Chapter 4

Question 1

What are the main function of feathers?

Answer 1

locomotion, thermoregulation, communication, and protection

Question 2

Give two basic names of flight feathers

Answer 2

• remiges (wing flight feathers) and Retrices(tail flight feathers)

Question 3

Name 3 basic structures of flight feathers

Answer 3

Rachis, Calamus, and Vane

Question 4

Calamus

Answer 4

proximal, stick like end part of the feather

Question 5

Rachis

Answer 5

shaft of feather

Question 6

Vane

Answer 6

• feather-like portion of flight feather
• has (from proximal to distal) a Plumulaceous portion, closed pennaceous portion, and open pennaceous portion

Question 7

Describe the relationship between, barbs, barbules, and hooklets

Answer 7

• barbs provide a “branch” for proximal barbules on bottom side and hooklets(distal barbules) on top
• hooklets(distal barbules) connect one to the other to hold the structure seen as a feather(like velcro)

Question 8

What are the three sets of remiges?

Answer 8

primaries(most 9-10), secondaries(varies from 9-25) and tertials( 3-4 usually)

Question 9

What are contour feathers?

Answer 9

• primary body feathers of a bird
• has proportion of Plumulaceous barbs and a portion of Pennaceous barbs that are about equal
• has more plumulaceous barbs than a flight feather

Question 10

What are afterfeathers?

Answer 10

• the secondary body feathers of a bird
• it primarily provides insulation
• forms from same follicle of a typical contour feather

Question 11

Bristiles

Answer 11

• specialized feathers with both sensory and protective functions
• often have shaft and aftershaft to collection sensory information
• just have a straight rachis-like structure

Question 12

Describe the sequence of development in feathers: epidermis to follicle

Answer 12

Feather growth begins with a thickening of the epidermis, the placode, over a condensation of cells in the dermis.
The placode elongates into the tubular feather germ.
Cells proliferate in a ring around the feather germ to create the follicle; production of new keratinocyte cells in the follicle collar push older cells up and out to create the tubular feather.

Question 13

Describe the follicle development structure in feathers

Answer 13

• The outermost layer becomes the sheath, whereas the inner layer divides into a series of barb ridges that develop into the barbs of the feather

Question 14

Describe the sequence of development in feathers: follicle collar to fully formed feathers

Answer 14

The feather emerges and unfurls from the sheath into its final shape.The follicle collar forms the calamus at the base of the feather.

The branching structure of the rachis and the barbs are created by helical growth of barbs ridges from the ventral to the dorsal side of the follicle:

First, barb ridges fuse to form the rachis, later barb ridges fuse to the rachis. The afterfeather develops by the same mechanism with helical growth toward the ventral side of the follicle.

Question 15

Which part of the feather follicle makes the feather?

Answer 15

The inner layer

Question 16

What is the Dermal papilla?

Answer 16

the structure hump/indent out into the dermis to make the tubular feather germ

Question 17

How many stages are in the hypothesized feather evolution?

Answer 17

5 stages

Question 18

Stage I of hypothesized feather evolution

Answer 18

• starts with 1st hollow cylindrical filamentous feather
• starts with follicle collar structure

Question 19

Stage II of hypothesized feather evolution

Answer 19

• origin of barbs
• there is differentiation of the follicle collar
• barbs have formed, a tuft of unbranched barbs attached to the calamus

Question 20

Stage III of hypothesized feather evolution

Answer 20

• 2 possibilities: evolution of barbules or evolution of rachis
• a feather with barbs and barbules attached at the base to a calamus, includes origin of barbule plates
• a planar feather with unbranched barbs fused to a central rachis, includes the rachis ridge and origin of helical growth and formation of rachis
• Leads to planar feather with branched bard and open vane

Question 21

Stage IV of hypothesized feather evolution

Answer 21

• evolution of hooklets
• we have the closed pennaceous vane (hooklets on one barbule attach to grooves on barbules of adjacent barb)
• includes differentiation of barbule plates

Question 22

Stage V of hypothesized feather evolution

Answer 22

• we have evolution of a closed asymmmetrical vane (resembling modern flight feathers)
• includes addition of more barb ridges on one side