Final Exam: Vision, smell, taste, magnetic sense

• what 3 things happens to light as it passes through the water column

• what 3 things is the amount of visibility and light affected by

• what are the 3 main light zones of the ocean

• how is light affected by depth

• what wavelength is filtered out first and last

• how do MM function in regard to light

• light is absorbed, refracted, and scattered as it passes through the water column

• wavelength of light, concentration of chlorophyll in water, and concentration/type of DOM

• photic => disphotic => aphotic

• light intensity decreases exponentially w/ depth

• red is filtered out first while blue is last

• MM are functionally crepuscular meaning they exist in light like its dusk and dawn all the time

• what are the 2 main eye components used for detection and acuity

• what is the trade-off b/w seeing in water and air

• cornea = outside cover of eye, on land accounts for 2/3 of focusing power, no refraction under water => loss of focusing power

• lens = clear, opaque marble inside eye that becomes more spherical w/ age; much stronger in MM

• causes severe myopia (near-sightedness) when out of water

• describe the lens of cetaceans

• spherical and lacking ciliary muscles

• pupillary contraction => horizontal slit = infinite depth of field

• dolphins are not near-sighted or far-sighted

what type of eyes do verts have

compound

describe the visual detection of…

• pinnipeds

• polar bears

• sea otters

• sirenians

• pinnipeds

  • lens shape is intermediate

  • ciliary muscles to distort thick lens

  • so they can see better in water than more land based MM

• polar bears

  • see like terrestrial mammals

  • little adaptation to see underwater

• sea otter

  • sees well in air and water by changing the radius of the curvature of its lens (sphere, oval, football)

• sirenians

  • poor vision bc they live in coastal murky water so its vision is not used very well; has minimal predators, and their food is in shallow water on the bottom

• define retina

• what are the 2 purposes of a pigmented retina

• what type of receptors does it contain

• what are the 2 benefits of the receptors

• retina = layer of thin tissues on back of eye

• purposes

  • absorbs light

  • helps adapt to dark and light

• contains photoreceptors which is good evidence they have rods and cones

• benefits of photoreceptors

  • see prey from below = sensitivity detectors

  • prey seen from side = contrast detectors

• define rods

• define cones

• what is the sex difference w/ rods

• rods = specialized for low light level (sensitivity) (not color sensitive)

• cones = specialized for high light (color), used for contrast

• males have more rods than females

• what is the relationship b/w receptors and sensitivity?

• human vs. seals vs. dolphins vs. nocturnal fish

• high density of receptors increases sensitivity

• human at 120,000 receptors per mm > seals > dolphins at 400,000 receptors per mm > nocturnal fish at 800,000 receptors per mm

• describe the travel of chemicals in water compared to water

• what are the senses aligned w/ chemoreception

• the diffusion of chemical is 1000x slower in water than air due to the increased density of water

• smell and taste aligned closely (90% of our tast is smell)

• describe the state of knowledge w/ the olfactory system

• not well developed so not well studied

describe the olfaction of

• cetaceans and sirenians

• odontocetes

• mysticetes and sirenians

• Otariids, phocids, and polar bears

• cetaceans and sirenians have less developed sense of smell than other mammals

• odontocetes lack olfactory bulb

• mysticetes and sirenians have rudimentary bulb => a structure that is present but not actively used (vestigal structure)

• otariids, phocids, and polar bears have a well-developed sense of smell bc they spend lots of time on land

  • fur seal female smelling bc mamas need to smell their babies to bring them food

  • elephant seal pup smelling

why was taste important in early healthy evolution

bc it indicated what was edible and inedible

describe the gustation in…

• odontocetes and sirenians

• otariids, ex of california sea lion

• odontocetes and sirenians have taste buds in grooves and pits of tongue

  • they cannot detect salt

• otariids have taste buds

  • Ex = california sea lion can detect citric acid, difference b/w FW and SW to maintain osmoregulation

what are 3 variations of sensitivity in gustation

• detect bitter compounds

• insensitive to salt

• no ability to detect sweet

describe the tactile sensation in dolphins

• well-studied

• have tactile sensors across body that are sensitive to pressure => allows them to flex body away from high pressure and toward low pressure

describe the tactile sensation in Pinnipeds

• in the form of vibrissae

• provides information on displacement and vibrations

• each whisker is innervated w/ up to 2000 nerve fibers

• displacement sensitivity

• vibration sensitivity for ice holes

how does water effect magnetic flux density

water has little effect on magnetic flux density

• define magnetite

  • what does it function as

  • where is it found

  • how well is it studied

  • describe use in cetaceans

  • what 2 things can be detected

• magnetite = crystals formed through biochemical processes w/in the body

  • function as magnetic detector

  • found in dura matter of brain in cetaceans

  • hard to study

  • evidence that cetaceans using magnetic info to guide their movements and positioning

  • standings and magnetic lows