College Knowledge

College adds over $1Million to your lifetime family income…

But only if you grow up now to take advantage of this opportunity!

Your Middle and High School teachers are there to help you open this door…

You need to accept their help!

Heed their advice!

If it is to be, it is up to me!

I’m

Ross KoningProfessor of Biology

at

Eastern ConnecticutState University

Biology Department

PhD 1981University of Michigan

I teach the introductory biology course for biology majors

here.

Notice, like you, I have TWO EYES!

Are they identical?

Use both eyes…at arm’s length, center target within finger OK signLock hand in position…see which eye is still aligned by closing the otherThe eye with good alignment is your dominant eye!

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Figure 46-7

Ommatidia are the functional units of insect eyes.       Ommatidia contain receptor cells that send axons to the CNS.

Lens

Receptor cells

Ommatidia

Axons

Insects appear to have two eyes also, but they are compound!Each ommatidium sends separate information to their brain.

Human vs Insect VisionC

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ight

Nor

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Pres

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Man

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Spiders have up to 8 eyes looking in different directions!!

It makes you wonder what exactly they see!

Vertebrate Eye

blind spot

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ht N

orto

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controls light

focuses image

senses image

sends image to brain

What?

Use right eye only (close left eye)…focus only on the target for this test!Lock head in position…hold one finger up at arm’s length to cover view of targetMove arm slowly outwards from target (to right for right eye)Find your blind spot for that eye…is it only off to ONE side? try the other side!Does the blind spot extend upwards or downwards?

Try with your left eye…is its blind spot on the same side or on the other?Try with BOTH eyes open…do you have a blind spot now? Why not?

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Use right eye only (close left eye)…our target is a row of numbers

Focus on each number in turn, until the break in the blue lines is in your blind spot. What is different when the blind spot holds a blank area?

1 2 3 4 5 6 7 8 9

blind spot

Figure 46-8

The structure of the vertebrate eye. In the retina, cells are arranged in layers.

Ganglion cells Connecting neurons Photoreceptor cellsPigmented epithelium

Retina

Direction of light

Fovea

Optic nerve (to brain)

Sclera

Iris

Pupil

Cornea

Lens

Axons to optic nerve

Figure 46-9

Cornea Lens

Retina (photoreceptors are on the inside surface) Sensory

nerves to brain

The Cephalopod Eye

This “design” is “more intelligent” than that of mammals (humans) because it lacks the blind spot and maximizes light exposure to receptors

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Eye Evolution

Vertebrate Retina

cone

rod

light

Figure 46-10

Rods and cones contain stacks of membranes. Rhodopsin is a transmembrane protein complex.

Cone Rod

Light Light

Rhodopsin

Retinal (pigment)

Opsin (protein component)

The retinal molecule inside rhodopsin changes shape when retinal absorbs light.

Light

trans conformation (activated)

Opsin

cis conformation (inactive)

0.5 µm

Opsin

Use both eyes, stare at area shown in blue for 15 seconds or so

What do you see on this blank white slide? Blink if needed!

This is called an “after image”Does it move around as you move your gaze?

Light: An Energy Waveform With Particle Properties Too

wavelength (nm)10-9 meter

0.000000001 meter!

400 500 600 700 nm

wavelength

visible spectrum

Vertebrate Retina

cone

rod

light

Figure 46-13Visible spectrum

S opsin 420

M opsin 530

L opsin 560

Use both eyes, stare at the parrot’s eye for 15 seconds or so

What color is the bird in the cage?Blink if needed

Use both eyes, stare at the parrot’s eye for 15 seconds or so

What color is the bird in the cage?Blink if needed

Use both eyes, stare at the parrot’s eye for 20 seconds or so

What color is the bird in the cage?This color is a bit harder to visualize

Use both eyes, stare at the white dot for 20 seconds or so

http://www.cagle.com/working/100427/cagle00.gif