Class - Aves & Pisces | Biology for JAMB PDF Download

About Aves

The Aves belong to the phylum Chordata of the animal kingdom. It has about 9,000 species. Aves are adapted to fly. All the birds come in the class Aves. They show courtship, parental care, nest building, and territorial behaviour.

Class of Aves

Characteristics of Aves

• Originated at the end of Jurassic period of Mesozoic era & advancement took place in cretaceous.
• Study of birds is known as ‘‘Ornithology’’
• Dr. Salim Ali was the great ornithologist of India and known as ‘‘Birdman of India’’
• Study of bird's egg is known as Oology.
• Study of bird's Nest is known as Nidology.
• Birds are glorified reptiles stated by Huxley.
• Arrangement of wings on the body of bird is known as Pterylosis.
• Body is boat-shaped. It is divided into head, neck, trunk and tail. Neck is long and flexible.
• A cover of soft feathers (derivative of stratum corneum) is present all over the body, that is called ‘‘plumage’’
• Scales are found only on hind limbs.
• Birds are warm-blooded or Homeothermic or endothermic animals i.e. Body temperature remains almost constant.
• Skin is dry and without glands. But oil glands or Preen glands are found on tail or Uropygium. These glands secrete oil, which makes feathers soft and waterproof.
• Two pairs of limbs are present. Birds are feathered bipeds.
• Forelimbs (with three digits) are modified into wings, which help in flying.
• Four clawed digits are found on hind limbs. these are best adapted for perching, for walking on land, or for swimming in water.
• Oesophagus is modified into Crop for quick food ingestion and storage and Gizzard for crushing the food which is swallowed unmasticated. Pigeon milk is secreted by both sexes (Crop product).
• Gall bladder is absent.
• A three-chambered cloaca is present in the birds.
• Teeth are absent in jaws. Jaws are modified into horny beak. Beak is toothless. An epidermal horny sheath is present on beak, which is called Ramphotheca.
• Spongy lungs are present for respiration. Air sacs are also found attached to lungs forming accessory resp. organs help in flying.
• Sound producing organ at the junction of trachea and bronchi of birds is called syrinx.
• The heart is four-chambered.
• The hepatic portal system is well developed in birds, but renal portal system is vestigeal developed. Sinus venosus absent. Only Right aortic arch persist.
• R.B.Cs are nucleated, small and oval. No. of RBC/mm³ is max. in among animals.
• Endoskeleton is bony. These bones are hollow, are is filled, and are called pneumatic bones. These make the body light in weight and help in flying.
• Skull monocondylic.
• Centrum of the vertebra is heterocoelous. (Saddle - Shaped).
• Some vertebrae of the posterior body portion join together to form synsacrum.
• Last four caudal vertebrae fuse to form pygostyle.
• Sternum is large. Swollen basal part of sternum is called ‘‘Keel’’ This keel offers a joint plane for flight muscles.
• Keel is highly developed in flying birds.
• Ribs of birds are bifid and uncinate processes are present in ribs.
• Exoskeleton is in the form of soft feathers all over the body (except hind limbs).
• Foramen of triosseus is found in their pectoral girdle.
• Two bones, clavicle and interclavicle fuse to form V - shaped furcula or wish bone or Merrythought bone. Act as a spring between two girdles .
• Furcula is absent in flightless birds.
• Kidneys metanephric (Trilobbed). Ureters open into cloaca.
• Members are always Uricotelic.
• Uric acid is a semisolid substance. Excreta of marine birds is known as guano.
• Most of the birds do not have urinary bladder.
• Brain is large, smooth, highly developed. Cerebellum is well developed for aerial mode of life.
• Cranial nerves are 12 - Pairs.
• The skin around the nostrils is sensory in birds, that is called ‘‘Cere’’.
• Eyes are large and well developed which are surrounded by rings made up of bony plates known as Sclerotic ossicles.
• Eyes are large and nictitating membrane is present. Vision is monocular.
• A specific comb-like structure Pecten is found in the eyes of all birds except kiwi's eyes. Pecten helps in Acomodation of eye and provides nutrition of eye balls . It also control pressure of liquid present in  eye. Acute and Telescopic vision of birds is due to pecten.
• External ears are present but ear pinnae are absent. Columella bone (Stapes) (one ossicle) is found in middle ear. Cochlea (not coiled) is present in internal ear.
• Olfactory organs are less - developed.
• Birds are monodelphic i.e. only left ovary and left oviduct is functional in females.
• Birds are unisexual. Sexual dimorphism is well marked. Copulatory organ absent in males.
• Fertilization is internal, oviparous. Eggs are large, megalecithal, telolecithal and cleidoic. Shell is perforated. Cleavage is meroblastic and discoidal.
• Embryonic development is direct. Birds are included under group amniota. 
• Parental care is well marked. Young one without feather is known as Nidiculous and with feather is known as Nidifugous.

Scientific Name of Birds

1. Pavo - cristatus : Peacock: It is the national bird of India.
2. Psittacula krameri : Indian parrot. (upper jaw movable - Psittaciformes)            
3. Columba livia : Blue rock pigeon its crop glands secrete pigeon milk (columbiformes)
4. Streptopelia : Dove
5. Passer domesticus : Sparrow: It shows commonsalism with man.
6. Corvus splendens : Crow
7. Molpaster : Bulbul
8. Cygnus : Swan - Aquatic bird having webbed limbs
9. Bubo bubo : Bubo or owl or ‘‘III of oman’’
10. Cuckoo : It lays its eggs in the nest of other birds (Crow)
11. Eudynamis : Indian Koel (Nest - Parasitism)
12. Anas : Duck
13. Phoenicopterus : Flamingo
14. Alcedo : King fisher
15. Raphus didus: Dodo (Mauritian extinct bird in 17^th centuary)
16. Dinopium : Wood pecker : Kathphorva
17. Diomedea : Albatross : Marine bird with largest wings in flying birds.
18. Milvus : Kite (Predatory birds)
19. Falcon : Falcon (Predatory birds)
20. Neophron : Vulture (Scavenger bird)
21. Choriotis-nigriceps state : Great Indian bustard. It is also called Gondavan. It is the bird of Rajasthan. (local name - Godavan)
22. Helena : Humming bird - It is also called sunbird. It feeds on nector of flowers it is the smallest bird. It is found in cuba. It can fly in forward and backward both the directions. It can fly like helicopter. Its size is about 3 to 4 cm. 
23. Ploceous : Weaver bird (Baya)
24. Micropodus : Pitohiudicthous/pathua - It is the only poisonous bird, which is found in Newguinea.
25. Swift spine tailed : Fastest flying bird, it is found in Japan.
26. Poor bill : Bird which shows sleeping stage and undergoes hibernation. Migratory Birds (Phenolosy = Study or bird migration)
27. Pluvialis dominica : It is an American bird which migrates from south to north and from north to south.
28. Scolopax eusticoa : It migrates from hill area to planes.
29. Himalyan partiges : It can fly over 6000 miles
30. Sterna parasisaea - Champion bird - Arctic to Antarctic and back. 

Feathers

There are different types of feather namely:

1. Quill (flight feather) consists of:
   (a) Remiges - feather of wings
   (b) Retrices - feather of tail.
2. Coverts - small just like quill for filling gap on wings & tail.
3. Contours - small feather to cover the body.
4. Filoplums - Beneath the contours.
5. Down feather - Cover the body of newly hatched bird. (Filoplume and Down feather make body surface as heat - resistant.)

Introduction

These are true, jawed vertebrates with specific organs for respiration, excretion and blood circulation. The organisms belonging to this class are poikilotherms, meaning that they cannot regulate their own body temperature. Essentially, all the fish come in this category.

Kingdom: Animalia

Phylum: Chordata

Class: Pisces

Class: Pisces

Characteristics of Class - Pisces

– "Devonian period" is called "Golden period of fishes"

– Study of fishes Icthyology.

– Includes true fishes. Fresh water or marine.

– Body is long, boat shaped and streamlined, which is divided into head, trunk and tail.

Neck is absent.

–    Slime glands are present on the skin.

– Body is covered by dermal scales. But Catfish, Torpedo & Wallago are scaleless.

–    Colour in fish is produced by iridocytes present in the dermis.

– Paired fins are present for swimming. e.g. Pectoral and pelvic fins are paired.

–    Unpaired fins are also found on the body e.g., mid dorsal fin and caudal fin.

– External nares are one pair. [Dirhynous condition.]

– External and middle ears are absent, only internal ear is present in which three semi - circular canals are present. Eyes are without lids.

– Respiration by gills, gills are 4 to 7 pairs. Naked or covered by operculum.

– "Air bladder" is present in bony fishes only which helps in swimming as well as in respiration.

– Heart two chambered, known as "Venous heart", because it contains only impure blood, which from heart goes to gills for purification, pure blood is then distributed to all parts of body directly from gills,
i.e. circulation of blood is unicircuit.

– RBC are nucleated. Sinus venosus, renal and hepatic portal systems are found in circulatory system.

– Endoskeleton is made up of cartilage or bones.

– Vertebrae in fishes are amphicoelous. (centrum is concave at both the surfaces)

– Only one occipital condyle is present, so that skull is monocondylic type.

– Cranial nerves are 10 - pairs.

– Lateral line system is present in the body of fishes, which can detect vibrations (Rheoreceptor) and Electric field.

– Kidneys in fishes are mesonephric type.

– Cartilagenous fishes excrete urea, Marine bony fishes excrete trimethylamine oxide and fresh water fish excrete ammonia. Urinary bladder is absent.

– Fishes are unisexual.

– Fertilization is internal or external.

– Eggs are mesolecithal or megalecithal type.

– Extra embryonic membranes are absent [anamniota].

– Development is direct.

– These are cold blooded, poikilothermic animals (Exception - Tuna fish, endothermic).

– Small fishes (Baby fishes) are called Fry or Hatchling.

– Fishes show a seasonal migration:

[A] Anadromous migration : Migration of fishes from marine water to fresh water.

e.g. (1) Salmon         (2) Sturgeon               (3) Hilsa

[B] Catadromous migration : Migration of fishes from freshwater to marine water

e.g.  Anguila

[C] Potamodromous migration : Migration of fishes from Fresh water to fresh water

[D] Oceanodromous migration : Migration of fishes Marine to Marine water

Stenohaline : - Fish which can tolerate a narrow range of salinity in water.

Euryhaline : - Fish which can tolerate a wide range of salinity in water.

Classification of Pisces

Class Pisces has been classified into 3 classes:

(A) Placodermi   

(B) Chondrichthyes                       

(C) Osteichthyes

Placodermi

–    In this class, extinct fishes (Fossil fish) are included, which use to live from devonian era to permian era. So these were the first freshwater true fishes.

–    Their body was covered by bony plates, so these are called "Armoured fishes"

e.g.: -  Climatius – First jawed fish

Dinichthyes

Chondrichthyes or Elasmobranchi

– This includes cartilagenous fishes i.e. endoskeleton is made up of cartilage.

– Fishes are generally marine.

– Exoskeleton over the skin is made up of placoid scales. These scales are like denticle and are originated from dermis of skin.

– In these fishes, 5 - 7 pairs of gills are present, which open directly outside the body by gill slits, operculum is normally absent in these fishes, except is chimaera where operculum is present.

– Mouth is present at the ventral surface of head.

–    Suspensorium of jaws is Hylostylic type.

– Air - bladder or lungs are absent.

– Spiracles present.

– A spiral valve or scroll valve is found in intestine.

– Cloacal aperture is present.

– There is special structure at the dorsal surface of head in these fishes, which is called "Ampulla of Lorenzini", this works as thermoreceptor.

– Tail is heterocercal type.

– Genital ducts open into cloacal aperture.

– Fertilization is internal – male fishes have "Claspers" as copulatory organs, which are developed by the inner edges of pelvic fins.

– Fishes are oviparous or viviparous (few have yolk sac placenta).

–    Scoliodon : - Dog fish - Dog like sense of smell. It is also known as Indian shark - viviparous

–    Sphyrna/Zygaena - Hammer headed shark

–    Stegostoma - Tiger Fish / Zebra shark

–    Carcharodon - great white shark

–    Rhinobatus - Guitar Fish

–    Pristis : - Saw - fish

–    Trygon : - Sting ray - Its dorsal fin has poisonous spines.

–    Torpedo : - Electric ray - In this fish an electric organ is found which is a modified muscle, it can give shock of about 100 volts. Scales are absent.

–  Rhinodon : - Whale shark - It is the largest fish. Its length is 13 – 14 meters.

–  Chimaera : - "Ratfish" or "King of herrings" or Ghostfish. Connecting link between bony & cartilagenous fish. Operculum present. Cartilage fish with operculum is placed under holocephali group.

Osteichthyes or Teleostomi

– Includes Bony fish. Endoskeleton of these fishes is made up of bones.

– Found in fresh water as well as marine water.

– Exoskeleton is made up of scales, such as cycloid or ctenoid or ganoid type. Placoid scales are absent.

– Respiration by 4 - pairs of gills. These are covered by operculum.

– Mouth is normally terminal or subterminal.

–   Suspensorium of Jaw is autosytylic.

– Accessory respiratory organ "air bladders" is present. This helps in swimming as well as in respiration both.

– Spiracle is absent.

– Scroll valve in intestine is absent.

– Cloaca absent, in place of cloacal aperture anus is present.

– No Ampulla of Lorenzini.

– Tail is normally homocercal type but sometimes it may be diphycercal type.

– Genital ducts open outside the body through separate apertures.

– Fertilization is external, claspers are absent in male fishes.

– Fishes are oviparous but maybe ovoviviparous or viviparous.

–  Labeo "Rohu" or "Indian carp" - It is a fresh water fish.

–  Clarias "Cat fish" or magur

–   Wallagon  Lachi (scale less)

–    Catla - Catla (Fresh water)

–    Heteropneustis - Singhi

–    Channa – Lata Fish

–    Laphius – Angler Fish

–  Hippocampus -   "Sea – horse" or "Pregnant male" : - It swims in water in its vertical position. A pouch like structure is present at the abdomen of male fishes known as "Brood - pouch" in this pouch male collects the eggs. Secondary vivipary and parental care is found in Hippocampus.

–    Anabas - Climbing perch.

–    Sardinella - Salmon

–    Acipensor - Sturgeon - Endoskeleton is cartilaginous.

–    Betta -  Fighting Fish

–    Pterophyllum - Angel Fish

–    Exocoetus - Flying fish - Its dorsal fin is long, it can fly (glide) over 400 metre with the help of this fin.

–    Anguila - Eel : - Snake like. migrate to sea for spawning. Young eel (Elver) migrate back to fresh water

–    Solea - Flat fish

–    Fistularia - Flute fish

–    Harpodon - Bombay Duck

–    Amia - Bow fish

–    Echeneis (Remora) - Sucker fish. Shows commensalism with shark and whales. Dorsal fin modified into sucker.

–    Mystus - Singhara

–    Cirrhinia - Mrigal

–    Latimaria or coelacanth - Living fossil – It is the oldest living vertebrate known till date. Belongs to group Crossopterygii.

–    Chenocephalus - Ice fish only vetebrate without haemoglobin.

–    Opsanus  - Toad fish

–    Synanceja horrida - Stone fish it is the most poisonous fish.            

–    Gambusia (Top minnow) - Larvivorous fish.

Dipnoi Group

–    Fishes of dipnoi group are called Lung-fishes or "Uncle of amphibia" because lungs helps in respiration.

– Three chambered heart.

– External and internal both the nares are present.

– Their tail is heterocercal type, Scale is cycloid type.

– These are freshwater fishes.

–    Lepidosiren : - South American lung fish. Respire though lungs only.

–    Protopterus : - African lung fish : - It is living fossil fish. Paired lungs are present.

–    Neoceratodus : - Australian lung fish. Respire by gills only. single lung is present which is used in stressful condition.

Shagreen is dried skin of Cartilaginous fish.

Cod liver oil is rich in Vitamin D, Shark liver oil is rich in Vitamin A

Maltese cross is found in vertebra .of cartilaginous fishes such as shark.

Mermaid's purse refers to Egg capsule of shark.

Isinglass is a gelatinous product from air bladder of certain fish for making cement, Jelly & for cleaning of wine & beer.

Smallest fish Mystichthyes - Goby fish - Pandaka (8 - 10 mm)

Additional Information

Classification of Aves

The class Aves is divided into two categories:

(i) Subclass - Archaeornithes

• Primitive ‘‘Reptile like birds’’ are included in this subclass, which belong to Jurassic period. All the members have becomes extinct.
• Wings are ill-developed, i.e. capacity of flying was very less.
• Pygostyle was absent.
• Keel on sternum was absent.
• There were present 3 - 3 clawed digits of forelimb at the free edges of wings.
• Uncinate processes on ribs were absent.
• Teeth were present in the jaws of skull.
• All the members of this sub-class are the connecting links between reptiles and birds.
• Archaeopteryx lithographica - Lizard bird. (Extinct in Cretaceous period) Its fossil was discovered by Andreas wagner in 1861 from Bavaria (Germany).
• Archaeornis

(ii) Subclass - Neornithes

• This includes living as well as extinct birds of post jurassic period.
• Wings are well developed which are used in flying (except some birds)
• Last few vertebrae fuse to form pygostyle.
• Sternum is bigger and with keel.
• Digits of forelimbs are fused and claws absent.
• Thoracic ribs are having uncinate processes.
• Except some species (which are extinct) rest of the birds are toothless.
• In living members of this subclass, vertebrae are heterocoelous.
• Last few vertebrae joins to form pygostyle.

This subclass is classified under four super orders.

(a) Super order - Odontognathae

• These extinct birds were having teeth.
• Pygostyle was absent.
• Keel in sternum is absent.
• Hesperornis  (Flightless marine bird)
• Cthyornis  (Flightless marine bird)

(b) Super order - Palaeognathae or Ratitae   

• It includes large and massive birds, which are flightless in nature.
• These are able to run fast. Wings are reduced/rudimentary/vestigeal or absent.
• Caudal vertebrae are free and pygostyle is absent.
• Sternum is raft like which lacks Keel.
• Uncinate processes on ribs, Oil glands or preen glands and sound producing organ syrinx is absent.
• Struthio - African ostrich or Camel-bird - It is the largest living bird of modern period. Polygamous, male incubate the eggs (Largest egg). In this bird urinary bladder and penis is present.
• Rhea - South american ostrich :- It also has urinary - bladder and penis.
• Apteryx -  Kiwi - It is National bird of New zealand. It has hair like feathers all over its body. It is smallest flightless bird.
• Dromaeus - Emu - It is a monogamous bird in which only males look after their young ones and eggs.
• Aepyornis - Elephant bird
• Casuarius - Cassowary (found in New Guinea/Australia)

(c) Super order - Impennae

• All are  aquatic birds
• Forelimbs are modified into flippers
• Limbs are webbed.
• Teeth are absent
• Sternum without keel.
• Spheniscus - Penguin - It is also called ‘‘sea bird of Antarctica’’ (Emperor Penguin)
• Aptenodytes - Penguin

(d) Super order - Neognathae or Carinatae

• This super order includes flight birds of modern era. Wings are well developed.
• Pygostyle is present.