Diversity: – Every organism of the living world, whether it is a plant, an animal or a microorganism is unique in itself. This makes a differentiation between organisms. It is known as diversity.
Biodiversity: – The diversity of plants and animals is known as Biodiversity. This term was coined by Walter G. Rosen in 1986. Biodiversity includes diversity within species, between species and of ecosystems.
Scientific Naming: – This is the uniform system of naming organisms in which a single name is given to a particular type of organism which is followed all over the world. This overcomes the problem of common vernacular names which are different for a particular type of organism from region to region. Scientific names are guided by a set of rules stated in the International Code of Biological Nomenclature.
Binomial Nomenclature: – This is the system of scientific naming in which every organism is given two proper names. The first name is the genus to which the organism belongs and the second name is its species.
For example a common frog is known as Rana tigrina (both names should be in italics or underlined and only first letter of first name should be capital). This system was given by Carolus Linnaeus (also known as father of taxonomy)
Classification of Organisms:- The method of arranging organisms into groups or sets on the basis of similarities and dis-similarities (differences) is called classification. The science of classification is known as taxonomy.
Importance of Classification
Due to following reasons we need to classify organisms:-
- Classification makes the study of a wide variety of organisms easy. Classification is the tool by which one can deal with great diversity of living forms.
- Classification projects before us a picture of all life forms at a glance.
- Classification is essential to understand the interrelationships among different groups of organisms.
- Classification forms a base for the development of other biological sciences. We can consider the case of the science of biogeography which is the study of geographical distribution of plants and animals. Biogeography is the totally dependent on the information supplied by classification
Classification Systems:- several systems of classification have been given by different biologists-
- Two kingdom classification ( by Linnaeus- 1735)
- Three kingdom classification(by Haeckel-1866)
- Five kingdom classification (by R.H. Whittaker-1969)
The Five Kingdom Classification:- Margulis and Schwartz revised the five kingdom classification in 1982. It is based on complexity of cell structure, complexity of organism’s body and mode of nutrition.
Summary of Five Kingdom Classification :
|I. Monera||Unicellular, Prokaryotes, Autotrophic and Heterotrophic nutrition, Important decomposers and mineralisers.
Examples : Bacteria, Blue green algae.
|II Protista||Unicellular, Eukaryotes, Autotrophic and Heterotrophic nutrition, Producers, consumers and decomposers.
Examples : Phytoplanktons, Zooplanktons and Protozoans.
|III. Plantae||Multicellular, cells have cellulose wall and contain chlorophyll. Mainly autotrophic nutrition. Major Producers on land.
Examples : Red, brown, green algae, Mosses, Ferns, Seed plants.
|IV. Fungi||Unicellular or Multicellular. Body made of filaments (hyphae), Mainly saprophytic nutrition, Major decomposers.
Examples : Yeast(unicellular), Moulds, Mushrooms.
|V. Animalia||Multicellular, cells without cell walls or chloroplast. Heterotrophic nutrition, Basic Consumers on earth.
Examples : sponges, Invertebrates and Vertebrates.
VIRUSES : – Viruses are simple, acellular, sub-microscopic entities consisting of one more molecules of either DNA or RNA enclosed in a coat of protein and able reproduce.
The study of viruses is known as ‘Virology’.
Examples : Tobacco mosaic virus, Polio virus, Bacteriophages and
Characterstics of Five Kingdoms :
- Kingdom Monera : – Monerans are the most plentiful living organisms on the earth. They are the smallest and hence are visible through the microscope only. A teaspoon of rich soil contains billions of them. These are found almost every where around us and on earth. They have following characterstic features : –
- Simple Prokaryotic Unicellular
- Lack a well defined nucleus or any membrane bound organelle.
- Most have rigid cell wall
- Have various modes of nutrition. Could be autotrophs or
- Known as decomposers and mineralisers in the biosphere
- Kingdom Protista :
Structure : –
- They have a typical eukaryotic structure with a membrane bound nucleus.
- The cytoplasm has number of membrane bound organelles like mitochondria, golgi complex, endoplasmic reticulum, chloroplasts (autotrophs) etc.
- Some may have flagella or cilia for locomotion.
- The photosynthetic forms have a cell wall.
- Some protists (Protozoans) have holozoic nutrition and hence have elaborate organelles for ingestion.
Locomotion In Protists :- protests show locomotion by flagella, cillia and pseudopodia.
- Flagella : – These are long, whip-like, fine structures which help organisms to propel. Some protists have only one flagellum like in Euglena while others may have more than one.
- Cillia : – These are short, fine, hair like structures present all over the body. They move in coordinated manner to bring about the locomotion. With the help of these, cilliates move rapidly, they can turn, tumble and
- even reverse. Cilliates are considered to be the fastest predatory protists. e.g., Paramaecium.
- Pseudopodia : – These are also known as false feet. These are blunt protoplasmic extensions which give an irregular shape to the organisms and help in the movement by getting extended in a particular direction. e.g., Amoeba
Reproduction in Protists : – protists show both asexual and sexual modes of reproduction
Cyst Formation :- it is not a mode of reproduction but a means to save a cell from unfavourable conditions like drying up of a pool of water.
Phylum Protozoa of Protists : – Unicellular or acellular, microscopic organisms possessing typical cell structure.
General Characters of Phylum Protozoa :
- Small usually microscopic and can be seen with naked eyes.
- Body : – Acellular with one or more than one nuclei.
- Symmetry : – Non-symmetrical, bilateral, radial, spherical.
- Body covering : – A pellicle
- Shape : – Usually constant.
- Division of Labour : – No physiological division of labour hence acellular.
- Locomotion : – By Pseudopodia, flagella and cilia. Other organs are absent.
- Nutrition : – Holozoic, holophytic, parasitic or saprozoic.
- Excretion : – Through contractile vacuoles or generally through body surface.
- Reproduction : – Asexually and sexually.
- Habit and habitat : – These are ubiquitous or cosmopolitan. Free living protozoans are usually aquatic(marine or fresh water). Several protozoans are commensal, symbiotic and parasitic species. Parasitic protozoans are internal or external. Most protozoans are solitary but colonial also.
Examples : Euglena, Trypanosoma, Amoeba and Paramecium.
- Kingdom Fungi : (L. fungus- a mushroom)
General Characterstics of Fungi : 1) Fungi are ubiquitous. They are found in every conceivable habitat, mostly terrestrial, but a few are aquatic.
2) Fungi are heterotrophic. They live either as saprophytes, parasites or symbionts.
- Their cells grow as elongated filaments called ‘hyphae’. The body of multicellular and filamentous fungus is called
- The fungal cell contains the usual cell organelles, all similar to eukaryotes, except plastids. Cell wall is usually made up of chitin, some with cellulose and a few have both.
- Reserve food material is in the form glycogen and oil droplets.
- Many fungi are ‘eucarpic’ e., only a part of the mycelium is involved in the development of reproductive organs.
- Many fungi form fruit bodies like ascocarps, basidiocarps etc.
- Fungi propagate vegetatively by fragmentation and asexually by spores or conidia. Sexual reproduction takes place by gametangial copulation or by somotogamy.
Examples : Mucor, Rhizopus,Yeast, Penicillium, Aspergillus and Agaricus
- Lichens : Lichens are formed by symbiotic association of algae and Algae photosynthesis the food and fungi provided the attachment, water and mineral nutrients. The algal component of the lichen is known as phycobiont and the fungal component as mycobiont. They are the first organisms that appear in a new terrain.
Examples : Rhizocarbon, Parmelia and Alectoria
- Mycorrhiza : Mycorrhiza are symbiotic associations of fungi with plant roots. The fungus provides the moisture, nitrogen and minerals and the root sugars and vitamins. In the absence of mycorrhiza, plant growth may become stunted in certain plants
Examples : Anabaena cycadae is the fungi found in the roots of Cycas( a gymnosperm)
- Kingdom Plantae : plants are multicellular eukaryotes with cellulose cell walls. They are autotrophs and use chlorophyll for photosynthesis. All plants are included in this group forming visible biodiversity.
CLASSIFICATION OF KINGDOM PLANTAE
Description of Plant Kingdom
1.Division Thallophyta :
(Gr. Thallus- plant body without root, stem and leaves; phyton- a plant)
- Most primitive and simple plants. The plant body is not differentiated into stem, root and leaves, but it is in the form of an undivided
- Most algae are water-growing or aquatic, both marine and fresh water; some are terrestrial, i.e. live on land near moist places.
- Autotrophic and reserve food is generally starch.
- Mechanical and conductive tissues are absent( no vascular system)
1.algae- Ulothrix, Spirogyra, Ulva and chara.
- Division Bryophyta(Gr. Bryon-a moss, a liverwort)
- Bryophytes are small multicellular green land plants. These simplest land plants are confined to shady damp places. They lack true roots, stem and leaves and no flower. They are also called amphibians of the plant kingdom.
- Plant body is flat, green thallus in liverworts(Riccia, Marchantia) and leafy, erect structures in mosses( Funaria, Sphagnum)
- vascular system is absent.
- Sex organs(Archegonia and Antheridia) are multicellular.
- An embryo is formed upon fertilization
Examples : Riccia, Marchantia, Anthoceros and Funaria
Tracheophyta : –It includes all vascular plants. The plant body has specialized conducting tissues xylem and phloem. Their deep roots, leaves covered with cutin and woody tissues are the resons of their dominance on earth.
- Division Pteridophyta(Gr., pteris,- idos – fern)
- They are found mainly in shady or damp places.
- The plant body is made up of root, stem and leaves.
- They have well developed vascular system ( xylem and phloem) for the conduction of water and other substances from one part of the plant body to another.
- These plants have no flower and do not produce seeds.
- The leaves of ferns have various shapes and are called as
- Sex organs are multicellular and protected by sterile cells.
- Fertilised egg develops into embryo
Examples : Club mosses- Selaginella, Lycopodium. Horsetails- Equisetum and Ferns- Marsilea, Azolla and Adiantum
Phanerogamae or Spermatophyta (Gr., sperma,-atos-seed)
- Phanerogamae includes higher plants that bear flowers and seeds, Seeds are the result of the reproductive process. They consist of the embryo along with stored food , which serves for the initial growth of the embryo during germination.
- The plant body is differentiated into root, stem and leaves.
- Vascular system (xylem and phloem ) is well developed.
- Sex organs are multicellular.
- An embryo develops from fertilized egg.
Phanerogames are further divided in to two divisions on the basis of absence or presence of fruits and the group of seed bearing plants.
- Division Gymnospermae (Gr., gymno- naked; sperma- seed)
- They are most primitive and simple seed plants.
- The seeds produced by these plants are naked and are not enclosed within fruits.
- Usually perennial, evergreen and woody plants.
- They xerophytic ( capable of living in water lacking conditions) in nature.
Examples : Cycas, Pinus, Cedrus (deodar), Ginkgo
- Division Angiospermae (Gr., Angeion-case; sperma- seed)
- Angiosperms are highly evolved plants and they produce seeds that are enclosed within the fruit.
- The reproductive organs are aggregated in a flower. Since these plants have flowers, they are called flowering plants.
- Plant embryos in seeds have structures, called Cotyledons are called ‘seed leaves’ because in many cases they emerge and become green when the seed germinates. Thus, cotyledons represent a bit of pre-designed plant in the seed.
On the basis of number of cotyledons( fleshy embryonic leaves ), the angiosperms are divided in two classes dicotyledonae and monocotyledonae.
- Dicotyledonae (Dicots) :
- The seeds produced by these plants have embryos with two fleshy leaves, the
- Their leaves have reticulate venation, with network of veins.
- The root system has a prominent tap root.
- The flower have five or multiple of five petals (Pentamerous)
- Leaves are dorsiventral (upper and lower surfaces are distinct)
- The vascular bundles are arranged in a ring . They are open( i.e. cambium present) and undergo secondary growth.
Examples : Pea (Pisum sativem), Potato (Solanum tuberosum), Sunflower (Helianthus annus), rose(Rosa indica), neem (Melia indica)
Monocotyledonae (Moncots) :
- The seeds of these plants have only one cotyledon.
- Their leaves have parallel venation
- The root system consists of similar fibrous roots.
- The flowers are trimerous, i.e., have three or multiple of three petals
- Leaves are Isobilateral i.e., upper and lower surfaces are similar.
- The vascular bundles are scattered and closed ( cambium absent) and secondary does not occur.
Examples : Maize(Zea mays), wheat (Triticum), rice(Oryza sativa), onion (Allium cepa), sugarcane (Saccharum officinarum), banana (Musa paradisiacal)
- Kingdom Animalia : Animals are acellular or multicellular organisms. Multicellular animals are heterotrophs. Animal are motile and are provided with sensory or nervous system. The only exception is porifers. They are devoid of proper nerve cells.
Note : – Before study animalia everyone should understand some facts and terms concerning animals-
Body Organisation of Animals : Body organisation of animals can be studied under following heads-
- Body Plan : It can be further divided into three basic plans :
- Cell aggregate Plan : Cells are loosely arranged in groups. The tissue or organ system is absent e.g. porifers.
- The blind sac plan : It is more evolved plan than the cell aggregate plan. The alimentary canal has only single opening which opens outside. This is the opening for ingestion and egestion both. Division of labour is developed. This type of digestive tube is known as blind sac. e.g., coelenterates and flatworms.
- The tube within a tube plan : The digestive system is provided with mouth and anal opening. Ingestion by mouth and egestion by anus. More evolved and complex form.
- Symmetry : – It is divided as follows-
- Asymmetrical : An animal which cannot be divided into two equal and similar halves from any point. Such symmetry is known as asymmetry. e.g., Snail
- Bilateral symmetry : when an animal is cut lengthwise in the middle vertical plane, then it is divided into two equal mirror halves i.e. opposite right and left halves. This symmetry may not be internal symmetry also, e.g. frog, man, earthworms, insects etc. (most of the animals)
- Radial symmetry : When an animal is divided through its longitudinal axis through any diameter, then body will have two equal halves, e.g., hydra, star fish etc
3.Body cavity or Coelom : The body cavity or coelom is present only in the animals with tube with in a tube body plan. Their cavity is filled with the fluid. This is known a body coelom. The coelom gives flexibility to the body. All the internal organs are suspended in the coelom. Thus coelom protects and acts as a shock absorber. Except in roundworms, the coelom develops from embryonic mesoderm in all animals. Porifers, coelenterates and platyhelminthes are devoid of coelom, hence also known as acoelomates.
4.Body segmentation : The body is divided into constricted body segments. These segmentation arises in the annelids and is also present in the arthropods and all chordates.
5.Body support and protection : Soft bodied animals are provided with exoskeleton. e.g. foraminifera (protozoans), coelenterates, arthropods and most of the molluscans. The exoskeleton is formed by the deposition of hard substances or shell. The exoskeleton is also present in the vertebrates such scales, feathers, hairs, nails etc.
Hard bony and cartilaginous tissue forms the skeleton of the body especially of vertebrates. Notochord supports the body of primitive adult chordates whereas vertebral column is a supporting skeleton of vertebrates. Appendicular skeleton provides a mean of locomotion and brain case (cranium ) and vertebral column protects the central nervous system in vertebrates. The axial skeleton gives the length or height to the animals.
Description of Animal Kingdom :
- Phylum Porifera :
- Habit and habitat : Aquatic, sedentary, mostly marine but fresh water also. Commonly known as sponges
- Body : Diploblastic and non cellular. Mesenchyma layer is present in between two layers ( ectoderm and endoderm). Loosely arranged cells with tissue grade system.
- Shape : Variable plant like.
- Symmetry : Radial (mostly) or asymetrical.
- Surface bears numerous minute pores known as These are openings of canal system. One large opening osculum forming the blind sac body plan.
- Canal system : water current in the body is maintained by the canal system
- Mouth : Absent
- Digestion : These are biofilters
- Skeleton : Internal and is made of spicules and spongin fibres. These spicules are chemically made up of silicon, calcium and sponging fibres and are proteinaceous in nature.
- Locomotion :
- Great power of
- Sex : Hermaphrodite or unisexual
- Reproduction : Asexual by buds and regeneration and sexual by gametes.
Examples : Sycon, Euplectella, Spongila etc.
- Phylum Coelenterata :
- Habit & Habitat : Exclusively aquatic, mostly marine and few fresh water. Solitary or colonial and sedentary or free living.
- Body : Diploblastic and non- cellular intermediate supporting layer known as mesoglea.
- Symmetry : Radial symmetry.
- Tissue Grade System : Low grade.
- Mouth : Present and encircled by tentacles.
- Characterstic interstitial cells and nematocyst : Nematocyst serves for stinging, adhesive, offence and defence and food capture.
- Gastro-vascular cavity : Lined with endoderm called coelenteron.
- Digestion :
- Skeleton : External or internal lining or in the form of scelerites or as continuous mass.
- Locomotion : Due to smooth muscle fibrils in the epithelial cells.
- Reproduction : Asexual by budding and sexual by ova and sperms. Cleavage holoblastic
- Respiratory, circulatory and excretory organs absent
Examples : Hydra, Physalia (Potugese man-of war ) and Aurelia( Jelly fish)
- Phylum Platyhelminthes :
- Habit & habitat : Free living, aquatic, both marine and fresh water and a few are terrestrial and rest are parasitic.
- Body : Thin, soft, leaf-like or ribbon like;Triploblastic & acoelomate
- Shape : Worm like but may be ribbon like or broad leaf like
- Symmetry : Bilateral symmetry
- Size : Generally of moderate size but few are of 10-15 metres.
- Adhesive organs : Secretion or /and suckers; hooks etc.
- Skeleton : Absent but contains organs which are cuticularised with scleroprotiens only. These hard organs are provided with hooks, spines, thorns, spicules etc. which are of cuticle
- Digestive System : Absent in acoela and flatworms but rest of these animals are provided with digestive system.
- Excretory system : By protonephridia which are provide with special type of cells- the flame cells.
- Sex : Mostly Hermaphrodite (both male and female reproductive organs occur in the same individual)
- Circulatory and respiratory system are absent
- Reproduction : Reprproductive system well developed. Asexual reproduction in planaria is by fission and sexual reproduction by generalized formation of ova and sperm fusion.
Examples : Planaria, fasciola hepatica (liver fluke), Taenia solium (pork tape worm)
- Phylum Nematoda or Ascahelminthes :
- Habit & habitat : Most forms are parasitic but some are free living in soil or water. Parasitic nematodes are pathogenic i.e. they produce diseases in the hosts, e.g., elephantiasis(by Wuchereria bancrofti), ascariasis(By Ascaris) and enterobiasis (by Enterobius)
- Body : Unsegmented, round, tube-like or worm-like(round, slender and tapering at the two ends); triploblastic and body cavity is pseudocoel.
- Symmetry : Bilateral symmetry
- Digestive System : Alimentary canal is complete(tube within tube organization) with mouth and anus.
- Head is well formed.
- Body is covered with a tough, resistant cuticle; cilia absent
- Exceretory system : Consists of protonephridia and canals to remove the wastes from the body..
- Sex : separate and exhibit distinct sexual dimorphism.
Examples : Ascaris, wucheria and Enterobius
- Phylum Annelida (L., annelus- a ring; segmented worms )
- Habit & habitat : Mostly aquatic, marine and fresh water. Some are terrestrial burrowings animal, some are symbiont and some are parasite.
- Body : Truely segmented(metamerically segmented externally by transverse grooves and internally by septa) worm’s body is externally as well as internally divided by a number of rings or annuli; Triploblastic and coelomate
- Symmetry : Bilateral symmetry
- Organ system grade body organization in which organs form the system
- Locomotion : By chitinous setae or muscular parapodia.
- Digestive system : Well developed and extracellular digestion
- Blood circulatory system : Closed type. Respiratory pigment dissolved in plasma.
- Respiration : By humid skin or parapodia or cephalic gills.
- Excretory system : Segmentally arranged
- Sense organs : organs of touch, taste buds, statocyst, photosensitive cells and eye with lens.
- Sex : Hermaphrodite or unisexual.
12)Reproduction : By sexual means.
Examples : Neries(clam worm or sand worm), Aphrodite( sea mouse), Pheretima posthuma( earthworm), Hirudinaria (Indian cattle leech)
- Phylum Athropoda (Gr., arthros- jointed; podos- foot; jointed-legged animals)
- Habit & habitat : Free living, aquatic and parasitic. The variety of habits and habitats are present in the animal of arthropods
- Body : organ system grade body organization; Triploblastic, segmented; Body divides into head, thorax and abdomen. Head and thorax often fused to form Cephalothorax
- Body coelom : Haemocoel filled with haemolymph.
- Symmetry : Bilateral symmetry
- Locomotion : By segmented legs for walking and running and wings for flying.
- Skeleton : Chitinous cuticularised exoskeleton which is periodically casted off.
- Digestive system : Complete; mouth parts are adopted for differentially feeding mechanism.
- Circulatory System : Open type; consists of a dorsal pericardial, a middle perivisceral and a ventral perineural sinus along with one heart, arteries and veins.
- Respiration : From general surface, gills, trachea and book lungs.
10) Excretion : By green glands and malpighian tubules; true nephridia absent.
11) They have complex muscular system with exoskeleton for attachment, striated muscles for rapid actions and smooth muscles for visceral organs. They lack the cilia.
12) Sense organs : Simple and compound eyes and sense of touch.
13) Sex : Usually separated
14) Reproductive system : Paired gonads with ducts
15) Fertilization : Internal, oviparous and ovoviviparous; often with metamorphosis.
Note : – Arthropoda probabley form the largest ( 75% species of all animals) phylem of animal kingdom. About 900,000 species are known.
Examples : Palaemon (prawn), Cancer (true crab), Scolopendra( centipede), Julus (millipede), Musca (house fly), Apis ( honey bee), Culex (mosquito)
- Phylum Mollusca (L. molluscus- soft)
- Habit & habitat : Terrestrial, aquatic, marine or fresh water.
- Body : Organ system grade of body organization; Body soft, without appendages triploblastic, coelomate unsegmented (except monoplacophora) and divided into anterior head, a ventral muscular foot, a hard dorsal visceral mass. The size of body varies from a microscopic to a giant form such as Octopus of up to 50 feet.
- Body coelom : Restricted mainly to the pericardial, gonadal and renal sinuses; Body cavity is haemocoel
- Symmetry : Bilateral symmetry
- Skeleton : The entire body is covered by a fold of thin skin, called mantle which secretes a hard calcareous shell of one or more pieces. Shell is monovalvular or bivalvular; sometimes absent or internal.
- Digestive system : Complete, glands, liver and hepatopancreas.
- Circulatory system : Closed type mainly, but in some cases it is open type and opens in to some sinuses, heart with auricle and ventricle, haemocyanin is the respiratory pigment.
- Respiration : By gills or lungs or both
- Excretion : By nephridia or kidney.
- Sense organs : Eyes, statocyst, sense of touch, smell and gustatory.
- Reproductive system : Dioecious or monoecius, gonads with one or two ducts. Sexes usually separate.
- Fertilization : External or internal.
Examples : Chiton, Pila (apple snail), Unio (fresh water mussel), Sepia ( cuttle fish ) and Octopus (devil fish)
- Phylum Echinodermata (Gr., echinos- spiny or hedge hog; derma- skin; spiny skinned animals )
- Habit and Habitat : Exclusively marine, free living or sedentary or gregarious (colonial)
- Body : Organ system grade of body organization; Triploblastic, coelomate; Unsegmented globular, star shaped, oval, disc shaped and exetended lengthwise; Body lacks head, but oral and aboral surfaces. Oral surface of body has five radial areas called ambulacra
- Symmetry : Secondary radial symmetry ( Bilateral in embryonic stages and radial in adult stages)
- Pentamerous body surface radiated into ambulacral and interambulacral region alternately present.
- Locomotion : By tube feet or podia
- Skeleton : Dermal spines or dermal calcarious stipules form the internal skeleton.
- Body coelom : Enterocoelic type includes perivisceral coelom and water vascular cavities.
- Body cavity is modified into a unique water vascular system which moves respiratory and locomotory organs, the tube feet or
- Digestive system : Complete, but sometimes anus is absent; Alimentary canal straight or coiled
- Circulatory system : Perihaemal blood vascular system.
- Excretory system :
- Sense organs : Organs of touch , chemoreceptors, internal tentacles, photoreceptors, statocyst very less developed.
- Sex : Generally unisexual.
- Reproductive system : Reproductive organs large gonads and numerous gonoducts.
- Fertilization :
- Regeneration power present.
Examples : Antedon (Feather star), Holothuria (Sea cucumber), Echinus ( Sea cucumber), Ophioderma (brittle star), Asterias (star fish)
- Phylum Chordata ( Gr., chorda- string )
General characters : These characters may be divided into-
- Fundamental chordate characters.
- Common characters of chordates and non-chordates.
- Advance chordate characters
- a) Fundamental chordate characters : These characters are present in any stage of life history essentially. There are three unique morphological characters-
- Dorsal,hollow tubular nerve chord
- Notochord or chorda dorsalis ( Gr., noton = back + L. chorda = cord ) : It is a long rod-like support structure that runs along back of the animal separating the nervous tissue from the gut. It provides a place for muscles to attach for ease of movement. It occurs ventral to nerve to nerve chord and is replaced by bone or cartilage to form a vertebral column in higher vertebrates.
- Paired pharangeal gill-slits
- b) Common characters of chordates and non-chordates :
- Bilateral symmetry
- Triploblastic condition
- c) Advance chordate characters :
- Living endoskeleton
- Efficient respiration
- Ventral heart
- Hepatic portal system
- RBC or erythrocytes
- Post anal tail
vii) Centralization of nervous system
Chordata is the advance group of animals. It is further divided into two groups-
- Protochordata :
- This group contain the primitive characters of chordates
- Nerve chord present in the larval form and it degenerates in the form of small ganglion in the adult.
- Notochord may or may not be present in the adult but it must be present in larval stages.
- Pharyngeal gill slits are present generally in adult stages.
- Exoskeleton, head, jaws and paired fins are absent
- May be metameric or non-metameric.
- Marine, solitary and colonial
Examples : Balanoglossus ( acorn worm or tongue worm), Herdmania and Branchiostoma (lancelet)
- Vertebrata : This is most advance group of all animals. The Notochord develops in vertebral column. Central nervous system present. It has been divided in to following Superclasses and Classes-
- a) Superclass Pisces :
- Habit & Habitat : Aquatic, fresh water or marine, cold blooded vertebrates (ectothermal).
- Skin : Covered with scales, boney plates or dermal denticles.
- Body : It is usually streamlined but some are elongated, few are dorso-ventrally compressed and some are snake like.
- Fins : Paired or unpaired with soft of spiny rays.
- Endoskeleton : Cartilaginous and bony.
- Respiratory organs : Gills, but accessory respiratory organs are also present. The slits open outside. These are covered in bony fishes. These gill slits are never more than seven.
- Lateral line system : Well developed.
- Heart : Venous heart i.e., only deoxygenated blood is transported through the heart. Two chambered- one auricle and one ventricle.
- Excretory system : Two mesonephric type kidneys. Excrete ammonia (ammonotelic animals)
- Cranial nerves : Ten pairs.
- Ear : Only internal
- Sex : Unisexual
- Development :
- Reproductive organs : One pair of gonads with gonoducts.
Examples : Scoliodon (dog fish, Indian shark ), Torpedo ( electric ray ), Labeo (rohu, carp), Hippocampus (sea horse)
- b) Class-Amphibia ( amphi = double; bios = life ) :
- Habit & Habitat : Amphibians are primarily aquatic because they lay eggs in water and early development of life takes place in aquatic medium and secondarily they are terrestrial. They are cold blooded animals (ectothermal).
- Skin : Smooth or rough glandular kept moist by the glandular secretion.
- Scales are hidden in the skin if present
- Body : With distinct head and trunk, no neck. Mouth usually large.
- Limbs : Tetrapodus ( four in number) and pentadactylus (five fingers/digits in each limb). Digits or toes without claws. Limbs may be absent in some cases.
- RBC : Biconvex, oval and nucleated.
- Heart : Three chambered- one ventricle and two auricles with sinus venosus symmetrical aortic arches.
- Respiration : Either by gills, lungs, skin or the mouth lining. Gills present at least during early stages of development.
- Excretion : By mesonephric kidneys. They excrete either ammonia or urea.
- Lateral line system : Present during some stages of development.
- Cranial nerves : 10 pairs.
- Reproduction : Oviparous, lay yolk-ladden eggs with gelatinous covering usually in water. Fertilization external in frogs and toads, but internal in salamanders and apoda..
- Development : Generally with aquatic larval forms. Metamorphosis present
Examples : Rana tigrina (bull frog ), Bufo (toad), Hyla (tree frog), Salamandra
- c) Class-Reptilia (, repre = to crawl; creeping vertebrates )
- Habit & Habitat : Cold blooded, terrestrial and aquatic.
- Body covering : With horny scales or scutes.
- Skin : Dry; devoid of glands
- Body : Varies in form and is usually divided into head, neck, trunk and tail.
- Limbs : Tetrapodus and pentadactylus, with clawed digits. Limbs absent in snakes and some lizards.
- Respiration : By lungs
- Heart : Three chambered- Two auricle and incompletely divided ventricle. Only crocodiles have four-chambered heart. Right and left aortic arches are complete.
- Teeth are present in all reptiles except in tortoises and turtles
- RBC :
- Excretion : By metanephric kidneys and each kidney is provided with a separate ureter. Terrestrial reptiles such as snakes and lizards excrete uric acid ( uricotelic animals)
- Cranial nerves : 12 Pairs.
- Reproduction : Most reptiles are oviparous and lay their eggs with tough covering and do not need to lay their eggs in water. A few reptiles are viviparous (e.g., lizards and snakes). Fertilization internal and development on land.
Examples : Hemidactylus flaviviridis (house wall-lizard), Crocodilus, Gavialis (Alligator), Varanus(Indian monitor), Python, Naja naja(cobra), Chamaeleon.
- Class-Aves (, avis = bird)
- Habit & Habitat : Warm blooded (endothermal) with various flight adaptations
- Skin : Only oil glands on tail.
- Body : Spindle or boat shaped and divisible in to head, neck, trunk and tail.
- Exoskeleton : Horny scales persists on the feet but feathers cover most of the body. Beak is also horny and without teeth in living birds.
- Endoskeleton : Spongy and light weight containing air.
- Limbs : Forelimbs modified in to wings provided with feather or flight. Hindlimbs bear four clawed digits and adopted for walking or swimming and pearching.
- Digestive system : Crop (a storage organ) is formed by the gullet. Stomach divided into proventriculus (glandular) and gizzard (muscular. Cloaca true with three chambers.
- Respiratory system : Respiratory organs are spongy and non-distensible lungs. Air sacs present and communicate with the air cavities in the bones.
- Sound production : By a swollen part syrinx.
- Heart : Four chambered, double circulatory. Only right aortic arches are present.
- RBC : Oval and nucleated.
- Excretory system : Metanephric kidneys; three lobed excretory duct, the ureters open directly into cloaca. They excrete semisolid urine having uric acid (uricotelic animals). No bladder.
- Brain : Cerebellum most developed.
- Reproductive system : only left ovary is present. They are oviparous and lay large, yolk-laden eggs having hard shell. Fertilization internal
- Birds have highly developed voice, hearing and vision. They also have specialized sense for nest building and care for the young (parental care)
Examples : Gallus (chicken), Passer (house sparrow), Corvus (crow), Columbia (pigeon), Psittacula (parrot), Pavo (Peacock), Eudynamys (koel), Bubo(owl)
- Class-Mammalia (L., mamma- breast)
- Habit & Habitat : Mammals are warm blooded ( endothermic and homeothermic ) and most evolved animal of Animal Kingdom.They live in all kinds of habitats. They are primarily terrestrial animals.
- Skin : Covered with hairs with sudorific ( sweat) glands and sebaceous (oil) glands. Hairs are present on the body.
- Mammary glands : Female have milk producing mammary glands which secrete milk for the nourishment of the young.
- Body : Divisible in to head, neck, trunk and tail.
- Limbs :Two pairs of pentadactyl limbs are present. Digits in the fore-limbs and hind limbs are never more than five and ending in claws, nails and hoofs and are either plantigrade or digitiigrade or unguligrade. Limbs are variously adapted for walking, running, climbing, burrowing, swimming or flying.
- Muscular diaphragm : Separates the thoracic cavity with abdominal cavity.
- Heart : Four chambered, double circulatory. Only left aortic arch is present
- RBC : Biconcave and non-nucleated.
- Sense organs : External (pinna),middle and internal ear, eyes, sense of touch(skin), tongue and nose/nostril(smell)
- Digestive system : Well developed. Teeth are present in the mouth and are thecodont (embedded in sockets in the jaws ) and heterodont (differentiated into incisors, canines, premolars and molars ).
- Respiration : By lungs only.
- Excretion : By metanephric kidneys. They excrete urea (ureotelic animals)
- Brain : Four optic lobes (corpora guadrigemina)
- Reproduction : Most mammals familiar to us produce live young i.e., they are In them the young develops in the uterous of mother for some time, receiving its nourishment and oxygen through placenta and disposing its wastes by way of the maternal circulation . However, a few of them ( such as platypus and the echidna) lay eggs, e.g., they are oviparous. Still some other, such as kangaroos, give birth birth to very poorly developed youngs.
- Penis is always present Fertilization internal.
- Parental care is highly developed.
Examples : Macropus (kangaroo), Pteropus (Bat, flying fox), Funambulus (squirrel), Rattus (rat), Oryctolagus (rabbit), Felis (Cat), Panthera (lion, tiger, leopard), Canis (dog), Camelus(camel), Elephas (elephant), Ursus (bear), Balaena (whale), Macaca (monkey), Homo sapiens (man)