Diversity in Living Organisms Class 9 Notes

The earth is filled with a lot of different species of various shapes and sizes. There are diverse species present around the globe. Diversity in living organisms is 7th chapter in Class 9th Science syllabus. The chapter is important as well as a scoring one in the curriculum. Read this blog further to understand this chapter through summarized notes and important topics you must cover.

Classification

In the chapter titled Diversity in Living Organisms, the concept of classification is very important. Let us begin with classification first. 

The process of arranging different organisms or species into a set of groups on the basis of similarities and dissimilarities is called classification. 

The classification of different organisms is done on the basis of the characteristics they possess i.e. organisms with similar characteristics are placed in the same group.

Why is There a Need for Classification?

• At times it gets really difficult to study so many diverse organisms one by one because of the huge diversity in living organisms. Thus, in order to help in the process of studying the organisms, the process of classification started.
• It helps to study the interrelationship between different organisms.
• It helps to understand the evolution of organisms over time.

Basis of Classification

In the chapter Diversity of Living organisms, the basis of classification is explained din great detail.

• Number of cells in organisms– Organisms are classified based on the basis of them being unicellular or multicellular. Unicellular organisms are organisms with a single cell and multicellular organisms are organisms with more than a single cell.
• Mode of nutrition– Organisms are classified based on the basis of them being autotrophs or heterotrophs. Autotrophs are organisms that produce their own food. All green plants are autotrophs as they can facilitate photosynthesis.
• Presence or absence of nucleus in cells– Organisms are classified based on the basis of them being Prokaryotes or Eukaryotes. Prokaryotes are organisms which have cells without a well defined nucleus. Eukaryotes are organisms which have cells within a well defined nucleus.

Classification System

The classification in the diversity of living organisms is important. Different kinds of organisms are grouped together. 

• Two-kingdom Classification– Carolus Linnaeus made two groups in order to classify different organisms i.e plants and animals.
• Whittaker’s Five Kingdom Classification– H.Whittaker classified organisms into five groups named as-

1. Monera- 
2. Protista
3. Fungi
4. Plantae
5. Animalia.

Five Group Classification

Monera

• Monera are prokaryotes meaning that nuclear materials are not membrane bound in them.
• They can be both autotrophic or heterotrophic.
• All organisms of this kingdom are found to be unicellular.
• They may or may not have a cell wall.
• Examples- Bacteria, blue green algae, mycoplasma

Protista

• Protista can be both autotrophic or heterotrophic.
• They are Eukaryotes.
• All organisms are unicellular.
• Some organisms use cilia or pseudopodia for locomotion.
• Examples- Amoeba, Paramecium, Euglena.

Fungi

• Fungi are heterotrophic with a cell wall which is made up of chitin.
• Most of the fungi are unicellular but many organisms have the capacity to become multicellular at a certains stage of life.
• Their mode of nutrition is called saprophytic i.e. they feed on decaying organic materials.
• Fungus is made up of long filaments called hyphae and their network is called mycelium.
• Examples- yeast, rhizopus

Plantae

• Plantae are multicellular organisms.
• They are Eukaryotes with a cell wall.
• They are autotrophs which use chlorophyll for photosynthesis.
• Their body exhibits a high level of tissue differentiation which has specialized body organs.
• Examples- trees, plants

Animalia

• Animalia are multicellular organisms.
• These are Eukaryotes
• They are heterotrophic
• The cell wall is absent.
• Examples- fish, insects, humans, animals, birds.

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The Plant Kingdom

In the study of diversity in living organisms, the plant kingdom has an important role to play. The plantae kingdom in Robert Whittaker classification kingdom model consists of about 300,000 different plant species. The kingdom is considered to be one of the most important one being the source of food for all other living creatures on the planet earth. It consists of all the trees, shrubs, aquatic plants, desert plants, flowering and non-flowering plants.

The plant kingdom is further classified into 5 division based on the following characteristics- 

Thallophyta

• Plant body is simple thallus type.
• The plant body is not differentiated into root, stem, and leaves.
• They are generally called algae.
• Mainly found in water.
• Examples- Spirogyra, Chara, volvox

Bryophyta

• Plant body is differentiated into stem and leaf-like structure.
• No vascular tissue present.
• Reproduces through spores.
• Also known as the amphibians of the plant kingdom as they need water in order to complete a part of their life cycle.
• Examples-  Marsilea, ferns etc.

Pteridophyta

• Body is differentiated into stems, leaves and roots along with the presence of a vascular tissue.
• They don’t bear seeds, hence called cryptograms.
• They reproduce through spores.
• Examples- fern, horsetails etc.

Gymnosperms

• They have differentiated body parts .
• They bear naked seeds as the word ‘gymnos’ means naked and ‘sperma’ means seeds.
• They are perennial plants.
• Examples- Pine, cycas, deodar

Angiosperms- 

• Their seeds are covered.
• They are also called as flower-bearing plants as a flower is a specialized organ meant for reproduction.
• Angiosperms can further be divided into two more groups i.e.- 
  • Monocotyledonous – There is a single seed leaf in a seed. Examples- Wheat, Rice etc.
  • Dicotyledonous– it means the presence of two cotyledons in a seed. Examples- Mustard, Mango etc.

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The Animal Kingdom

The study of diversity in living organisms also comprises the animal kingdom. Animal kingdom consists of a maximum number of species across all kingdoms.

Animal kingdom being so large, is further divided into the following-

Porifera

• Body is not differentiated into tissues
• The body is covered with a hard outer skeleton.
• These are commonly known as sponges.
• They are marine animals.
• Examples- Sycon, spongilla, euplectella, etc

Coelenterata

• Their body is made up of a coelom with a single opening.
• They can move from one place to the other.
• Their body wall is made up of two layers of cells.
• Examples- Hydra, Jellyfish

Platyhelminthes

• They are also called flatworms.
• Their body is flattened from top to bottom
• They are parasitic animals.
• They don’t have a coelom present.
• Examples- liver fluke

Nemathelminthes

• Their body is bilaterally symmetrical
• Triploblastic
• Their bodies are covered with shells.
• Animals are cylindrical in shape.
• Examples- Roundworms, pinworms

Annelida- 

• True body cavity
• The body is divided into segments which are lined one after the other and contains a set of organs.
• Examples- Earthworm, Leeches etc.

Echinodermata

• Body is symmetrical.
• Body is covered with spines.
• Skeletons are made of calcium carbonate.
• Examples- starfish, sea urchins etc.

Arthropoda

• They have joint appendages
• This is the largest phylum which consists of about 80% of all the species in the animal kingdom
• Circulatory system is open.
• Examples- spider, prawn etc.

Mollusca

• Circulatory system is open
• Animals have a soft body
• A kidney like organ is present for the purpose of excretion.
• Examples- snail, octopus etc.

Protochordate

• Triploblastic
• Symmetrical
• Notochord is present
• Provides attachment for muscles
• Examples- Balanoglossus, herdmania

Chordata

• Notochord is present
• Dorsal nerve cord is present
• Triploblastic and coelomate.

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Pisces

• These are fish.
• Their body is streamlined
• Paired gills are present
• Cold-blooded animals

Amphibia

• They can live on both water as well as land
• Their heart has three chambers
• Cold-blooded animals
• Examples- frog, toad etc.

Reptilia

• They crawl in order to move from one place to the other
• They have hardened skin
• They have three chambered hearts except crocodile which has four chambered hearts.
• Examples- snakes, lizards etc.

Aves

• Their body is covered with feathers
• Their heart has four chambers
• Forelimbs are modified into wings
• Examples- All the birds

Mammalia

• Their body is coerced with hair
• Skin has sweat glands and sebaceous glands.
• Mammary glands are present in females
• Examples- Humans, Lion etc.

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This was all for the chapter diversity in living organisms. We hope that these notes helped you boost your preparation process. We wish you all the best for all your upcoming examinations. Hoping to pursue a career in biology? Get in touch with  Leverage Edu experts to get complete assistance in choosing the right course and get admission in your dream university. Sign up for a free session with us now!