aves general characters

1. Class:AVES-General characters
B.Ashok Kumar
Assistant Professor
KRK Govt. Degree College
Addanki-523201
9652929696
ashokkumarzoology@gmail.com

2. Class Aves
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3. Introduction
• Includes birds
• The feathered bipedal vertebrates
• Homeotherms- successful in life
• Origin- therapod dinosaurs-Jurassic period
• Advanced over reptiles
• T.H.Huxley- “Glorified Reptiles”
• J.Z.Young- “The Masters of air”
• Ornithology-Study of Birds
• Largest bird- Ostrich(Struthio camelus)
• Smallest bird- Bee Humming bird-Mellisuga helenae

4. • Largest
• Smallest birds pics

5. The Origin of Birds
• Most paleontologists agree that the common
ancestor of all existing birds was a type of small,
feathered dinosaur.
• Recent fossil discoveries of feathered dinosaurs in
China support this hypothesis.
Caudipteryx zoui Sinornithosaurus milleniiMicroraptor gui
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6. Caudipteryx
• Feathered dinosaur
• Flightless
• Transitional fossil
–Dinosaur arms
–Dinosaur teeth
• Only front of
upper jaw
–Bird feathers
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7. Archaeopteryx
• Represents an animal that lived about
150 million years ago.
• Unlike modern birds, Archaeopteryx
had clawed forelimbs, teeth, and a
long tail with vertebrae—all reptilian
characteristics.
• In fact, if the feathers had not been
preserved in the fossil, Archaeopteryx
probably would have been identified
as a small dinosaur.
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9. Microraptor gui
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10. Characteristics of Birds
Homeotherms/Endotherms/
warm blooded
Body-head, long neck, trunk
& a short tail
Boat shaped & streamlined
Bipedal , forelimbs-wings,
hind limbs-bears body weight
Adopted- walking, running,
swimming, percing etc.
Skin-dry, only gland-
Preen/Uropygeal-base of tail
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11. Internal Anatomy

12. Characteristics of Birds

13. Exoskeleton
• Epidermal feathers
• Scales on legs
• Claws on toes
• Rhamphotheca on beak

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15. Endoskeleton
• Pneumatic bones- without bone marrow
• Monocondylic skull
• Two sacral vertebrae
• Synsacrum- last thoracic, lumbar, sacral, few
caudal vertebrae- fused with pelvic girdle for
support to hind limbs
• Pygostyle- posterior most caudal vertebrae
fused- supports tail feathers

16. Skull
• Most bones fused
• Much lighter than
reptile or mammal skull
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17. Pygostyle – support for tail
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18. Endoskeleton
• Sternum-
keel/carina-
attachment of flight
muscles
• Ribs double headed
• Furcula- clavicle,
interclavicle unite-
‘v’ Shaped(wish
bone)

19. Flight muscles
• Powerful flight muscles
• Pectoralis major-large-red-
connected to lowerside of head
of humerus & keel of sternum-
downstroke (Depressor muscle)
• Pectoralis minor-arise from
sternum-connected to dorsal
sideof humerus-
upstroke(Elevator)
• Coracobrachialis- connects
corocoid & lowerside of head of
humerus(depressor)

20. Digestive System
• Edentate
• Crop-Storage
• Stomach-Proventriculus
– Enzymes
• Gizzard
– Grind food
• Cloaca- coprodeum,
urodeum,& proctodeum
– Waste
– Reproduction
– Bursa of Fabricius-blind
sac with lymphoid
tissue-proctodeum
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21. Respiratory System
• Lungs- spongy, alveoli absent
• Nine air sacs-unpaired
interclavicular, paired-
cervical, anterior thoracic,
posterior thoracic, &
abdominal
• Fresh air always moving
inside
• Trachea large & coiled
• Syrinx-junction of trachea &
bronchi- sound producing
organ 21

22. High Metabolic Rate
• Birds have a system of branching air sacs
that function with their lungs in respiration.
• The system of air sacs supplies the high levels of
oxygen needed to support a high rate of
metabolism for the hard-working flight muscles.
• This high metabolic activity also
provides heat for endothermy.
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23. Circulatory System
• Four chambered heart- two
atria & two ventricles
• Sinus venosus & truncus
arteriosus absent
• Two aortic arches- right
systemic arch & pulmonary
arch- present
• Renal portal system-
reduced
• Erythrocytes- oval &
Nucleated
• Complete double circulation
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24. Excretory system
• Metanephric kidneys- three lobed
• Urinary bladder absent except in ostrich
• Uricotelic animals

25. Nervous system
• Two meninges- Duramater, Pia-Arachnoid
membrane
• Cerebral hemispheres, optic lobes cerebellum
are large
• Cranial nerves – 12 pairs

26. Sense organs
• Eyes-large-possesses nictitating membrane
• Sclerotic plates in sclerotic layer- maintain
shape of the eye
• Comb shaped pecten- projects into vitreous
humour- probably nourishes, removes wastes
• External ear openings present, middle ear
with single ossicle- columella auris, cochlea
with organ of corti in internal ear
• Olfactory sense is poor except in kiwi

27. Vision
• Up to 8 times keener
than human vision
• Each eye moves
indendtantly
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28. Reproduction
• Copulatory organ absent except decks, geese,
swans, flightless birds
• In female- right ovary, right oviduct- rudimentary
• Fertilisation internal
• Oviparous- megalecithal, cleidoic eggs
• Meroblastic cleavage
• Four extra embryonic membranes- appear during
development

29. Avian Reproduction
• In the males of species without a phallus, sperm is
stored within the proctodeum compartment within the
cloaca prior to copulation.
• During copulation, the female moves her tail to the side
and the male either mounts the female from behind or
moves very close to her.
• He moves the opening of his cloaca, or vent, close to
hers, so that the sperm can enter the female's cloaca, in
what is referred to as a cloacal kiss. This can happen very
fast, sometimes in less than one second.

30. Avian Reproduction
• The sperm is stored in the female's cloaca for
anywhere from a week to a year, depending
on the species of bird.
• Then, one by one, eggs will descend from the
female's ovaries and become fertilized by the
male's sperm, before being subsequently laid
by the female.
• The eggs will then continue their
development in the nest.

31. Avian Reproduction
• Many waterfowl and some other birds, such as
the ostrich and turkey, do possess a phallus.
• Except during copulation, it is hidden within the
proctodeum compartment within the cloaca, just
inside the vent.
• The avian phallus differs from the mammalian
penis in several ways, most importantly in that it
is purely a copulatory organ and is not used for
dispelling urine.

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• Female

33. • Male

34. The End
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