3. The Eye

Question 1

UV Photoreceptors in birds
Courtship

Answer 1

Males have UV feathers which a female can see due to their photoreceptors

Question 2

UV Photoreceptors in birds
Foraging

Answer 2

Waxy surfaces of fruits have UV light that birds can see with their photoreceptors

Question 3

UV Photoreceptors in birds
Prey identification

Answer 3

Rodents discharge reflects UV light which birds can see giving them a trail to the rodent

Question 4

Photoreceptors in the eye

Answer 4

Cones
Rods

Question 5

Predators have binocular vision

Answer 5

Each eye overlaps at the front creating a single 3D image
Eyes at the front of the head
Better depth perception

Question 6

Prey have monocular vision

Answer 6

Each eye works separately with little overlapping
Eyes positioned on the side for wider field of vision, good for detecting predators
Poorer depth perception

Question 7

Owl

Answer 7

Visual field: 110
Elongated so can’t rotate in the sockets, turn their head instead
Large number of rod cells wide range of pupil size, helps them hunt in low light

Question 8

Sheep

Answer 8

Visual field: 270
Located high in the skull, better vision when grazing
Rectangular pupils increase the accuracy of depth perception

Question 9

Cornea

Answer 9

Description: transparent covering on the eye
Purpose: protection of the eye

Question 10

Retina

Answer 10

Description: layer of photoreceptors at the back of the eye
Purpose: detecting light rays that are focused by the cornea and lens

Question 11

Choroid

Answer 11

Description: layer of blood vessels with a black pigment
Purpose: nourishing the eye and absorbing light

Question 12

Cilliary body

Answer 12

Description: attached to the underside of the lens
Purpose: helps with focusing by altering the shape of the lens

Question 13

Pupil

Answer 13

Description: hole in the middle of the iris
Purpose: allowing light to enter the eye

Question 14

Lens

Answer 14

Description: transparent, flexible and can change shape due to the cilliary body
Purpose: focuses light onto the retina and focuses objects

Question 15

Iris

Answer 15

Description: ring of muscles around the pupil
Purpose: provides eye with the colour, controls the amount of light that enters the eye

Question 16

Fovea

Answer 16

Description: spot located on the macula, has a high density of cone cells
Purpose: sharp central vision, light is focused into this spot by the lens

Question 17

Optic disc

Answer 17

Description: blind spot where there are no photoreceptors
Purpose: where the optic nerve leaves the eye

Question 18

Optic nerve

Answer 18

Description: bundle of fibres
Purpose: relaying information from the retina to fovea to the brain

Question 19

How does the eye work?

Answer 19

Light enters the eye through the cornea and lens
Muscles in the iris contract/relax to control how much light enters
Lens focuses the light
Projects light to the retina
Photoreceptors in the retina covert light energy to electrical signals
Signals sent to the brain

Question 20

Structure of the retina
Inner neutral layer

Answer 20

Contains photoreceptors, bipolar neurons and ganglion cells

Question 21

Structure of the retina
Outer pigmented

Answer 21

Helps absorb light

Question 22

Cones

Answer 22

Higher intensity than rods
Allows us to see colour
High level of visual sharpness
Each cone is connected to optic nerve

Question 23

Rods

Answer 23

Light sensitive and functions in the dark
Can’t detect colour
Many rod cells share a connection with optic nerve