COM S2

Question 1

Name anatomical parts of the eye.

Answer 1

Conjunctiva, Cornea, Sclera, Choriod, Retina, Iris, Lens, Aqueous and Vitreous Humor, Ciliary Body, Optic Nerve

Question 2

Give the description and function for the Conjunctiva

Answer 2

 Delicate membrane
 Covers the surface of the eye and inside eyelids

Protects front part of eye

Question 3

Give the description and function for the Cornea

Answer 3

 Front part of eyeball
 Transparent & relatively thick

Refracts light rays as they pass through

Question 4

Give the description and function for the Sclera

Answer 4

 White part of eye
 Continuous with cornea but not transparent

Protects eye
Helps maintain shape

Question 5

Give the description and function for the Choroid

Answer 5

 Inside of sclera
 Thick, black layer containing blood vessels

Carry oxygen and nutrients to eye & remove carbon dioxide and wastes
Prevents light in eye from reflecting internally

Question 6

Give the description and function for the Retina

Answer 6

 Inner most layer of eye & lines back of eyeball
 Contains photoreceptors (rods & cones)
 Contains retinal nerve cells – convert incoming light into nerve impulses

Receives light  changes into electrical impulses that travel via the optic nerve to the brain
- Allow us to see shape, movement and colour

Question 7

Give the description and function for the Iris

Answer 7

 Coloured part of eye
 Ring of muscles with a hole in middle (the pupil)

Controls amount of light entering the eye

Question 8

Give the description and function for the Lens

Answer 8

 Transparent, biconvex protein disc behind the pupil and iris

Focuses light rays onto the retina

Question 9

Give the description and function for the Aqueous and Vitreous Humor

Answer 9

Aqueous humour
Viscous liquid  fills front chamber of eye
Vitreous humour
Jelly-like  fills larger back chamber of

Help keep eyeball in spherical shape
 Refract light as pass through

Question 10

Give the description and function for the Ciliary Body.

Answer 10

 Connects choroid with lens
 Contains suspensory ligaments and ciliary muscles

Suspensory ligaments  Hold lens in position
Ciliary muscles  Alter shape of lens

Question 11

Give the description and function for the Optic Nerve

Answer 11

 Connects eye to brain
Blind spot: has no photoreceptors and cannot produce an image

Carries nerve signals from retina to visual cortex in brain  interprets them as images

Question 12

First-hand investigation of a mammalian eye to gather first-hand data to relate structures to functions, name an aim.

Answer 12

Aim: To dissect a cow’s eye so that various structures can be identified and related to their function

Question 13

First-hand investigation of a mammalian eye to gather first-hand data to relate structures to functions, name a method can be summarised.

Answer 13

1. Collect dissecting scissors, scalpel forceps, newspaper and eye
2. Observe exterior
   • 4 muscle attachments  move eye from side to side
   (Trim off muscle and fat)
   • Sclera  protects and maintain shape of eye
   • Cornea  transparent opening that allow light to enter and refract light
   • Optic nerve  lower back – white cylinder – transmits impulses to visual cortex of brain that then interprets them as an image
3. Used scalpel to make incision at junction of cornea and sclera
    Clear liquid that flows out = aqueous humour (helps eye maintain pressure)
4. Make incision around circumference of sclera
    Jelly-like liquid = vitreous humour (helps eye retain its shape and refract light)
5. Observe front half of eye
    Clear biconcave lump of thick jelly = lens (changes shape to focus)
6. Iris
    Surrounds the lens
    Opens and closes to regulate amount of light entering
    Associated with ciliary body (set of muscles which change shape of lens)
7. Back of eye:
    Retina = blood vessels (contains rods and cones that detect light and colour)
8. Behind the retina (ONLY SPECIFIC TO COWS)
    Tapetum  Bright coloured layer that helps reflect light in dark
    Specific to nocturnal animals
    Sits in front of choroid layer = prevents internal reflection

Question 14

First-hand investigation of a mammalian eye to gather first-hand data to relate structures to functions, name a conclusion.

Answer 14

• The structures of the eye relate to its function of admitting light, refracting and focusing it to form an image and converting this to an impulse that is presented to the brain

Question 15

Identify the limited range of wavelengths of the electromagnetic spectrum detected by humans

Answer 15

• Electromagnetic spectrum = range of wavelengths of electromagnetic radiation
• Can detect wavelengths between 380 and 780 nm of the electromagnetic spectrum
• Range = visible light (what we can only see)  colours red, orange, yellow, green, blue, indigo and violent
• Blue-green (500nm)  Most effective wave lengths for human eye

Question 16

Identify the limited range of wavelengths of the electromagnetic spectrum detected by vertebrates

Answer 16

• Can detect different ranges of electromagnetic ranges compared to humans
• Many not able to distinguish colours
• Dogs  see similarly to human who is red-green colour blind
• Rattlesnakes  have receptors in pits between eye and nostril  detect infrared radiation
 Helps locate prey (animals radiate heat, a form of infrared radiation)
• Fish and snakes can see longer wavelengths  so can detect infrared radiation (heat)
• Birds  detect greater wavelength than humans
 Some very sensitive to ‘red’ end of spectrum
 Can detect infrared radiation ‘ Some can detect UV light – reflected by white and violet-coloured flowers and insects (see below)

Question 17

Identify the limited range of wavelengths of the electromagnetic spectrum detected by invertebrates

Answer 17

• Can detect different ranges of electromagnetic radiation
• Spiders & Insects (e.g. Bees)  see UV light
• Less sensitive to higher wavelengths (red end) of the spectrum

Question 18

The rattlesnake and the electromagnetic spectrum.

Answer 18

A vertebrate, infra red and visible, wave lengths detected = 850-480 nm

Question 19

Wave lengths detected by a human?

Answer 19

700-400nm and detected in the visible section of the Electro magnetic spectrum.

Question 20

The Honey Bee and the electromagnetic spectrum

Answer 20

Invertebrate, detects ultraviolet and visible, wavelengths detected = 700-300nm

Question 21

Use available evidence to suggest reasons for the differences in range of electromagnetic radiation detected by humans and other animals

Answer 21

• Colour sensitivity is related to the structure of the eye
• Number of types of colour-sensitive cones + sensitivity range = determines colour vision
• Some organisms with compound eyes (e.g. bees)  have visual cells sensitive to different ranges of electromagnetic radiation
• Colour vision  related to evolution
• Believed that humans and our primate line evolved from nocturnal ancestor  our colour vision evolved separately from many of the other placental mammals

Question 22

Compare the differences in range of electromagnetic radiation in vertebrates with a Rattle snake and a human.

Answer 22

Rattle snake =
Infrared and visible Active at night
Detect infrared from their prey
Allows snake to hunt successfully at night
Human =
Visible Active during day  uses colour for perception of objects

Question 23

Compare the differences in range of electromagnetic radiation of invertebrates with a honey bee and a monarch butterfly

Answer 23

Honey Bee =
UV and visible Can detect ultraviolet markings on flowers that we cannot see
> Patterns guide the insect to pollen or nectar source
Monarch Butterflies =
UV Use UV to navigate in the sky when migrating over great distances