CBSE Class 9 Science Revision Notes Chapter 7

CBSE Class 9 Science Revision Notes Chapter 7 – Diversity in Living Organisms

The goal of classification in biology is to establish a distinct hierarchy of relationships among the many living organisms. This system of biological classification is known as taxonomy. Class 9 Chapter 7 Science Notes on Diversity in Living Things lay the foundation for classification.

For this chapter, students need to have a methodical approach to comprehend the classification system explained. They can refer to Chapter 7 Science Class 9 Notes as all the information is organised logically. The notes provide concise content on the important concepts of the chapter.  Extramarks Class 9 Science Chapter 7 Notes are easily accessible and help students review this chapter to score better in exams.

Access Class 9 Science Chapter 7 – Diversity in Living Organisms

  1. What is the basis of classification?
  • The shape, structure and manner that different organisms have are different. They would be grouped based on their similarities.
  • It is easier to explore the evolutionary connections between creatures by classifying closely related species.
  • Classification is the division of organisms into groups and subgroups according to their characteristics.
  • A unique shape or function could be a characteristic.
  1. Classification and Evolution:
  • The existence of most living things on Earth today are the consequence of a series of body-design changes that have improved the quality of life for the creatures that inhabit them.
  • It is reasonable to assume that older species are simpler and younger organisms are more complex because design complexity may increase over time.
  1. The Hierarchy of Classification Groups:

Charles Darwin put forth the idea of evolution in his book The Origin of Species, which was published in 1859.

Scientists like Carl Woese, Robert Whittaker, and Ernst Haeckel divided living species into kingdoms.

Robert Whittaker proposed the “Five Kingdoms Classification” of living things in 1969.

To illustrate the hierarchy, the kingdom can be subdivided into phylum for animals and division for plants, class, order, family, genus, and species.

Because of this, species serve as the basis for taxonomy.

The term “species” refers to all living things that can reproduce sexually and give birth to procreative offspring.

The following system illustrates how the sub-groups are further classified by naming them at various levels.

3.1 Monera:

This system includes membrane-bound cell organelles and prokaryotic cells without nuclei.

Others lack cell walls, while some do. Some monerans are heterotrophic, while others are autotrophic.

Mycoplasma, cyanobacteria, blue-green algae, and other organisms are all members of the kingdom Monera.

3.2 Protista:

It includes protozoans, diatoms, and algae.

These unicellular eukaryotes are the simplest because they can feed both autotrophically and heterotrophically.

Movement is made possible by hair-like cilia, whip-like flagella, and finger-like pseudopodia.

Examples include protozoans, diatoms, and unicellular algae.

3.3 Fungi:

  • These multicellular eukaryotic saprophytes are eukaryotes.
  • The fungus’s cell wall is made of chitin.
  • They consume dead and decaying matter.
  • Rhizopus, mucor, and mushrooms are a few of them.
  • Some fungi coexist harmoniously with algal cells.
  • These symbionts are known as lichens.

3.4 Plantae:

This category encompasses all multicellular, eukaryotic, and non-motile creatures with cell walls made of cellulose.

They are complex, photosynthesis-capable organisms.

Cells with substantial cell walls make up plants.

3.5 Animalia:

It describes all eukaryotic, multicellular, motile animals that lack cell walls.

It shows a diverse range of species.

The creatures that make up this kingdom have multiple tissues.

  1. Plantae

4.1 Thallophyta:

Cryptogams and Phanerogamae are two subkingdoms of the plant kingdom, according to Eichler.

This sub-kingdom includes plants with covert reproductive organs that do not produce flowers or seeds.

Three cryptogam subgroups include Thallophyta, Bryophyta, and Pteridophyta.

The simplest plants are Thallophyta, which lack any recognisable body structure.

Algae is the common name for the plants in this group.

They are mainly aquatic.

Other examples include Spirogyra, Ulothrix, Cladospora, and Chara.

Bryophytes are known as the amphibians of the plant kingdom because they require both terrestrial and aquatic habitats to complete their life cycle.

It is common for the plant body to differentiate to produce stem- and leaf-like structures.

Examples include funaria or moss.

The fern plant class Pteridophyta has a body made up of stems, leaves, and roots.

They have naked embryos in the form of spores underneath the leaf.


These are eukaryotic, multicellular, heterotrophic organisms.

They lack cell walls in their cells.

Most animals can move around.

Animals are divided into groups based on traits like body symmetry, coelom type, segmentation or lack of segmentation, and cellular or tissue-level body organisation.

Invertebrata and Vertebrata are the two kingdoms that form Animalia.

5.1 Invertebrata:

It describes a class of creatures without a vertebral column.

Some of the phyla of invertebrates include Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, and Echinodermata.

5.2 Vertebrata:

These animals are the most developed because they have a strong endoskeleton and a real vertebral column.

Vertebrates are categorised according to their bilateral symmetry, notochord, dorsal nerve cord, paired gill pouches, triploblastic structure, and coelomate structure.

The five classes are Pisces, Amphibia, Reptilia, Aves, and Mammalia.

Diversity in Living Organisms Class 9 Notes

In Chapter 7 of the Science Class 9 Notes, the hierarchy of classification groups is addressed. Animals and plants are grouped according to phylum, or division, respectively. Class, order, family, genus, and species are listed after those. The species serves as the basic unit of classification.

The Classification of Kingdoms is:


Prokaryotic cells are devoid of a cell membrane and a well-organised nucleus. Both autotrophic and heterotrophic growth is possible. Bacteria, cyanobacteria, mycoplasma, and other examples are given.


The most basic type of unicellular eukaryote is a protozoan. For locomotion, flagella or cilia may be present. Diatoms, algae, and protozoans are a few examples.


Fungi are multicellular, eukaryotic saprophytes. Chitin is a component of the cell wall. It gets its nutrition from dead and decaying matter. Mucor, mushrooms, and rhizopus are a few examples of fungi.


All multicellular, eukaryotic, non-motile plants are classified as Plantae. The cell walls are made of cellulose and are very thick.

Notes for Class 9 Science Chapter 7 Mentions the Sub-Groups as:


Thallophyta have a poorly differentiated plant body. Some of them include Ulothrix, Spirogyra, and Chara.


Bryophytes are classified as amphibians in the plant kingdom, as they can survive in both terrestrial and aquatic environments. Funaria and Moss are two examples.


It mainly consists of plants with distinct bodies made of leaves, stems, and roots.

  1. Animalia

Animalia has been described as multicellular, eukaryotic, and heterotrophic without cell walls in Chapter 7 Science Class 9 Notes.

Invertebrata and Vertebrata are the subgroups.

The Class 9 Chapter 7 Science Notes help students in developing a clear understanding of the chapter. They can refer to Extramarks’ Class 9 Science Notes Chapter 7 to clear their doubts about this chapter.

FAQs (Frequently Asked Questions)

1. What are the characteristics of an amphibian?

Amphibians are defined in Class 9 Science Notes Chapter 7 as any member of the vertebrate animal group with the ability to live in both terrestrial and aquatic habitats.

The traits of amphibians include:

(1) Life is spent on land and in water. 

(2) They are carnivorous. 

(3) Their lungs are undeveloped, and they breathe through their skin. 

(4) They are cold-blooded. 

(5) Their eggs are fertilized externally.

2. What are the main features of the kingdom of Fungi?

The main features of kingdom Fungi include:

a) They are not green because chlorophyll is not present.

b) They are heterotrophic because they obtain their nourishment from decaying and dead organic debris.

c) Their cell wall is cellulosic and chitinous, and their body organisation is mycelial or secondary unicellular. 

d) They reproduce either through sexual or asexual means.

e) They spread spores to reproduce. 

3. Why are mosses found in moist, humid environments? Explain.

Mosses easily absorb water because they are generally located in moist, humid environments. Moss sperm are connected to flagella, which are primarily motility organelle, and need a water medium to go to the Archegonia for reproduction and other physiological tasks. Therefore, water is essential to the life cycle of mosses.