2. •Feathers probably arose as new structures
under and between reptile scales, not as
modified scales. Many birds have scales on
their lower legs and feet where feathers are
not developed
•Feathers originate in a skin layer deep
under the outer layer that forms scales.
3. • feathers did not evolve for flight. They
evolved for some other function and were
later modified for flight.
•Feathers may have evolved to aid
thermoregulation.
4. DEVELOPMENT OF A FEATHER
- It is initiated by formation of a dermal papilla
An early dermal papilla associated with
formation of a placoid scales
5. -The growth of papilla, and its inductor effect on the
overlying epidermis, results in a pimple like elevation
---- feather primordium, on the surface of the skin.
-When the dermal papilla becomes vascularized :
it is the source of nutrients and oxygen for the
developing feather
A collecting site for metabolic wastes that are then
carried away in the blood stream
6. - The feather follicle develops around its base as the
feather primordium elongates
- Between the dermal
papilla and the epidermis,
at the base of the feather
follicle ---- a mitotically
active growth zone
proliferates tall columns of
epidermal cells that
pushes towards the distal
tip of the growing feather,
now a feather sheath
- These epidermal columns separate from one another,
cornify, and develop into barbs
7. -When the feather sheath splits open, the fluffy barbs
stretch out of their cramped quarters and the shaft
elongates.
8. •The contour feathers used for flight are known as
remiges and rectrices, can be divided into three
groups: primaries, secondaries and tertiaries.
9. •The primary feathers propel the bird through the
air.
•The secondary flight feathers run along the "arm"
of the wing and sustain the bird in the air, giving it
lift.
•The Tertiaries are the few flight feathers and the
numbers vary among species.
10. Morphological varieties of feathers:
1. Flight Feathers
•these feathers have developed into long showy
plumes used in visual courtship displays
12. -Consists of a horny shaft and two flattened vanes ; the
base of the shaft is the calamus ; the vane- bearing
segment is the rachis ; each vane consists of a row of barbs
that have barbules and flanges
-Arising from a notch, the superior umbilicus, is an
afterfeather
usually shorter than the main feather
13. 3. Down Feathers
-small, fluffy feathers lying underneath and between
contour feathers.
- They have a short calamus, with a crown of barbs
arising from the free end, and no hooklets
- It helps insulate birds
14. 4. Hair Feathers
-Also known as
Filoplumes
-Are hair-like feathers
consisting chiefly of a
threadlike shaft
-They are scattered
throughout the skin
among contour feathers
- The long colorful feathers of a peacock are filoplumes
