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Diversity in Living Organism CBSE Notes for Class 9

Important Topics of Diversity in Living organism:

  • Taxonomy
  • Importance of classification
  • Base of classification
  • Classification and evolution
  • The Hierarchy of Classification- Groups
  • Monera, Protista, Fungi, Plantae, Animalia, Plantae
  • Plantae categories – Thallophyta, Bryophyta, Ptreridophyta, Angiosperms, Gymnosperms
  • Animalia categories – Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata, Protochordata, Vertibrata
  • Fungi Categories – Saprophytic, Parasitic, Symbiotic
  • Grouping of Vertebrates – Cyclostomata, Pisces, Amphibia, Reptila, Aves, Mammalia
  • Nomenclature

Introduction to diversity in living organism:

  • We are already familiar with our surrounding which contains a variety of living organisms.
  • These different varieties of organisms existing on this earth is said to be
  • Biologists have grouped all the living organisms on the basis of the similarities and the differences into different categories.
  • A total of 2 million species exist on this earth which are different from each other in either way round.
  • To study the features and structures of organisms a different branch of biology is assigned and is called Taxonomy.
  • Taxonomy is the branch of Biology which deals with the identification, classification and nomenclature of living organisms.
  • Carolus Linnaeus is known as the father of taxonomy.


  • Categorizing living organisms into different groups on the basis of their properties are said to be
  • Aristotle (The Greek Thinker) classified living organisms on the basis of their habitat.
  • He classified organisms as land, water or air living animals.
  • But we see that many organisms from same habitat are different from each other.
  • Therefore the classification of organisms on the basis of hierarchy.

Importance of classification:

  • It makes easy the study of organisms.
  • It helps us to understand the evolution of organisms.
  • By it, we can identify the relationship between different types of organisms.
  • We can also explain the fact that different organisms residing at different geographic location.

What is Evolution?

  • Evolution is the change in the inheritable characteristics of a species after several successive generations of living organisms.
  • Charles Darwin gave the theory of evolution and considered natural selection as the prime factor.


Classification of organisms in kingdoms:

Different biologists contributed their idea on classification of organisms. They called it kingdom system of classification. The basis of classification was the characteristics of organisms. Organisms having similar features were kept in specific kingdoms.

Two kingdom classification by Carolus Linnaeus:

In 1758, Carolus Linnaeus proposed classification of all living organisms into two kingdoms. They are:

  • Plants
  • Animals

two kingdom system of classification

Five Kingdom classification by H Whittaker:

In 1959, A famous Biologist classified all living organisms into five kingdoms. They are:

  • Monera
  • Protista
  • Fungi
  • Plantae
  • Animalia

Five kingdom system of classification

Classification of Kingdom Monera:

Further, in 1977, Carl Woese further classified Kingdom Monera into two groups. They are:

  • Archaebacteria
  • Eubacteria

Classification hierarchy:

  • Hierarchy is the classification of living organisms on the basis of their taxonomy.
  • The level of complexity and their characteristics is considered this type of arrangement.
  • Kingdom occupies the top level whereas species are at the bottom.
  • Hierarchy best defines diversity in living organisms.

Order of classification (taxonomy hierarchy):

  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
Hierarchy levels of classification/order
Fig – Order of classification

On the basis of a hierarchy of characteristics, organisms are grouped into smaller and smaller groups, we came to the basic level i.e. species.


  • The living organisms which have similar characteristics, up to the extent that they can breed and perpetuate among themselves are said to be in same species.

Characteristics considered for classification of organisms:

1. Cellular organization:

On the basis of Cellular organization Cells are of two types:

  • Prokaryotic Cells
  • Eukaryotic Cells

Difference between prokaryotic and Eukaryotic cell:

Prokaryotic Cells

Eukaryotic Cells

Cells have no definite nucleus.

Cells have a definite nucleus.

These cells do not contain
membrane-bound organelles.

These cells contain membrane
-bound organelles like the nucleus.

Prokaryotes carry simple
Cell division.

Eukaryotes undergoes tough
cell division.

prokaryotic cells

Eukaryotic cells

2. Body Organization:

On the basis of body organization, organisms are of two types:

  • Unicellular Organisms
  • Multicellular Organism

Unicellular Organisms

Multicellular Organism

Organisms composed of
single cells.

Organisms composed of
a large number of cells.

Every life activities are
carried out by that cell.

A number of cells involved
in doing different activities.

Amoeba unicellular organism

Multicellular organism

3. How organisms obtain their food?

On the basis of their mode of nutrition, Living organisms are categorized into two groups. They are:

  • Autotrophs
  • Heterotrophs



These organisms prepare
their own food.

These organisms depend on
other for their food.

Autotrophs need sunlight to
prepare their food.

Heterotrophs eat autotrophs
and other heterotrophs.

autotrophs classification on the basis of food obtaining mode

heterotrophs animal

Five-kingdom system of classification:

H. Whittaker grouped living organisms into 5 Kingdoms. Diversity in living organism notes contains all the kingdoms as:

1. Monera Kingdom:

  • They are unicellular prokaryotes.
  • Some possess autotrophic mode (blue-green algae) while the other heterotrophic.
  • Some have cell walls other lacks it.
  • Bacteria, Blue-green algae etc. are examples of Monera.
monera kingdom
Fig. Monera kingdom

Archaea Kingdom:

  • Carl Woese further grouped Kingdom Monera into two categories, which are archaebacteria and Eubacteria.
  • These are microbes (bacteria) which can survive even in harsh conditions.
  • They are also said to be extremophiles as it can survive in high temperatures.
  • These do not have cell walls.
  • Their cell membrane is composed of lipids.
Archea from monera
Fig. Archea

2. Protista kingdom:

  • They are unicellular eukaryotes.
  • Some are Autotrophs while others heterotrophs.
  • A few of them use Cilia or flagella for movement.
  • Some have cell walls.
  • Amoeba, Paramecium, Euglena are some of its examples.
Kingdom protista
Fig. Protista Kingdom

3. Fungi Kingdom:

  • They are multicellular non-green eukaryotes.
  • They possess a parasitic, saprophytic or symbiotic mode of nutrition.
  • The body of the fungus is composed of long filament called hyphae. Mycelium is the network of hyphae.
  • They have cell walls composed of a complex sugar called chitin.
  • Rhizopus, yeast, Mushroom are some examples of fungi.
Fungi Kingdom
Fig. Fungi Kingdom

4. Plantae Kingdom:

  • They are Multi-cellular eukaryotes.
  • Possess autotrophic mode of nutrition.
  • Plantae has complex level of tissue differentiation.
  • They have defined body organs.
  • Plants, trees are examples of Plantae.


plantae kingdom
Fig. Plantae kingdom

The Plantae Kingdom (plants) is further grouped into different categories. They are:

  1. Thallophyta:

  • Elementary plants having undifferentiated body structure.
  • Vascular tissues are not present.
  • No seeds are there.
  • Usually found in aquatic habitat and hilly areas.
  • Reproduction takes place through spores.
  • Spirogyra, Ulva, Cladophora are some examples of Thallophyta.


  1. Bryophyta:

  • They have a little differentiated body structure.
  • Leaves and stems are present.
  • Although body is not fully developed.
  • Vascular tissues are absent.
  • Reproduction takes place through spores and require water bodies.
  • These are said to be amphibians of Plantae Kingdom as it is found on both land and water.
  • Moss, riccia, hornwort are some of the examples of bryophyte.
Riccia from Bryophyta
Fig. riccia
  1. Pteridophyta:

  • Leaves, stems and roots are differentiated.
  • Vascular tissues are present.
  • Reproduction takes place through spores.
  • Seeds are not present.
  • It is found in dry terrestrial land.
  • Ferns, Marsilea etc are some examples of Pteridophyta.
Pteridophyta Marsilea
Fig. Marsilea
  1. Gymnosperms:

  • Gymno means ‘naked’ sperm means ‘seeds’.
  • Body parts are well differentiated.
  • Vascular tissues are present.
  • Seeds are naked without containing any fruits or flowers.
  • These Plantae kingdoms are woody and evergreen.
  • Cycus, pines are some examples of gymnosperms.
cycus Gymnosperms
Fig. Cycus
  1. Angiosperms:

  • ‘Angio’ means covered and sperm means ‘seed’.
  • These are flower-bearing plants.
  • The flower matures and get converted to fruits.
  • Fruits contain seed inside it.
  • They grow for varied time periods.
  • Cotyledons (seed leaves) are the structure present within embryo of seeds.

Angiosperms are further classified into two categories on the basis of cotyledons present in it. Take a look at the differences between monocotyledons and dicotyledons:

Monocotyledons or Monocot plants:

  • Embryo contains only one cotyledon.
  • Have long leaves.
  • Monocots possess parallel venation.
  • These have fibrous roots.
  • Floral parts are always multiple of 3.
  • Corn, wheat and grass are some examples of monocots.
monocots from Angiosperms
Fig. Monocot plant

Dicotyledons or Dicot plants:

  • Embryo contain two cotyledons.
  • These have broad leaves.
  • Dicots possess reticulate venation.
  • Have long taproots.
  • Floral parts are always multiple of fives.
  • Rose, oak trees are some examples of dicots.
Dicot plants from angiosperms
Fig. Dicot plants

5. Animalia Kingdom:

  • They are also multicellular eukaryotes.
  • They possess heterotrophic mode of nutrition.
  • They have specialized organ for life activities.
  • Animalia kingdom has complex level of tissue differentiation.
  • They are present at all types of habitat i.e. aquatic, terrestrial or aerial.
  • Animalia kingdoms have both cold blooded and warm blooded animals.
  • Diversity of reproduction is seen to be sexual as well as asexual.
  • Animals, Insects and Humans (homo-sapiens) are examples of animal kingdoms.
animalia kingdom1
Fig. Kingdom Animalia

Phylum Classification:

Porifera or Sponges- Phylum 1:

  • Possess cellular level of Organization – Cells are present.
  • These are asymmetrical.
  • They are non-motile animals.
  • Segments are not present.
  • Body has pores (holes) which fform canal system for circulation of food and water as well as removal of waste.
  • Hard covering layer called skeleton (composed of spongin protein and calcium carbonate) is present.
  • No body cavity (coelom) is present.
  • Organs are absent.
  • These are mainly found in aquatic habitat.
  • Sycon, Euspongia, Spongilla are some of the examples of porifera.
Fig. Spongilla

Coelenterata (Cnidaria) – Phylum 2:

  • These are primitive, multicellular, aquatic animals.
  • Cells of Coelenterata are well organized into tissues.
  • Cells have two layers so said to be diploblastic.
  • Their body shows radial symmetry.
  • They possess hollow gut.
  • They show movement.
  • They contain a large cavity on their body which is called
  • Nematocysts cells are present on the body for defence, offence and to capture food.
  • Some possess solitary live like Hydra, while others like corals live in colonies.
  • Jellyfish, Sea anemone are some examples of Coelenterata.
jellyfish coelentreta
Fig. Jellyfish

Platyhelminthes – Phylum 3:

  • Possess the organ level of organization.
  • These are also called flatworms as they have flat bodies.
  • Coelom is absent so called acoelomates.
  • They are triploblastic (cells contain 3 layers).
  • Have bilateral symmetry.
  • Either they are parasites or free-living like planaria
  • Tapeworm, liver fluke are some of the examples of Platyhelminthes.
Fig. Liver fluke

Nematoda – Phylum 4:

  • They possess tissue level of organization.
  • No real organs are present.
  • They are also triploblastic.
  • Have bilateral symmetry i.e. Left and right half are identical.
  • Nematodes have false coeloms (Pseudocoelom).
  • Usually, they are cylindrical in shape. So they are called round worms.
  • They are parasitic worms thus cause diseases.
  • Nematodes show sexual dimorphism (i.e. different male and female worms)
  • Ascaris, Wulchereria, filarial worms etc. are some examples of nematode.
Nematoda Ascaris
Fig. Ascaris Nematoda

Mollusca – Phylum 5:

  • Possess Organ system.
  • They are called triploblastic as cells contain three layers.
  • Also, they are bilaterally symmetrical.
  • Body cavity is haemocoel.
  • Generally not segmented.
  • If segmented, little segmentation is there.
  • They have head, visceral mass and muscular foot (for movement).
  • Some Mollusca possess hard external shell like snail while some other have reduced shell like octopus.
  • Open circulatory system is present.
  • For excretion, kidney is present.
  • Usually separate sexes are present.
  • Snails, octopus, pino are some of the examples of Mollusca.
Fig. Snail

Annelida Phylum 6:

  • This is the second largest phylum of Animalia kingdom.
  • They possess organ system level of cell organization.
  • They are also triploblastic.
  • Annelida are bilaterally symmetrical.
  • These are well segmented (each segments are specialized for different functions and can be identified easily).
  • True body cavity are present so said to be coelomates.
  • Mainly they are found in fresh water or marine water.
  • They possess closed circulatory system.
  • Leech and earthworms are examples of Annelida.
leech Annelida
Fig. Leech

Arthropoda – Phylum 7:

  • It contains 80% of all species and considered to be the largest phylum.
  • They possess organ systems.
  • Bilateral symmetry is observed.
  • Commonly this phylum is called insects.
  • True body cavity (coelom) is present.
  • Arthropoda are also well segmented (each segments are specialized for different functions and can be identified easily).
  • They have jointed legs and antenna.
  • They have tough exoskeleton of chitin.
  • Possess open circulatory system.
  • No well-defined blood vessels are present.
  • Prawn, cockroach, spider, butterfly are some examples of Arthropoda.
cockroach Arthropoda
Fig. Cockroach

Echinodermata – Phylum 8:

  • They have organ system and are triploblastic.
  • They possess bilateral symmetry in early age but adults have radially symmetrical body.
  • No segmentation is observed.
  • True body cavity or coelom is present.
  • Definite organs are present for each specific activities.
  • There outer surface have spiny dermis made of calcium carbonate.
  • They have water vascular system which help in locomotion.
  • Their endoskeleton is composed of calcium carbonate.
  • Starfish, Sea cucumber, echinus are some examples of Echinodermata.
Fig. Starfish

Chordata – Phylum 9:

  • This phylum have notochord present in their body.
  • Notochord is rod shaped that provides skeletal support to the body.
  • Have Bilateral symmetry.
  • The cells contain three layers so they are triploblastic.
  • The chordates have nerve connecting brain (Dorsal nerves).
  • Aquatic chordates have gills for respiration.
  • Post-anal tail present at some stage of life which helps in balancing their body.

Chordata phylum- Pisces, reptiles, amphibians, aves and mammals

Chordata phylum is subdivided into two sub-phylums:

  1. Protochordata:

  • They have cell organization level of organ system.
  • Notochord is present and provides muscles to attach at a place for easy movement.
  • They are mainly marine animals.
  • In some phases of life gills are present.
  • No segmentation is there.
  • Balanoglossus, ascidia, amphioxus are some of its examples.
  1. Vertebrata:

  • They have organ system with complex designed tissues.
  • Cells contain three layers so they are triploblastic.
  • They are bilaterally symmetrical.
  • Differentiated segmentation is present.
  • They have 2, 3, 4 chambered heart.
  • Separate organs for each specific activity is present such as kidney for excretion.
  • Well defined body coelom is present.
  • Notochord converted into vertebral column in vertebrates.
  • A dorsal hollow nerve chord is present.
  • A pair of appendages is there.
  • Humans, mammals, fishes etc. are some examples of vertebrata.

 Cold blooded and warm-blooded animals:

The main properties, similarity and differences between cold blooded and warm blooded animals are given as:

Cold-blooded Animals

Warm-blooded Animals

Cannot maintain constant body

Maintains a constant body temperature.

They gain heat from the environment
surrounding them.

They gain heat from the food they eat.

The body temperature is same as the

Irrespective of the surrounding temperature,
they maintain a temperature of around
35 – 40 degree Celsius.

They regulate heat in their bodies by

Mechanisms such as hibernation and
help to regulate heat
throughout the body.

Fishes, Reptiles, Amphibians etc. are
examples of cold-blooded animals.

Birds and mammals are examples of
cold-blooded animals.

Nomenclature of living organisms (species):

  • Why we need nomenclature of living organisms?
    In everyday life, we see that the same organism has different names at different places. This creates confusion in studies as well as research. To ease it Binomial nomenclature is needed.
  • A single name for each type of organism made it easy to understand.
  • Anywhere in the world, this binomial names can be understood.
  • Carolus Linnaeus gave binomial nomenclature which is used in naming different types of living organism.

Some conventions in writing the scientific names i.e. binomial nomenclature:

  • Genus name starts with a capital letter and should be written after species.
  • The first letter of Species name must be a small letter.
  • The binomial name of an organism is written in Italics while printing
  • When one is writing in a copy then genus name and species name should be underlined separately.

Binomial Nomenclature (scientific names of organism)


Homo sapiens


Panthera tigris


Panthera leo


Mangifera indica


Rosa indica



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