Chapter-7 Diversity in Living Organisms

Biodiversity or Biological Diversity is the sum of all the different species of animals, plants, fungi, and microbial organisms living on Earth and the variety of habitats in which they live.

Plants and animals have different body plans and internal structures which help them survive. External and internal features are used to classify things. Some organisms can't be classified as plants or animals

Importance of Classification

By making a comparative study and assorting the similarities and differences amongst the various varieties of species, organisms can be classified into groups or sets.

Taxonomy is a regular branch of science that is involved with the purpose of arranging or grouping organisms.

Importance of classification

It makes the study of such a wide variety of organisms easy.

It projects before us a good picture of all life forms at a glance.

It helps us understand the interrelationship among different groups of organisms.

It serves as a base for the development of other biological sciences such as biogeography etc.

Various fields of applied biology such as agriculture, public health and environmental biology depend on classification of pests, disease vectors, pathogens and components of an ecosystem.

Variations in the Living World:Life occurs in different forms on earth.

Variations in Size: There are microorganisms that are a few micrometers in size and there a few plants and animals that are huge like the red wood trees (100 meters) and blue whale (30 meters).

Variations in Age: There are some species of pine trees that live for thousands of years while there are some mosquitoes that live for a few days.

Variations in Colour: There are some worms which are colourless while there are many varieties of birds and flowers which are brightly coloured.

Basis of Classification:

 Organisms are classified based on characteristics. Characters are details of appearance of behaviour, ie. Form and function of a living organism. The broadest divisions are made based on the most basic characters, for eg: when we divide all living organisms as prokaryotes and eukaryotes, it is the broadest division and the characters based on type of nuclear region in the cell is most basic.

Some basic characters used in classification are:

Prokaryotes & Eukaryotes Unicellular and multicellular organisms Autotrophs and heterotrophs Level of organisation of organisms that perform photosynthesis Type of body development and nature of specialised organs for different functions

Classification and Evolution:

Classification of life forms depends on evolution too. Evolution is a complex process by which the characteristics of living organisms change over many generations as traits are passed from one generation to the next.Characteristics that came into existence earlier are more basic than characteristics that have come into existence later. Based on evolution we can divide the organisms into two groups: Primitive or lower organisms and advanced or higher organisms.

Primitive organisms Advanced organismsThese are organisms with ancient body designs that have not changed much hence they are termed as

lower organisms.

This group of organisms have acquired their body designs relatively recently hence they are known as

higher organisms.These organisms are considered older on the

evolutionary scale and have simpler body designs. These organisms are considered younger and complex on the evolutionary scale as their complexity in design

has increased over time.

Hierarchy of Classification- Groups

Ernst Haeckel (1894), Robert Whittaker (1959) and Carl Woese (1977) tried to classify all living organisms into broad categories. Classification proposed by Whittaker includes Five Kingdoms and is widely followed.

Five Kingdoms proposed by Whittaker are : MONERA, PROTISTA, FUNGI, PLANTAE and ANIMALIA.

The kingdoms are classified further using the following subgroups:

KingdomPhylum (for animals) / Division (for plants)ClassOrderFamilyGenusSpecies

Important Characters of the Five Kingdom System of Classification:

Kingdoms MONERA PROTISTA FUNGI PLANTAE ANIMALIACharactersCell Type Prokaryote Eukaryote Eukaryote Eukaryote EukaryoteCell Number

Unicellular Unicellular Unicellular/ Multicellular

Multicellular Multicellular

Mode of Nutrition

Autotrophic / Heterotrophic

Autotrophic / Heterotrophic

Heterotrophic-(Saprophytic)

Usually Autotrophic

Heterotrophic

Presence of Cell wall?

May / May not be present

May / May not be present

Present (Made of chitin)

Present Absent

Any other special feature

Some members are very primitive (Archaebacteria

Some members have appendages (cilia, flagella, pseudopodia) for

Lichens are symbiotic life forms- an association of

Photoautotrophs- Use solar energy to make food

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Let us take an example by classifying Human beingsKingdom:   Animalia      Phylum:   Chordata          Subphylum:   Vertebrata               Class:   Mammalia                    Subclass:   Theria                         Infraclass:   Eutheria                              Order:   Primates                                   Suborder:  Anthropoidea                                        Superfamily:   Hominoidea                                             Family:   Hominidae                                                  Genus:   Homo                                                       Species:   sapiens

A species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring.

) locomotion cyanobacteria and fungus.

by Photosynthesis

Examples Bacteria (Lactobacillus), Blue green algae (Anabena), Mycoplasma

Unicellular Algae (Chlamydomonas), Diatoms, Protozoans (Amoeba)

Yeast, Mushrooms, Bread Molds (Mucor), Penicilium.

Spirogyra, Riccia, Moss, Fern, Pinus, Apple tree

Round worm, Tape worm , Hydra, House- fly, fish, man.

Kingdom Plantae

Basis of classification of Plant Kingdom into groups: Differentiation of the plant body Presence of specialised tissues for various functions (Transport of water etc.) Ability to bear seeds Are the seeds enclosed within fruits or not.

Cryptogams Phanerogams

Groups Thallophyta Bryophyta Pteridophyta Gymnosperms AngiospermsCharactersDifferentiation of plant body

Plant body is not well differentiated

Plant body poorly differentiated into root-like, stem-like and leaf-like structures.

Plant body differentiated into root, stem and leaves.

Plant body differentiated into root, stem and leaves.Seed bearing structures are also present

Plant body differentiated into root, stem and leaves. Flowering plants with seeds enclosed in fruits.

Presence of specialised

tissues

Not Present Not Present Present-Specialised tissues for conduction of water and other substances.

Present-Specialised tissues for conduction of water and other substances.

Present-Specialised tissues for conduction of water and other substances.

Ability to bear seeds

No No No Yes Yes

Flowering plants (Seeds

enclosed within fruits)

No No No NoSeeds are naked (Gymno means naked and sperma means seed.

Yes- seeds develop inside an organ that is modified to become a fruit.

Any other special feature

Commonly called algae, are predominantly

Called ‘amphibians of the plant kingdom’

Life cycle shows alternation of generation

Usually perennial, evergreen and woody plants.

Plant embryos in seeds have structures called

The Plant kingdom is broadly divided into two groups on the basis of reproductive organs and embryo structure. These are Cryptogams and phanerogams.

Cryptogams(Those with hidden reproductive organs)

Phanerogams(Seed bearing plants)

Reproductive organs are inconspicuous

They have naked embryos called spores.

Plants with well differentiated reproductive tissues that make seeds

Seed consists of with stored food.

aquatic cotyledons.Examples Spirogyra,

Ulothrix, Cladophora, Chara

Riccia, Marchantia, Funaria (Moss)

Marilea, Ferns, Horsetails.

Pinus, Cycas, Deodar, Araucaria

Mango tree, Banana Plant, grasses etc.

Angiosperms are divided into two groups on the basis of number of cotyledons present in the seed. These groups are: Monocotyledonous plants and Dicotyledonous plants.

Monocotyledonous plants Dicotyledonous plants

Single cotyledon present in the seed Fibrous root system Leaves with parallel venation Petals of flowers are usually in multiples of

three

Two cotyledons present in the seed Tap root system Leaves with reticulate venation Petals of flowers are usually in fours or

fives.

Nomenclature

Carl Linnaeus, father of modern botany, was a Swedish naturalist who laid the foundation of modern classification and nomenclature in 1758. He devised a binomial system of nomenclature (naming system) in which an organism is given two names: 

A generic name (name of genus) which it shares with other closely related organisms which has features similar enough to place them in the same group. 

A specific name ( name of species) which distinguishes the organism from all other species. No other organism can have the same combination of genus and species. The scientific name derived by using the system of nomenclature is followed all over the world as they are guided by a set of rules stated in the International Code of Nomenclature.Certain conventions are followed while writing the scientific names:

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.

Assignment:

1. On what basis did Aristotle classify living organisms? What were the drawbacks of this method?2. What was the modification introduced by Woese in Whittaker’s five kingdom system of

classification?3. Why are blue green algae termed as cyanobacteria?4. Differentiate between: Bryophytes and pteridophytes5. Why is Spirogyra known as a thallophyte?6. Why are advanced organisms also called complex organisms.7. Place the following organisms in groups. The first one is done for you

a) Chara- Plant Kingdom – Group: Thallophytab) Cyanobacteriac) Pinusd) Mustard plant

e) Fernf) Funaria