Question 1

Question 1Define the following terms:(a) Conjunctiva(b) Lysozyme(c) Adaptation(d) Power of accommodation(e) Ear ossicles

Accepted Answer

(a) Conjunctiva — A thin membrane covering the entire front part of the eye . It is continuous with the inner lining of the eyelids.(b) Lysozyme — Lysozyme is an enzyme present in tear which has antiseptic property.(c) Adaptation — Adaptation of the eye is the process by which the eyes adjust to changes in light levels, allowing us to see clearly in both bright and dim environments.(d) Power of accommodation — Power of accommodation is the ability of the eye lens to focus near and far object clearly on the retina by adjusting the thickness of lens (and hence focal length).(e) Ear ossicles — The three bones present in ear, i.e. malleus, incus and stapes; together are called ear ossicles.

Question 2

Question 2Differentiate between members of each of the following pairs with reference to what is asked in brackets.(a) Myopia and hyperopia (type of lens used for correction)(b) Rods and cones (sensitivity)(c) Aqueous humour and vitreous humour (location)(d) Near and distant accommodation (shape of lens)(e) Dark and light adaptation (pigments which will be regenerated)(f) Night blindness and colour blindness (sensory cells which cannot function properly)

Accepted Answer

(a) Difference between myopia and hyperopia (type of lens used for correction) —MyopiaHyperopiaMyopia can be corrected by suitable concave (diverging) lens which causes the light rays to diverge before they strike the lens of the eye.Hyperopia can be corrected by suitable convex (converging) lens.(b) Difference between rods and cones (sensitivity) —RodsConesRods are sensitive to dim light but do not respond to colour.Cones are sensitive to bright light and are responsible for colour vision.(c) Difference between aqueous humour and vitreous humour (location) —Aqueous humourVitreous humourAqueous humour is the front chamber between the lens and the cornea.Vitreous humour is larger cavity of the eyeball behind the lens.(d) Difference between near and distant accommodation (shape of lens) —Near accommodationDistant accommodationFor near accommodation, the lens becomes more convex or rounded.For distant accommodation, the lens is more flattened or thinner.(e) Difference between dark and light adaptation (pigments which will be regenerated) —Dark adaptationLight adaptationFor dark adaptation, visual purple or rhodopsin pigment will be regenerated.For light adaptation, visual violet or iodopsin pigment will be regenerated.(f) Difference between night blindness and colour blindness (sensory cells which cannot function properly) —Night blindnessColour blindnessIn night blindness, the rod cells cannot function properly.In colour blindness, the cone cells cannot function properly.

Question 3

Question 5Describe the mechanism of focusing the image of a distant object in your eye when you raise your head after reading a book.

Accepted Answer

Light rays from the object enter the eyes through the transparent structures.For distant vision, the lens is more flattened or thinner.For near vision, the lens becomes more convex or rounded.While reading a book, the lens is more convex or rounded due to contraction of ciliary muscles because the book is usually read from a short distance. When we raise our head and look at a distant object, the ciliary muscles relax to build the tension on the suspensory ligament so that they can stretch the lens. This change in the curvature of the lens makes us focus on distant object.

Question 4

Question 11When a person comes out of a cinema hall after a noon show, he experiences a dazzling effect for a short period of time. It happens due to degeneration of (P) ............... and regeneration of (Q) ............... pigments. Which of the following options is correct for P and Q ?P - Iodopsin, Q - RhodopsinP - Rhodopsin, Q - IodopsinP - Visual violet, Q - Visual purpleP - Iodopsin, Q - Visual violet

Accepted Answer

P - Rhodopsin, Q - IodopsinReason — Rhodopsin pigment is responsible for vision in low light and iodopsin pigment is responsible for vision in bright light. When we enter into bright light from low light the rhodopsin pigment bleaches (degenerates) rapidly due to intense light which causes dazzling effect.

Question 5

Question 3The figure given below refers to the vertical section of the eye of a mammal. Study the figure carefully and answer the following questions.(a) Label the guidelines shown as 1 to 10.(b) Write one important role of parts shown as 3 and 7.(c) Write one structural difference between the parts shown as 9 and 10.(d) Mention one functional difference between the parts shown as 6 and 8.

Accepted Answer

(a) The guidelines are labelled below:1 → Aqueous chamber2 → Lens3 → Iris4 → Cornea5 → Conjunctiva6 → Sclera7 → Choroid8 → Retina9 → Yellow spot10 → Optic nerve (Blind spot)(b) Part 3 (Iris) — It contains radial muscles to dilate the pupil and circular muscles to constrict the pupil.Part 7 (Choroid) — It is the middle layer of the eyeball, richly supplied with blood vessels and provides nourishment to the eye.(c) Part 9 (yellow spot) contains sensory cells especially the cone cells while part 10 (blind sport) contains no sensory cells.(d) Part 6 (sclera) gives shape to the eyeball and part 8 (retina) acts as screen to form image of an object.

Question 6

Question 4Given below is a diagram depicting a defect of the human eye? Study the same and answer the questions that follow:(a) Name the defect shown in the diagram.(b) Give two possible reasons for this defect.(c) Name the parts labelled 1 to 4.(d) Name the type of lens used to correct this eye defect.(e) Draw a labelled diagram to show how the above mentioned defect is rectified using the lens named above.

Accepted Answer

(a) Myopia(b) The two possible reasons for myopia are either the eye ball is lengthened from front to back or the lens is too curved.(c) Parts labelled 1 to 4 are:1 → vitreous humour2 → blind spot3 → lens4 → pupil(d) Concave lens(e) The below diagrams show the condition of Myopia and how it is corrected using a Concave Lens:

Question 7

Question 6Given below is a diagram of a part of the human ear. Study the same and answer the questions that follow:(i) Give the collective biological term for Malleus, Incus and Stapes.(ii) Name the parts labelled A, B and C in the diagram.(iii) State the functions of the parts labelled 'A' and 'B'.(iv) Name the audio receptor region present in the part labelled 'A'.

Accepted Answer

(i) Ear ossicles(ii) The labelled parts are:A → CochleaB → Semicircular canalsC → Ear ossicles(iii) Cochlea helps in transmitting impulses to the brain via the auditory nerve. Semicircular canals help in maintaining dynamic equilibrium of the body.(iv) Organ of Corti

Question 8

Question 7Draw a labelled diagram of the inner ear. Name the part of the inner ear that is responsible for static balance in human beings.

Accepted Answer

Below is the labelled diagram of the inner ear:Utriculus and Sacculus collectively termed as vestibule are responsible for maintaining static balance in human beings.

Question 9

Question 8Have a look at the posture of this girl who is reading a book and answer the questions which follow:(a) Name the problem she is facing.(b) What are the two conditions shown in sections A and B of the eye as applicable to her?(c) What kind of reading glasses does she need ?

Accepted Answer

(a) Myopia(b) The condition shown in section A is Hyperopia as the image is formed behind the retina. The condition shown in section B is Myopia as the image is formed in front of the retina.(c) She needs reading glasses with concave lens.

Question 10

Question 9The figure given below shows the principal parts of a human ear. Study the diagram and answer the following questions.(a) Label the parts 1 to 8.(b) State the role of parts 6, 7 and 8.(c) Why is it harmful to use a sharp object to remove ear wax? Mention the number and name of the part involved.

Accepted Answer

(a) The labelled parts are:1 → External ear (pinna)2 → Ear drum (tympanum)3 → Auditory canal4 → Malleus5 → Semicircular canals6 → Cochlea7 → Auditory nerve8 → Eustachian tube(b) Part 6 (Cochlea) — It contains sensory cells for hearing.Part 7 (Auditory nerve) — It transmits impulse of hearing to the brain.Part 8 (Eustachian tube) — It equalizes air pressure on both the sides of the tympanum.(c) It is harmful to use a sharp object to remove ear wax as it can rupture the ear drum.The part involved is part 2 — Ear drum (tympanum).

Question 11

Question 10Given below is the internal structure of the human ear. Match the structures marked (a) to (e) with their correct function.

Accepted Answer

(a) Semicircular canals - Concerned with balance and spatial orientation.(b) Ampulla - Contains sensory cells for dynamic balance.(c) Utriculus and Sacculus - Concerned with static balance.(d) Auditory nerve - Transmits impulses from ear to brain.(e) Cochlea - Responsible for hearing.

Sense Organs

Descriptive Type

Multiple Choice Type

Structured Application Skill Type