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Animal Biology > Sensory System - The Eyes > Flashcards

Sensory System - The Eyes Flashcards

1
Q

What are the features of the eye?

A

cornea
pupil
iris
ciliary body
lens
sclera
retina
rod and cone cells
choroid
fovea
optic disc
optic nerve
medial and lateral rectus muscles

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2
Q

What is the cornea?

A

a thin, transparent disc at the front of the eye that bends light in order that it can be focused on the retina

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3
Q

What is the pupil?

A

the opening in the centre of the eye which lets light through

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4
Q

Why is the pupil completely black?

A

the light that enters is absorbed within the inner eye

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5
Q

What is the iris?

A

the coloured structure surrounding the pupil which can widen and narrow to let more or less light pass through the pupil in order to provide optimal vision

this widening and narrowing is involuntary and depends on how light or dark it is

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6
Q

What is the ciliary body?

A

a ring of tissue at the front of the eye and is connected to the lens and contains a muscle which can change the shape of the lens

it is also responsible for producing aqueous humor, a liquid which provides nutrients to the lens and the cornea

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7
Q

What is the lens?

A

a transparent and flexible tissue whose job is to change shape in order to bend light beams by different amounts

this is because good vision requires light beams to focus on the retina

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8
Q

What is the sclera?

A

the outer layer of the eye, visible as the whites of the eye

protects the delicate and sensitive interior

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9
Q

What is the retina?

A

the inner layer of the eye made up of light-sensitive (photosensitive) cells

these cells react to light hitting them, triggering a response that is sent up the optic nerve and to the brain

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10
Q

What are rod and cone cells?

A

light-sensitive cells that make up the retina

rod cells are very sensitive to light but not to different colours
cone cells are sensitive to different colours and are responsible for colour vision but they are not as sensitive to light as rod cells

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11
Q

What is the choroid?

A

a layer of tissue between the retina and sclera that contains lots of blood vessels

these blood vessels are responsible for providing nutrients to and removing waste from the cells that make up the retina

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12
Q

What is the fovea?

A

a small pit in the retina that only contains densely-packed cone cells

it is responsible for the sharpest, most detailed vision

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13
Q

What is the optic disc?

A

the point where the optic nerve begins and leaves the eye

there is no light-sensitive cells at the site of the optic disc and therefore this part of the eye does not detect light

location of a small blind spot

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14
Q

What is the optic nerve?

A

made up of neurons which transport signals received at the retina to the brain

part of the central nervous system

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15
Q

What are the medial and lateral rectus muscles?

A

muscles that sit on the left and right of each eye

medial rectus moves the eye to look inwards

lateral rectus moves the eye to look outward

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16
Q

Why can’t mammals discriminate between reds and greens?

A

they only have two types of cone cells which can detect blues and greens but not reds

17
Q

What animals share the same version of vision with humans?

A

primates

18
Q

How many types of cone cells do primates have?

A

three types of cones which can detect red, green and blue

19
Q

How many types of cone cells do birds and fish have?

A

four types of cones which extends their vision into ultraviolet

20
Q

What is an example of animals that have five types of cones?

A

pigeons

21
Q

What are double cones?

A

cones that are even more sensitive than mammal cones

found in birds and some reptiles and fish

22
Q

What is the name of the structure that forms part of the cone structure and acts as a light filter?

A

oil droplets

23
Q

What is the structure that birds and reptiles have that is like a third eyelid.

A

a nictitating membrane

used for blinking and lubrication

24
Q

What adaptations do nocturnal animals have?

A

additional structure called a tapetum lucidum which is a membrane behind the retina that reflects any light that has not been absorbed

more rods than cones

large pupils to let in as much light as possible

slit pupil to prevent light from damaging the eye

multifocal lens is arranged in rings, each of which bends different frequencies of light

25
Q

What adaptations do predatory species have?

A

have eyes on the front of the head and see almost the same image

this allows for 3D binocular vision - the brain can combine the slightly different images from each eye to build up an accurate sense of depth

this allows predators to perceive where objects, including prey, are in three dimensions

the field of view is much narrower for animals with binocular vision

26
Q

What adaptations do prey species have?

A

have eyes on the side of the head to give a wide field of view so that predators cannot sneak up unseen

this is known as monocular vision

this means that the image in each eye is vastly different and the brain cannot combine these into one 3D image

27
Q

What adaptations do owls have?

A

excellent night vision due to the density of rods

less good colour vision because they don’t see lots of different colours in the dark

very effective binocular vision as their eyes are on the front of their face

28
Q

What adaptations do birds of prey have?

A

have a very high density of rods and cells

eyes are largely relative to their body to let lots of light in

have two fovea which means they can focus on two different things at once

some can see in ultraviolet

29
Q

What adaptations do snakes have?

A

some have developed the ability to see in infrared

30
Q

What adaptations do goats have?

A

have unusual and rectangular pupils to provide very wide monocular vision

31
Q

What adaptations do cats have?

A

pupils are able to open very wide to let in lots of light but can also narrow to a slit in daylight conditions

ciliary body is made up of two muscles instead of one

relatively poor colour vision because they rely on detecting movement more than colours

32
Q

What adaptations do arctic reindeer have?

A

can see in ultravoilet

33
Q

What is light?

A

a vibration of electric and magnetic fields

34
Q

How can animals sense light?

A

when the electric and magnetic fields vibrate at a particular rate animals can sense it

35
Q

What can cone cells detect?

A

specific vibration frequencies which are perceived as different colours

36
Q

What are all vibrations of the electric and magnetic fields?

A

ultraviolet
infrared
radio waves
microwaves
x-rays

animals that can see in ultraviolet can detect these frequencies

Animal Biology (16 decks)

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