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CBSE NOTES CLASS 9 SCIENCE CHAPTER 7

DIVERSITY

Types of diversity

Why do we classify organism?

What is the basis of classification of organism?

Cell type – Prokaryotic or Eukaryotic

Uni-cellular or Multi-cellular

Level of organisation of body

Evolution and Classification

Primitive and advanced body designs

Biodiversity

Hierarchy of classification

Classification of organisms into kingdoms

Monera

Protista

Fungi

Lichens

Plantae

Thallophyta

Bryophyta

Pteridophyta

Cryptogamae

Phanerogams

Gymnosperms

Angiosperms

Animalia

Porifera

Coelenterata

Platyhelminthes

Coelom

Triploblastic

Bilaterlly Symmetrical

Nematoda

Annelida

Arthropoda

Mollusca

Echinodermata

Protochordata

Vertebrata

Pisces

Amphibia

Reptilia

Aves

Mammalia

Viviparous

Oviparous

Nomenclature of organism

CBSE NOTES CLASS 9 SCIENCE CHAPTER 7

DIVERSITY

Diversity

Difference in characteristics of various organisms is called diversity.

Different kinds of life forms show great diversity among themselves in following ways,

Size: From microsercopic bacteria of a few micrometers to blue whale (30 metres) and red wood trees of California (100 metres).

Life Span: Insects (few days) to pine trees (thousands of years).

Colour: Colourless or even transparent worms to brightly coloured birds and flowers.

Habitat – The place of living. For example, Land, Water, Air, Cold climate to hot deserts

Why classification?

The variety in organism and the diversity is very vast and it is almost impossible to study them individually. To make the study of living things systematic and easier, we put them into different classes, groups and sub groups on the basis of similarities and differences in their body design in form and function.

What is the basis of classification of organism?

Characteristics - a characteristic is a particular form or a particular function.

A hierarchy of mutually related characteristics is used for classification.

Some characteristics are more basic than others. Important characteristics used for hierarchical classification are

(i) Cell Type – Prokaryotic or Eukaryotic.

(a) A eukaryotic cell has membrane-bound organelles, including a nucleus, which allow cellular processes to be carried out efficiently in isolation from each other.

On the other hand Prokaryotes, i.e., organisms which do not have a clearly demarcated nucleus and other organelles would need to have their biochemical pathways organised in very different ways.

(b) Nucleated cells can participate in making a multicellular organism because they can take up specialised functions.

Therefore, this is a basic characteristic of classification.

(ii) Uni-cellular or Multi-cellular

Uni-cellular organisms perform all the life processes using the single cell.

On the other hand, multicellular organism use the principle of division of labour. In such a body design, all cells would not be identical. Groups of cells will carry out pecialized functions.

This makes a very basic distinction in the body designs of organisms. As a result, an Amoeba and a worm are very different in their body design.

(iii) Autotrophic or Heterotrophic - Do organisms produce their own food through the process of photosynthesis?

Being able to produce own food versus having to get food from outside would make very different body designs, necessary. Hence plants and animals form different groups.

(iv) Level of organisation of body, how does the individual’s body develop and organises its different parts, and what are the specialized organs found for different functions?

The characteristics of body design used for classification of plants will be very different from those important for classifying animals.

This is because the basic designs are different, based on the need to make their own food (plants), or acquire it (animals). Therefore, these design features (having a skeleton, for example) are to be used to make sub-groups, sub groups among plants and animals.

Evolution & Classification

Evolution: The process by which different kinds of living organism are believed to have developed from earlier forms by accumulation of changes in body design that allow the organism to survive better, during the history of the earth.

Some characteristics are likely to make more wide-ranging changes in body design than others. Time also plays a big role. So, once a certain body design comes into existence, it will shape the effects of all other subsequent changes, because it already exists.

Characteristics that came into existence earlier are likely to be more basic and likely to be found in larger portion of the population than characteristics that have come into existence later.

Primitive and advanced body designs

A primitive organism is a lower organism which exhibits simple body structure and simple organization. They are said to have ancient body designs.

An advanced organism exhibits complexity in the body structure and organization. They are said to have advanced body designs. These organisms show high level of division of labour, by formation of organs and organ systems.

The changes in the body structure and design may result from adaptations developed by the organism to the environment.

In reality, these terms are not quite correct since they do not properly relate to the differences. Complexity of design does not mean efficiency or better adaptation to the environment.

We can only say that some are ‘older’ organisms, while some are ‘younger’ organisms. Complexity in design increases over evolutionary time. Hence older organisms are simpler, while younger organisms are more complex.

Biodiversity means the diversity of life forms and refers to the variety of life forms found in a particular region.

Diverse life forms share the environment, and are affected by each other.

The diversity in such communities is affected by particular characteristics of land, water, climate, and so on. Humans have changed the balance of such communities.

The warm and humid tropical regions of the earth, between the tropic of Cancer and the tropic of Capricorn, are rich in diversity of plant and animal life. This is called the region of megadiversity.

Hierarchy of Classification

The classification Whittaker proposed has five kingdoms. These are formed on the basis of their cell structure, mode and source of nutrition and body organisation.

The modification Woese introduced by dividing the Monera into Archaebacteria (or Archaea) and Eubacteria (or Bacteria) is also used.

Further classification is done by naming the sub-groups at various levels as follows,

Kingdom

   Phylum (for animals)/Division (for plants)

    Class

      Order

        Family

          Genus

            Species

By separating organisms on the basis of a hierarchy of characteristics into smaller and smaller groups, we arrive at the basic unit of classification, which is a ‘species’. A species includes all organisms that are similar enough to breed and perpetuate.

Classification of organisms into kingdoms

Based on the above criterion the organisms have been divided into 5 kingdoms.

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Monera

Protista

Fungi

Plantae

Basis of Further Classification of Plants

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Thallophyta

Bryophyta

Pteridophyta

Cryptogamae

The plants,, in which the reproductive organs are hidden, are cllaed cryptogamae. They do not produce seeds. The thallophytes, the bryophytes and the pteridophytes have naked embryos that are called spores and do not produce seeds. The reproductive organs of plants in all these three groups are very inconspicuous (hidden), and they are therefore called ‘cryptogamae’, or ‘those with hidden reproductive organs’.

Phanerogams

Gymnosperms

Angiosperms

Animalia

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Porifera

Coelenterata

Platyhelminthes

Nematoda

Annelida

Arthropoda

Mollusca

Echinodermata

Protochordata

Vertebrata

Pisces

Amphibia

Reptilia

Aves

Mammalia

Nomenclature

Why is there a need for systematic naming of living organisms?

It is difficult for people speaking or writing in different languages to know when they are talking about the same organism. This problem is resolved by agreeing upon a ‘scientific’ name for organisms just like chemical symbols and formulae for various substances the world over.

The scientific name for an organism is unique and can be used to identify it anywhere in the world. Proposed by Carolus Linnaeus.

The scientific name of an organism is the result of the process of classification which puts it along with the organisms it is most related to.

It includes the name of the genus and species of that particular organism.

Both these names are to be used in Latin forms.

Naming Conventions

1. The name of the genus begins with a capital letter.

2. The name of the species begins with a small letter.

3. When printed, the scientific name is written in italics.

4. When written by hand, the genus name and the species name have to be underlined separately.

Tiger, Peacock, Ant, Neem, Lotus, Potatoe.

Tiger

Panthera tigris.

Peacock

Pavo cristatus.

Ant

Formicidae.

Neem

Azadirachta indica.

Lotus

Nelumbo nucifera.

Potato

Solanum tuberosum