A note on the SAC

• Generally looked pretty good- I will have them marked and returned next Monday

• One question that stumped a coupleQuestion 5: What might happen on a cellular level if the

internal body temperature of one of these organisms exceeded safe limits

a) Too cold: water content of the cell freezes- water expands when it freezes- cell ruptures

b) Too hot: Proteins denature (lose shape and ability to function) which stops many important cell functions

Next Topic

• How do living things detect change in the environment and respond to this1) Detecting: The senses and sensory organs2) Nerve cells- structure and function3) Responding: Central nervous system- voluntary

and involuntary response4) Responding: Endocrine system (chemical

messengers and hormones)

Today: Senses

THE SENSES

What sense is most important to you?

SIGHT

• What you are actually seeing is beams of light bouncing of objects and into your eyes.

• The iris is the coloured ring around the pupil. It controls the amount of light rays that enter the eye.

• The lens focuses the light onto the back surface of the eyeball, which is called the retina.

Photoreceptors

• The light sensitive cells in the retina send the information to the brain via the optic nerve.

• There are two types of receptor cells– Cones: detect colour– Rods: detect movement

Focus

• The shape of the lens changes depending on whether the person is looking at something close up or far away.

• The shape makes the light entering the eye focus onto the retina.

Short-sighted

People are short-sighted when the light entering the eye focuses in front of the retina.

Long-sighted

• People are long-sighted when the light entering the eye focuses past the retina.

Getting older

• As we get older, the lens in our eye becomes less flexible.

• This is why older people have trouble focusing on images close up and need glasses

Upside down

• The lens in our eye also turns the image upside down.

• Our brain learns to interpret the image the correct way.

• When a baby is first born it actually sees the world upside down.

The upside down glasses experiment

• In the 1890’s George Stratton experimented on himself to see if the brain could make sense of an upside down image

• He wore glasses with mirror to invert the image for several days and found that the brain would eventually right the image

• When he took the glasses off, he saw the world upside down for a short period

• It was very confusing!!!!!!!!!!!!!

Eye shine

• Eye shine is caused by something called the tapetum which is found behind the retina.

• This reflects light back through the retina and improves an animals night vision.

Some more facts

• The eyeball of an ostrich weighs more than their brain.

• If we only had one eye we would see a 2 dimensional world.

• A chameleon can look in opposite directions at the same time.

• An owl can see a mouse from over 50m away at night.

Why is sight important?

• Obviously eye-sight is useful if we want to move around and see where we are going.

• Write down all the ways you can think of that humans and other animals use sight to help them survive.

Optical illusions

• The brain is an amazing organ, filling in gaps in the information sent to it.

• Optical illusions work by using this .

• Creating one image– Close one eye and look at your thumb.– Now switch eyes. Notice how you thumb appears to

move positions.– Now hold your thumbs together and focus on something

just above and past where they join.

Filling in the gaps

• Aoccdrnig to rscheearch at an Elingsh uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, olny taht the frist and lsat ltteres are at the rghit pcleas. The rset can be a toatl mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae we do not raed ervey lteter by ilstef, but the wrod as a wlohe.

The great dragon illusion!!!!!!

Touch

• List the ways that touch helps us and other animals to survive

Nerves ending everywhere!!!

• The nerves in our skin allow us to feel pain, heat, cold and pressure

What if?

• Imagine what would happen if you could not feel pain?– Hurt yourself badly and not realise it

• What if you could not feel hot or cold?– Your brain receives information from your nerves

and responds to this. It tells you to remove you finger when it is burned. It tells your body to shiver when it is cold.

Some facts

• You have more pain receptors than any other type of nerve ending.

• Rattlesnakes sense heat through their skin to locate their prey

• The skin is the largest organ in the body• Some parts of the body are more sensitive to

touch and others. Where do you think these are?

Taste

• The tongue is covered with thousands of taste buds which send messages to the brain about what you are tasting.

• Your tongue recognises four main types of taste– Sweet, salty, sour and bitter– Bitter is important in detecting poisons

Tongue map

This is the old map- It is now thought that all taste buds can detect all tastes

My tastes have changed!

• When you are a baby, your mouth is covered with taste buds. They cover the tongue, roof and sides of the mouth.

• As you get older the taste buds are only on your tongue.

• As you age and your taste buds become less sensitive you will be able to eat things that you found too strong as a child.

How do we distinguish taste?• If taste buds only detect sweet, sour, salt,

bitter how can we tell the difference between so many things?

• Answer: Taste is combination of taste, temperature, texture and smell

Smell

• What you smell is tiny Lipid soluable particles. • The nasal cavity filters these particles through

cilia (or tiny hairs), then through thick mucus (snot) to the olfactory bulb.

• Here, molecules fit to a nerve cell receptors (lock and key) and the message is sent to the brain

Types of smells

• Like with taste, there are only a few main types of smells that we recognise– Camphoric eg. Mothballs– Musky eg. Perfume/Aftershave– Floral eg. Roses– Pepperminty eg. Mint Gum– Etheral eg. Dry Cleaning Fluid – Pungent eg. Vinegar– Putrid eg. Rotten Eggs

Pheremones

• A sense of smell is more important than you might realise.

• Smells can tell us who we are attracted to (the t-shirt smelling experiment). These are called pheremones

• Other animals use pheremones to mark their territory, attract mates and warn predators

• Flowering plants use smells to attract insects so that they can pollinate other plants

Why is taste and smell important?

• List the ways that a sense of taste and smell help plants and animals to survive

Alien (1979)‘In space no one can hear you scream’

Hearing• Sounds are vibrations of molecules travelling

through the air.• These vibrations cause your eardrum to

vibrate and these messages are sent to the brain via the auditory nerve.

• The structure of the ear is designed to amplify and simplify the sound.

Balance

• Liquid in your ear moves when you move and tells your brain when you are moving.

• It is through your ear that you get your balance.• How else is hearing important for the survival of

animals?

• Dolphins can hear 14 times better than humans. Why do you think this is?

Task

• Complete a fact sheet for one sense (use the text book): I will assign these

• Complete this using word• Include – Diagram– Summary of how the sense works – Glossary of new terms

• Upload this document onto the wiki