1) Birds are warm-blooded vertebrates with lightweight skeletons adapted for flight. Their forelimbs are modified as wings and their sternum and shoulder girdle attach flight muscles. 2) They are covered in feathers and have a beak with no teeth. Their bones contain airspaces connected to lung air sacs, making them light enough for flight. 3) Birds are classified into two subclasses: Archaeornithes, now extinct birds with primitive wings that could fly little, and Neornithes, living and extinct modern birds, divided into flightless ratites and flying carinates.

1. Birds/Aves
By
Ikram Ullah

2. CLASS AVES (Birds)
Latin Aves means birds.
- Body is perfectly adapted for flight.
- Light-weight bones: hollow (Pneumatic).
- The fore limbs are modified into wings.
- Sternum and shoulder girdle are specialized for
attachment of muscles.
Bird/Aves

3. General characteristics
1. Birds are warm-blooded specially adapted for aerial mode of life.
2. Body is streamlined and spindle shaped.
3. Body is divided into four regions. Head, neck, trunk and tail.
4. Fore-limbs are modified into wings. Hind limbs are used for
walking, perching, food capturing, swimming etc.
Hind limbs bear four toes with claws.
Bird/Aves

4. General characteristics
5. Body is covered with feather. Feathers are epidermal
derivatives.
6. Scales are present on legs.
7. A horney beak with no teeth.
8. Skull is large with one occipital condyle.
9. Bones of skeleton are spongy, light and contain airspaces,
which are connected with the air sacs of lungs.
Bird/Aves

5. 9. Breast bone or sternum is broad with a ventral keel.
10. Large brains due to which they show highly organized
behavior in the form of
- Nest building
- Courtship,
- Parental care and
- Migration.
11. Birds have good sense of hearing, keen vision and a
good physical equilibrium.
Bird/Aves

6. 12. Heart is completely four chambered with two auricles and
two ventricles.
13. They have nucleated RBC’s.
14. Respiratory system much extended. Lungs have extension
called air sacs. Air sacs extend into bones.
15. Excretion by kidneys. Kidneys have no bladder.
Bird/Aves

7. 16. Larynx is without vocal cords. A sound box or syrinx
producing voice. Syrinx lies at the junction of trachea and bronchi.
17. Well-developed third eyelid or nictitating membrane. It is
used for cleaning of eyeball.
Bird/Aves

8. 18. Female lay eggs with a large yolk. The egg is enclosed in a
calcareous shell.
19. Sexes are separate. Male has paired abdominal testis while
female has a single left ovary.
20. Fertilization is internal. Development is direct.
21. Parental care is well developed.
Bird/Aves

9. Classification of Aves
Bird/Aves

10. Classification
Class Aves is divided into two sub-classes.
A)Subclass Archaeornithes.
B)Subclass Neornithes.
Bird/Aves

11. Sub class archaeornithes:-
Greek: Archaios = ancient + ornithos = birds.
a. They are extinct.
b. Wings were primitive – little power of flight.
c. Skull has teeth in both jaws.
d. Sternum with out keel.
Examples is Archaeopteryx.
Classification of Aves

12. ii. Sub-class Neornithes:
Greek: Neos = modern + ornithos = birds.
Neornithes includes the living as well as extinct birds.
a. Wings usually well-developed and adapted for flight with
few exception.
b. Teeth absent in jaws.
c. Sternum usually with a keel.
Classification of Aves

13. Neornithes is further divided into two groups.
a. Ratitae or Flightless birds.
b. Carinatae or Flying birds.
Classification of Aves

14. a. Ratitae:
Characteristics are:
1. They are the running or flightless birds.
2. They are of usually large size.
3. Wings may be absent or rudimentary.
4. Sternum is broad and without a keel.
5. Tail feathers are irregularly arranged or absent.
Examples: Emus, Ostrich, Cassowary, Kiwi and Penguin etc.
Note: In penguin fore limbs have modified into paddles or flippers for
swimming in water. Thus they have adapted for aquatic mode of life.
Some penguin also lives in Antarctica.

15. b. Carinatae
They are flying birds.
Characteristics
• Well developed wings for flight.
• Sternum is keeled.
• Tail feathers are used for steering during flight.
Examples: Sparrow, parrot, pigeon, dove, ducks, crow, owl etc

16. Elaborate structure
(e.g., osprey)
Resource defense
polygyny
Resource defense
polyandry

17. Merci Beacoup