Week 1 - Light & Vision

Question 1

What wavelength does organic matter absorb and scatter?

Answer 1

Absorbs short-wavelength (blue) and reflects long-wavelength (red)

Question 2

What happens when light hits the water

Answer 2

refraction and speed change

Question 3

What wavelength do water molecules absorb and scatter?

Answer 3

Absorbs long wavelength and scatters short wavelength, that is why the deep sea is blue

Question 4

What wavelength does vegetation absorb and scatter?

Answer 4

Absorbs range of wavelengths, EXCEPT GREEN RANGE

Question 5

Veiling Effect

Answer 5

When suspended organic matter scatters extra light into the eye and creates a foggy image

Question 6

What wavelengths are more common deeper in the sea

Answer 6

short wavelengths, causing water to be blue

Question 7

Why is shallow/lowland water less blue

Answer 7

Suspended organic matter and plants in shallow waters absorbs short wavelength and scatters long wavelength

Question 8

Why are tropical blackwaters, swamps, marshes darker in colour

Answer 8

high in organic matter, leaves and twigs dropping absorbing short wavelength and scattering long wavelength

Question 9

Pupil

Answer 9

Allows light into eye (hole in eye)

Question 10

Iris

Answer 10

Coloured part of eye, associated with muscles controlling amount of light reaches retina

Question 11

Retina

Answer 11

Layer of light detecting pigment in back of eye (sensory cells)

Question 12

How do ray-finned fishes control light allowed into eye

Answer 12

By moving photopigment (deeper into eye = less light)

Question 13

What kind of fish can fix pupil size

Answer 13

Some shallow-water cartilaginous fish

Question 14

Cornea function

Answer 14

protects exposed part of eye (external environment)

refracts light in some environments

Question 15

Why does refraction occur

Answer 15

When the speed of light changes between 2 mediums (ex. air-> water)

Question 16

Refractive index

Answer 16

how much light slows down when entering medium

Question 17

High refractive index

Answer 17

More bending

Question 18

Low refractive index

Answer 18

Less bending

Question 19

Why does cornea not refract light in fish but does in terrestrial vertebrates

Answer 19

Because cornea has same refractive index as water, same mediums so no refractions between 2 mediums

Question 20

Define accommodation

Answer 20

change in lens by muscles helping focus light from different distances on retina

Question 21

Emmetropia

Answer 21

Ability to change lens shape to focus

Question 22

Myopia

Answer 22

cannot see far, focal point too close

Question 23

Hyperopia

Answer 23

cannot see close, focal point too far back

Question 24

Fish Lens property

Answer 24

hard, round helps bend light and focus on retina

Question 25

Which direction does lens go in accommodation in sharks

Answer 25

Close objects - forward | Distant object - backward (resting)

Question 26

The normal state of the lens in sharks

Answer 26

Focuses on distant object (back)

Question 27

Which direction does lens go in accommodation in ray-finned fishes

Answer 27

Close object - forward | Distant object back

Question 28

Normal state of ray-finned fishes

Answer 28

Focuses on close objects (forward)

Question 29

Do prey or predators have better-developed eye muscles

Answer 29

predators have better eye muscles

Question 30

Evolutionary trade-off in fish on the lens

Answer 30

Hard lens needed to refract light but cannot accommodate as fast

Question 31

What is tapetum lucidum

Answer 31

carpet of guanine crystals associated with retina at back of the eye

Question 32

Function of guanine crystals (tapetum lucidum)

Answer 32

Scatters light inside eye to increase detection by retina, improves sensitivity to light in darker environments

Question 33

Tapetum lucidum location in sharks vs ray-finned fishes

Answer 33

Sharks- behind retina | Ray-finned fishes- within the retina

Question 34

Where are photoreceptors

Answer 34

On retina

Question 35

What are photoreceptors

Answer 35

modified neurons that detect photons

Question 36

2 types of photoreceptors

Answer 36

Rods & Cones

Question 37

Rods or cones good at detecting movement but not fine detail?

Answer 37

Rods

Question 38

What wavelength does rods respond to?

Answer 38

Blue to green wavelength

Question 39

Rod or cone saturates faster?

Answer 39

Rods, very sensitive

Question 40

What happens when photon is absorbed?

Answer 40

Opsin protein binding to retinal (modified vit A) is released and signal sent to brain near photopigments

Question 41

What happens when only one type of receptor in retina? What will you see?

Answer 41

No colour

Question 42

If you only have blue-shifted rods, what will you see when you see blue?

Answer 42

Will not see blue, will see light when you see blue. | Whatever X shifted light you will see X as light and everything else as shadow

Question 43

Define colour vision

Answer 43

Ability to discriminate objects based on differences in spectral reflectance (wavelength) INDEPENDENT OF INTENSITY (brightness).

Question 44

What is sensitivity for UV light most commonly used for?

Answer 44

Detection of plankton for food

Question 45

What advantage does a blue coloured fish have?

Answer 45

Blends into spacelight

Question 46

How do fish become a certain colour?

Answer 46

Diet.

Question 47

Chromatophores

Answer 47

selectively absorbs/ scatters lights of different wavelength to become a specific colour

Question 48

How are carotenoids (red, yellow, orange) obtained?

Answer 48

Diet

Question 49

Non-pigment based colours

Answer 49

reflecting or scattering light by crystalline (guanine) structures. iridiophore

Question 50

Reflected light structure function

Answer 50

reflects light at same incidence angle ( mirror )

Question 51

Scattered light structure function

Answer 51

random scattering (shiny)

Question 52

Where do iridiophores usually sit?

Answer 52

on top of melanin-absorbing layer to absort other wavelengths

Question 53

What makes the blue pigment?

Answer 53

phycocyanin from cyanobacteria