Category: Class 11 Biology Objective Questions

Biology Multiple Choice Questions on “Transpiration”.

1. Isobilateral leaf has equal number of stomata on both surfaces of the leaf.
a) True
b) False
Answer: a
Clarification: Isobilateral leaf is found in monocotyledonous plants and it contains equal number of stomata on both sides of the leaf. Dorsiventral leaf is found in dicotyledonous plants and it has been more stomata on the lower surface of the leaf.

2. Which of the following is not a function of stomata?
a) Regulation of turgidity of guard cells
b) Loss of water vapor
c) Loss due to guttation
d) Exchange of O₂ and CO₂
Answer: c
Clarification: Loss due to guttation is not a function of stomata. Regulation of entry and exit of water into the guard cells, loss of water by transpiration and exchange of O₂ and CO₂ are among the major functions of the stomata.

3. Statement A: C3 plants are twice efficient as C4 plants in terms of fixing carbon dioxide.
Statement B: C4 plant loses twice the amount of water as C3 plant for same amount of CO₂ fixed.
a) Both the statements are true
b) Both the statements are false
c) Statement A is true but Statement B is false
d) Statement B is true but Statement A is false
Answer: b
Clarification: C4 plants are twice efficient than C3 plants in terms of fixing CO₂. C4 plants lose half the amount of water than C3 plants for same amount of CO₂ fixed. C4 plants have properties to maximize the availability of CO₂.

4. In the figure given below, guard cells are shown by?

a) By region of color
b) By region of color
c) By region of color
d) By region of color
Answer: b
Clarification: A: Epidermal cell
B: Guard cell
C: Stomatal aperture
D: Cell wall.

5. Which among the following is an external factor affecting transpiration?
a) Light
b) Number of stomata
c) Canopy structure
d) Water status of plant
Answer: a
Clarification: Light and temperature are among the most important factors affecting transpiration externally. Number of stomata, canopy structure and water status of plant are internal factors regulating transpiration.

6. Which among the following is an internal factor affecting transpiration?
a) Temperature
b) Humidity
c) % open stomata
d) Wind speed
Answer: c
Clarification: % open stoma is an important determinant of the loss due to transpiration. If less number of stomata is open, less transpirative loss will occur. Temperature, humidity and wind speed affect transpiration externally.

7. Transpirative loss is studied through girdling experiment.
a) True
b) False
Answer: b
Clarification: Transpirative loss is studied through cobalt chloride test. The color changes when water is absorbed. Girdling experiment is used to test that phloem tissue is responsible for translocation of food. When a ring of bark is removed up to the depth of the phloem layer and in the absence of downward movement of food, the portion of the bark above the ring of the stem is swollen after a few weeks.

8. The small diameter of the tracheary elements increases ___________
a) adhesion
b) cohesion
c) tensile strength
d) capillarity
Answer: d
Clarification: In plants, capillarity is aided by the small diameter of the xylem elements, i.e., the tracheids and vessel elements. Capillarity is the ability to rise in thin tubes. Cohesion is mutual attraction between molecules of H2O. Adhesion is attraction of water molecules to the surfaces of tracheary elements. Tensile strength is ability to resist a pulling force. Adhesion, cohesion and tensile strength are properties of xylem which enables the ascent of xylem sap.

9. Statement A: Inner wall is pushed outwards
Statement B: Outer wall is pulled outwards
a) Both the statements are true
b) Both the statements are false
c) Statement A is true but Statement B is false
d) Statement B is true but Statement A is false
Answer: d
Clarification: Thin outer wall bulges out due to change in turgidity of guard cells during the shift from night to day. This leads to thick inner wall being pulled outside by the outer wall, thereby forming crescent shape.

10. Statement A: Transpiration creates pressure in xylem sufficient enough to transport water up to 130 m high.
Statement B: Transpiration creates a pushing force.
a) Both the statements are true
b) Both the statements are false
c) Statement A is true but Statement B is false
d) Statement B is true but Statement A is false
Answer: c
Clarification: Transpiration is the loss of water in the gaseous phase from the leaves. It is a necessary evil. It might be a major cause of loss of water but it is the driving force for ascent of xylem sap, therefore, conduction of water and minerals. It creates pressure in xylem which can allow water conduction up to 130m height. Transpiration is a pulling force while root pressure is a pushing force.

Botany Aptitude Test on “Higher Plants Photosynthesis – ATP and NADPH-2”.

1. Which of these is not a stage of the Calvin cycle?
a) Carboxylation
b) Reduction
c) Regeneration
d) Oxidation
Answer: d
Clarification: The Calvin cycle is a pathway of light independent reactions of photosynthesis. It depends on the energy carriers ATP and NADPH and hence, Calvin cycle indirectly depends upon light.

2. Which is the most crucial step of the Calvin cycle?
a) Oxidation
b) Reduction
c) Carboxylation
d) Regeneration
Answer: c
Clarification: The Calvin cycle is a pathway of light independent reactions of photosynthesis. The most crucial step of the Calvin cycle is carboxylation, where carbon dioxide is fixated into a stable organic intermediate.

3. Which of these undergoes carboxylation during Calvin cycle?
a) NADPH
b) ATP
c) RuBP
d) PGA
Answer: c
Clarification: The most crucial step of the Calvin cycle is carboxylation, where carbon dioxide is fixated into a stable organic intermediate. This organic intermediate is RuBP or ribulose bisphosphate.

4. Which of these substances catalyse carboxylation?
a) RuBP carboxylase
b) Pyruvate carboxylase
c) Propionyl-CoA carboxylase
d) Acetyl-CoA carboxylase
Answer: a
Clarification: The most crucial step of the Calvin cycle is carboxylation, where carbon dioxide is fixated into a stable organic intermediate, known as ribulose bisphosphate. RuBP carboxylase catalyses carboxylation.

5. What is the product of carboxylation?
a) 2-PGA
b) 3-PGA
c) RuBP
d) Rubisco
Answer: b
Clarification: 3-PGA or 3-phosphoglyceric acid is the product of carboxylation. It is a 3-carbon organic acid. RuBP or ribulose bisphosphate is the primary carbon dioxide acceptor which undergoes carboxylation.

6. How many molecules of PGA are produced on carboxylation?
a) 3
b) 1
c) 2
d) 4
Answer: c
Clarification: 3-PGA or 3-phosphoglyceric acid is the product of carboxylation. It is a 3-carbon organic acid. RuBP or ribulose bisphosphate undergoes carboxylation to produce two molecules of 3-PGA or 3-phosphoglyceric acid.

7. Which of these statements is false about reduction in the Calvin cycle?
a) It is the third step of the cycle
b) It leads to the formation of glucose
c) It utilizes NADPH for reduction
d) It utilizes ATP for phosphorylation
Answer: a
Clarification: Reduction is the second step of the Calvin cycle. It results in the formation of glucose. Reduction utilizes NADPH for reduction and ATP for phosphorylation which results in the production of glucose.

8. How many turns of the Calvin cycle are required for the formation of 3 glucose molecules?
a) 15
b) 16
c) 12
d) 18
Answer: d
Clarification: The formation of one molecule of glucose requires the fixation of 6 carbon dioxide molecules and hence six turns of the Calvin cycle. Hence, 3 glucose molecules will require 18 turns of the cycle.

9. Which of these molecules is regenerated during the Calvin cycle?
a) NADPH
b) ATP
c) RuBP
d) CO₂
Answer: c
Clarification: Regeneration is the third and final step of the Calvin cycle. In this step, the CO₂ acceptor molecule RuBP or ribulose bisphosphate is regenerated. The regenerated RuBP is again used for the next Calvin cycle.

10. Regeneration during the Calvin cycle requires 3 ATP molecules. True or false?
a) True
b) False
Answer: b
Clarification: Regeneration is the third and final step of the Calvin cycle. In this step, the CO₂ acceptor molecule RuBP is regenerated. Regeneration requires 1 ATP molecule for the purpose of phosphorylation.

11. How many molecules of NADPH are required for each Calvin cycle?
a) 3
b) 1
c) 4
d) 2
Answer: d
Clarification: For every carbon dioxide molecule used up in the Calvin cycle, 2 molecules of NADPH are required. Six cycles are required to produce one glucose molecule; hence 12 NADPH molecules are required to produce one molecule of glucose.

12. How many molecules of ATP are required for each Calvin cycle?
a) 1
b) 2
c) 3
d) 4
Answer: c
Clarification: For every carbon dioxide molecule used up in the Calvin cycle, 3 molecules of ATP are required. Six cycles are required to produce one glucose molecule; hence 18 ATP molecules are required to produce one molecule of glucose.

13. How many molecules of NADP are produced as a result of six Calvin cycles?
a) 9
b) 18
c) 12
d) 24
Answer: c
Clarification: For every carbon dioxide molecule used up in the Calvin cycle, 2 molecules of NADPH are required. Hence, 2 molecules of NADP are produced. For six Calvin cycles, 12 molecules of NADP are produced.

14. How many molecules of ADP are produced as a result of six Calvin cycles?
a) 18
b) 24
c) 12
d) 32
Answer: a
Clarification: For every carbon dioxide molecule used up in the Calvin cycle, 3 molecules of ATP are required. Hence, 3 molecules of ADP are produced. For six Calvin cycles, 18 molecules of ADP are produced.

15. How many molecules of carbon dioxide are required in the Calvin cycle to produce 3 molecules of glucose?
a) 9
b) 18
c) 6
d) 15
Answer: b
Clarification: To make one molecule of glucose six molecules of carbon dioxide are required. Hence, six cycles of the Calvin cycle are required. To make three molecules of glucose, 18 molecules of carbon dioxide are required.

To practice Botany Aptitude Test,

Biology Multiple Choice Questions on “Plant Growth and Development – Photoperiodism and Vernalisation”.

1. Which of the crops doesn’t show vernalisation?
a) Wheat
b) Barley
c) Rice
d) Rye
Answer: c
Clarification: Rice doesn’t show vernalisation. Other crops such as Wheat, Barley and rye which are have two varieties: spring and winter require cold treatment to stimulate photoperiodic response of plants.

2. Plants are able to measure the duration of exposure to light.
a) True
b) False
Answer: a
Clarification: Flowering in plants depends upon the period of exposure of light to the plant. Plants are able to measure the duration of sunlight received through leaves. A hypothetical hormone Florigen is said to be responsible for flowering.

3. Statement A: Critical duration is different for different plants.
Statement B: The plants which are dependent on critical duration are called day-neutral plants.
a) Both the statements are true
b) Both the statements are false
c) Statement A is true but Statement B is false
d) Statement B is true but Statement A is false
Answer: c
Clarification: Critical duration is a well-defined period of exposure of plant to light and dark conditions for initiation of flowering in plants. It is different for different plants. Some require exposure less than critical duration such as short day plants. Some plants require exposure more than the critical duration such as long day plants. Also there are plants which are independent of the critical duration. They are called as day-neutral plants.

4. Which of the following plants is a polycarpic plant?
a) Sugarbeet
b) Cabbage
c) Carrots
d) Apple
Answer: d
Clarification: Polycarpic plants are plants that set seeds numerous times before senescence. Apple is a polycarpic plant. Sugarbeet, Cabbage & Carrots are some of the common biennials. Biennials are plants that take 2 seasons to complete their lifecycle.

5. Statement A: Short day plants required more exposure to light than the critical duration.
Statement B: Long day plants required less exposure to light than the critical duration.
a) Both the statements are true
b) Both the statements are false
c) Statement A is true but Statement B is false
d) Statement B is true but Statement A is false
Answer: b
Clarification: A well-defined exposure to light and dark conditions are pre-requisite for initiation of flowering in plants. Short day plants required less exposure to light than the critical duration. Long day plants required greater exposure to light than the critical duration.

6. Statement A: Vernalisation prevents precocious reproductive development.
Statement B: Vernalisation promotes flowering by cold treatment.
a) Both the statements are true
b) Both the statements are false
c) Statement A is true but Statement B is false
d) Statement B is true but Statement A is false
Answer: a
Clarification: Vernalisation is the process which improves qualitative and quantitative flowering in plants by exposure to cold conditions. It has dual functions. It allows the plants to attain full maturity. It also stimulates early flowering of plants by providing the desired conditions.

7. Duration of light period is more important than the duration of dark period.
a) True
b) False
Answer: b
Clarification: Both the durations of light and dark are equally important. The critical duration of the periods is essential for the proper functioning of phytochromes present in the plant.

8. Statement A: Response of plants to low temperature is regulated by a hypothetical hormone.
Statement B: Response of plants to different periods of light is also regulated by a hypothetical hormone.
a) Both the statements are true
b) Both the statements are false
c) Statement A is true but Statement B is false
d) Statement B is true but Statement A is false
Answer: a
Clarification: Vernalisation is the process which improves qualitative and quantitative flowering in plants by exposure to cold conditions. Response of plants to low temperature is regulated by a hypothetical hormone, Vernalin. Photoperiodism is the response of plants to duration of exposure to light and dark conditions. It is also regulated by a hypothetical hormone, Florigen.

9. Which is the site for perception of light/dark duration?
a) Leaves
b) Stem
c) Roots
d) Apical bud
Answer: a
Clarification: Leaves are the site for perception of light/dark duration. Florigen is responsible for flowering. Shoot apices are modified to flowering apices prior to flowering. The hormone further migrates to stem and roots.

10. The hormone responsible for flowering is ________
a) vernalin
b) cytokinin
c) ABA
d) florigen
Answer: d
Clarification: The hypothetical hormone florigen is said to be responsible for flowering in plants. Vernalin is promotes early maturity leading to flowering. ABA is majorly an inhibitor and functions in stressful conditions. Cytokinin stimulates shoots development.

Biology Multiple Choice Questions on “Body Fluids and Circulation Basics”.

1. Which of the following is the most commonly used body fluid?
a) Blood
b) Plasma
c) Lymph
d) Serum
Answer: a
Clarification: Blood is the most commonly used body fluid by most of the higher organisms including humans for the transportation of essential nutrients to the body tissues. Another body fluid, lymph also helps in the transport of certain substances.

2. Which of the following is absent on blood?
a) Fluid matrix
b) Plasma
c) Fibroblast
d) Formed elements
Answer: c
Clarification: Fibroblast are special cells which are responsible for the formation of fibres in the areolar tissue which is a type of connective tissue. Blood is a special type of connective tissue which consists of a fluid matrix, plasma and formed elements.

3. How much percentage of plasma is present in the blood?
a) 35%
b) 45%
c) 50%
d) 55%
Answer: d
Clarification: Plasma constitutes nearly 55% of the blood. 90-92% of plasma is water and proteins contribute 6-8 per cent of it. Fibrinogens, albumins and globulins are the major proteins.

4. Which of the following are needed for clotting of blood?
a) Fibrinogen
b) Albumin
c) Globulin
d) Magnesium ions
Answer: a
Clarification: Fibrinogens are needed for clotting or coagulation of blood. Globulins primarily are involved in defence mechanisms of the body and the albumins help in the osmotic balance.

5. What is plasma without clotting factors known as?
a) Blood
b) Serum
c) Lymph
d) Fluid
Answer: b
Clarification: Plasma without the clotting factors is known as serum. Factors for coagulation or clotting of blood are also present in the plasma in an inactive form.

6. Which of the following is not a formed element?
a) Erythrocytes
b) Leucocytes
c) Platelets
d) Lymph
Answer: d
Clarification: Erythrocytes, leucocytes and platelets are collectively called as formed elements. They constitute nearly 45% of the blood. A reduction in these number can lead to numerous disorders.

7. RBCs are formed in the thymus.
a) True
b) False
Answer: b
Clarification: RBCs are formed in the red bone marrow in the adults. RBCs are devoid of the nucleus in most of the mammals and are biconcave in shape. They have a red coloured iron-containing pigment called haemoglobin.

8. What is the average life span of RBCs?
a) 120 seconds
b) 120 hours
c) 120 days
d) 120 weeks
Answer: c
Clarification: RBCs have an average life span of about 120 days after which they are destroyed in the spleen which is also known as the graveyard of RBCs. These molecules play a significant role in the transport of gases.

9. What is the colour of leucocytes?
a) White
b) Black
c) Red
d) Colourless
Answer: d
Clarification: Leucocytes which are also known as white blood cells because they are colourless in nature as they lack haemoglobin. They are nucleated and are relatively lesser in number as compared to RBCs.

10. WBCs are characterised into 4 main categories.
a) True
b) False
Answer: b
Clarification: WBCs are characterised into 2 main categories- granulocytes and agranulocytes. Neutrophils, eosinophils and basophils are different types of granulocytes while lymphocytes and monocytes are the agranulocytes.

11. Which of the following are the most abundant in WBCs?
a) Neutrophils
b) Basophils
c) Eosinophils
d) Lymphocytes
Answer: a
Clarification: Neutrophils are the most abundant cells of the total WBCs as they constitute about 60-65 per cent of the total. Basophils are the least amongst as they constitute only 0.5-1 per cent of the total WBCs.

12. Which of the following is not secreted by basophils?
a) Histamine
b) Serotonin
c) Heparin
d) Serum
Answer: d
Clarification: Basophils secrete histamine, serotonin and heparin which are involved in the inflammatory reactions. Histamine acts as a vasodilator while serotonin acts as a vasoconstrictor.

13. Which of the following WBCs are involved in allergic reactions?
a) Basophils
b) Eosinophils
c) Neutrophils
d) Monocytes
Answer: b
Clarification: Eosinophils resist infections and are also associated with allergic reactions. Neutrophils and monocytes are phagocytic cells which destroy foreign organisms entering the body.

14. Lymphocytes constitute how much per cent of the total WBCs?
a) 10-15%
b) 20-25%
c) 40-50%
d) 56%
Answer: b
Clarification: Lymphocytes constitute for about 20-25% of the total WBCs. These are of two major types-B and T forms. Both B and T lymphocytes are responsible for the immune responses of the body.

15. Platelets are produced from which of the following cells?
a) Erythrocytes
b) Thrombocytes
c) Megakaryocytes
d) Lymphocytes
Answer: c
Clarification: Platelets are also called thrombocytes which are the cell fragments produced from megakaryocytes which are the special cells in the bone marrow.

Biology Multiple Choice Questions on “Regulation of Excretory System”.

1. Which of these are not involved in the regulation of kidney function?
a) Hypothalamus
b) Heart
c) JGA
d) Spleen
Answer: d
Clarification: The functions of the kidneys are regulated by several organs of the body, such as the hypothalamus, the heart and the JGA or the juxtaglomerular apparatus, and some of their hormones.

2. Which of these do not activate osmoreceptors?
a) Blood volume
b) Body fluid volume
c) Homoeostasis
d) Ionic concentration
Answer: c
Clarification: Osmoreceptors are activated by the blood volume, the body fluid volume and the ionic concentration. When these elements are within the normal range, or during homeostasis, the osmoreceptors are not active.

3. What is another name for ADH?
a) Oxytocin
b) Noradrenaline
c) Vasopressin
d) Ghrelin
Answer: c
Clarification: Another name for ADH or the antidiuretic hormone is vasopressin. It is released from the pituitary gland. The functions of ADH or vasopressin include prevention of diuresis and increasing blood pressure.

4. Where is vasopressin released from?
a) Neurohypophysis
b) Pineal gland
c) Adrenal gland
d) Pancreas
Answer: a
Clarification: Vasopressin or the antidiuretic hormone (ADH) is released from the neurohypophysis or the posterior lobe of the pituitary gland. Oxytocin is also released from here. ADH prevents diuresis.

5. Which of these is not a function of ADH?
a) Stimulates water reabsorption
b) Decreases blood pressure
c) Prevents diuresis
d) Decreases perspiration
Answer: b
Clarification: ADH or the antidiuretic hormone is also known as vasopressin. Vasopressin stimulates water reabsorption from the kidneys, prevents diuresis, decreases perspiration and increases blood pressure.

6. Which of these hormones do not lead to the constriction of blood vessels?
a) Epinephrine
b) Angiotensin II
c) ANF
d) ADH
Answer: c
Clarification: Epinephrine, which is released from the adrenal medulla, ADH or vasopressin, which is released from the posterior pituitary gland and angiotensin II lead to the constriction of blood vessels. They are vasoconstrictors.

7. Which of the following can increase GFR?
a) Increase in blood pressure
b) Decrease in blood pressure
c) Increased Bowman’s capsule hydrostatic pressure
d) Ureteral constriction
Answer: a
Clarification: GFR or the glomerular filtration rate of the kidneys can be increased by increasing the blood pressure. The higher the pressure with which blood flows through the glomerulus, the higher is the rate of filtration.

8. On which of these does ADH act upon?
a) Glomerulus
b) Loop of Henle
c) PCT
d) Collecting duct
Answer: d
Clarification: ADH or the antidiuretic hormone acts upon the latter parts of the nephron to increase reabsorption and prevent diuresis. Hence, ADH or vasopressin mainly acts upon the DCT and the collecting duct.

9. A fall in GFR can stimulate the juxtaglomerular cells to release which hormone from the kidney?
a) Angiotensinogen
b) ADH
c) Renin
d) Angiotensin I
Answer: c
Clarification: A fall in the GFR or the glomerular filtration rate leads to the release of renin from the kidney. Renin converts the inactive angiotensinogen present in blood to its active form, angiotensin I.

10. Aldosterone decreases the reabsorption of sodium ions. True or false?
a) True
b) False
Answer: b
Clarification: Aldosterone is a hormone which is released from the adrenal cortex. It increases the reabsorption of sodium ions and water from the latter parts of the nephrons, such as the DCT and the collecting tube.

11. Which of these hormones converts angiotensinogen to angiotensin I?
a) Aldosterone
b) ADH
c) Angiotensin II
d) Renin
Answer: d
Clarification: Renin is a hormone released by the juxtaglomerular cells of the kidney when there is a fall in the glomerular filtration rate (GFR). It converts the inactive angiotensinogen present in blood to angiotensin I.

12. Which of these hormones activates the adrenal cortex to release aldosterone?
a) ADH
b) Angiotensinogen
c) Angiotensin II
d) Angiotensin I
Answer: c
Clarification: When the GFR decreases, the juxtaglomerular cells of the kidney release renin, which converts angiotensinogen to angiotensin I and further to angiotensin II. Angiotensin II activates the adrenal cortex to release aldosterone.

13. Which of these hormones can decrease blood pressure?
a) Epinephrine
b) ADH
c) ANF
d) Angiotensin II
Answer: c
Clarification: Angiotensin II, epinephrine and ADH or the antidiuretic hormone or vasopressin are vasoconstrictors. They can increase blood pressure. ANF or the Atrial Natriuretic Factor is a vasodilator and can decrease blood pressure.

14. Which of these hormones acts as a check on the renin-angiotensin mechanism?
a) ANF
b) ADH
c) Renin
d) Angiotensinogen
Answer: a
Clarification: ANF or the Atrial Natriuretic Factor is a vasodilator and can decrease blood pressure. It acts as a check on the renin-angiotensin mechanism that is activated when the glomerular filtration rate decreases.

15. Where is aldosterone released from?
a) Pituitary gland
b) Adrenal cortex
c) Pineal gland
d) Adrenal medulla
Answer: b
Clarification: Aldosterone is released from the zona glomerulosa of the adrenal cortex. It is a mineralocorticoid hormone that increases the reabsorption of sodium ions and water from the distal parts of the nephron.

Biology Online Quiz for AIIMS Exam on “Neural Control and Coordination – Eye-2”.

1. What is the inner layer of the eye known as?
a) Sclera
b) Cornea
c) Choroid
d) Retina
Answer: d
Clarification: Each eyeball is surrounded by three layers. The outermost protective layer is the sclera. The middle one is known as choroid. The innermost layer is the retina. It contains light-sensitive photopigments.

2. Which of these structures hold the lens in place?
a) Cartilage
b) Tendons
c) Ligaments
d) Adherens junctions
Answer: c
Clarification: The lens present in the eye is a transparent crystalline structure through which light passes before it falls on the retina. The lens is held in place by the ligaments which are attached to the ciliary body.

3. Which of these is surrounded by the iris?
a) Cornea
b) Sclera
c) Pupil
d) Lens
Answer: c
Clarification: The iris is a continuation of the ciliary body. It is a part of the choroid. The pupil, which is the aperture located just in front of the transparent lens, is surrounded by the pigmented and opaque iris.

4. Which of these cells are not present on the retina?
a) Mast cells
b) Photoreceptor cells
c) Ganglion cells
d) Bipolar cells
Answer: a
Clarification: The retina is the innermost layer surrounding the eye. It contains three types of neural cells-the ganglion cells, the bipolar cells and the photoreceptor cells. The light entering the eye falls on the retina.

5. Which of these statements is false regarding photopigments of the eye?
a) Scotopic vision is a function of rods
b) Visual purple is a derivative of rhodopsin
c) They are light sensitive proteins
d) There are three types of cones
Answer: b
Clarification: Rods and the three types of cones are the photoreceptor cells of the retina. Photopigments are light sensitive proteins. Scotopic vision is a function of rods. Visual purple is also called rhodopsin.

6. To which of these colors are the cone cells of the eye unresponsive?
a) Red
b) Blue
c) Yellow
d) Green
Answer: c
Clarification: Rods and cones are the photoreceptor cells of the retina. There are three types of cone cells which are responsive to three different colors of light. These colors are red, blue and green, but not yellow.

7. The sensation of what color is produced when all cones are stimulated equally?
a) White
b) Black
c) Yellow
d) Purple
Answer: a
Clarification: Each type of cone cell is responsive to different colors of light and various degrees of combinations give sensations of different colors. when all cones are stimulated equally, a sensation white light is perceived.

8. What is the point of exit of optic nerves and entry of blood vessels in the eye?
a) Choroid
b) Fovea
c) Macula lutea
d) Blind spot
Answer: d
Clarification: The point on the retina from which optic nerves exit the eye and through which retinal blood vessels enter the eye is known as the blind spot. No photoreceptor cells are present in this region.

9. In which of these structures are cone cells densely packed?
a) Choroid
b) Blind spot
c) Fovea
d) Cornea
Answer: c
Clarification: Cone cells are densely packed in the fovea, which is the central pit of the macula lutea. The macula lutea is a yellow-pigmented region present near the center of the retina, which is the innermost layer of the eye.

10. The space between the cornea and the lens is called the vitreous chamber. True or false?
a) True
b) False
Answer: b
Clarification: The space between the cornea and the lens is known as the aqueous chamber. It contains a fluid known as aqueous humor. The space between the lens and the retina is known as the vitreous chamber.

11. Which of these is not a protein?
a) Iodopsin
b) Rhodopsin
c) Opsin
d) Retinal
Answer: d
Clarification: Iodopsin and rhodopsin are photosensitive pigments which are proteinaceous in nature. Opsin is also a protein. However, retinal is not a protein. It is an aldehyde of vitamin A.

12. In which of these structures is visual acuity the greatest?
a) Lens
b) Blind spot
c) Fovea
d) Cornea
Answer: c
Clarification: Visual acuity or resolution is the greatest at the fovea. The fovea is the central pit of the macula lutea, which is a yellow-pigmented region of the retina. The fovea contains a large number of cone cells.

13. Which of these does not take place when light falls on the photopigments of the eye?
a) Opsin undergoes conformational changes
b) Action potentials are generated in the ganglion cells
c) Retinal and opsin bind together
d) Potential differences are generated in the photoreceptor cells
Answer: c
Clarification: When light falls on the photopigments, retinal and opsin dissociate and opsin undergoes conformational changes. Potential differences are generated in the photoreceptor cells which lead to action potentials being generated in the ganglion cells.

14. Which of these structures are present on the retina?
a) Macula lutea
b) Macula densa
c) Macula adherens
d) Macula flava
Answer: a
Clarification: The retina is the innermost layer that surrounds the eye. It contains a yellow-pigmented region near its center at the posterior pole of the eye known as the macula lutea. The central pit of the macula lutea is the fovea.

15. Identify the structure in the given diagram.

a) Lens
b) Cornea
c) Iris
d) Pupil
Answer: b
Clarification: The given diagram is that of the cross section of the eye. The indicated structure is present at the anterior pole of the eye, on the outermost layer called sclera. It is identified to be the cornea.

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