of life?

In order to fully understand our own biological evolution, we need to be aware that humans are animals and that we have close relatives in the animal kingdom.  Grasping the comparative evolutionary distances between different species is important to this understanding.  In addition, it is interesting to learn about other kinds of creatures.

When did scientists begin classifying living things?

Before the advent of modern, genetically based evolutionary studies, European and American biology consisted primarily of taxonomy, or classification of organisms into different categories based on their physical characteristics and presumed natural relationship.  The leading naturalists of the 18th and 19th centuries spent their lives identifying and naming newly discovered plants and animals.  However, few of them asked what accounted for the patterns of similarities and differences between the organisms.  This basically nonspeculative approach is not surprising since most naturalists two centuries ago held the view that plants and animals (including humans) had been created in their present form and that they have remained unchanged.  As a result, it made no sense to ask how organisms have evolved through time.  Similarly, it was inconceivable that two animals or plants may have had a common ancestor or that extinct species may have been ancestors of modern ones.

Carolus Linnaeus

One of the most important 18th century naturalists was a Swedish botanist and medical doctor named Karl von Linn�.  He wrote 180 books mainly describing plant species in extreme detail.  Since his published writings were mostly in Latin, he is known to the scientific world today as Carolus Linnaeus, which is the Latinized form he chose for his name.

In 1735, Linnaeus published an influential book entitled Systema Naturae in which he outlined his scheme for classifying all known and yet to be discovered organisms according to the greater or lesser extent of their similarities.  This Linnaean system of classification was widely accepted by the early 19th century and is still the basic framework for all taxonomy in the biological sciences today.

The Linnaean system uses two Latin name categories, genus and species, to designate each type of organism.  A genus is a higher level category that includes one or more species under it.  Such a dual level designation is referred to as a binomial nomenclature or binomen (literally "two names" in Latin).  For example, Linnaeus described modern humans in his system with the binomen Homo sapiens, or "man who is wise".  Homo is our genus and sapiens is our species.

  species     species     species     species  

Linnaeus also created higher, more inclusive classification categories.  For instance, he placed all monkeys and apes along with humans into the order Primates.  His use of the word Primates (from the Latin primus meaning "first") reflects the human centered world view of Western science during the 18th century.  It implied that humans were "created" first.  However, it also indicated that people are animals.

  species     species     species     species     species     species     species     species  

Charles Darwin

While the form of the Linnaean classification system remains substantially the same, the reasoning behind it has undergone considerable change.  For Linnaeus and his contemporaries, taxonomy served to rationally demonstrate the unchanging order inherent in Biblical creation and was an end in itself.  From this perspective, spending a life dedicated to precisely describing and naming organisms was a religious act because it was revealing the great complexity of life created by God.

This static view of nature was overturned in science by the middle of the 19th century by a small number of radical naturalists, most notably Charles Darwin.  He provided conclusive evidence that evolution of life forms has occurred.  In addition, he proposed natural selection as the mechanism responsible for these changes.

Late in his life, Linnaeus also began to have some doubts about species being unchanging.  Crossbreeding resulting in new varieties of plants suggested to him that life forms could change somewhat.  However, he stopped short of accepting the evolution of one species into another.

Why do we classify living things today?

Since Darwin's time, biological classification has come to be understood as reflecting evolutionary distances and relationships between organisms.  The creatures of our time have had common ancestors in the past.  In a very real sense, they are members of the same family tree.

The great diversity of life is largely a result of branching evolution or adaptive radiation.  This is the diversification of a species into different lines as they adapt to new ecological niches and ultimately evolve into distinct species.  Natural selection is the principal mechanism driving adaptive radiation.


Copyright � 1998-2012 by Dennis O'Neil. All rights reserved.
illustration credits

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