Nomenclatures are of two types viz.
(i) Binomial nomenclature and
(ii) Trinomial nomenclature.
Bionomial nomenclature : This classification was proposed by Linnacus (a Swedish taxonomist) in 1758. According to this classification,
(a) Two names to any species were given by him.
(b) First name is generic and second name is of the species.
(c) This name distinguishes the animal from other animal.
(d) These names are always written in italics or underlined in the text.
(e) First letter of generic name is always written in capital while that of species is written in small letters.
(f) The generic and species words are written separately for example the name of frog-Rana tigrina.
Trinomial nomenclature : In this the name includes generic, specific and sub-specific names for example crow-corvus splendens. (Indian and Pakistani) Crow-corvus splendens isolens (Burmese) crow-corvus splendens protegattus (Ceylon)
Animal Kingdom
Animals are organisms which are acellular or multicellular in nature. About 10 million species of living organisms are known. All, species differ from each other in shape, size, structure and ways of living. Body Organisation of Animals The body organisation of animals is divided as follows—
1. Body plan : It is further divided into three basic plans:
(a) Cell aggregate plan : Cells are arranged in groups. The tissue or organ system is absent.
(b) The blind sac plan : In this 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. This is found in coelenterates and flatworms.
(c) The tube within a tube plan : Digestive system has mouth and anal opening. Ingestion is by mouth and egestion by anus.
2. Symmetry : Symmetries are of three type—
(a) Asymmetrical : In assymmetrical structure an animal cannot be divided into two equal and similar halves from any point. e.g. snail.
(b) Bilateral symmetry : When an animal is cut in a vertical plane lengthwise in the middle, then it is divided into two equal mirror halves. This symmetry is found in frog, man, earthworms, insects etc.
(c) Radial symmetry : In this an animal is divided through its longitudinal axis through any diameter, then body will have two equal halves. Hydra, star fish etc. have radial symmetry.
3. Body cavity : The body cavity or coelom is found only in the animals with tube within a tube. Their cavity is filled with a fluid which is known as body cavity.
The coelom provides flexibility to the body. All the internal organs are suspended in the coelom. Thus coelom protects and acts as a shock absorber.
4. Body segmentation : Body segmentation means that the body is divided into constricted segments. The segmentation arises in the annelids. It is present in the arthropods and all chordates.
5. Body support : Soft bodied animals have exoskeleton. Example are formanifera (protozoans), coelenterates, arthropods and most of the molluscans. The exoskeleton is made up of hard shells.
Hard, body and cartilaginous tissue makes the body exoskeleton especially of vertebrates. Notochord supports the body of primitive adult chordates whereas vertebral column supports skeleton of vertebrates. Appendicular skelecton provides a means of locomotion. Vertebral column protects the central nervous system in vertebrates. The height is provided by the axial skeleton to the animals.
Invertebrates : Animals which do not have vertebral column are known as invertebrates. There are about 30 phyla of invertebrates. It is proved from the evolutionary studies that animals of same phylum have directly or indirectly originated from a single common ancestor.
Lower and higher invertebrates : The lower invertebrates usually are of small body size and of simple body organisation. The lower invertebrate include protozoa, porifera, coelenterata, platyhel minthes and nematoda.
The higher invertebrates have large body structure with complex body organisation. Higher invertebrates include annelida, mollusca and echinodermata.
Different phylums are discussed below—
1. Phylum Protozoa
Protozoans are unicellular or acellular microscopic organisms having typical cell structure.
General Characters
1. Can be seen with naked eyes. The name was first coined by Goldfuss and were first observed by Leeuwenhoek.
2. They are primitive and simplest forms; hence the name protozoa.
3. They are found in solitary or colonial form.
4. Their body consists of a single cell with a single or many nuclei.
5. They are spherically symmetrical, asymmetrical or bilaterally symmetrical.
6. Body is covered by plasma membrane, pellicle or shell.
7. The body form may be variable or constant.
8. Locomotion is by pseudopodia, flagella or by cilia and in sporozoan parasites locomotory organelles are totally absent.
9. Nutrition is of the following modes:
(a) Holozoic : Amoeba.
(b) Holophytic : Euglena viridis.
(c) Saprozoic : Trypanosoma.
(d) Mixotrophic : Euglena.
(e) Coprozoic : Rhyncomonas.
Digeston is intracellular and is carried out in the food vacuole.
10. Respiration is by diffusion.
11. Excretion is carried on by diffusion through general body surface primarily and also by contractile vacuole and marine secondarily.
12. In the freshwater protozoans, contractile vacuole performs osmoregulation. In parasitic and marine protozoans contractile vacuole is absent.
13. Many protozoans are free-living. Some are parasites and some are symbionts e.g., Trichonympha (a flagellate protozoan, lives in the gut of termites. It digests cellulose).
14. Reproduction is by asexual and sexual methods. Asexual reproduction takes place by binary fission, multiple fission or by budding. Some multinucleate protozoans show plasmotomy. In this a sexual reproduction cytoplasm divides and nuclei do not divide sexual reproduction is by syngamy, conjugation, antogany etc.
15. Encystment is common in many protozoans.
Body size of protozoans varies from 0.0002 mm to 16 mm.
They are globoid or round or flat. They show spherical symmetry, or bilateral symmetry.
Protozoans were first formed in the precambrian period nearly 30,000 species of these are present.
On the basis of presence or absence of locomotory organs this phylum is divided into following classes.
1. Rhizopoda : e.g. amoeba, entamoeba, arcella, polystomella etc. 8000 species.
2. Mastigophora or Flagellata : e.g. crytomonas, euglena, volvox, giardia etc. 2000 species.
3. Sporozon : e.g. monocystis, coccidium, plasmodium etc. 2000 sps.
4. Cillata : e.g. opalina, paramecium, vorticila etc. 2500 sps.
5. Suctoria : e.g. acineta, ephelota, aendrosoma 200 sps.
2. Phylum—Porifera
They evolved from colonial protozoans and thus porofera are more complex than protozoans. They have about 10,000 living and 1400 fossil species.
General Characters
1. Sponges are aquatic. Many are marine and few are freshwater.
2. These are sedentary, attached to a substratum.
3. Sponges are solitary or Colonial (Spongilla).
4. They are mostly asymmetrical. Few are radially symmetrical (Sycon, Leucosolenia).
5. They are multicellular and cellular grade animals. Tissues are not formed.
6. The two layers present in the body are named according to the cell type present in each layer. The outer layer shows Pinacocytes and it is called Pinacoderm. The inner layer contains Choanocytes and is called Choanoderm. In between these two layers, Mesenchyma is present.
7. Pinacoderm will have a number of pores over it referred to as ‘ostia’. Water enters into the body through these pores; hence these are also referred to as incurrent pores or inhalent pores.
8. In between the two layers Mesenchyma is seen.
9. Mesoglea is secreted by both Pinacoderm and Choanoderm.
10. Amoebocytes show division of labour. Accordingly they are of many kinds:
(a) Chromocytes : Pigmented cells.
(b) Trophocytes : Distribute digested food.
(c) Myocytes : Work as muscle cell and form sphincter around openings.
(d) Archaeocytes : Totipotent, reserve cells of the body. Responsible for regeneration. Produce germ cells.
(e) Scleroblast Cells : Produce skeleton which is the form of specules and spongin fibres.
(i) Calicoblast Cells : Produce (CaCO3) specules.
(ii) Silicoblast Cells : Produce siliceous specules.
(iii) Spongioblast Cells : Produce spongin skeleton.
(f) Thesocytes : Store the reserve food in the form of glycogen.
11. Choanoderm is formed by Choanocytes. These are nutritive in function. The collar present in these cells help in filtering the food. Choanocytes regulate water current by the flagellar movement.
12. The space inside the body is called Spongocoel or Paragastric cavity.
13. Spongocoel opens through a big opening present at the free end called osculum. Water moves out through this opening so it is called excurrent or exhalent opening.
14. The most characteristic feature of sponges is that they have canal system. It increases the space in the spongocoel. The canals are formed by the outpushing of the choanoderm. According to the complexity, a canal system is of four types :
(i) Ascon,
(ii) Sycon,
(iii) Leucon,
(iv) Rhagon.
15. Nutrition is holozoic. Digestion is intracellular as in protozoa.
16. Respiration is through diffusion.
17. Sponges excrete Ammonia.
18. Nervous system is absent. So the cells are independent.
19. Reproduction is both asexual and sexual. Asexual reproduction is by budding. It occurs during favourable conditions.
Sponges are hermaphrodites or bisexual or monoecious. Archaeocytes produce sperms and ova. But ova are produced earlier, so sponges are protogynous. Fertilization is internal. Development includes larvae:
(i) Parenchymuta (leucosolenia).
(ii) Amphiblastula (Sycon).
20. Sponges exhibit regeneration. Archaeocytes are responsible for regeneration.
21. These sponges are available from Arctic region to tropical region.
Different Classes—
1. Calcarea—e.g. leucosolemia, grantia, scypha, sycon etc.
2. Hexactinellida or Hyalosponglae—e.g. culpectella, lyalonema.
3. Demosponglae—cliona, spongilla etc.
6. Phylum—Arthropoda
Arthropoda are jointed limbed animals. In these animals segments are fused to form the head, thorax and abdomen.
About 9,00,000 species are known at present.
General Characters
The term Arthropoda was coined by Von Siebold.
It is the largest phylum in the animal kingdom.
1. They are triploblastic, bilaterally symmetrical.
2. They show heteronomous metameric segmentation.
3. They have jointed appendages, hence the name Arthropoda.
4. Body is divisible into head, thorax and abdomen.
5. True coelom is confined to gonads and gonoducts. The cavity present around the visceral organs is called perivisceral cavity. It is filled with blood. Such a cavity is called haemocoel.
6. They show exoskeleton. It is made up of chitinous sclerites.
7. Every segment is covered by 4 exoskeletal sclerites dorsal tergal plate, ventral stemal plate and two lateral pleural plates. Two sclerites are connected by arthrodial membrane. Arthrodial membrane allow the movement of the sclerites.
8. The sclerites invaginate into the body and form apodemes. They form internal endoskeleton.
9. Digestive system is well-developed.
10. Respiration is carried out by different respiratory organs.
11. Circulatory system is open type.
12. Heart is long and tubular.
13. In many arthropods, blood is colourless. In crustaceans blood contains a respiratory pigment called haemocyanin. Blood is without RBC, hence it is called haemolymph.
14. Excretory system includes malpighian tubules, green glands, coxal glands etc.
15. Nervous system shows a nerve ring around the oesophagus and a double ventral nerve cord.
16. Sense organs include simple eyes, compound eyes, antennae, anal cerci ventral nerve cord.
17. For the first time in the animal kingdom, striated muscles appear in arthropoda.
18. Arthropoda are unisexual animals.
19. The development of these animals may be direct or indirect.
Classification
Class-1-M Esotomata e.g. limulus etc.
Class-2-Arachnida e.g. buthus chelifer etc.
Class-3-Crustacea e.g. apus, argulus, lepus etc.
Class-4-Diplopoda e.g. millipede, julus etc.
Class-5-Chilopoda e.g. centipede, lithoblus etc.
Class-6-Insects e.g. silver fish, cricket, apis etc.
7. Phylum—Mollusca
Mollusca are soft bodied animals. They are bilataterally symmetrical, non-segmental and protected by a hard shell.
General Characters
Aristotle coined the word mollusca.
This is the second biggest phylum. It contains 1,12,000 species.
1. Molluscans are soft bodied animals.
2. They are mostly aquatic mostly marine, few fresh water and terrestrial.
3. Bilateral symmetry.
4. They have shell on the body.
5. Complete digestive system with glands, liver and hepatopancreas.
6. Closed type circulatory system.
7. Circulatory system with gills or lungs.
8. Excretory system by nephridia orbidney.
9. Senses are usually separate.
10. Nervous system is well-developed.
11. Have sense organs like eyes, smell and statocyst.
12. Development is direct or indirect.
13. Fertilization is external or internal.
14. Reproductive system is with dioecious or monoecious.
Classification
Class-1-Monoplacophora e.g. neopilina.
Class-2-Amphineura e.g. chiton.
Class-3-Scaphopoda e.g. dentallum.
Class-4-Gastropoda e.g. patella.
Class-5-Pelecypoda e.g. ostrea.
Class-6-Cephalopoda e.g. neutilus.
8. Phylum—Echinodermata
Echinodermata are radially symmetrical animals usually pentamerous and marine livings.
General Characters
Echinodermata term was coined by Jacob Klien.
It was treated as phylum by Leuckart.
1. These are marine animals.
2. Most are free living, creeping slowly at the bottom of the sea.
3. They have non-radial symmetry.
4. They have unsegmented, globular, star shaped, oval, disc shaped and extended lengthwise body.
5. These are with dermal spines or dermal calcarious stipules form the interskeleton.
6. Their locomotion is water vascular system with podia and tube-feet madreporite mostly present.
7. Body coelom is with enterocoelic type.
8. These are with straight or coiled canal.
9. They have perihaemel blood vascular circulatory system.
10. Respiratory system includes branchial, tubefeet, respiratory trees and burr sac.
11. In their nervous system circum oral ring and radial nerves are present and brain absent.
12. They have organ of touch, chemoreceptors, internal tentacles and photoreceptors.
13. They do not have excretory system.
14. They are unisexual.
15. Reproductive organs have large gonads and numerous gonoducts.
16. They have external fertilization.
17. Development is indirect with free swimming larval forms.
18. Exclusively marine.
Classification
Class-1-Asteroidea e.g. asterias.
Class-2-Ophiuroidea e.g. ophiura.
Class-3-Echinoida e.g. echinus etc.
Class-4-Holothuroidea e.g. cucumaria, synepta.
Class-5-Crinoidea e.g. antedon.
9. Phylum—Chordata
Chordata is the last phylum in animal kingdom. These are free living and non chordate. About 65,000 species are known as living chordates. General Characters The name chordata was coined by Balfour (1880).
1. They have notochord or chorda dorsails.
2. These have Dorsal tubular nerve cord.
3. These animals have pharyngeal gill slits.
4. They have bilateral symmetry.
5. Their body has three layers—Outer ectoderm, middle mesoderm, and inner endoderm.
6. They have repeated body segments.
7. They are with living endoskeleton.
8. Higher chordates have efficient respiratory system.
9. They are ventral heart.
10. They contain RBC (Naemog-lobin).
11. They have centralization of nervous system.
12. They have hepatic portal system.
10. Super Class—Pisces
Pisces means fishes.
General characters
1. Fishes are aquatic organisms.
2. Their body is divided into three parts—head, trunk and tail. Fishes do not have neck.
3. Fishes are cold blooded.
4. The skin shows shine glands which reduce friction during swimming.
5. Body is covered with exoskeleton made by scales.
6. Head shows terminal mouth in bony fishes and ventral mouth in cartilage fishes.
7. External and middle ears are absent. Internal ears are present. Each internal ear shows 3 semi-circular canals.
8. Fins are present. They help in locomotion.
9. Endoskeleton is body or cartilaginous.
10. Skull is present in fishes.
11. Jaws show homeotent teeth.
12. Respiration is by gills.
13. Fishes contain heart with two chambers. It is ‘S’ shaped. In Dipnoi fishes incompletely divided three chambered heart is present.
14. In fishes, the functional kidney in adults is mesonephric kidney. Urinary bladder is absent. They excrete ammonia.
15. The brain of fishes is small.
16. They have separate sexes.
17. Gonads are paired.
18. Fertilization is either external or internal.
19. Most of the fishes lay eggs but some give birth to young ones.
20. Their development is direct.
21. They have internal ears.
22. They have ten pairs of nerves.
Classification
Class-1-Elasmobrachil-e.g. trygon.
Class-2-Holocephalii e.g. chimaera.
Class-3-Dipnol e.g. protopterus.
Class-4-Teleostoml e.g. amia, flying fish etc.
11. Class—Amphibia
Frog, Toat, etc. fall in this class
General Characters
1. Amphibians’ body is divisible in to head, trunk and tail. Tail is absent in Anura and Apoda.
2. They are cold blooded vertebrates.
3. They live on land and in water. Hence they are called as amphibians.
4. The moist scaleless skin will help in respiration in many amphibians.
5. They show paired appendages.
6. Homodoni teeth is present on upper jaws.
7. A pair of eyes are present. Each eye is covered by movable upper eyelid.
8. External nostrils open into buccal cavity through internal nostrils. They are useful for respiration.
9. External ear is absent. For the first time in the animal kingdom tympanum is developed in frogs and toads. Apoda and urodela will not show tympanum.
10. Endoskeleton is mainly made up of bones.
11. Skull has two condyles.
12. Stemum is developed for the first time in amphibia in the animal kingdom. It is absent in apoda.
13. They have three chambered heart. It has two auricles and one ventricle.
14. In larval forms and some aquatic amphibians gills are present for respiration.
15. Amphibians have two kidneys.
16. They excrete urea. They are called ureotelic animals.
17. Brain is well-developed. Olfactory lobes are small. Cerebellum is less developed. Corpora bigemina (two optic lobes) is seen.
18.Ten pairs of cranial nerves are present.
19. Sexes are separate.
20. They are oviparous.
21. Fertilization is external. But in apoda fertilization is internal.
22. They show holoblastic unequal cleavage.
23. Development may include a larval form.
Classification
Order-1-Labyrinthodontia (extinct) e.g. eryops.
Order-2-Phyllospondyli (extinct).
Order-3-Lepospondyli (extinct).
Order-4-Gymnophiona or Apoda or Caecilia (living) e.g. ichthyophis.
Order-5-Condata or Urodela (lving) e.g. amblystoma, salamandra (salamander), triton.
Order-6-Anura or Salientia (living) e.g. alytes (midwife toad), pipa (Surinam toad), buto (Toad), hyla (Tree frog), Rana tigrina (common frog).
12. Class—Reptilia
The word reptilia is derived from the latin word reptus which means crawl means these are crawling animals. The study of reptiles is called Herpetology. These are the true terrestrial vertebrates. Reptiles include turtles, tortoises, crocodiles, lizards, snakes etc. About 7000 species of reptiles are known.
1. They are the first true terrestrial vertebrates. They lay eggs on the dry land.
2. They are cold blooded animals.
3. The body shows elongated axis. It is divisible into head, neck, trunk and tail.
4. They show two pairs of pentadactyl limbs.
5. Skin is covered by horny epidermal scales.
6. Skull is monocondylic. It may show temporal fossae or they may be absent.
7. Autostylic jaw suspension is seen.
8. Single ear ossicle columella is present in the middle ear.
9. ‘T’ shaped intercleicle is present in the pectoral girdle.
10. First vertebra is atlas and second vertebra is axis.
11. Teeth are present on both jaws.
12. Heart is incompletely four chambered. It has two auricles and ventricle is incompletely divided into two but crocodiles show completely four chambered heart.
13. A pair of distensible sac like lungs are present to perform aerial respiration.
14. Brain is fairly well-developed.
15. Two metanephric kidneys are present.
16. They excrete uric acid.
17. They are unisexual animals.
18. They have penis so fertilization is internal.
19. Development is direct.
20. Many of them are oviparous.
Classification
Sub-Class-1 Anapsida-marine turble trionyx etc.
Sub-Class-2-Parapsida e.g. ichthyosaurus.
Sub-Class-3-Diapisida-calotes, typhlops etc.
Sub-Class-4-synapsida-cynognathus.
13. Class-Aves (Birds)
Birds are feathered vertebrates. According to Huxley they are known as “glorified Reptiles”.
General Characters
1. Their body is divisible into head, neck, trunk and tail.
2. Birds show boat shaped body which is adapted for flying.
3. Birds are warm blooded.
4. Fore limbs are modified into wings. They bear quill feathers.
5. Skin is dry and thin.
6. Beak is present. It is covered by horny rhamphotheca.
7. Teeth are absent.
8. Stomach is divisible into glandular proventricules and muscular gizzard for grinding the food.
9. Cloaca is three chambered.
10. Compact spongy and solid lungs are present. They perform respiration.
11. Nine air sacs are associatd with the lungs.
12. At the base of the trachea a Syrinx is present. It is useful to produce sounds in birds.
13. Heart is 4 chambered. It shows 2 auricles and 2 ventricles.
14. Brain is large and round.
15. External ear is absent. Middle ear shows columella auris. Internal ear shows curved cochlea with an organ of corti.
16. Skull is monocondylic.
17. They are heterocoelous.
18. Sternum shows Keel.
19. By the fusion of clavicles a ‘V’ shaped furcula bone is formed.
20. Bones are pneumatic (filled with air).
21. They show 2 metanephric kidneys. Each kidney is 3 lobed.
22. Urinary bladder is absent.
23. They excrete uric acid.
24. Male and female birds are separate.
25. Fertilization is internal.
26. They are oviparous. They lay eggs.
Classification
Sub-Class-1Archae ornithes e.g. archae ornis.
Sub-Class-2-NEO Rnithes-Kiwi, duck, parrot etc.
14. Class-Mammalia
Name mammals was coined by Linnacus in 1758 with reference to the milk producing animals.
General Characters
1. They are warm blooded animals.
2. Skin is covered with hairs.
3. They have mammary glands.
4. Skin shows sweat glands.
5. The body is divided into head, neck, trunk and tail.
6. They show two pairs of pentadactyl limbs.
7. They are milk producing animals.
8. The body cavity is divided into upper thoracic cavity and lower abdominal cavity by muscular diaphragm. It helps in respiration.
9. Larynx is well-developed.
10. Respiration is by lungs. Only pulmonary respiration is seen in mammals.
11. Heart is completely 4 chambered. It shows double circulation.
12. Brain is well developed.
13. The skull is dicondylic.
14. Vetebrae are amphiplatyon type. They are connected by intervertebral discs.
15. Two kidneys are present.
16. They are ureotelic animals.
17. Well developed endocrine system is seen with pituitary as the master gland.
18. Sexes are separate
19. Gonads are paired.
20. Fertilization.
21. Most of the mammals are viviparous.
21. Embryo develops in the uterus of the mother.
22. During embryonic development extra embryoni membranes are present.
Classification
Sub-class-1-Prototh eria : Egg laying primitive mammals e.g. echidna
Sub-class-2-THERIA—K.s. Kangaroo,mole, hare, squirrel etc.
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