Chapter 15 (eyes and vision)

Question 1

HEY! LOOK AT THE EYE!

Answer 1

(oooh im so glad i looked at that eye…)

Question 2

what are major features of a vertebrate’s eye?

Answer 2

anterior chamber (filled with aqueous humour), iris, lens, posterior chamber (filled with vitreous humour) lined with the retina.

Question 3

what does the spherical lens connect to?

Answer 3

cornea.

Question 4

the cornea is a transparent section of WHAT of the eyeball?

Answer 4

Scleroid coat

Question 5

how is the lens suspended?

Answer 5

suspensory ligament

Question 6

what is between the retina and the sclera (scleroid coat)?

Answer 6

highly vascularized choroid layer. (BLACK) (absorbs stray light)

Question 7

CHOROID BODY

Answer 7

IS A RETE MIRABILE. prominent in the choroid layer of many teleosts (and bowfin). structure and function similar to that of the gas gland.

Question 8

WHAT IS THE FUNCTION OF THE CHOROID BODY?

Answer 8

serving to provide a high partial pressure of oxygen to the retina.

Question 9

what do you call a shark eyelid?

Answer 9

nictitating membrane

Question 10

shark eyeballs? slide four. maybe check it with Jer.

Answer 10

ok

Question 11

what is dependant upon for calm water to be able to reflect up to 80% of the light striking it

Answer 11

dependant upon the angle of incidence.

Question 12

what is SNELL’S WINDOW?

Answer 12

a circle subtended by a 97.2% cone above each eye. (refraction or bending of light rays entering water)

Question 13

at what angle do rays become reflected as they hit the water’s surface?

Answer 13

<40degrees

Question 14

what does refraction and image formation depend almost entirely on?

Answer 14

on the lens

Question 15

how does a fish’s eye move between near and far sightedness in comparison with a tetrapod?

Answer 15

tetrapod: lens changes shape
fish: slight anterior and posterior movement of the lens that change the distance between the lens and retina.

Question 16

are lampreys near sighted or far sighted?

Answer 16

near-sighted (myopic)

Question 17

the closer the lens moves toward the retina the:

Answer 17

narrower the field of view but the better the distance vision.

Question 18

what muscle fibres in elasmobranchs, that are located in the anterior part of the choroid layer that pull the lens outward, away from the retina and closer to the cornea?

Answer 18

protractor muscles

Question 19

elasmobranchs are known as being near or far sighted?

Answer 19

farsighted (hyperopic)

Question 20

Tapetum lucidum

Answer 20

amplifies light

Question 21

why is the benefit of a spherical lens in an elleipsoid retina?

Answer 21

the effect acheived is that relatively distant objects lateral to the fish are in focus but close objects are not. anteriorly objects in the binocular field are in better focus than more distant objects

Question 22

IN REGARDS TO EYESIGHT, TELEOSTS ARE THOUGHT AS BEING:

Answer 22

1) HYPEROPIC (FAR SIGHTED LATERALLY)

2) MYOPIC (NEAR SIGHTED ANTERIORLY)

Question 23

how does light regulation occur and its adaption to light/dark?

Answer 23

• swim to or away from the source of illumination
• pigment in the cornea or lens that filters
• most elasmobranchs and some teleosts have contractile irises
• some fish have pupillary operculum that expands/cuts off light
• nictitating membranes
• movements of pigments and visual cells

Question 24

how does the eye adapt under bright illumination?

Answer 24

movement of melanin toward the visual cells, movement of rods into pigmented area where they are sheilded from light

Question 25

in dim light, what moves?

Answer 25

cones opposite to rods,

Question 26

how long does it take for light adaptation to occur?

Answer 26

30 minutes for light, hour for dark

Question 27

what are responsible for absorbing light?

Answer 27

visual pigments, or retinenes

Question 28

general rules for relating visual pigments to visual tasks

Answer 28

1- deep sea species have rod pigments that absorb maximally at a relatively short wavelength (470-490nm)

• marine fishes living at intermediate depths~460-540
• benthic fw fish: 530-620
• fw fish in shallows: 430
• anadromous salmon shift their wavelengths