Lecture 15 Sounds and Colors

Vert Zoology

What is Sound

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

How is a sound wave transmitted into information by the mammalian ear

outer ear catches sound waves and funnels them into the ear canal
Wave hits the ear drum and vibrates it

Vibration moved to oval window (opening of the inner ear via the malleus, incus, and stapes (ossicles)

the ossicles amplify the sound waves

Inner ear parts

cochlea (hearing) and vestibular organ (balance)

Shared hearing / ear features amongst vertebrates

All terrestrial vertebrates have eardrums that connect to oval windows and onto organs that have hair cells where sound waves are transmitted as signals to the brain

The bones that transmit and amplify sound waves from outside to inside of the ear are derived from the jaw

What is different among vertebrate group ears?

The number of bones → Fewer bones translates into less amplification

Tonotopic

The hair cells in the ear are tonotopic, meaning that the types respond only to particular sound frequencies (Hz). The more types of hair cellsm the greater the range of hearing. The cochlea has several varieties of hair cells.

Acoustic Communication Origin

Associated with nocturnal activity → acoustic signals can function in darkness while most visuals cannot. evidence: acoustic communication not seen for lepidosaurs but is seen in the nocturnal Gekkota

Functions of Hearing/Sound in Vertebrates

• Perceive the environment (hearing is a sense)

• Complex Communication

  • Reproductive calls

  • Mating displays

  • Individual Recognition

  • Parental Care

  • Aggression

  • Signaling Territory

Example of vertebrate non-vocal sound

Woodpecker drumming → it can serve the same function as vocal sounds

Information in Bird Songs

• Regional location of the singer

• Reproductive mode, in territory, and available for mating

• Quality of territory (sing more bc he has food)

• Health ( size of repertoire/ consistency/ frequency)

• Mating status (sings all day, is not mated)

• Longevity (size of repertoire)

Echolocation Water

• Cetaceans (dolphin and whales) use ultrasound (above 20kHz)

• Sound travels faster in water (sound wave is longer than in air)

• Cetaceans emit sounds with short wave length to find fish (high pitched sounds)

Melon

Part of the dolphin - sound beam is reflected off the front of the skull and focused by this oil-filled body part

Incoming Cetacean Sounds

• Sound return through thin bone near the lower jaw → waves pass through the bones into a fat body inside the mandible that extends back to the inner ear (this is when inner ear gets the sound) sound travels into all parts of a vertebrate underwater

Sonogram

time on x-axis and frequency on y-axis
- allow us to see subtle changes in frequency

Wavebands

• the waveband to which different photoreceptor cells respond depends on light-absorbing pigments they contain within the cones

Rods vs Cone

Cones - color

Rods - associated with the ability to see low intensity light

Color Vision

• depends on having different cones tuned to differenth wavebands

  • NOT a product of how much a cone is stimulated

• Depends on how much a cone is stimulated RELATIVE to the others

• Humans - trichromatic

• Horse - dichromatic

Tetrachromatic

• four cones → finer discrimination in color

• Fish, amphibians, reptiles, and birds

• Allows color vision in the UV spectrum

• Allow birds to have a private channel of communication that mammals cannot see → birds secretly UV colorful

Trichromatic

humans and most primates

• 3 cones ( red, green, and blue)

• Long (L) Medium (M) short (S)

• Evolved to aid in the detection and discrimination of fuits for ripeness

Dichromatic

• Most eutherian mammals are dichromats

• Contain only a single short-wave sensitive cone in the UV or violet waveband and a long-wave sensitive cone in the green-yellow waveband

• These mammals cannot discriminate between reds, yellows, and greens

Monochromatic

• many marine mammals like cetaceans, sea lion, owl monkey

• they see in gray, black, and white

Cost to tetrachromy

• More cones in tetrachromy lead to fewer rods

• The tetrachromatic eye is well designed for high color discrimination but only in bright light

• Whereas the typical mammalian eye has more rods and is well designed for high light capture but poor color discrimination

Carotenoid-Based Coloration

• The second most common pigment in vertebrates, with melanin being the first

• Not produced by the organism itself, but through its diet

• In birds, if they don’t have a good access to carotenoids in their diet when they molt, they will be yellow instead of red → females don’t like this

Melanin-Based Coloration

• Melanin is the most abundant and widespread pigment in vertebrates and other animals

• manufactured by the organism and is controlled by melanocytes (production can be turned on or off)

• indole biochromes - absorb more light

• two major kinds: Eumelanin and Phaeomelanin

Eumelanin

• more common

• Blacks and Browns in vertebrates

Phaeomelanin

• lighter pigment

• usually reddish-browns, chestnuts, yellowey

Melanin Functions

• Antioxidants

• Tissue Strengtheners

• Antimicrobials and Parasite Deterrents

• Photoprotectants

• Thermoregulation

Structural Color-Based Coloration

• produced by light interacting physically with the skin

• Responsible for many of the blues, purples, and greens

• Responsible for iridescence

• Structural light is created through hyper-specific reflection, not absorption (the majority of color we see is based on absorption of light)

Incoherent scattering

individual light-scattering objects are responsible for differentially scattering light waves - each work independentally often canceling each other out producing white

Coherent scattering

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

mostly greens, blues and iridescence