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EEB382 > Week 1 - Light & Vision > Flashcards

Week 1 - Light & Vision Flashcards

1
Q

What wavelength does organic matter absorb and scatter?

A

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

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2
Q

What happens when light hits the water

A

refraction and speed change

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3
Q

What wavelength do water molecules absorb and scatter?

A

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

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4
Q

What wavelength does vegetation absorb and scatter?

A

Absorbs range of wavelengths, EXCEPT GREEN RANGE

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5
Q

Veiling Effect

A

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

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6
Q

What wavelengths are more common deeper in the sea

A

short wavelengths, causing water to be blue

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7
Q

Why is shallow/lowland water less blue

A

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

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8
Q

Why are tropical blackwaters, swamps, marshes darker in colour

A

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

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9
Q

Pupil

A

Allows light into eye (hole in eye)

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10
Q

Iris

A

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

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11
Q

Retina

A

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

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12
Q

How do ray-finned fishes control light allowed into eye

A

By moving photopigment (deeper into eye = less light)

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13
Q

What kind of fish can fix pupil size

A

Some shallow-water cartilaginous fish

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14
Q

Cornea function

A

protects exposed part of eye (external environment)

refracts light in some environments

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15
Q

Why does refraction occur

A

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

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16
Q

Refractive index

A

how much light slows down when entering medium

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17
Q

High refractive index

A

More bending

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18
Q

Low refractive index

A

Less bending

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19
Q

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

A

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

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20
Q

Define accommodation

A

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

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21
Q

Emmetropia

A

Ability to change lens shape to focus

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22
Q

Myopia

A

cannot see far, focal point too close

23
Q

Hyperopia

A

cannot see close, focal point too far back

24
Q

Fish Lens property

A

hard, round helps bend light and focus on retina

25
Q

Which direction does lens go in accommodation in sharks

A

Close objects - forward

Distant object - backward (resting)

26
Q

The normal state of the lens in sharks

A

Focuses on distant object (back)

27
Q

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

A

Close object - forward

Distant object back

28
Q

Normal state of ray-finned fishes

A

Focuses on close objects (forward)

29
Q

Do prey or predators have better-developed eye muscles

A

predators have better eye muscles

30
Q

Evolutionary trade-off in fish on the lens

A

Hard lens needed to refract light but cannot accommodate as fast

31
Q

What is tapetum lucidum

A

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

32
Q

Function of guanine crystals (tapetum lucidum)

A

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

33
Q

Tapetum lucidum location in sharks vs ray-finned fishes

A

Sharks- behind retina

Ray-finned fishes- within the retina

34
Q

Where are photoreceptors

A

On retina

35
Q

What are photoreceptors

A

modified neurons that detect photons

36
Q

2 types of photoreceptors

A

Rods & Cones

37
Q

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

A

Rods

38
Q

What wavelength does rods respond to?

A

Blue to green wavelength

39
Q

Rod or cone saturates faster?

A

Rods, very sensitive

40
Q

What happens when photon is absorbed?

A

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

41
Q

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

A

No colour

42
Q

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

A

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

43
Q

Define colour vision

A

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

44
Q

What is sensitivity for UV light most commonly used for?

A

Detection of plankton for food

45
Q

What advantage does a blue coloured fish have?

A

Blends into spacelight

46
Q

How do fish become a certain colour?

A

Diet.

47
Q

Chromatophores

A

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

48
Q

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

A

Diet

49
Q

Non-pigment based colours

A

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

50
Q

Reflected light structure function

A

reflects light at same incidence angle ( mirror )

51
Q

Scattered light structure function

A

random scattering (shiny)

52
Q

Where do iridiophores usually sit?

A

on top of melanin-absorbing layer to absort other wavelengths

53
Q

What makes the blue pigment?

A

phycocyanin from cyanobacteria

EEB382 (5 decks)

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