SSLC Biology: Chapter 02 Windows of Knowledge - Questions and Answers

Study Notes for Class 10 Biology (English Medium) അറിവിന്റെ വാതായനങ്ങള്‍ | Text Books Solution Biology Chapter 02 Windows of knowledge

Class 10 Biology Chapter 02 Windows of Knowledge

* Study Notes
* Sensory organs are the windows to get information from the surroundings to our senses. Our brain analyses the information given by the sensory organs and helps to communicate, search for food, hear the sound, etc. Feeling of senses is possible only when impulses from sense organs reach the brain through the sensory nerves. Eyes, Ears, Nose, Tongue & Skin are our sense organs.

I. Eye:- Sensory organ for vision.
Our eyes are protected by
a) Eye fixed within the eye socket with the help of 3 pair external eye muscle – protection from injury.
b) Eyebrow, eyelashes, eyelid – protection from dust, sweat.
c) Conjunctiva - secretes mucus which protects the anterior portion of the eyeball from being dry.
d) Tears – 
⦁ lubricate the anterior part of the eyeball
⦁ Wipes out the dust 
⦁ Lysozyme – destroys the germs that enter the eye. 

* Structure and function 


* The 3 layers of the human eye? 
a. Sclera –The outermost layer, that gives firmness to the eye. Its transparent anterior portion is the cornea. The conjunctiva covers the front part of the Sclera, except at the cornea.
b.Choroid - Middle layer of blood capillaries, which supply nutrients and oxygen. Its anterior dark screen with the pupil is the iris. The pigment, melanin gives colour to the iris. A convex lens, which is connected to ciliary muscles by ligaments, is placed behind the iris.
c. Retina - The innermost layer on which, the image forms. Retina contains photoreceptors (cone cells and rod cells). Yellow spot which contains plenty of photoreceptors is the point of maximum visual clarity and the blind spot where no photoreceptors seen due to the beginning of optic nerve is the point of no vision. The optic nerve starts from the retina. 

* The fluids filled in the chambers of the eye?
⦁ Aqueous humour – A watery fluid seen in the aqueous chamber [between cornea and lens], oozes from the blood. This fluid supplies nutrients and oxygen to the cornea and lens.
⦁ Vitreous humour - A jelly-like fluid-filled within the vitreous chamber [between lens and retina]. It helps to maintain the shape of the eyeball.

* Regulation of Light in the Eye
⦁ Radial muscles and circular muscles in the iris regulate the size of the pupil according to the intensity of light.
In dim light, radial muscles contract to increase the size and in intense light, circular muscles contract to decrease the size of the pupil.

* Vision - phases
Step 1. Regulation of focal length 
⦁ The ability of the eye to adjust the focal length of the lens by changing its curvature in accordance to the distance of the object from the eye and form the image on the retina is called the power of accommodation of the eye.
⦁ Ciliary muscles adjust the curvature of the eye lens and thereby adjusting the focal length. While viewing nearby objects, ciliary muscles contract to increase the curvature of the lens to decrease the focal length. While viewing the distant object, ligaments stretch to relax the ciliary muscles and the curvature of the lens decreases to increase the focal length.
Step 2. Images on the retina 

Flow chart of light rays coming from the object
Light → Cornea → Aqueous humour → Pupil → Lens → Vitreous humour → Retina
* Peculiarities of image 
⦁ Real 
⦁ Small 
⦁ inverted 
Step 3. Structure of retina and changes due to the formation of images

The basis of vision is that the dissociation of visual pigments, rhodopsin and photopsin/iodopsin present in rod and cone cells respectively. The visual pigments are formed from opsin (protein) and retinal, derivative of Vit. A.

* Rod cells (12 lakh) – Activated in dim light. It enables black&white vision. Rhodopsin dissociated into retinal and opsin. These fuses in the absence of light. 
* Cone cells (6 lakh) – Stimulated in bright light. These cells have the ability to detect colour (because of the dissociation of photopsin/iodopsin only in bright light).
* The human eye has 3 types of cone cells, which are stimulated by the red, green and blue light rays. This diversity is due to the difference in the amino acids in the opsin molecule.
* The three types of cone cells (red, green & blue) provide colour vision.
Retinal, the visual pigment found in the photoreceptors, is formed from vitamin A.
* Under the dim light, rhodopsin dissociates to form retinal and opsin to produce impulses. Under intense light, photopsin (iodopsin) dissociates to form retinal and opsin to produce impulses. These impulses are transmitted through the optic nerve to the cerebrum. Thus vision made possible.

Step 4. Impulses to the brain – the sense of sight  
(Flowchart:- The image on the retina – stimulation in the photoreceptors – dissociation of rhodopsin/ photopsin – impulses form –  optic nerve – coordination of images by cerebrum – perfect vision).
i. Photoreceptors are stimulated when the light (image) falls on the retina
ii. Impulses are generated 
iii. Impulses reach the cerebrum through the optic nerve 
iv. Cerebrum enables three-dimensional image by combining 2 images of the same object from both eyes. This is called binocular vision.

* Binocular vision is the ability of both the eyes to focus on the same object to get a perfect image when the brain combines these images. This helps us to get a three-dimensional image of the object and also to calculate the correct distance, depth, height and width of the object.

* Defects and diseases of eyes:
1. Hypermetropia (long sight): Cannot see nearby objects clearly due to shortened eyeball.
2. Myopia (short sight): Cannot see distant objects clearly due to elongated eyeball.
3. Night blindness: No clear vision in dim light due to deficiency of vitamin A.
4. Colour blindness: Fails to detect red or green colours due to defects in red and green cone cells.
5. Xerophthalmia: Conjunctiva and cornea become dry and opaque due to prolonged deficiency of vitamin A.
6. Cataract: Lens become opaque resulting in blindness
7. Glaucoma: When re-absorption of aqueous humour obstructed pressure inside the eyes increases, resulting in damage to the retina and photoreceptors. This ultimately leads to blindness.
8. Conjunctivitis: Infection of bacteria or virus causes red-eye with pain 

* Points related to the health of our eyes.
- Avoid falling bright light like sunlight to the eyes.
- Avoid the habit of reading under dim light.
- Do not watch TV or other screens continuously.
- Frequently wash our eyes.
- Include vitamin A rich food.
II. Ear: for hearing and body balance.
⦁ The sensory organ for hearing
⦁ Also, the ear helps to maintain body balance.
* Main parts:
a. External ear: Pinna, auditory canal and tympanum.
b. Middle ear: Ear ossicles (malleus, incus, stapes) and eustachian tube.
c. Internal ear: Cochlea, Auditory nerve, Vestibule, 3 semicircular canals and vestibular nerve. 
* Oval window and round window.


* Fluids inside the internal ear: Endolymph and perilymph.
* Eustachian tube connects the middle ear to the pharynx. It protects the tympanum by balancing the pressure on either side of it.
* Ear ossicles (malleus, incus, stapes) amplify and transmit the vibrations of the tympanum to the internal ear.
* Oval window is attached with stapes, so as to speed the vibrations of ear ossicles to the internal ear.

* Internal Ear

The internal ear constitutes a membraneous labyrinth, seen inside a bony labyrinth. A coiled tube-like the cochlea, auditory nerve, the vestibular apparatus (vestibule & 3 semi-circular canals)and vestibular nerve are the parts of the internal ear. 
The membraneous labyrinth is filled with a fluid, endolymph and the space between the bony labyrinth and membraneous labyrinth is filled with another fluid, named perilymph. The part, cochlea functions in hearing, while the vestibular apparatus helps to maintain body balance through transmitting impulses to the cerebellum.

* Auditory receptors are the hair cells seen in the Organ of Corti of the cochlea. Sensory hair cells are also seen in the vestibule and semicircular canals.

* Sense of hearing  (Flowchart).
Sound waves → Pinna → Auditory canal → Tympanum → Ear ossicles → Oval window → Cochlea  → Impulse → Auditory nerve → Perilymph → endolymph → Organ of Corti → Cerebrum → Sense of hearing

* Role of the ear in maintaining the equilibrium: Receptors (hair cells) seen inside the vestibule and semicircular canals are stimulated according to the movement of the head. The impulses formed are transmitted to the cerebellum through the vestibular nerve. Cerebellum functions so as to maintain the equilibrium of the body.

III. Tongue
⦁ The taste buds seen in the tongue and cheek are helped in the detection of taste
⦁ There are different types of taste buds to detect different tastes like sweet, sour, bitter, salt and umami.
* Structure:
* Sense of Taste:  Chemoreceptors are seen inside the mouth and tongue to help us to detect taste. They seen inside the papillae of the tongue are the taste buds. 
The different taste buds of the tongue include Sweet, salt, sour, bitter, umami etc. When substances dissolve in saliva, chemo-receptors in the taste buds stimulate and impulses reach the brain through the respective nerves. 
Then we experience taste.

IV. Nose
* Structure:

* Sense of smell
⦁ Aromatic particles diffuse in the air and enter the nostrils
⦁ These particles dissolve in mucus and reach the olfactory receptors
⦁ Olfactory receptors are stimulated and impulses generated
⦁ Impulses reach the site of smell in the cerebrum
⦁ Sense of smell

V. Skin
* Structure
* Skin:
⦁ Temperature, pressure, pain, touch, cold receptors get stimulated
⦁ Impulses generated
⦁ Impulses reach the cerebrum through related nerves
⦁  Experiences different sensations 

* Receptors in a few organisms :
⦁ Eyespot in Planaria ( to detect light)
⦁ Ommatidia (cluster of photoreceptors in housefly)
⦁ Jacobson's organ in snake (to detect smell)
⦁ Receptors in the Lateral line of shark (to detect changes in the balancing of the body)
⦁ Olfactory receptors in shark are highly sensitive.
PRACTICE QUESTIONS AND ANSWERS

1. We can see nearby and distant objects clearly.
a) The ability of the eye to adjust the focal length is called --------------.
b) What change occurs in the curvature of the lens while viewing near objects?
c) How the above change in the curvature of the lens is accomplished?
Answer:
a) Power of accommodation of the eye.
b) Curvature of lens increases.
c) Ciliary muscles contract and the ligaments get relaxed.

2. From the following, select the correct statements.
1. Semicircular canal and vestibule help in body balancing.
2. Perilymph is seen in the membraneous labyrinth of the inner ear.
3. Organ of Corti helps in maintaining body balance.
4. The hair cells in semicircular canals helps maintains body balance.
Answer:
1. Semicircular canal and vestibule help in body balancing.
4. The hair cells in semicircular canals helps maintains body balance.

3.The possibility of occurrence of night blindness in Vitamin A deficient children is high. Based on this statement, answer the following questions.
a) How does the deficiency of vitamin A relate to night blindness?
b) Name any other disease caused by vitamin A deficiency.
Answer:
a) The deficiency of vitamin A causes the deficiency of Rhodopsin. Hence vision in dim light decreases.
b) Xerophthalmia.

4. Select the correct pair from the following.
a) The vibration of stapes: The movement of fluid in the cochlea.
b) The hair cells in the basilar membrane: Maintenance of body balance.
Answer:
a) The vibration of stapes: The movement of fluid in the cochlea.

5. The major parts related to the process of hearing is given. Prepare a flow chart by arranging them from the cerebrum to the oval window.
a) Auditory nerve b) Endolymph c) Hair cells d) Oval window e) Cerebrum f) Basilar membrane.
Answer:
Oval window- endolymph- basilar membrane- hair cells- auditory nerve- cerebrum.

6. From the following, find the reason for excess pressure inside the eye in Glaucoma.
a) The pressure in the eye exerted by the unabsorbed blood.
b) The defect in the formation of aqueous fluid.
c) The defect in the reabsorption of aqueous fluid.
d) The excess vitreous fluid.
Answer:
c) The defect in the reabsorption of aqueous fluid.

7. Certain parts related to the process of hearing are given below. Write the major functions of each.
a) Ear ossicles.
b) Eustachian tube
c) Round window
Answer:
a) Ear ossicles- Amplify and transmit the vibrations of the tympanum to the internal ear.
b) Eustachian tube- Protects the tympanum by balancing the pressure on either side of the tympanum.
c) Round window- Helps in the movement of fluid inside the cochlea.

8. Write reasons for each of the following statements.
a) We are able to view objects in three-dimensional form.
b) Vitamin A is needed for the resynthesis of rhodopsin.
c) The disease glaucoma can be cured by laser treatment.
Answer:
a) The images from two sides of the same object are formed in the left and right eye. When these two images combine as a result of the activities of the brain, a three-dimensional image of the object is formed. So we are able to view objects in three-dimensional form.
b) The retinal of rhodopsin is formed from Vitamin A. So after the dissociation of rhodopsin into retinal and opsin, vitamin A is necessary for the resynthesis of rhodopsin.d) If the reabsorption of aqueous humour does not occur, it causes an increase in the pressure inside the eyes and is called glaucoma. The reabsorption of aqueous fluid can be rectified by laser surgery.

9. From the following statements, select the correct one.
a) Prolonged night blindness leads to xerophthalmia.
b) Many blood vessels are seen in Retina.
c) Sound receptors are found in the Organ of Corti.
d) Jacobson's organs are located in the tongue of the snake.
Answer:
a) Prolonged night blindness leads to xerophthalmia.
c) Sound receptors are found in the Organ of Corti.

10. Arrange columns B and C in accordance with column A.

11. From the following, select the correct statements.
a) There is a difference in the amino acids of the opsin molecules of the three types of cone cells. 
b) The opaqueness of the cornea is a symptom of a cataract.
c) The eustachian tube protects the eardrum.
d) Perilymph is the fluid present inside the membraneous labyrinth of the internal ear.
e) The sound receptors are present in the organ of Corti.
Answer:
a) There is a difference in the amino acids of the opsin molecules of the three types of cone cells.
e) The sound receptors are present in the organ of Corti.
12. Deficiency of Rhodopsin leads to Night blindness and deficiency of Photopsin leads to colour blindness. Evaluate this statement and justify your opinion.
Answer:
Partially correct-Deficiency of Rhodopsin leads to Night blindness. The second part of the statement is wrong. The retina contains cone cells that can detect red, green and blue colours. Due to the defect of concerned cone cells, certain people cant differentiate red and green. This condition is colour blindness.

13. A person is suffering from dryness of his cornea. Formulate any three hypotheses on the circumstances that may lead to this condition.
Answer:
Maybe a deficiency of vitamin A.
Conjunctiva may lose the ability to secrete mucus.
Tear secretion may be blocked.

14. Some of the parts related to the process of hearing are given below. Write the major function of each.
a) Ear ossicles
b) Eustachian tube
c) Round window
Answer:
a) Ear ossicles - Enhances and convey the vibrations of the eardrum/ tympanum to the internal ear.
b) Eustachian tube- Keeps the pressure equal on both sides of the tympanum.
c) Round window- Helps the movement of the fluid in the cochlea.

15. Answer the following questions.
a) Which is the photoreceptor that enables colour vision? 
b) The change in amino acids in the opsin protein has a crucial role in colour vision. Substantiate.
Answer:
a) Cone cell.
b) Colour vision is due to 3 types of cone cells that help to detect 3 primary colours. The 3 types of cone cells occur due to a change in amino acid in the opsin molecule.

16. Select the suitable pair from the following.
a) The movement of fluid in the cochlea: The vibration of Stapes.
b) The hair cells in the basilar membrane: Maintenance of body balance.
Answer:
a) The movement of fluid in the cochlea: The vibration of Stapes.




BIOLOGY Textbook (pdf) - Click here 


ഈ ബ്ലോഗിലെ എല്ലാ പോസ്റ്റുകളും ഒരുമിച്ച് കാണാനും ആവശ്യമുള്ളവ എളുപ്പത്തിൽ തിരഞ്ഞെടുക്കാനും ഇവിടെ ക്ലിക്കുക.

PSC Solved Question Papers ---> Click here 
PSC TODAY's EXAM RESULTS ---> Click here
PSC EXAM PROGRAMME -> Click here
CURRENT AFFAIRS QUESTIONS -> Click here
PSC Degree Level Questions & Answers - Click here
PSC 10th, +2 Level Questions & Answers - Click here
PSC SHORTLISTS -> Click here
PSC RANK LISTS -> Click here
TEACHING APTITUDE TEST (K-TET, C-TET,, etc.) ---> Click here