AP State Syllabus 9th Class Biology Solutions 6th Lesson Sense Organs
9th Class Biology 6th Lesson Sense Organs Textbook Questions and Answers
Improve Your Learning
I. Give reasons for :
We usually do not see bright colours in dim light.
- Retina contains cells called rods and cones.
- Nearly 125 million tiny rods are present In our eye which contain pigment ‘rhodopsin’.
- Rods detect low intensity of light at night.
- Rods cannot make the fine distinctions of bright colours in dim light.
Removal of wax layer too often will raise incidence of ear infection.
- External ear or pinna has wax producing ceruminous glands and oil producing sebaceous glands.
- These glands help to keep the ear canal lubricated prevent the dust and other par¬ticles from entering into the ear canal called Auditory Meatus.
- If we remove wax layer ear diseases like formation of pus, infection of eardrum etc. may be caused by bacterial and fungal infections.
During severe cough and cold we lose taste of food.
When we suffering from severe cold and cough our nasal passages are completely blocked, food becomes tasteless as we are unable to smell the foods delicious aromas.
While cutting onions our tears start flowing.
- The cells of onion contains amino acids like mithionine and enzyme cystine. They are kept separate in the onion cell.
- When we cut the onion, enzymes start mixing and produce propanethiol. Sulpher oxide, which is a volatile compound that starts moving towards our eyes.
- The gas that is emitted reacts with the water of our eyes and forms sulphuric acid.
- The sulphuric acid thus produced causes burning sensation in our eyes and this, in turn, leads to the tear glands secreting tears.
- Thus we end up with watery eyes every time we cut onions at home.
II. Find out the false statements and rewrite them as correct ones.
1. The rationale behind seeing is just the impression of the image in the retina.
2. Ear functions only to hear.
Correct statement: Ear helps in hearing and also in maintaining the equilibrium of our body.
3. Iris patterns are like fingerprints used in identifying individuals.
4. Saliva helps the taste buds in taste sensation.
Correct statement: Taste receptors help the taste buds in taste sensation.
5. We are not able to adapt to sensations.
Correct statement: We are able to adapt to sensations.
III. State the differences between the two.
1. Rods and cones.
|1) Rods are responsible for detecting the dim lights only with black and white.||1) Cones are responsible for detecting the bright lights with colour.|
|2) 125 million rods are present in retina.||2) Seven million cones are present in retina.|
|3) Rods contain the pigment rhodopsin.||3) Cones contain the pigment idopsin.|
|4) Defect in rods causes night blindness.||4) Defect in cones causes colour blindness.|
2. Iris and pupil.
|1) This is the coloured part of our eye around pupil.||1) It is the hole located in the centre of the eye.|
|2) The colour of the iris may be brown, blue, green or grey.||2) The colour of the pupil is black.|
|3) It does not dialate or contract according to the intensity of light.||3) It dialates or contracts according to the intensity of light.|
3. Pinna and tympanum.
|1) It is also known as external ear.||1) It is also known as ear drum.|
|2) Pinna is the visible part of the ear on either side of our head.||2) It is present in between external and middle ear.|
|3) It is a flap (ring) like structure.||3) It is in the shape of a cone.|
|4) Pinna is made up of cartilage.||4) It is a thin membranous layer.|
|5) It collects the sound waves.||5) Sound waves strikes the tympanum and vibrates.|
|6) It is the first part of external ear.||6) It is the last part of the external ear.|
4. Nasal cavity and ear canal.
|Nasal cavity||Ear canal|
|1) It is the cavity present in external nostrils.||1) It is the canal in the external ear.|
|2) Nasal cavity opens into internal names.||2) At the end of ear canal ear drum is present.|
|3) It filters the air that entering into internal names.||3) It carries the sound waves from external ear to ear drum.|
IV. How do the following processes occur?
When we see an object, a real inverted image is formed on the retina.
- When we see an object the eye gathers light through a convex lens, focusses it and forms an image in the retina at the back of the eye.
- The lens turns the image left to right and upside down.
The sound waves, collected by the pinna are changed as vibrations.
- External ear or pinna collects the sound waves.
- They enter into the auditory meatus or ear canal. Then they strike the tympanum.
- The vibrations from the tympanum reach the malleus, incus and stapes in the middle ear.
- They magnify the intensity of the sound vibrations and send them to the membrane of oval window in middle ear.
We move our hand away from a hot object.
- Moving our hand from a hot object is an unconditional reflex.
- Unconditional reflexes are inherited and shown from birth.
- Unconditional reflexes are present in all individuals and are basically same.
A pungent odour, makes us close our nose.
- The olfactory receptors sense pungent odour, that information is sent to brain in the form of nerve impulses through sensory nerve.
- The brain interprets the information and identifies it as pungent odour.
- It sends message to our hand to close the nose immediately.
- The brain also sends information in the form of nerve impulses through motor nerves as we are unable to smell the food’s delicious aromas.
V. Fill in the blanks with suitable words. Then give reasons why the words are suitable.
1. Choroid layer provides ………………… to the eye.
2. The relationship between the tongue and ……………………. is more.
3. Iris pattern is used for individual …………………… .
4. Area where optic nerve leaves the eye is called the ……………………..
5. The ear drum is the …………………….
- Blind spots
- Vibrating membrane
VI. Choose the correct option.
1. This vitamin is essential for the health of eye.
a) Vitamin ‘A’
b) Vitamin ‘B’
c) Vitamin ‘C’
d) Vitamin ‘D’
a) Vitamin ‘A’
2. Sensation is a complex pathway involving
a) Sense organs
b) Sense organs and nerve impulses
c) Sense organs, nerve impulses, brain
d)Brain and nerve impulses
c) Sense organs, nerve impulses, brain
3. The sound waves if not focused by external pinna and ear cannal will result in
a) Hearing several types of sound loudly
b) Not hearing anything
c) Slight hearing
d) Not being able to make out the type and origin of sound
b) Not hearing anything
4. The muscles of the eyeball of a person becomes non functional, the invariable effect would be
a) The person fails to close eyes
b) Fails to move eye and see colours clearly
c) Feels pain in the eye
d) The nerves reaching the muscles become non-functional.
b) Fails to move eye and see colours clearly
5. The tongue of a person is exposed to a high salty taste then:
a) The person learns to taste salty things better
b) Loves tasting salty things
c) Hates tasting salty things
d) Fails to taste a less salty thing just after the exposure.
d) Fails to taste a less salty thing just after the exposure.
VII. Draw and label the diagrams, showing the structure of the
VIII. How would you pay concern towards disabled people who is lacking sensory organs?
- 1 will show utmost sympathy forwards disabled people who is lacking sensory organs.
- I will give my full cooperation in leading normal lives.
- With my deeds I will bring confidence among the disabled people.
- If the disabled people are blind everyday I will show the way to school and from school to home.
- I will see that the disabled people get the government help in a proper way.
- I will give my support to deaf people by giving symbols and signals to understand things.
- I will join the disabled people who are in the school age in the school mend for them.
IX. How do you appreciate the functions of sensory organs which helps us to enjoy the beauty of the nature?
- Sense organs help us to enjoy the beauty of the nature.
- We enjoy the beauty of nature with our eyes, the melodious music with our ears, the taste of food with our tongue and feel the cool breeze on our skin.
- All these situations show just how our senses pick up information and react to them.
- Our sense organs are not just parts of us because nothing that we experience in our life, from the most important to the most boring, would be possible without the complicated power of our sense organs.
- Nothing in the entire universe of scientific exploration can even come close to match-ing the ability of our brain to use information sensed by our eyes, ears, skin, tongue and nose to produce a rich sensory experience in a matter of milli seconds.
X. Form a group with five students in your class and collect eye diseases and its char-acteristics by talking with ophthalmic assistant.
|Eye disease or defect||Characteristics|
|1. Age related macular degeneration||It is an eye condition that leads to the deterioration of the centre of the retina called macula.|
|2. Astigmatism||It is an imperfection in the curvature of retina.|
|3. Cataract||It is the clouding of the eye lens causing vision problems.|
|4. Central retinal vein occlusion||It is a blockage of the main vein in the retina.|
|5. Colour blindness||Occurs when we are unable to see colours in a normal way.|
|6. Conjunctivitis||It is the swelling of the conjunctiva, the eye becomes red, burning sensation in the eye, releases water.|
|7. Corneal transplant||Scars, swelling or an irregular shape can cause the cornea to scatter or distart light resulting in glare or blurring vision.|
|8. Diabetic retinopathy||It is a common diabetic eye disease caused by changes in retinal blood vessels.|
|9. Dry eye or Xeropthalmia||It is a condition where the eyes do not produce enough tears or the right quality of tears to be healthy or comfortable and eye becomes dry.|
|10. Far sightedness (Hypermetropia)||It is a refractive error, which means the eye does not bend or refract light properly. Images are formed behind the retina.|
|11. Glaucoma||It is a disease that damages the eyes optic nerve. This leads to high pressure in the back of the eye.|
|12. Kerolitis||It is a condition where the cornea becomes swollen or inflamed, making the eye red and painful effecting vision.|
|13.Macular edema||It is a swelling or thickening of the macula, the area of the retina responsible for central vision.|
|14. Near sightedness (Myopia)||It is a refractive error, which means the eye does not bend or refract light properly. Image is formed in front of the retina.|
|15. Optic neuritis||It is an inflammation of the eye’s optic nerve.|
|16. Retinopathy of prematurity||Retinopathy of prematurity is an eye disease that occur in a small percentage of premature babies where abnormal blood vessels grow on the retina.|
|17. Scleritis||It is a painful swelling of the white part of the eye, which is also known as sclera.|
|18. Detached retina and Torn retina||A torn retina is when the retina tears in one or more places. A detached retina is when the retina is lifted off the wall of the eye.|
|19. Night blindness||Person suffering from night blindness cannot see things in dimlight or at nights.|
|20. Trachoma||It is an eye infection affecting both eyes, is the world’s leading cause of preventable blindness. It is caused by a bacterium called Chlamydia Trachomatis.|
XI. What happens if our skin loses its sensory nature?
- The skin contains numerous sensory receptors which receive information from the outside environment.
- The sensory receptors of the skin are concerned with at least five different senses: pain, heat, cold, touch and pressure.
- The five are usually grouped together as the single sense of touch in the classification of the five senses of the whole human body.
- If the skin loss its sensory nature we cannot experience the pain, heat, cold, touch and pressure.
XII. Sagar is not able to listen things properly. Guess what would happen to him. What suggestions would you like to give him?
- Sagar may be exposed to too much loud noise. This condition is noise induced hearing loss.
- Some times loud noise can cause a ringing, hissing or roaring sound in the ears called Tinnitus.
- Hearing problems may also be caused by a virus or bacteria.
- Hearing impairment happens when there is a problem with one or more partsflof the ear.
- So, I suggests Sagar to identify the reason for not listening things properly.
- I also advise him to consult a specialist called audiologist in ear problems.
9th Class Biology 6th Lesson Sense Organs InText Questions and Answers
9th Class Biology Textbook Page No. 76
Do you think our sense organs work together? Why, why not?
- Yes, our sense organs work together.
- Every single function of the body is managed and controlled by the brain, including our organs and senses.
- Otherwise, we would have different interpretations of a stimulus, resulting confusion.
- But to be clear it is not the organs working together it is the brain constantly receiving stimuli from different senses.
- The brain is responsible for assimilating information and filling the pieces together.
9th Class Biology Textbook Page No. 85
If we do not have our external ear what will happen to us?
- If we have no external ears, sound waves may not be collected by it.
- So we cannot hear anything and it leads to deafness.
9th Class Biology Textbook Page No. 87
If you are suffering from cold do you smell things in the natural way?
- No, we cannot smell things in the natural way.
- When we have cold, we will notice foods seem tasteless because your nasal pas¬sages are blocked.
Do you find any relation between smell and taste?
- Like smell, taste is also a sense based on identifying chemicals in food and the texture of it.
- The sense of taste and smell have a close and cooperative working relationship.
9th Class Biology Textbook Page No. 90
How sensitive is our skin?
- Different parts of our body have different sensitivity and the skin around the neck and finger tips is more sensitive than skin on the palm, knee and arm.
- This is because sensitivity of our skin depends on
a) thickness of our skin.
b) the number of sensory receptors.
9th Class Biology Textbook Page No. 82
What will happen if we have no eyelashes?
- The purpose of eyelashes is to keep moisture like sweat from setting into our eyes.
- Eyelashes protect the eye from debris and they are sensitive to being touched.
- If lashes are absent moisture like sweat will not be setting into our eyes.
- There will not be protection from debris to our eyes.
Are tears good for us?
- Yes, tears are good for us.
- Whenever unwanted substances come in contact with the conjunctiva the lachry¬mal glands are stimulated to produce tears to wash the substances out of the eye.
9th Class Biology Textbook Page No. 89
Why are we suggested not to take too cool or too hot food material?
To cool or too hot food material causes damage the sense of smell. It also damage the taste buds. If we take too cool or too hot food materials we will loose sense of smell and taste.
If you are suffering from fever that time you are not able to enjoy the taste of food why?
- During fever, the temperature of our body increases from the normal body temperature of 98.6°F to high temperature sometimes to 105°F.
- At this temperature, the function of the enzymes in our tastebuds stop since they can work efficiently only in the temperature range of 77 to 98.6°F.
- The cells in the tastebuds cannot send messages to the nerve centres in the brain.
- That is why during fever we are not able to enjoy the taste of food.
9th Class Biology 6th Lesson Sense Organs Activities
Activity – 1
Note down a few lines of any text in your book. Write about the stimuli and re¬sponses and the sensory and motor functions with respect to the sense organs in¬volved.
(Stimuli from the environment around are received by our body through some sense organs. As we already know, they are the eyes, ears, nose, tongue and skin. Let’s try to understand the path of receiving a stimulus to expressing a response (sensation))
- The sense organs involved in writing the para above are eyes and skin.
- Asking to write few lines in textbook is stimulus and writing the lines is response.
- The sensory nerve in the eye take the information about writing lines to brain in the form of nerve impulses.
- The brain interprets the signals and send the message through motor nerves to write the lines.
- The skin in the palm helps to hold the pen in writing the lines.
Activity – 2
Testing tastes with tongue.
- Dissolve a pinch of sugar in a glass of water.
- Drink a little of this. It doesn’t taste good.
- Try this for different concentrations of sugar adding by proper quantification that is weighing and preparing solutions to find out taste.
- You could take l/4th teaspoonful sugar each time which would be nearly 2 grams.
- After adding three spoons of sugar the taste of water becomes sugary.
Activity – 3
1. Observe the external structure of your friend’s eye, draw the diagram and lable it.
2. Observe the eye ball of your friend in normal light. Then focus a beam of torch light on youj^friend’s eye.
- Our eye contains eyelids, eyelashes, eyebrows and lachrymal glands.
- In normal light my friend’s eye ball is normal as usual, but after focusing a beam of torch light he immediately closed his eyes.
- After closing the eyes for two minutes, the black portion of eye is somewhat big in size.
- After opening forcibly when we throw the beam of torch light, the size of the small dark portion decrease.
- The small black portion in the centre of the eye expands in dark whereas in bright light it decreases in size.
Activity – 4
Testing the visual system.
- Hold the text at arm’s length, close your right eye, and fix your left eye straight on the figure.
- Keep your right eye closed and bring the book slowly closer.
- When it is about 8 to 10 inches away the gap disappears as it is on the blind spot of your left eye.
- But you will not see a ‘hole’ in your visual field.
- Instead, your visual system “fills in” the missing area with information from the blue line on either side.
Activity – 5
Observe the iris and its surrounds of your friend’s eye. Can you find the pupil? Observe the colours and patterns in the iris of your friend’s eyes. Is there any difference from one another?
- I found pupil in my friend’s eye.
- The colour of iris in my friend’s eyes are different.
- The colour of iris are blue in some, green in some and grey or brown in some of my friend’s eyes.
- The colour of iris are different but their shape is round in all my friend’s eyes.
Activity – 6
Enter into a dark room from a very bright place. What happens? Sit in a dark room for sometime. Then go into a bright light room. What happens?
- If we enter into a dark room from a very bright place first we cannot see anything in the room.
- Because the pupil is very small in size and very less amount of light enters into the eyes.
- As the time progresses the pupil becomes large in size and we will be able to see things properly.
- If we go into a bright light room from a dark room, at first we cannot see anything in light from because the pupil does not bear the intensity of light.
- The pupil gradually lessens its size and we are able to see things properly.
Activity – 7
Eye and illusions.
- Take two pieces of white papers with same size.
- Draw the picture of a cage on one pa¬per and the parrot on the other.
- Then insert a stick and attach the blank sides of the papers with gum, see the figure.
- Let it dry then twist the stick rapidly.
- When we twist the stick rapidly, we see the parrot in the cage. What we are experi¬encing is an illusion.
Activity – 8
Testing of sound.
- Take a plastic or iron funnel.
- Stretch a piece of rubber balloon and cover the wide part of the funnel with it.
- Tie it with rubber band.
- Ask your friend to shout ‘Oh’ at the narrow opening of the funnel.
- Observe the movements of the rubber sheet while he is shouting.
- Observe the rice grains also.
- Due to the vibrations in the rubber balloon the rice grains move up and down when we shout ‘Oh’ at the narrow opening of the funnel.
- When we put the narrow end at the opening of our eye we hear the sound of heart as lub dub, lub dub …………….
Activity – 9
- Blindfold your friend and ask him/her to identify different things by smell like lemon, tea, coffee, potato, tomato, tamarind, spinach, curd, brinjal etc.
- Keep as many things but be careful in choosing them.
- They should not be in powdered form.
- Don’t allow your friend to touch them.
- Biologically, the sense of smell or olfaction, begins with chemical events in the nose.
- Their odours interact with receptor proteins associated with specialized nerve cells.
- These cells incidentally are the body’s only nerve cells that come in direct contact with the outside environment.
- Receptors present at the base of the skin lining the inner walls of the nose are highly sensitive to odour chemicals.
- These odour chemicals can be complex and varied.
- Close the eyes of your friend with a piece of cloth.
- Give her/him a piece of ginger, garlic, tamarind, banana and jaggery one by one.
- Ask her/him to taste by just taking these one at a time on the tongue.
- Remember that your friend needs to rinse his/her mouth between each test.
- Could your friend tell the taste by just putting the substances on the tongue? Yes, my friend told the taste.
- Now repeat the above experiment by asking your friend to take a bite and press the food on the plate.
- As food enters our mouth, we bite and chew it and press it against the palate with our tongue.
- This releases chemicals in food that trigger off our taste buds to act and carry stimulus to the brain to be processed for recognition of taste.
- The same taste bud is capable of producing different signals corresponding to the different chemicals in food.
Observe your tongue by standing in front of the mirror by sticking your tongue out. See how many different kinds of structures you can see on your tongue. Compare with the given diagram.
- We can clearly see flake like structures that are filiform papillae.
- The roundish structures are fungi¬form papillae.
- There are large roundish ones at the back of the tongue which are circumvallate papillae.
- On the sides of the tongue, the bump like structures are foliate papillae.
- Taste buds are present on all of these except the filiform papillae that are not the sites of taste sensation.
- Blindfold your friend and ask him/her to close his or her nose as well.
- Give a few cumin seeds to your friend and ask him/her to chew.
- Ask your friend to identify what you have gave.
- You could try this with a small piece of potato as well.
- My friend has identified the cumin seeds and piece of potato.
Activity – 13
1) Make bundles of three toothpicks.
2) See to it that their pointed ends are at the same level.
3) Now ask your friend to make an outline of one of her/his palm.
4) Ask your friend to close her/his eyes. Now starting from the tip of the thumb keep pricking lightly with your toothpick bundle all over the plam.
5) Ask your friend how many points she/he could identify each time.
6) Repeat this with some of your friends.
Answer the following questions.
a) Where do you find maximum sensation on the palm?
In the centre of the palm we find maximum sensation.
b) Where do you find minimum sensation?
We find minimum sensation on the beginning of the palm.
c) Are palm sense patterns same for all your friends?
Yes, palm sense patterns are same.
Activity – 14
Press your thumb gently on the tip of a sharpened pencil. Later press it on the blunt end of the pencil. How do you feel? Why?
- When we press our thumb gently on the tip of a sharpened pencil it makes us feel pain.
- The sensory receptors sense the sharpened pencil’s press and the message is sent to brain through sensory nerve.
- Then the brain interprets the message and sends signals to feel pain through motor nerves.
- When we press our thumb with the blunt end of the pencil we do not feel pain because the sensory receptors (touch receptors) sends the message to brain through sensory nerve.
- Brain interprets the message and sends signals to our thumb to feel soft through motor nerves.