Vert Zoo Lecture 15: Sounds and Colors

What is sound?

produced by vibrating objects and reaches the listener’s ears as waves in the air or other media (water and even solids)

How sound works

vibrations move back and forth, as it moves forward it pushes air in contact with surface, create a positive (higher) pressure by compressing air. when the surface moves in the opposite direction, it creates a negative (lower) pressure by decompressing the air.

wavelength

the measure of displacement over distance

Period

measure of displacement over time

Amplitude

the distance above or below the centerline or the x-axis the greater the distance away from the centerline the more intense the signal.

Frequency

the rate at which the signal repeats at a 360 degree cycle of positive and negative amplitude over a period of time.

How is a sound wave transmitted into info by the mammalian ear?

outer ear catches sound waves and funnels them into ear canal → wave hits the ear drum and vibrates it → this vibration is moved to the oval window that is opening to the inner ear via the malleus, incus, and stapes (ossicles) → ossicles amplify the sound waves

parts of the inner ear

cochlea (hearing) and vestibular organ (balance)

cochlea

where wave are transferred into electrical signals that are interpreted by the brain as “sound” via specialized hair cells

shared hearing/ear features

all terrestrial verts have ear drums that connect to oval windows and on to organs that have hair cells where sound waves are transmitted as signals to the brain, bones that transmit and amplify sound were derived from the jaw.

tonotopic hair cells

only respond to particular sound frequencies

origins of acoustic communication are associated with __

nocturnal activity

Info in bird song

• regional location

• reproductive mode, on territory, available for mating

• quality of singers territory

• general health

• mating status

• longevity

Reasons for mimicry

• may signal fitness

• may warm the mimicked species away from territory

• mockingbirds with largest repertoires have the best territories filled with food

• brood parasites learn to mimic sounds of the chicks in the nests they invade

• some birds mimic alarm calls

cetaceans must emit sounds with extremely __ wave lengths to locate fish, and to do that in water they must emit extremely _ frequency sounds

short, high

Cetaceans emit sound by moving air back and forth between air sacs in the nasal passages. Sound beam is reflected off the front of the skull and focused by an oil-filled body called the

Melon

Caetaceans: sound waves pass through the bone and into a

fat body inside the mandible that extends back to the inner ear

echolocating bats emit a stream of ultrasounds from the __, which is enlarged but not greatly modified from the general mammal form

larynx

sonogram

has time on the x-axis and frequency on the y-axis

Vert eyes

• photoreceptors respond selectively to different wavebands

• cone are for color

• perception of color is not the product of how much a given cone is stimulated, it is dependent on how nye a cone is stimulated relative to the other cone type

• product of the upstream nerve cells and the optical lobe of the brain and less by the physical action of light hitting cones

Ancestrally, vertebrates had __ cones

4, tetra chromatic

Color vision in humans

• based on three cones (red green blue)

• absorb light in the long (L) medium (M) and short (S) wave portions of the human visible spectrum

most eutherian mammals are __ (vision type)

dichromats, only a single short-wave sensitive cone in the UV or violent waveband and another long-wave cone in the green-yellow waveband (these mammals are color-blind, do not differentiate between red yellow green).

Why might of trichromatic vision (receptivity to medium wave-bands) evolved??

so primates can discriminate between fruit ripeness

Trichromaic vision allows for vision in the __ spectrum

UV

About/Function of UV color vision

• provides a “private channel” of communication that mammalian predators cant see

• produced by nanostructure in the feathers

• backgrounds such as leaves and bark reflect little UV, so good contrast

monochromatic vision

many marine mammals, see in gray black and white

Cost of tetrachromy

• have many cones: trade off having fewer rods

• well designed for high color discrimination but only at high light intensities

• typical mammalian eye well designed for high proton light capture but poor color discrimination

what is the first and second most common pigment in vertebrates

1. melanin

2. carotenoids

carotenoid are obtained from __ while melanin is _

diet, produced by the organism

Eumelanin

black and brown

Phaeomelanin

reddish brown

melanocytes

where melanin production is controlled, can be turned on and off

Melanin functions: Antioxidants

melanins can act as valuable free radical scavengers. Patches or stripes produced can act as honest signals of an individual’s health.

Melanin function: Tissue strengtheners

offer structural support and strength to tissues, black feathers are more durable and resist abrasion as compared to other feathers

Melanin function: Antimicrobials and parasite deterrents

by strengthening the tissues through which microbes and other parasites must chew, melanin may slow feather fur or skin degradation

Melanin function: Photoprotectants

the absorption of most wavebands of light makes melanin and important line of defense from solar rays

Melanin functions: thermoregulation

also a product of melanin absorbing most wavebands of light, they convert the photon energy of the sun into heat. Thus, melanin is part of an individuals ability to thermoregulate and maintain high body temps.

structural colors

produced by light interacting physically with nanometer scale variation the structure of skin feather, eyes, fur (responsible for blue, purple, green)

Incoherent scattering

occurs when individual light scattering objects are responsible for differentially scattering light waves.

Coherent scattering

occurs when the spatial distribution of light scatters is not random with respect to the light waves.

structural color is created through __ not absorption

hyper-specific reflection