DIVERSITY IN LIVING

ORGANISM S

Basis of

Classification• Why do we classify things?

• * Classification provides scientists and

students a way to sort and group

organisms for easier study.

* There are millions of organisms on

the earth! (approximately 1.5 million

have been already named)

• Organisms are classified by their:

* physical structure (how they look)

* evolutionary relationships

* embryonic similarities (embryos)

* genetic similarities (DNA)

* biochemical similarities

Kingdom : Monera

(1) Nucleus :•    (a) Organisms of this kingdom do not possess a

well-developed nucleus.   (b) Nucleolus and nuclear membrane are absent.   (c) The genetic material occurs in the form of a mass of nucleoproteins.

(2) Organelles of cytoplasm :Membranous organelles are also absent in the cell.

(3) Types :Bacteria are the sole members of the kingdom Monera.This kingdom is divided into two divisions.

(a) Schizophyta or Bacteria, (b) Cyanophyta

(4)Nutrition:Bacteria live mainly as transformers, decomposers and also as parasites, e.g. E.coli Cyanophyta are also known as blue-green algae or cyanobacteria. They are autotrophic and posses photosynthetic pigments.

e.g. Spirulina, Oscillatoria.  

Kingdom : Protista

• (1) Structure :   Organisms are unicellular or multicellular.

• (2) Nucleus :   They possess a well developed nucleus.

• (3) Organelles :   Membranous organelles like mitochodria, golgibody etc. are present. They do not exhibit division of labor.

• (4) Method of nutrition :   They are autotrophic, heterotrophic and symbiotic methods of nutritions. Accordingly, protista are classified into autotrophs, phagotrophs or heterotrophs and symbionts.

• e.g. Algae, Protozoa and Fungi.

Kingdom: Fungi

• (1) Cellwall :    It is made up of chitin and cellulose or chitin.

• (2) Organelles :    Mitochondria with flat cristae, organelles like lomasomes which are responsible for chemical constitution or Cellwall and Scattered ribosomes are representative characters of fungi.

• The fungal cell wall is composed of glucans and chitin

• (3) Nutrition : They exhibit saprophytic or parasitic mode of nutrition.

• (4) Body organization :•  Their body is called mycelium and the filament –

like structures are called hyphae. (singular : hypha)

•  • (5) Example : Yeast, mucor.

The chart given below briefly outlines the classification of

The plant kingdom

The Animal Kingdom is divided in several phyla mainly on the basis of the cell organisation, symmetry, presence or absence of notochord and body cavity. Animals are arranged progressively from simple single-celled protozoans to highly complex mammals. Given below are some of the main characteristics of each phyla.

Phylum: Porifera (the

sponges)

• The simplest multicellular animals. The cells are loosely held together and do not form tissues

• Aquatic in habitat (mostly marine)• The body is covered with pores• Food and oxygen enter the organism

along with water into a canal system• They are non-motile animals attached

to some solid support• Reproduction may be sexual, asexual or

budding• Example: Sycon, Spongilla, Euptectella

Ph

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Coele

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rate

• These animals live in water

• Colentrates show more body desigh differentiation

• The body is made up of two layers of cells- one makes up cells on the outside and other makes the inner lining of the body

• Some of the species live in colonies(corals) while others have a solitary life-span

• E.g. Sea anemone, Jellyfish

Phylum: Platyhelminthes (Flatworms)

• Simplest triploblastic organisms showing bilateral symmetry

• Mostly parasites in other animals• Body in dorsoventrally flat and leaf-like or ribbon-

like with bilateral symmetry• The body cavity has only one opening which

serves as both the mouth and the anus• Example: Planaria, Liver Fluke, Tape Worm

Phylum: Nematoda

• Triploblastic body showing bilateral symmetry

• Parasitic or free living• Body is long, smooth

and cylindrical• Alimentary canal

begins with the mouth and ends with the anus

• Example: Ascaris (Round worm), Enterobius (Pinworm)

Phylum: Annelida(Segmented worms)

)

• These animals are found in a variety of habitats- fresh water, marine water as well as land

• They are bilaterally symmetrical, triploblastic animals

• Annelids are the first animals with true body cavity

• They have metameric segmentation with extensive body differentiation

• E.g. Earthworm, Leech

Phylum Arthropoda (animals with jointed legs)

• This is the largest phylum with almost 80% of the animal kingdom

• Body is bilaterally symmetrical and segmented. It is divided into head, thorax and abdomen

• Possess jointed legs which may be modified for walking, swimming feeding and feeling

• The coelomic cavity is blood-filled• Open circulatory system is present• E.g. Prawn, Butterfly, Spider,

Mosquito

Phylum: Mollusca (soft-bodied animals)

• Aquatic in habitat but some land forms are also seen

• Bilateral symmetry is present

• The coelomic cavity is reduced and there is little segmentation

• Open circulatory system is present and kidney-like organs for excretion

• The soft body is supported by a hard shell

• Locomotion is brought about with muscular foot

• E.g. Octopus, Pila

Phylum Echinodermata (spiny-skinned

animals)

• Marine in habitat• Body is triploblastic and has a

coelomic cavity• They have a peculiar water-

driven tube system for locomotion

• Skeleton is made of hard calcium carbonate structures

• E.g. Star fish, Sea cucumber

Protochordata

• They are exclusively marine, triploblastic and coelomate

• Bilateral symmetry is present

• A long rod-like support structure called notochord is present at some stage of life.

• E.g. Balanoglossus

Sub-phylum Vertebrata

• This includes the majority of chordates• Head is prominent• Nervous system and exoskeleton are highly

developed• Notochord is replaced by a jointed vertebral

column• Two pairs of appendages (limbs)• Aquatic animals have gills• Vertebrates are grouped into five classes:• Pisces, Amphibia, Reptilia, Aves and Mammalia

Class: Pisces

• These are fishes and exclusively water living animals

• The body is covered with scales• Body - streamlined• Fins – present, limbs -absent• Muscle tails is present which is

used for movement• Respiration through gills• Cold-blooded, two chambered heart• egg laying.

They are two types based on• The nature of their skeletons:

1) Cartilaginous fish- Their skeleton is made of cartilage such as sharks, rays etc.

2) Bony fish- Their skeleton is made of bones such as Rohu,

Seahorse etc.

Class: Amphibia

• Live in both water and on land• Respiration is by gills, lungs or skin• 3 chambered heart• Is cold blooded• Have two pairs of pentadactyl (5 digit)

limbs which may be absent in some cases

• They lay eggs• E.g. Frog, Salamanders

Class: Reptilia

• Mostly terrestrial• Heart is 3 chambered, is cold

blooded• Breathe through lungs• Body covered with scales• Have two pairs of pentadactyl (five

digit) limbs which are absent in snakes

• They lay eggs• The heart is three-chambered• E.g. Snakes, Lizards, Crocodiles.

Class: Aves (birds)

• Arboreal in habitat i.e., they live on trees

• Warm blooded. 4 chambered heart

• Body covered with feathers• Lungs have membranous

extensions called air sacs to make the body light

• Mouth is surrounded by a beak. Teeth are absent

• Fore-limbs are modified into wings

• E.g. Sparrow, Pigeon

Class: Mammalia (Mammals)

• Most intelligent of all organisms• Warm blooded with 4 chambered

heart• Give birth to young ones• The mother suckles her young ones

on milk secreted by special glands called mammary glands

• Body covered with hair• Have two pairs of pentadactyl limbs• Breathe through lungs• E.g. Humans, Whales, Elephant

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

• 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.

• E.g. Mango (Mangifera indica)• Tiger (Panthera tigris)

The end