Welcome to Class 9 Diversity in living organisms notes Notes for Chapter 7.The topics in this page are Purpose of Classification ,Classification and Evolution,Binomial Nomenclature,Hierarchy of Categories,Five-Kingdom System of classification, Plant Kingdom and Animal Kingdom. This is according to CBSE and the NCERT textbook. If you like the study material, feel free to share the link as much as possible.
The term “biodiversity” is a concise form of “biological diversity” and was coined by Walter G. Rosen in 1986.
Biodiversity is the occurrence of diverse or varied forms of living beings which differ from one another in external appearance, size, color pattern, internal structure, nutrition, behavior, habitat etc.
Note: Mega diversity is the high degree of richness of different types of forms found in an area. The area or region of mega diversity on earth is humid tropical region lying between tropic of Cancer and tropic of Capricorn.
The system of grouping of living forms on the basis of similarities and differences is called classification.
The branch of biology concerned with classification is called taxonomy. Taxonomy is a biological science which deals with identification, nomenclature and classification of organisms following certain rules.
Purpose of Classification (Importance of classification):
Classification makes the study of a wide variety of living organisms easier.
Classification helps in understanding the phylogeny of organisms.
Classification provides knowledge about the origin and genetic relationship among living beings.
Classification forms a base for the development of other biological sciences.
Classification and Evolution:
Early systems of classification were artificial i.e., they were based on a few arbitrarily chosen criteria such as size, colour and nature of the organisms.
In the 19th century, the artificial systems of classification were replaced by natural systems of classification. The important aspects of this natural basis of classification are:
It considers a number of characters.
It include internal (anatomical) as well as external (morphological) characters.
It indicated overall similarities and differences between the organisms.
It places related organisms in the same group.
The classification of life forms is closely related to their evolution. The idea of evolution was first described by Charles Darwin in his book, the Origin of species in 1859.
He explained that first formed (older) organisms were simpler, while younger organisms (modern) are more complex, i.e., complexity in design of simple forms has increased over evolutionary time and has become modern complex form.
Binomial nomenclature is a system of giving distinct and proper names to organisms with each name consisting of two words, generic and specific.
Binomial nomenclature was proposed by Carolus Linnaeus (Karl von Linnaeus).
Hierarchy of Categories or Groups:
The main aim of a taxonomic study is to assign organism an appropriate place in a systematic framework of classification. This framework is called taxonomic hierarchy by which the taxonomic groups are arranged in definite order, from higher to lower categories.
A category is called taxon (plural taxa). The taxa or categories used in the classification of animals are kingdom, phylum, class, order, family, genus and species.
The categories used in plants are kingdom, division, class, order, family, genus and species.
Note: Species is a group of individuals with similar morphological characters, which are able to breed among themselves and produce fertile offspring of their own kind.
Living organisms have been classified variously according to different criteria; however, the following two systems are most in use.
Two-Kingdom System of classification:
This system of classification was given by Carolus Linnaeus (1758). According to this system, the whole living beings are put into two kingdoms- Plant kingdom and Animal kingdom.
Later taxonomic studies indicated that certain organisms did not fit either under Plant kingdom or Animal kingdom. Accordingly, a German Zoologist, E.H. Haeckel (1866) raised a third kingdom Protista for unicellular organisms.
Five-Kingdom System of classification:
R. H. Whittaker (1959) has classified the living organisms into following five kingdom:
Kingdom Monera (Prokaryotic bacteria and Blue green algae)
Kingdom Protista (Unicellular eukaryotic organisms- protozoans, fungi and algae)
Kingdom Fungi (Multicellular fungi)
Kingdom Plantae (Multicellular green plants and advanced algae)
Kingdom Animalia (Multicellular animals)
Characteristics of Five-Kingdom:
The monerans are extremely small and structurally the simplest of all the living beings.
The organisms belonging to this group are simple, unicellular and microscopic. These organisms are prokaryotic.
Cell wall is present in some organisms and absent in others.
They do not possess a defined nucleus and lack cell organelles.
Some organisms can synthesize their food (autotrophic), while some organisms exhibit heterotrophic mode of nutrition.
This group includes Bacteria, mycoplasma and blue-green algae.
This group consists of many types of unicellular eukaryotes.
They have a defined nucleus and also membrane-bound organelles.
Some of these organisms use appendages, such as hair-like cilia or whip-like flagella for moving around.
Their mode of nutrition can be autotrophic or heterotrophic.
This group includes Diatoms, protozoans and unicellular algae.
Fungi are simple, eukaryotic non-green (lacking chlorophyll) organisms.
Cell wall is present. It is made up of a tough complex sugar called chitin.
They are non-photosynthetic. The mode of nutrition is heterophic. Most of then use dead and decaying organic matter as food and are therefore called saprophytes. Some of them are parasitic.
Some fungal species live in permanent mutually dependent relationships with blue-green algae (or cyanobacteria). Such relationships are called symbiotic. These symbiotic life forms are lichens.
Most fungi are multicellular. Yeast is a unicellular fungus.
This group includes Mucus, Penicillium, yeast etc.
This group consists of multicellular eukaryotic organisms.
They are autotrophs and use chlorophyll for photosynthesis.
They possess a cell wall made of cellulose.
Kingdom Plantae is further classified as Thallophyta, Bryophyta, Pteridophyta, Gymnosperms and Angiosperms.
This group includes all photosynthetic plants.
This group consists of all multicellular eukaryotes which do not possess a cell wall.
These organisms are heterotrophic.
Cell wall is absent.
Kingdom Animalia is further classified as Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata, Protochordata and Vertebrata.
This group includes all animals.
Plant Kingdom ( Plantae):
The plant kingdom has been divided into two sub-kingdoms- Cryptogamae and Phanerogamae.
Cryptogams includes seedless and flowerless plants. These plants reproduce by producing spores.
It includes three divisions- Thallophyta, Bryophyta and Pteridophyta.
Most primitive and simple plants. The body is not differentiated into stem, root and leaves, but it is in the form of an undivided thallus.
They do not possess a vascular system.
The mode of nutrition is either photosynthetic (autotrophic) or heterotrophic.
They reproduce both asexually and sexually. Asexual reproduction is generally takes place by spore formation.
Sex organs are simple, single celled and there is no embryo formation after fertilization.
Examples- Green algae- Spirogyra, Chara etc.
They are small, multicellular green pants which inhabit shady damp places.
The plant body is commonly differentiated to form stem and leaf-like structures.
In them a true vascular system is absent.
The sex organs are multicellular. An embryo is formed upon fertilization. Water is required for fertilization so bryophytes are called amphibians of the plant kingdom.
Examples- Moss (Funaria) and Marchantia.
They have a well-differentiated body comprising of roots, stem and leaves.
They possess vascular system (xylem and phloem).
Sex organs are multicellular and jacketed by sterile cells/ fertilized egg develops into embryo.
Examples- Fern (Marsilea) and horse-tails.
Phanerogamae includes higher pants bearing flowers and seeds.
On the basis of presence and absence of fruits, the sub-kingdom phanerogamae is divided into two sub-divisions: Gymnosperms and Angiosperms. Gymnosperms:
They are most primitive and simple seed plants.
The seed produced by these plants are naked and are not enclosed within fruits.
Usually perennial, evergreen and woody plants. they do not have flowers.
Examples- Conifers- Pines, Firs and Cycades- Cycas etc.
They are highly evolved plants and they produce seed that are enclosed within fruits.
These are also called flowering plants.
Plant embryos in seeds have structures called cotyledons. Cotyledons are called ‘seed leaves’ because in many cases they emerge and become green when the seed germinates.
On the basis of number of cotyledons, angiosperms have further divided into two groups-
Monocotyledons ( plants with seed having single cotyledon) examples- wheat and rice
Dicotyledons (plants with seed having two cotyledons) examples- pea and potato.
Animal Kingdom (Animalia):
Characters to be considered for animal classification:
They are non-motile animals attached to some solid support.
Porifera means organisms with holes or pores all over the body. These lead to a canal system that helps in circulating water throughout the body to bring in food, water and oxygen.
They are mulicellular, diploblastic, radial symmetrical or asymmetrical organisms exhibiting cellular level of organization.
These animals are covered with a hard outside layer or skeleton.
They are commonly called sponges and are mainly found in marine habitats. Examples- Sycon, Spongilla.
Phylum- Coelenterata (Cnidaria):
Coelenterates are primitive, multicellular, aquatic animals. Their cells are organized into tissues.
They are diploblastic. Body shows radial symmetry.
Body contains a large cavity called coelenterons or gastrovascular cavity.
Body bears special cells called nematocysts for defence, offence and to capture food
Some of them live solitary life, e. g., Hydra while some live in colonies, e.g., corals.
Examples- Jellyfish, Sea anemone etc. Note: Coelenterates exist in two forms- an asexual polyp form and a sexual medusoid form.
They are bilaterally ssymmetrical, dorsiventrally flattened animals, commonly called flatworms.
They are triploblastic animals. They are without a body cavity.
Body is soft, leaf-life (liver fluke) or ribbon-like (tapeworm).
Excretory organs are in the form of flame cells. Digestive cavity (when present) with a single opening, the mouth (anus is absent).
Mostly parasitic (e.g. Tapeworm) but some are free-living forms (e.g. Planaria).
Mostly hermaphrodite, i.e., both male and female reproductive organs occur in the same individual.
Examples- Liver fluke, Planaria, Beef tapeworm.
Aquatic (freshwater or marine), terrestrial or parasitic forms, commonly called roundworm.
Bilaterally symmetrical, triploblastic, unsegmented and pseudocoelomate (false coelom) animals.
Body elongated, cylindrical, slender and tapering at the two end.
Straight alimentary canal with mouth and anus.
Reproduce sexually, sexes are separate, fertilization internal.
Examples- Rounworms (Ascaris), Filarialworm. Note: Parasitic nematodes are pathogenic, meaning they produce disease in the hosts. For example, elephantiasis.
Body triploblastic, bilaterally symmetrical, soft, elongated, vermiform and cylindrical.
Body metamerically segmented, i.e.m divisible into more or less similar segments.
True coelom present, which is divided into segments by internal septum.
Locomotory organs are setaeor parapodia.
Excretory organs arw nephridia. Circulatory system is of closed type.
Reproduction is by sexual means. Sexes may be united ( hermaphrodite) or separate.
Mostly aquatic, marine or freshwater, some are terrestrial, burrowing in tubes, some free-living forms.