TETRAPODA
Class-1: Amphibia (Gr. Amphi: dual, bios-life)General characteristics of Amphibia:
1. Amphibians can live in aquatic as well as terrestrial habitats.
2. Most of them have two pairs of limbs for locomotion.
3. Body is divisible into head and trunk.
4. Tail may be present in some.
5. Scales are absent.
6. Eyes have eyelids.
7. A tympanum represents the ear.
8. Alimentary canal, urinary and reproductive tracts open into a common chamber called cloaca which opens to the exterior.
9. Respiration is by gills, lungs and through skin (cutaneous).
10. Excretion by kidneys.
11. Heart is three-chambered (two auricles and one ventricle).
12. Organisms are cold-blooded (Poikilotherms).
13. Sexes are separate.
14. Fertilisation is external.
15. Organisms are oviparous.
16. Development is both direct and indirect.
Knowledge Booster:
1. Stone fish is the most poisonous fish.
2. Latimeria (Coelacanth). It is a “living fossil”. Latimeria is believed to be the oldest amongst living fishes. It’s a connecting link between fishes and amphibians. Though it is grouped in crossopterygi, but respires by gills.
3. Gambusia fish (carnivorous) was introduced into several tropical regions to control malaria.
4. Hilsa is the only Indian fish that migrates from the seas to the river for breeding.
5. Most primitive fish (fossil): Climatius (Placodermi).
6. Anabas (climbing perch). It has accessory respiratory organs for breathing atmospheric air which enables the fish to take long overland excursions in search of earthworms.
7. Pomfret is the most widely eaten fish in India.
8. Dipnoi or lung fish have incompletely divided three chambered heart.
9. Urinary bladder is absent in fishes.
10. Poisonous glands are found in sting ray, eagle ray, Chimaera, Diodon and Tetrodon.
11. Fish byproducts are – Fish meals and fertilizers; fish flour, fish proteins, fish oil, steaming. Floatations, shagreen, fish glue, isinglass, leather, artificial pearls etc.
12. Weberian Ossicles were discovered by Waber (1820). These connect air bladder with internal ear.
13. Commercial name of integument of Scoliodon is “shagreen”.
14. Parental care is well developed in Hippocampus.
15. Isinglass is a gelatinous product obtained from the air bladders of certain fishes such as carps, salmons, cat fishes etc. It is used for making cements, jellies and for clarification of wines and beers.
16. Fish taken out of water die of suffocation due to lack of oxygen. This is because the gill filaments stick together when taken out of water, thereby reducing the surface area.
17. Word Roots and Origin: Operculum from the Latin meaning “Cover”
18. The earliest known vertebrates to appear in fossil record were jawless primitive fish like animals collectively known as the Ostracoderms and placed under the class Ostracodermi. They resembled the present day cyclostomes in many respect and together with them, constitute a special group of jawless vertebrates the Agnatha.
19. Placodermi were earliest jawed vertebrates of fossil record. Placoderms survived for a short period only and are often considered as 'unsuccessful ancient experiment', in the evolution of gnathostomes.
20. Seymouria is a connecting link between amphibia and reptiles.
21. Centrum of 2-7th vertebrae–Procoelous (typical) vertebrae; 8th vertebrae–Amphicoelous; 9th vertebrae–Acoelous.
22. Amphiuma–has the largest RBCs among vertebrates.
23. Carboniferous Period–“Age of Amphibians”.
24. The Arrow poison frog secretes a powerful poison from the skin which can cause instant death.
25. Most poisonous frog–Golden dart poison frog from South America is the most poisonous frog. One adult frog contains enough poison to kill 200 people.
26. Larvae and tailed amphibians are ammonotelic; frogs and toads are ureotelic.
Class-2: Reptilia (Latin – Repere or reptum, to creep or crawl)General characteristics of Reptilia:
1. The class name refers to their creeping or crawling mode of locomotion.
2. These are the first true land vertebrates.
3. Their body is covered by dry and cornified skin, epidermal scales or scutes.
4. They do not have external ear openings.
5. Tympanum represents ear.
6. Limbs, when present, are two pairs.
7. Heart is usually three-chambered, but four-chambered in crocodiles.
8. Reptiles are cold-blooded or poikilotherms.
9. Snakes and lizards shed their scales as skin cast.
10. Sexes are separate.
11. Fertilisation is internal.
12. They are oviparous. Eggs are covered by a shell.
13. Development is direct.
Knowledge Booster:
1. Saurology is the study of lizards.
2. Serpentology or ophiology is the study of snakes.
3. Seymouria is considered as connecting link between amphibians and reptiles.
4. Ophiosaurus known as 'glass snake', 'blind worm', or 'slow worm', is a limbless lizard.
5. Most of the lizards show autotomy i.e. voluntary breaking off the tail to confuse enemy. The tail again regenerates.
6. Most lizards are oviparous; two viviparous lizards are Phrynosoma and Chameleon.
7. Hemidactylus or wall lizard (Gecko) is a swift runner on smooth vertical surface due to the presence of vacuum pads.
8. A limbless lizard can be distinguished from true snakes by the presence of movable eyelids and external ear opening which snakes lack.
9. A snake has no external ear.
10. Snakes shed scaly epidermis of skin periodically usually in one piece. This process is called moulting or ecdysis. Ecdysis of cornified cells of skin.
11. Most of the snakes are oviparous except Vipera russelli and Hydrophis.
12. All poisonous snakes have poison glands which are modified superior labial or parotid glands. There are two categories of snake venoms, neurotoxic and haemotoxic.
13. Sphenodon is the only living genus of Rhynchocephalia. It is called as living fossil.
14. Russel's viper is the largest Indian viper.
15. Largest snake - Python; Smallest snake - Thread snake
16. Largest lizard - Komodo dragon; Smallest lizard - Two species of dwarf Gecko
17. Long dinosaur - Diplodocus; Small dinosaur - Compsognathus
18. Poisonous sea snake - Hydrophis
19. Largest living carnivorous reptile is Crocodilus.
20. Therapsida is a group of reptiles which are considered to be the ancestors of mammals.
21. Chameleon shows camouflage and prehensile tail.
Class-3: Aves (Birds)
General characteristics of Aves:
1. Birds are feathered bipeds, truly flying vertebrate.
2. Most of them can fly except flightless birds (e.g. Ostrich).
3. They possess beak and have streamlined body.
4. Forelimbs are modified into wings.
5. The hindlimbs generally have scales and are modified for walking, swimming or clasping the tree branches.
6. Skin is dry without glands except the oil gland or preen gland at the base of the tail for lubrication of feathers.
7. Endoskeleton is fully ossified (bony) and the long bones are hollow with air cavities. Such bones are known as pneumatic bones.
8. The digestive tract of birds has additional chambers, the crop and gizzard.
9. Heart is completely four-chambered.
10. They are warm-blooded (homiothermous animals) i.e. they are able to maintain a constant body temperature.
11. Respiration is by lungs.
12. Air sacs connected to lungs supplement respiration.
13. Syrinx is present for producing voice, lies near the junction of trachea and bronchi.
14. Sexes are separate.
15. Fertilisation is internal.
16. They are oviparous and development is direct.
Knowledge Booster:
1. Bones present in aves are pneumatic and have no marrow.
2. The last three or four tail vertebrae fused to form a pygostyle.
3. Some of the birds have the habit of changing their habitats periodically between two locations; these are known as migratory birds which do not migrate are known as resident birds.
4. Kiwi is the smallest living flightless bird.
5. Humming bird (sunbird) is the smallest bird.
6. T.H. Huxley said "birds are glorified reptiles". The feathers are highly modified reptilian scales. Birds have scales on their legs. Their eggs resemble reptilian eggs in general but have a calcareous shell.
7. Oil glands, keel, pygostyle and syrinx are absent in flightless birds. Oil glands are present in kiwi
8. Erythrocytes are minute, oval and nucleated. It has more RBCs per cubic mm of blood than in any other animal. Thus, the blood of the birds may be called the richest blood.
9. Urinary bladder is absent in birds.
10. Aves are uricotelic i.e. they excrete uric acid (solid urine).
11. Single ovary is present in the female birds.
12. Famous Indian Ornithologist - Dr. Salim Ali
13. National bird - Pavo cristatus
14. Columbia has the world's richest diversity of birds.
15. Heaviest bird of prey - Vulture gryphus
16. African ostrich is the largest living bird. Egg of ostrich weighs 1.5 kg and is the largest egg among the animals. It is the male ostrich that incubates the eggs.
17. Study of birds is termed ornithology.
Class-4: Mammalia (L. Mamma = breast)General characteristics of Mamalia:
1. The most unique mammalian characteristic is the presence of milk producing glands (mammary glands) by which the young ones are nourished.
2. They are found in variety of habitats – polar ice caps, deserts, mountains, forests, grasslands and dark caves.
3. They have two pairs of limbs, adapted for walking, running, climbing, burrowing, swimming or flying.
4. The skin of mammals is unique in possessing hair.
5. External ears or pinnae are present.
6. Different types of teeth are present in the jaw.
7. Heart is four-chambered.
8. They are homoiothermous.
9. Respiration is by lungs.
10. Sexes are separate and fertilisation is internal.
11. They are viviparous with few exceptions. For example, Ornithorhynchus (Platypus), which is oviparous.
12. Development is direct.
13. Heart of mammal is four-chambered with two auricles and two ventricles, only the left aortic arch is present compared to birds. Erythrocytes are round, biconcave and non-nucleated (except in camel where they are oval).
14. Blue whale is the largest living animal.
15. Panthera tigris is National Animal of India.
16. Man has diphyodont, heterodont and thecodont type of teeth.
17. Marsupium is pouch on the female's belly for rearing the young one in the metatherian mammals.
18. Stripes of no two zebras are alike.
19. Retina of owls, rat and bat contains only rods (suitable for nocturnal habit).
20. Retina of fowls has only cones (suitable for diurnal habit).
21. Skin of mammals contains sweat gland, oil gland, milk gland, wax gland, tear glands.
Important Definitions:
· Classification is placing the different organisms into common groups on the basis of common fundamental features.
· The cells arranged as loose cell aggregates form the cellular level of organisation.
· The groups of cells performing the same function are called as tissues to form the tissue level of organisation.
· The tissues specialised to perform a particular function are grouped into organs to form organ level of organisation.
· The organs concerned with a specific physiological function associated to form organ-system level of organisation.
· When any plane passing through the central axis of the body divides the organism into two identical halves the body possesses radial symmetry.
· When body can be divided into identical left and right halves in only one plane, it is said to possess bilateral symmetry.
· Mesoglea is defined as an undifferentiated layer present in between outer ectoderm and inner endoderm in diploblastic organisation.
· The body cavity between the body wall and the gut wall, lined by mesoderm is called coelom.
· Metamerism is defined as the phenomenon of occurrence of external and internal division of body into segments with a serial repetition of at least some organs.
· Notochord is a mesodermally derived rod-like structure formed on the dorsal side of body during embryonic development.
· Animals which possess notochord are called chordates and those which do not possess notochord are called non-chordates.
· The alternation of two basic forms, polyp and medusa in some cnidarians is termed as metagenesis.
· Bioluminescence is the property of a living organism to emit light and thus shine in dark.
· Endoparasites are the organisms that live inside other organisms to thrive nutrition and protection from them.
· Regeneration is a form of asexual reproduction in which either the animal regenerates the lost part or produces new individual from a part of its body.
· Animals which remain permanently attached to the substratum and do not move about are said to be sessile.
· Animals which do not remain attached to the substratum and freely move are said to be freely moving (free-swimming, if aquatic).
· When eggs and sperms are produced by the same individual the animal is said hermaphrodite. Also called monoecious.
· When sexes are separate, animal is called dioecious or unisexual.
· Egg-laying animal is called oviparous while viviparous animals give birth to the young ones directly.
· When animal possesses an intermediate larval stage during its development, it is called indirect development.
· When animal does not possess any intermediate larval stage during its development, it is called direct development.
· Adaptive radiation: Evolutionary process in which descendants from an ancestral species multiply and diverge to occupy many different habitats and modes of life.
· Agnatha: Jawless vertebrates, which includes Ostracodermi and Cyclostomata.
· Amniotes: Vertebrates that possess an amnion or extraembryonic membrane that surrounds the embryo and encases it in amniotic fluid, including Reptilia, Aves and Mammalia.
· Anamniotes: Vertebrates that lack an amnion. Includes Cyclostomata, Chondrichthyes, Osteichthyes, Amphibia.
· Cleidoic egg: Self-contained egg that allows animal to bypass larval stage.
· Cloaca: Posterior chamber of most fishes, non-mammalian tetrapods and monotreme mammals into which the digestive tract and urogenital passages (discharge).
· Coelom: Body cavity completely lined with epithelium (cellular tissue).
· Gnathostomes: Vertebrates with jaws derived from the mandibular arch, which may have (in primitive vertebrates) supported gills. Includes Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, Mammalia.
· Heliotherm: Regulates body temperature by using solar radiation.
· Marsupium: Skin pouch in female belly in which immature young are carried. For example, in kangaroo.
· Neoteny: Paedomorphosis that results from the slowing down of somatic development relative to reproductive development. For example, in Ambystoma.
· Oviparous: Eggs are laid and the young develop outside of the mother.
· Ovoviviparous: Egg contained within the uterus, where the young develop and then hatch as miniature adults.
· Paedomorphosis: Retention of juvenile characters into the adult stage (same as Neoteny).
· Paedogenesis: Reproduction by larva.
· Pisces: Collective term for all fishes; includes Chondrichthyes, Osteichthyes.
· Placenta: Composed of parts of the uterine lining and fetal extraembryonic membranes through which exchanges between mother and embryo occur.
· Swim bladder or air bladder: Sac of air that acts as a hydrostatic mechanism, allowing a fish to control its vertical position in the water.
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Quick Recap:
1. From the indefinitely deep oceans to snow covered mountain peaks and from the poles of the earth to the equator, animals inhabit all the places. Hence from the habitats point of view, the animals can be:
a. Aquatic: which live in water (either marine or fresh water).
b. Marine: which live in oceans or any other water body having salinity.
c. Fresh water: which live in rivers, ponds, lakes, etc.
d. Terrestrial: which live on earth surface.
e. Arboreal: which live on trees.
f. Aerial: which fly in air.
2. Coral reefs: Coral colonies grow continuously in size and often form extensive masses known as coral reefs. It is a ridge or mound of limestone, the upper surface of which is near the surface of sea and is formed chiefly of calcium carbonate produced by some of its inhabitant, chiefly corals. Coral reef form stable marine ecosystem. One of the famous coral reef is Great Barrier Reef along the north-eastern coast of Australia.
3. Physalia (Portuguese man of war) : Physalia exhibits a remarkable example of polymorphism and division of labour. A gas gland present inside pneumatophore secretes a gas which helps the animal to float over the water surface.
4. Pennatula (Sea pen or sea feather): It looks like a quill (a type of feather or pen). It is carnivorous.
5. Gorgonia (Sea fan): All the branches form a hand held fan like network. So Gorgonia is commonly called as sea fan.
6. All animals are multicellular organisms having certain common basic characteristics like holozoic nutrition, neurosensory body control, locomotion, reproduction etc.
7. Animals can be broadly classified on the basis of basic fundamental features such as level of organisation, body symmetry, cell organisation, coelom, segmentation, notochord, etc.
8. Besides the fundamental features, there are many other distinctive features which are specific for each group of Kingdom Animalia.
