Grade Six Science
How have you been during the past week? School has closed, but I am sure that some of you had extra classes. Happy Easter to you all! I hope that your kite goes up very high into the air tomorrow. Do remember that Christ has risen as your kite rises.
Last week we looked at the eye and how we see.
Let’s find out how much you remember about the eye.
1. Draw and label a side view of the eye.
2. The eye is the organ of____________.
3. Light enters the eye through the _______________.
4. The________ regulates the amount of light entering the eye.
5. The image of an object seen is formed on the ___________________.
6. This image formed is seen _____________________.
7. What does the brain do with this image? ___________________________ 8. State at least four ways in which you can care your eyes. Discuss these ways
with your peers.
How well did you do?
This week let’s look at the ear and how we hear.
Let’s look at the ear.
Look at the ears of the animals in the pictures above. Can you identify these animals? Describe their ears to your friend. Are they all the same?
Some are long and pointed. Some are floppy and large and some are small. This is based on their environment.
● Name animals with:
● forward-facing ears …………………………..
● ears that can rotate ……………………………
● big ears ……………………………………….
● small ears …………………………………….
● sharp ears ……………………………………..
● visible ears …………………………………….
● invisible ears …………………………………..
● long ears ……………………………………….
● upright ears …………………………………….
● ears at the top of the head ………………………
● ears on both sides of the head …………………..
The middle ear contains three small ear bones. (Did you know that these are the smallest bones in the whole body?)
The inner ear has the cochlea which helps with hearing, and the three semi-circular canals which help us with keeping our balance.
How do we hear?
When someone speaks to you, his/ her voice forms sound waves in the air around him. Each word forms different sound waves. The sound waves travel through the air and reach your ears.
What happens when sound waves reach your ears? When the air around you vibrates, the sound waves are picked up by the outer ear, and sent through the hearing canal. The ear lobe acts like the wide mouth of a funnel, collecting sound waves from around you, just as the funnel collects liquids.
The hearing canal is like the stem of the funnel; sound waves pass through it to the middle ear. This outer ear acts as the funnel to collect the sound waves.
The sound waves strike against the eardrum. This is a very thin sheet of tissue, stretched like a drumhead across the inside end of the ear canal. Because it is sensitive, it begins to vibrate at exactly the same speed as the sound waves that strike it. It then passes on the vibrations to three tiny ear bones in the middle ear. The first of the ear bones is attached to the eardrum. So, when the eardrum vibrates, vibrations pass from it to the first ear bone, then to the second one and finally to the third ear bone. These ear bones make the vibrations stronger.
The third little bone fits into the window of a very delicate structure - the inner ear. The inner ear is filled with liquid contained in a coiled tube, called the cochlea. The vibrations are different for each word. The sound vibrations are changed into nerve signals. These signals travel through the hearing nerve to the brain. The brain figures out the meaning of the nerve signals. It is at this point that you really hear and understand the meaning of the sound waves. Of course, all of this happens in a few seconds! So, when you see someone’s lips moving, you seem to hear the words as they are spoken. If the sounds are too soft, these bones will not vibrate at all, so no nerve signals will be formed to be sent to the brain. In this case, you will not hear the sounds.
How do other animals hear?
Only mammals have ear flaps. The other vertebrates do not have ear-flaps; the ears are hidden inside the body. In frogs and toads, reptiles and birds, the ear drums are in hollows on the head. Some invertebrates, such as spiders and crickets, have their sense organs for hearing in their legs!
Do we need two ears?
What do you think? Yes, two ears help animals to judge the direction of the sounds.
Next week DV, we will find out about the tongue, the skin and the nose. Until then, goodbye Boys and Girls, and be safe!