Chapter 4: Part 2

Question 1

Describe how activation of genes Bmp2 and Shh account for the evolutionary development of feathers

Answer 1

• signaling of molecules reployed after the placode forms
• their domains of expression overlap, stimulating growth of an elongated epidermal tube
• both genes are re-deployed again to the sides of the shaft of growing feather; they mark tissue to be removed to form the barbs of a feather
• the pattern of the 2 genes change from vertical building; strips are forming on one side and stop on the other
• the side without formation forms the rachis rather than barbs

Question 2

2 types of feather color

Answer 2

• pigments and structural coloration

Question 3

Pigments

Answer 3

• in feather tissue itself
• proteins of colors
• includes melanins, carotenoids, pterin, porphyrins, and Psittacofulvins

Question 4

Melanins

Answer 4

• most common
• earth tones
• eumelanin(black and gray)
• Pheomelanin(red brown, rufous, and buff tan)

Question 5

Melanosomes

Answer 5

• melanin-containing bodies within skin cells and feathers
• shapes can often point to coloration with these

Question 6

Carotenoids

Answer 6

• yellow, orange, or red pigments
• zeaxanthin is yellow dietary example

Question 7

How do they produce different carotenoid plumage colors?

Answer 7

• they are produced by different pigment molecules, which vary in the length of the central chain of alternating carbon double bonds
• the birds can ingest pigment to modify their own pigment metabolically; pigments with longer or shorter chains of double bonds
• the longer the chain, the longer the wavelength of color

Question 8

Pigment Psittacofulvins

Answer 8

• bright yellow, orange, and red feathers in parrots
• tetradecahexanal

Question 9

Pigment Porphyrins

Answer 9

• chemically related to iron-containing red hemoglobin and to the manganese-containing green chlorophyll pigments of plants
  -turacin

(however, most greens are NOT pigments)

Question 10

Pigment Pterin

Answer 10

• the golden yellow crest and facial feathers of penguins

Question 11

Structural Colors

Answer 11

• produced by the structure of the feather instead of pigments
• deals with nanostructure (orientation and structure reflects certain wavelengths of light)

Question 12

Name the four types of structural colors

Answer 12

• Constructive interference
• Destructive interference
• Coherent Scattering
• Incoherent Scattering

Question 13

Constructive Interference

Answer 13

Occurs when the maxima of two waves add together (the two waves are in phase), so that the amplitude of the resulting wave is equal to the sum of the individual amplitudes

2 wavelengths add up to create a 3rd

Question 14

Destructive Interference

Answer 14

If the crests of one wave coincide with the troughs of the other wave, the resulting amplitude is decreased or may even be completely canceled

Question 15

Coherent Scattering

Answer 15

A form of electromagnetic wave in which photons share the same frequency and wavelengths are in phase with one another

Question 16

Incoherent Scattering

Answer 16

Photons are in different frequencies and are out of phase

Question 17

Examples of Constructive Interference

Answer 17

• iridescence: change in hue with angle of observation or illumination
  (from arrays of melanosomes in the beta-keratin of feather barbules)
• iridescent plumage colors are produced by constructive interference from arrays of melanin granules in the feather barbules

(Violet-backed starling, Bird-of-paradise)

Question 18

example of Incoherent reflectance

Answer 18

• produces white, Rock ptarmigan

Question 19

Describe Non-iridescent colors

Answer 19

• they are produced by spongy nanostructures made of air bubbles and beta-keratin inside of the medullary cells of feather barb rami
• light goes through spongy layer keratin/air matrix and bounces back desired color to bird(through color-producing cells that contain light scattering vacuoles), other wavelengths collected by a bottom black melanin layer

(ex: bluebird, Red-legged honeycreeper)

Question 20

Describe a bird with structural and pigmentary color

Answer 20

• Paradise Tanager (blue belly and neon green crown feathers)
• has identical feather nanostructures, but green crown contains yellow carotenoid pigments(zeaxanthin and lutein)
• yellow pigments absorb blue and ultraviolet wavelength to created a neon green color

Question 21

What are Pterylae?

Answer 21

• feather tracts

Question 22

What is Apteria?

Answer 22

few or no contour feathers

Question 23

Describe feather erector muscles

Answer 23

• runs between follicles of neighboring feathers within a feather tract
• contraction of erector muscles rotates the feathers upwards

Question 24

Depressor muscles

Answer 24

• run between the follicles of neighboring feathers within a feather tract

Question 25

What is the location of the uropygial gland?

Answer 25

• located at the base of tail, lower back of most bird

Question 26

What is the function of the uropygial gland?

Answer 26

• produces a rich oil of waxes, fatty acids, fat, and water
• Cleans feathers and preserves feather moistness and flexibility
• Functions as an insulating and waterproofing layer
• Helps to regulate the parasitic bacteria and fungi that grow on feathers