CBSE Class 9 Science Chapter 7 Revision Notes

Chapter 7: Diversity In Living Organisms Revision Notes



  • The occurrence of different creatures in the same habitat or geographical place is known as diversity.
  • Diversity increases the likelihood of a more balanced ecology.


  • Evolution is the gradual process through which organisms change in response to their demands in order to survive in their environment.
  • New organisms emerge as a result of evolution, and the ecosystem becomes more diverse.

Charles Darwin

  • Charles Darwin was a naturalist and a biologist from England.
  • He visited the Galapagos Islands in South America aboard the HMS Beagle.
  • In his book On the Origin of Species, he developed the hypothesis of evolution based on his observations.


  • The science of taxonomy is concerned with the classification of organisms.


Classification Hierarchy

  • Organisms are classified into groups or tiers based on their similarity.
  • As we move up the food chain, the organisms become less similar.

Hierarchy of ClassificationSource:


  • A kingdom is the highest level of classification, consisting of a group of related phyla or divisions (in the case of plants).


  • A phylum/division is a categorization level that consists of several classes with comparable traits.


  • A class is a level of classification that includes a group of orders that have comparable qualities.


  • An order is a classification level that includes a group of families with comparable traits.


  • A family is a level of taxonomy that includes many Genus that have similar traits.


  • A genus is a level of categorization that includes a group of species that share comparable traits.


  • A species is a level of classification that includes a group of creatures that have similar traits and may breed to produce fertile offspring.


Linnaeus Carolus

  • Carolus Linnaeus, popularly known as the “Father of Taxonomy,” is a Swedish botanist and physician.
  • He established the Binomial nomenclature and established the foundation rules for current taxonomy.

Binomial Nomenclature

  • Linnaeus introduced Binomial Nomenclature as a method of naming organisms in taxonomy.
  • It is divided into two sections.
  • The Genus name, which is printed in capital letters, is the first portion.
  • The species name, which is not capitalised, is the second portion.


  • R.H.Whittaker’s 5 Kingdom categorization is the most widely acknowledged way of classification.
  • This classification resolved the majority of taxonomic difficulties involving the location of bacteria and fungus.
  • Monera, Protista, Fungi, Plantae, and Animalia are the five kingdoms.

**Kingdom Monera **


  • This Kingdom is home to all prokaryotic creatures.
  • Kingdom Monera is made up of bacteria and archaebacteria, an ancient cousin of bacteria.
  • These organisms are prokaryotic, unicellular, and autotrophic/heterotrophic.
  • Bacteria have a polysaccharide-based cell wall.


  • The Monera kingdom’s category for species that can survive in extremely hot environments.
  • They are said to be the most ancient living organism on the earth.


  • Eubacteria is a Monera phylum that includes any bacteria that can thrive in a normal environment.
  • This category include all of the major beneficial and harmful bacteria that we are familiar with today.
  • Bacteria of Gram +ve/-ve Gram +ve/-ve Gram +ve/-
  • Because some bacteria have a thick cell wall, they absorb Gram stain and appear violet.
  • Other bacteria have a thin cell wall and appear pink when stained with Gram stain.
  • In most cases, gram +ve bacteria are harmful.



Except for yeast, all eukaryotic unicellular organisms belong to the kingdom Protista.


  • Protozoans are unicellular eukaryotic organisms that belong to the Protista Kingdom.
  • Paramecium, amoeba, Plasmodium, euglena, and leishmania are some examples.
  • Protists are fungi, and fungi are fungi.
  • Unicellular fungi such as yeast and moulds belong to this kingdom.
  • Some photosynthetic unicellular algae belong to the kingdom Protista.



  • The majority of the species in the Kingdom Fungi are saprophytic.
  • It is the only Kingdom in the world that contains both multicellular and unicellular species.
  • Chitin makes up the majority of their cell walls.



  • This Kingdom encompasses all of the plants and trees that we see around us.
  • They’re all autotrophic and have chloroplasts in their cells.
  • Cellulose makes up their cell wall.
  • Cryptogams and Phanerogams are the two major divisions of the plant kingdom.


  • Plants having hidden reproductive organs are known as cryptogams.
  • Cryptogams are plants that reproduce via spores rather than seeds.
  • As a result, there are no flowers or fruits on these plants.
  • Thallophytes, bryophytes, and pteridophytes are the three types of cryptogams.


  • Phanerogams are plants that reproduce by producing seeds.
  • Some of them do not bear flowers, while others do.
  • Gymnosperms and angiosperms are two types of phanerogams.


  • The first division of the plant kingdom is Thallophyta.
  • There are red, green, and brown algae in it.
  • They don’t have a lot of structure differentiation.


  • The plant kingdom is divided into two divisions: Bryophyta and Bryophyta.
  • These are the first plants that have roots and shoots that are distinct.


  • Pteridophyta is the plant kingdom’s third division.
  • The roots, stem, and leaves of these plants are all distinct.


  • The word gymnosperm means “bare seed.”
  • Because they produce seeds that are not encased in a fruit, they are the first phanerogams.


  • Angiosperm is the last division of the plant kingdom, and it contains the most advanced species on the planet, according to scientists.
  • They produce flowers and fruits, which contain the seeds.


  • Cotyledons are structures found in seeds that provide sustenance during germination, when the leaves have not yet formed.
  • Angiosperms are classified as dicots or monocots depending on whether they contain two or one cotyledon.

Monocots and Dicots

  • Angiosperms, the most advanced plants on the planet, are classed further based on the number of cotyledons in their seeds.
  • Seeds with two cotyledons are referred to as dicots.
  • Dicots have a reticulate venation and a tap root system. Mango, pea, beans, and other fruits and vegetables are examples.
  • Monocotyledons are seeds with only one cotyledon.
  • Monocots have a fibrous root system with venation that runs parallel to each other.
  • All grains, such as wheat, maize, and rice, are examples.



  • Eukaryotic, multicellular, heterotrophic creatures make comprise the kingdom Animalia.
  • They are either herbivores or carnivores, and their mode of sustenance is holozoic.
  • The majority of animals are mobile, meaning they can move around on their own in search of food, shelter, or a mate.
  • Animals are made up of a variety of organ systems that work together to accomplish certain duties that are essential for the organism’s existence.
  • The majority of animals are bilaterally symmetrical, with the exception of early species, which are asymmetrical, and cnidarians and echinoderms, which are radially symmetrical.


  • The sponges belong to this phylum.
  • They are largely marine, with only a few freshwater species.
  • The creatures are all sessile (fixed in one place).
  • The cells are placed in a haphazard manner (cellular grade of the organization).
  • The outer ectoderm and inner endoderm of animals are held together by the jelly-like mesoglea.
  • Exoskeleton in the form of silica or calcium carbonate spicules.
  • Pores can be found all over the body of sponges. Ostia refers to the pores on the body.
  • Water enters the body through the Ostia and exits through the osculum, a single big aperture.


  • These are generally marine species that live in water.
  • They can be solitary or colony in nature. Each individual is referred to as a zooid.
  • Animals have a radial symmetry.
  • Polyps are sessile creatures, while Medusa are free-living forms.
  • Tissues are made up of cells (tissue grade of the organization).
  • Diploblastic animals have outer ectoderm and interior endoderm. These two levels are separated by Mesogloea.
  • The hypostome is a single hole in the body surrounded by sensory tentacles.
  • The coelenteron is a body cavity (coelom) that serves as a gastrovascular cavity.
  • Nematocysts, a type of cell found in tentacles, are responsible for capturing and paralysing pray.
  • Hydra, jellyfish, corals, obelia, and sea-anemone are other examples.


  • Bilaterally symmetrical, triploblastic, and flattened organisms make up this phylum.
  • The organization’s organ-system grade is visible.
  • The outer ectoderm, middle mesoderm, and inner endoderm of animals are all triploblastic.
  • There is no bodily cavity in an acoelomate.
  • The digestive system is deficient or non-existent.
  • The majority are parasites, although a few are free-living.
  • Liver fluke and tapeworm are two examples.


  • The bodies of these animals are symmetrical on both sides, triploblastic, and cylindrical.
  • The organization’s organ system grade is visible.
  • There is Pseudocoelom present.
  • Have a digestive system that is tubular in shape and has openings on both ends.
  • They’re parasitic endoparasites.
  • Hooks and suckers are provided in the mouth.
  • Ascaris, hookworm, filarial worm, and other parasitic worms are examples.


  • These organisms are triploblastic and exhibit bilateral symmetry.
  • They are generally aquatic, with only a few exceptions.
  • These organisms are the first to have a genuine coelom.
  • Intersegmental septa divide the coelome into sections.
  • The body is lengthy and segmented metamerically (segmentation from outside and inside of the body).
  • Leech, earthworm, and other examples


Arthropoda examplesSource:

  • With 80 percent of all known living animals, this is the largest phylum.
  • Animals with appendages that can be joined (in Greek Arthron: jointed, poda: legs).
  • The head, thorax, and abdomen are the three segments/regions of the body.
  • An exoskeleton formed of chitin protects the body.
  • They have an open circulatory system and are bilaterally symmetrical.
  • There are compound eyes present.
  • Insects, scorpions, spiders, millipedes, centipedes, crabs, lobsters, and other animals are examples.


  • They are symmetrical on both sides, with a small coelomic cavity and little segmentation.
  • They have an open circulatory system and excretion organs that resemble kidneys.
  • The body is delicate and usually has a shell around it. It is possible for the shell to be external or internal.
  • They show that the Foot, Mantle, and Mantle Cavity are all present.
  • Pearl oysters, bivalves, sepia, octopus, snails, slugs, and other organisms are examples.


  • They have a spiky skin and live entirely in the sea.
  • Typically, the animals are pentamerous.
  • They have a coelomic cavity and are triploblastic.
  • They move forward using a water-driven tube system.
  • Starfish, sea urchins, sea cucumbers, sea lilies, and other sea creatures are examples.


  • Hemichordata is triploblastic and bilaterally symmetrical.
  • A notochord, which runs along the back of the animal and separates the nerve tissue from the intestine, is also present.
  • They are saltwater organisms that serve as a link between non-chordates and chordates.
  • Non-chordates/invertebrates range from Porifera to Echinodermata.
  • Balanoglossus, popularly known as the acorn worm, is an example.


  • A dorsal, tubular, hollow nerve cord is present.
  • Notochord is present.
  • Slits in the pharyngeal gills are present.
  • There is a post-anal tail present.
  • Body that is symmetrical on both sides.
  • Three germ layers are present.
  • Organization at the organ-system level.
  • The ventral heart and hepatic portal system are present.
  • Endocrine glands that are fully matured
  • The vertebral column replaces the notochord in all animals except a few primitive types. Vertebrates are the name given to these creatures.


  • All bony and cartilaginous fishes are classified as Pisces.
  • They are only found in water.
  • With paired and unpaired fins, the body is streamlined.
  • These are vertebrates with a cold blood supply.
  • The heart has two chambers.
  • The system of lateral lines is substantially established.
  • Sharks, rays, Rohu, Mrigal, green carp, and other species are examples.


  • Amphibians can live on land and in water, and they lay their eggs in the latter.
  • In the larval stage, breathing is done through the gills, while in the adult stage, breathing is done through the lungs.
  • They’re cold-blooded creatures.
  • They have a heart with three chambers.
  • Frogs, toads, salamanders, and other amphibians are examples.


  • These are the first animals that are entirely land-based.
  • Cold-blooded reptiles breathe through their lungs.
  • They lay eggs with tough covers and have a three-chambered heart (excluding crocodile).
  • Scales, scutes, or hard plates cover the body.
  • Snakes, crocodiles, turtles, lizards, and other reptiles are examples.


  • This category includes all birds.
  • They have a four-chambered heart and breathe through their lungs and are warm-blooded.
  • Their forelimbs have been transformed into wings to aid in flight.
  • Jaws have been transformed into beaks.
  • Bones are hollow, with the majority of them fused together to reduce body weight.
  • Feathers are used as an exoskeleton.


  • They have a four-chambered heart and are warm-blooded. They breathe through their lungs.
  • Mammalian characteristics include the presence of hair on their bodies, as well as perspiration and oil glands.
  • Only mammals have an external ear, which is known as a pinna.
  • They also have mammary glands, which they use to nourish their young.
  • Typically, they give birth to live young.
  • Humans, cattle, and other animals are examples.



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