Samacheer Kalvi Class 10 Science Solutions Chapter 16 Plant and Animal Hormones

Hormones	Disorders
A Thyroxine	(i) Acromegaly
B Insulin	(ii) Tetany
C Parathormone	(iii) Simple goitre
D Growth hormone	(iv) Diabetes insipidus
E ADH	(v) Diabetes mellitus

Answer:
A. (iii) Simple goitre
B. (v) Diabetes mellitus
C. (ii) Tetany
D. (i) Acromegaly
E. (iv) Diabetes insipidus
In simple words: This match shows how a lack of certain hormones can cause health problems. For example, not enough thyroxine can lead to goitre, and low insulin causes diabetes. Each hormone is important for keeping our body healthy.

🎯 Exam Tip: Focus on understanding the specific role of each hormone in regulating body functions. When a hormone is deficient, it directly leads to certain identifiable disorders, which is important to remember.

IV. State whether True or false, If false write the correct statement.

 

Question 1. A plant hormone concerned with stimulation of cell division and promotion of nutrient mobilization is cytokinin.
Answer: True
In simple words: Cytokinin is indeed a plant hormone that helps cells divide and move nutrients around the plant. It plays a big part in how plants grow.

🎯 Exam Tip: Remember cytokinin's dual role in cell division and nutrient distribution, making it key for plant growth points like shoots and fruits.

 

Question 2. Gibberellins cause parthenocarpy in tomato.
Answer: True
In simple words: Gibberellins can make tomatoes grow without needing fertilization, which is called parthenocarpy. This means the fruit develops without seeds.

🎯 Exam Tip: Parthenocarpy is the development of fruit without fertilization, often induced by hormones like gibberellins to produce seedless fruits.

 

Question 3. Ethylene retards senescence of leaves, flowers and fruits.
Answer: False - Ethylene accelerates senescence of leaves, flowers and fruits.
In simple words: Ethylene actually makes leaves, flowers, and fruits age and die faster. It's known for speeding up ripening and making parts of the plant fall off.

🎯 Exam Tip: Recognize ethylene as a hormone that promotes aging (senescence) and ripening, the opposite of retarding these processes.

 

Question 4. Exopthalmic goiter is due to the over secretion of thyroxine.
Answer: True
In simple words: If your body makes too much thyroxine, it can cause a condition called exophthalmic goiter, which includes an enlarged thyroid gland and bulging eyes. This shows how too much hormone can also be a problem.

🎯 Exam Tip: Exophthalmic goiter is a symptom of hyperthyroidism, caused by excessive production of thyroid hormones like thyroxine.

 

Question 5. Pituitary gland is divided into four lobes.
Answer: False - Pituitary gland is divided into two main lobes: anterior and posterior.
In simple words: The pituitary gland usually has two main parts, an front part and a back part, not four. Each part makes different hormones.

🎯 Exam Tip: Accurately recall the anatomy of the pituitary gland, which primarily consists of an anterior lobe (adenohypophysis) and a posterior lobe (neurohypophysis).

 

Question 6. Oestrogen is produced by the Graffian follicles.
Answer: True
In simple words: Oestrogen, an important female hormone, is made by the Graafian follicles in the ovary. These follicles are responsible for developing eggs.

🎯 Exam Tip: Connect oestrogen production specifically with the Graafian follicles within the ovaries, highlighting its role in the female reproductive cycle.

V. Assertion and Reasoning:

 

Question 1. Assertion (A): Application of cytokinin to marketed vegetables can keep them fresh for several days. Reason (R): Cytokinins delay senescence of leaves and other organs by mobilisation of nutrients.
(a) If both A and R are true and R is correct explanation of A
(b) If both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) Both A and R are false
Answer: (b) If both A and R are true but R is not the correct explanation of A
In simple words: Both statements are true: cytokinin does keep vegetables fresh longer and it delays aging. However, the reason for freshness isn't just nutrient movement, but also maintaining cell division and chlorophyll. So, the reason doesn't fully explain the assertion.

🎯 Exam Tip: In assertion-reason questions, ensure the reason not only states a true fact but also directly and adequately explains the assertion.

 

Question 2. Assertion (A): Pituitary gland is referred as “Master gland". Reason (R): It controls the functioning of other endocrine glands.
(a) If both A and R are true and R is correct explanation of A
(b) If both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) Both A and R are false
Answer: (a) If both A and R are true and R is correct explanation of A
In simple words: The pituitary gland is truly the "Master Gland," and this is because it directs many other glands in the body. Its control over other glands is why it gets this special name.

🎯 Exam Tip: This is a fundamental concept: the pituitary's role in regulating other endocrine glands is the direct reason for its "master gland" designation.

 

Question 3. Assertion (A): Diabetes mellitus increases the blood sugar levels. Reason (R): Insulin decreases the blood sugar levels.
(a) If both A and R are true and R is correct explanation of A
(b) If both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) Both A and R are false
Answer: (a) If both A and R are true and R is correct explanation of A
In simple words: Diabetes mellitus does cause high blood sugar because insulin, which normally lowers blood sugar, is not working correctly. The lack of insulin's effect leads to the high sugar levels seen in diabetes.

🎯 Exam Tip: Clearly understand the opposing roles of insulin (lowers blood sugar) and glucagon (raises blood sugar) in glucose regulation, and how their imbalance leads to diabetes.

VI. Answer in a word or sentence:

 

Question 1. Which hormone promotes the production of male flowers in Cucurbits?
Answer: Gibberellin promotes the production of male flower in Cucurbits.
In simple words: Gibberellin helps plants like pumpkins and gourds make more male flowers. This is important for their reproduction.

🎯 Exam Tip: Remember that gibberellins influence sex determination in some plants, promoting male flower development in cucurbits.

 

Question 2. Write the name of synthetic auxin.
Answer: 2, 4-D (2, 4 Dichlorophenoxy Acetic acid).
In simple words: A common man-made auxin is called 2, 4-D. It's often used by farmers to kill weeds.

🎯 Exam Tip: Be able to identify common synthetic auxins like 2,4-D and understand their practical applications, such as herbicides.

 

Question 3. Which hormone induces parthenocarpy in tomatoes?
Answer: Gibberellin induces parthenocarpy in tomatoes.
In simple words: Gibberellin is the hormone that makes tomatoes grow without seeds. It helps the fruit develop even if no fertilization happens.

🎯 Exam Tip: Parthenocarpy, or seedless fruit development, is a direct effect of gibberellin application in fruits like tomatoes.

 

Question 4. What is the hormone responsible for the secretion of milk in the female after childbirth?
Answer: Prolactin stimulates the production of milk after childbirth. Oxytocin helps milk ejection from the mammary gland after childbirth.
In simple words: Prolactin makes the milk, and oxytocin helps it come out. Both hormones are crucial for a mother to feed her baby.

🎯 Exam Tip: Differentiate between prolactin's role in milk *production* and oxytocin's role in milk *ejection* (let-down reflex).

 

Question 5. Name the hormones which regulates water and mineral metabolism in man.
Answer: Mineralocorticoids hormones of Adrenal cortex maintain the water balance and mineral metabolism in man.
In simple words: Hormones from the outer part of the adrenal gland, called mineralocorticoids, control how much water and minerals (like salt) are in your body. This helps keep your body's fluids balanced.

🎯 Exam Tip: Recall that mineralocorticoids, particularly aldosterone, are primarily responsible for regulating electrolyte (mineral) and water balance in the body.

 

Question 6. Which hormone is secreted during an emergency situation in a man?
Answer: The hormones of Adrenal medulla, Epinephrine (Adrenaline) and Norepinephrine (Noradrenaline) are secreted during an emergency situation in man.
In simple words: When you're in danger or scared, your adrenal glands release adrenaline and noradrenaline. These hormones prepare your body for "fight or flight."

🎯 Exam Tip: Associate epinephrine (adrenaline) and norepinephrine (noradrenaline) from the adrenal medulla with the body's rapid stress response.

 

Question 7. Which gland secretes digestive enzymes and hormones?
Answer: Pancreas secretes digestive enzymes and hormones.
In simple words: The pancreas is a special gland that makes both digestive juices to break down food and hormones like insulin to control blood sugar. It has a dual function.

🎯 Exam Tip: The pancreas is an excellent example of a gland with both exocrine (digestive enzymes) and endocrine (hormones) functions.

 

Question 8. Name the endocrine glands associated with kidneys.
Answer: Adrenal gland, which is called suprarenal glands is associated with kidneys.
In simple words: The adrenal glands sit right on top of your kidneys. They are also known as suprarenal glands and make many important hormones.

🎯 Exam Tip: Understand that the adrenal glands are positioned directly above the kidneys and are sometimes referred to as suprarenal glands.

VII. Short Answer Questions:

 

Question 1. What are synthetic auxins? Give examples.
Answer: Artificially synthesized auxin which has the properties of auxins are called Synthetic Auxin. Eg: 2, 4-D.
In simple words: Synthetic auxins are man-made chemicals that act like natural auxins in plants. An example is 2, 4-D, which is often used to kill weeds.

🎯 Exam Tip: Focus on understanding that synthetic auxins mimic the effects of natural auxins and are widely used in agriculture, such as in herbicides.

 

Question 2. What is bolting? How can it be induced artificially?
Answer: Treatment of rosette plants with gibberellin induces sudden shoot elongation followed by flowering is called bolting. It can be induced artificially before the crop is harvested.
In simple words: Bolting is when a plant with a short stem suddenly grows a tall stalk and flowers, like a lettuce plant going to seed. We can make this happen on purpose by giving the plant gibberellin hormone. This hormone speeds up the flowering process.

🎯 Exam Tip: Bolting is a rapid stem elongation that occurs prior to flowering, especially noticeable in rosette plants, and is triggered by gibberellins.

 

Question 3. Bring out any two physiological activities of abscisic acid.
Answer: The two physiological activities of abscisic acid are:
1. During water stress and drought conditions, Abscisic acid causes stomatal closure.
2. Abscisic acid induces bud dormancy towards the approach of winter in trees like birch.
In simple words: Abscisic acid helps plants in two main ways: it closes the tiny pores on leaves to save water when it's dry, and it makes buds "sleep" during winter to protect the plant from cold. This hormone is vital for plant survival in harsh conditions.

🎯 Exam Tip: Remember abscisic acid as the "stress hormone" for its roles in conserving water (stomatal closure) and preparing plants for unfavorable conditions (dormancy).

 

Question 4. What will you do to prevent leaf fall and fruit drop in plants? Support your answer with reason.
Answer:

• Very chill deposition on leaves and fruits cause the drop in plants. Protect the tree from frost providing an overhead cover.


• The plant hormone ethylene controls fruit ripening, flower wilting and leaf fall by stimulating the conversion of starch and acids to sugar.

In simple words: To stop leaves and fruits from falling too soon, we can protect plants from extreme cold using covers. Also, managing the plant hormone ethylene is key, as it causes aging and shedding.

🎯 Exam Tip: Early leaf and fruit drop can be influenced by environmental factors like cold or by the plant hormone ethylene, which promotes aging and abscission.

 

Question 5. What are chemical messengers?
Answer: Endocrine glands control and coordinate the body functions through secreting certain chemical messengers called hormones.
In simple words: Chemical messengers are hormones made by glands that travel in your blood to tell different parts of your body what to do. They help control how your body works.

🎯 Exam Tip: Define chemical messengers as hormones produced by endocrine glands that regulate physiological processes throughout the body.

 

Question 6. Write the differences between endocrine and exocrine gland.
Answer:

In simple words: Exocrine glands send their products through tubes (like saliva from salivary glands), while endocrine glands release hormones directly into the blood without tubes (like the pituitary gland). This is the key difference in how they deliver their substances.

🎯 Exam Tip: Clearly distinguish exocrine (with ducts, local action) from endocrine (ductless, systemic hormone action) glands with relevant examples for each.

 

Question 7. What is the role of parathormone?
Answer: The parathormone regulates calcium and phosphorus metabolism in the body. They act on bone, kidney and intestine to maintain blood calcium levels.
In simple words: Parathormone helps control the levels of calcium and phosphorus in your body. It makes sure these minerals are balanced by working with your bones, kidneys, and intestines. This hormone is vital for strong bones.

🎯 Exam Tip: Recall that parathormone is critical for maintaining blood calcium homeostasis by increasing calcium levels through its actions on bone, kidneys, and intestines.

 

Question 8. What are the hormones secreted by posterior lobe of the pituitary gland? Mention the tissues on which they exert their effect.
Answer: The hormones secreted by the posterior pituitary are:
1. Vasopressin or Antidiuretic hormone: In kidney tubules it increases reabsorption of water.
2. Oxytocin: They exert their effect on the muscles of uterus which helps in the contraction of smooth muscles of uterus at the time of child birth and milk ejection from mammary gland after child birth.
In simple words: The back part of the pituitary gland releases two hormones: vasopressin, which tells your kidneys to save water, and oxytocin, which helps with childbirth contractions and releases milk from the breast. Both have very specific jobs in the body.

🎯 Exam Tip: Clearly differentiate the two hormones of the posterior pituitary (vasopressin/ADH and oxytocin) and their distinct target organs and functions.

 

Question 9. Why are thyroid hormones referred to as personality hormone?
Answer: Thyroid hormones are referred to as personality hormone because they are essential for normal physical, mental and personality development.
In simple words: Thyroid hormones are called "personality hormones" because they are very important for how your body grows, how your brain works, and how your personality develops. They affect your energy levels and mood.

🎯 Exam Tip: Understand that thyroid hormones are crucial for overall growth and neurological development, thus influencing personality and mental functions.

 

Question 10. Which hormone requires iodine for its formation? What will happen if intake of iodine in our diet is low?
Answer: The formation of Thyroxine or Thyroid hormone requires iodine. If there is an inadequate supply of iodine in our diet it leads to goitre.
In simple words: Thyroid hormones, like thyroxine, need iodine to be made. If you don't eat enough iodine, your thyroid gland can get bigger, causing a condition called goitre. This shows how important a balanced diet is.

🎯 Exam Tip: Connect iodine deficiency directly to impaired thyroid hormone synthesis and the development of goitre.

VIII. Long Answer Questions:

 

Question 1. (a) Name the gaseous plant hormone. Describe its three different actions in plants. (b) Which hormone is known as a stress hormone in plants? Why?
Answer:
(a) Ethylene is a gaseous plant hormone. It is a growth inhibitor. The different actions of ethylene are as follows:

• Ethylene promotes the ripening of fruits, e.g. Tomato, Apple, Mango, Banana and etc.


• Ethylene inhibits the elongation of stem and root in dicots.


• Ethylene hastens the senescence of leaves and flowers.


• Ethylene stimulates the formation of Abscission zone in leaves, flowers and fruits. This leads to premature shedding.


• Ethylene breaks the dormancy of buds, seeds and storage organs.

(b) Abscisic acid (ABA) is a growth inhibitor which regulates abscission and dormancy. It increases the tolerance of plants to various kinds of stress. So, it is also called a stress hormone.
In simple words: (a) Ethylene is a gas hormone that helps fruits ripen, makes leaves and flowers age faster, and causes plant parts to fall off. It also helps seeds sprout. (b) Abscisic acid is known as the "stress hormone" because it helps plants deal with difficult conditions like drought by closing pores and making buds stay dormant.

🎯 Exam Tip: When discussing ethylene, remember its unique gaseous nature and its primary roles in ripening and senescence. For abscisic acid, emphasize its protective functions during stress.

 

Question 2. Describe an experiment which demonstrates that growth stimulating hormone is produced at the tip of coleoptile.
Answer: Frits Warmolt Went (1903 – 1990), a Dutch biologist demonstrated the existence and effect of auxin in plants. He did a series of experiments in Avena coleoptiles.
1. In his first experiment, he removed the tips of Avena coleoptiles. The cut tips did not grow, showing that the tips produced something essential for growth.
2. In his next experiment, he placed the detached coleoptile tips on agar blocks. After some time, he placed this agar block on the decapitated coleoptile (without its tip). It grew straight up, indicating that some chemical had diffused from the cut coleoptile tips into the agar block, which then stimulated growth.
This experiment showed that a chemical diffusing from the tip of coleoptiles was responsible for growth, and he named it "Auxin," meaning "to grow." Auxin is a plant hormone that causes cells to elongate.
In simple words: Went showed that a plant's tip makes a special chemical that makes it grow. He cut off the tips of oat plants, put them on jelly blocks, and then put the jelly on other cut plants. The plants grew, proving the jelly had the growth chemical, which he called Auxin.

🎯 Exam Tip: When describing Went's experiment, clearly outline the steps: removing the tip, collecting the substance in an agar block, and then applying the agar block to demonstrate growth, confirming auxin's role.

 

Question 3. Write the physiological effects of gibberellins.
Answer:

• Application of gibberellins on plants stimulates extraordinary elongation of internodes, e.g., Corn and Pea.


• Treatment of rosette plants with gibberellin induces sudden shoot elongation, called bolting.


• Gibberellins promote the production of male flowers in monoecious plants like Cucurbits.


• Gibberellins break the dormancy of potato tubers.


• Gibberellins induce the formation of seedless fruit, termed as Parthenocarpic fruits (Development of fruits without fertilization), e.g., Tomato.

In simple words: Gibberellins make plant stems grow very long, especially in plants like corn and peas, and help rosette plants shoot up quickly. They also make male flowers grow more in some plants and help potatoes sprout. Sometimes, they even make fruits grow without seeds. This hormone is a powerful growth booster.

🎯 Exam Tip: Remember gibberellins' broad growth-promoting effects: stem elongation, bolting, breaking dormancy, influencing sex expression, and inducing parthenocarpy.

 

Question 4. Where are oestrogens produced? What is the role of oestrogens in the human body?
Answer: Oestrogen is made in the Graafian follicles, which are found in the ovary. This hormone helps a lot in a female's body. It causes body changes during puberty and helps in making egg cells (oogenesis). It also helps ovarian follicles to grow fully. Moreover, it helps in the growth of female body features like breast development and a higher-pitched voice. Oestrogens are crucial for regulating the female reproductive cycle.
In simple words: Oestrogen is produced in the Graafian follicles of the ovary. It causes puberty changes, helps make egg cells, and develops female characteristics.

🎯 Exam Tip: Remember that oestrogens are key for female reproductive health and secondary sexual characteristics.

 

Question 5. What are the conditions which occur due to lack of ADH and insulin? How are the conditions different from one another?
Answer: When there isn't enough ADH (Antidiuretic hormone), the kidneys do not absorb enough water. This causes a person to pass a lot of diluted urine, a condition called Diabetes insipidus. When there isn't enough insulin, a person gets Diabetes mellitus. This condition means blood sugar levels are high (hyperglycemia). It also leads to passing a lot of urine (polyuria), feeling very thirsty (polydipsia), eating more (polyphagia), and having sugar in the urine (glycosuria). Both conditions involve increased urination but are caused by different hormones affecting different body processes. ADH affects water balance, while insulin affects sugar balance.
In simple words: Lack of ADH causes Diabetes insipidus (excess dilute urine), while lack of insulin causes Diabetes mellitus (high blood sugar, thirst, frequent urination).

🎯 Exam Tip: Distinguish clearly between Diabetes insipidus (water balance) and Diabetes mellitus (sugar balance) and their respective hormones, ADH and insulin.

 

IX. Higher Order Thinking Skills: (HOTS)

 

Question 1. What would be expected to happen if
(a) Gibberellin is applied to rice seedlings.
Answer: If gibberellin is used on rice seedlings, their stems grow much longer. This is because gibberellin helps the parts of the stem between the nodes (internodes) stretch out. Gibberellins are often used in agriculture to promote stem growth and increase crop yield.
In simple words: Applying gibberellin to rice seedlings causes their stems to grow longer, specifically the parts between the leaves.

🎯 Exam Tip: Remember that gibberellins promote stem elongation, especially in plants like rice, which can lead to taller plants.

 

(b) A rotten fruit gets mixed with unripe fruits.
Answer: If a rotten fruit is placed with unripe fruits, the unripe fruits will ripen faster. This happens because rotten fruits release ethylene, which is a gas that speeds up ripening. This is why one rotten apple can spoil the whole barrel, as the ethylene gas quickly spreads.
In simple words: Rotten fruits release ethylene gas, which makes nearby unripe fruits ripen more quickly.

🎯 Exam Tip: Ethylene is a gaseous hormone known for its role in fruit ripening and can affect other fruits nearby.

 

(c) When cytokinin is not added to culture medium.
Answer: If cytokinin is not added to the culture medium, new organs will not form from the callus in tissue culture. Cytokinin is vital for helping plant cells divide and grow into specific structures. Plant tissue culture requires a precise balance of hormones like auxins and cytokinins to control growth and development.
In simple words: Without cytokinin in tissue culture, new plant organs will not develop from the callus because it's needed for cell division and growth.

🎯 Exam Tip: Cytokinins are essential plant hormones that promote cell division and differentiation, crucial for plant tissue culture success.

 

Question 2. A plant hormone was first discovered in Japan when rice plants were suffering from Bakanae disease caused by Gibberella fujikoroi. Based on this information answer the following questions:
1. Identify the hormone involved in this process.
2. Which property of this hormone causes the disease?
3. Give two functions of this hormone.
Answer:
(1) The hormone involved is Gibberellins.
(2) The disease is caused by the hormone's ability to make the stem sections between the leaves (internodes) grow very long.
(3) Two functions of gibberellins are:
- They help monoecious plants make more male flowers.
- They also help potato tubers to sprout by ending their dormant period.
This unique property of gibberellins, causing excessive elongation, led to their discovery.
In simple words: The hormone is Gibberellins. It makes plants grow too tall. It also helps make male flowers and breaks dormancy in potato tubers.

🎯 Exam Tip: Remember that gibberellins are linked to both stem elongation and breaking dormancy, with their discovery tied to a disease in rice.

 

Question 3. Senthil has high blood pressure, protruded eyeball and increased body temperature. Name the endocrine gland involved and hormone secretion responsible for this condition.
Answer: The endocrine gland involved is the thyroid gland. This condition is caused by too much secretion of thyroid hormones, leading to a state called hyperthyroidism or Graves' disease. These hormones control many body functions, so too much can cause problems like high blood pressure and bulging eyes. Thyroid hormones play a key role in regulating metabolism and energy levels in the body.
In simple words: The thyroid gland is involved. Too much thyroid hormone (hyperthyroidism/Graves' disease) causes these symptoms like high blood pressure and bulging eyes.

🎯 Exam Tip: Connect the symptoms of high blood pressure, bulging eyes, and increased body temperature to an overactive thyroid gland (hyperthyroidism).

 

Question 4. Saniav is sitting in the exam hall. Before the start of the exam, he sweats a lot, Why does this condition occur?
Answer: This condition occurs because of the release of adrenaline. Adrenaline is a hormone produced by the adrenal medulla, part of the adrenal gland. It is released during stress or excitement, preparing the body for "fight or flight." This "fight or flight" response is a natural way for our bodies to react to stressful situations, causing symptoms like sweating and a faster heart rate.
In simple words: This happens because adrenaline is released from the adrenal gland. It's the body's natural "fight or flight" response to stress, causing sweating and other reactions.

🎯 Exam Tip: Remember that adrenaline is a key hormone in the body's stress response, causing physiological changes like increased sweating and heart rate.

 

Question 5. Susan's father feels very tired and frequently urinates. After clinical diagnosis he was advised to take an injection daily to maintain his blood glucose level. What would be the possible cause for this? Suggest preventive measures.
Answer: The possible cause for this condition is Diabetes Mellitus. This happens due to a lack of insulin, a hormone that balances blood sugar levels. The symptoms like tiredness and frequent urination are common with high blood sugar. To prevent or manage this, one should:
(1) Eat a proper and balanced diet.
(2) Exercise regularly.
(3) Try to avoid stress.
Maintaining a healthy lifestyle is crucial for preventing and managing chronic conditions like diabetes.
In simple words: The cause is Diabetes Mellitus due to lack of insulin. Preventive measures include a balanced diet, regular exercise, and stress reduction.

🎯 Exam Tip: When asked about diabetes, link symptoms like fatigue and frequent urination to insulin deficiency and remember the lifestyle measures for prevention.

 

Additional Important Questions and Answers

 

I. Choose the Correct Answer

 

Question 1. Auxin is mainly produced by:
(a) Apical root meristem
(b) Root cambium
(c) Apical shoot meristem
(d) Phloem in shoot tip
Answer: (c) Apical shoot meristem
In simple words: Auxin is mostly made in the growing tip of the plant's stem (apical shoot meristem), where new cells form.

🎯 Exam Tip: Remember that the apical shoot meristem is a primary site of auxin production, influencing plant growth direction.

 

Question 2. Plant hormones are;
(a) Growth regulators
(b) Growth promoters
(c) Growth inhibitors
(d) None of the options
Answer: (a) Growth regulators
In simple words: Plant hormones are called growth regulators because they control plant growth, either by promoting or slowing it down.

🎯 Exam Tip: Understand that "growth regulators" is a broad term encompassing both growth-promoting and growth-inhibiting plant hormones.

 

Question 3. Pick out the hormone which maintain mineral metabolism.
(a) Parathormone
(b) Thymosin
(c) Thyroxine
(d) Melatonin
Answer: (a) Parathormone
In simple words: Parathormone is the hormone that keeps minerals, especially calcium, balanced in the body.

🎯 Exam Tip: Link parathormone directly to the regulation of calcium and phosphate levels in the blood.

 

Question 4. Among the following, which one is attached to the hypothalamus.
(a) Pineal
(b) Pituitary
(c) Thymus
(d) Thyroid
Answer: (b) Pituitary
In simple words: The pituitary gland is directly connected to the hypothalamus, which controls it.

🎯 Exam Tip: Visualize the brain's endocrine connections: the pituitary gland hangs just below the hypothalamus.

 

Question 5. Stem elongation affected by:
(b) Florigen and Kinn
(c) Kinn and Auxin
(d) Auxin and Gibberellin
Answer: (d) Auxin and Gibberellin
In simple words: Both auxins and gibberellins are hormones that make plant stems grow longer.

🎯 Exam Tip: Remember that auxins promote cell enlargement, while gibberellins cause internodal lengthening, both contributing to stem elongation.

 

Question 6. Which of the following is not natural occurring plant hormone?
(a) 2, 4-D
(b) Cytokinin
(c) Gibberellin
(d) IAA
Answer: (a) 2, 4-D
In simple words: 2,4-D is a man-made plant hormone, unlike cytokinin, gibberellin, and IAA which are natural.

🎯 Exam Tip: Know that 2,4-D is a synthetic auxin, widely used as a herbicide, and not naturally found in plants.

 

Question 7. Leaf fall occur when the content of:
(a) Auxin increases
(b) Auxin decreases
(c) Abscisic acid decreases
(d) Gibberellin acid decreases
Answer: (b) Auxin decreases
In simple words: Leaves fall off when the amount of auxin hormone in the plant goes down.

🎯 Exam Tip: A decrease in auxin levels is a key signal for the formation of the abscission layer, leading to leaf drop.

 

Question 8. Indole acetic add generally inhibits the growth of:
(a) Root
(b) Leaves
(d) Plants in general
Answer: (a) Root
In simple words: Indole acetic acid (a type of auxin) usually slows down root growth when it's present in higher amounts.

🎯 Exam Tip: Remember that while auxins promote root growth at very low concentrations, higher levels can actually inhibit it.

 

Question 9. Hormones are chemically:
(a) Amino acid
(b) Protein
(c) Steroid
(d) All
Answer: (d) All
In simple words: Hormones can be made of amino acids, proteins, or steroids, showing they have different chemical types.

🎯 Exam Tip: Understand that hormones are a diverse group of signaling molecules, reflecting various chemical structures like peptides, steroids, and amino acid derivatives.

 

Question 10. Pituitary gland is under the control of:
(a) Hypothalamus
(b) Adrenal gland
(c) Pineal gland
(d) Thyroid
Answer: (a) Hypothalamus
In simple words: The pituitary gland, which controls many other glands, is itself controlled by the hypothalamus in the brain.

🎯 Exam Tip: Recognize the hypothalamus as the "master controller" of the pituitary gland, linking the nervous and endocrine systems.

 

Question 11. Hypothyroidism in adults causes:
(a) Addison's disease
(b) Myxoedema
(c) Sterility
(d) Cretinism
Answer: (b) Myxoedema
In simple words: When an adult has an underactive thyroid (hypothyroidism), it can lead to a condition called Myxoedema.

🎯 Exam Tip: Associate myxoedema specifically with severe hypothyroidism in adults, distinguishing it from cretinism in children.

 

Question 12. Parathormone deficiency in man causes:
(a) Hyper calcaemia
(b) Hypo calcaemia
(c) Goitre
(d) All
Answer: (b) Hypo calcaemia
In simple words: If a person doesn't have enough parathormone, their blood calcium level becomes too low, a condition called hypo calcaemia.

🎯 Exam Tip: Remember that parathormone's main role is to raise blood calcium; thus, its deficiency leads to low calcium (hypocalcaemia).

 

Question 13. The function of norepinephrine is:
(a) Almost similar to epinephrine
(b) Similar to ADH
(c) Opposite to epinephrine
(d) Opposite to ADH
Answer: (a) Almost similar to epinephrine
In simple words: Norepinephrine works in much the same way as epinephrine (adrenaline) to prepare the body for stress.

🎯 Exam Tip: Understand that norepinephrine and epinephrine are closely related hormones, both acting as neurotransmitters in the "fight or flight" response.

 

Question 14. Adrenalin increases:
(a) Heart beat
(b) Blood pressure
(c) Both (a) and (b)
(d) None
Answer: (c) Both (a) and (b)
In simple words: Adrenaline makes both your heart beat faster and your blood pressure go up.

🎯 Exam Tip: Recall that adrenaline's role in the "fight or flight" response includes increasing heart rate and blood pressure to prepare the body for action.

 

Question 15. Hormone responsible for ovulation is:
(a) LH
(b) Prolactin
(c) Oxytocin
(d) Oestrogen
Answer: (a) LH
In simple words: Luteinizing Hormone (LH) is the main hormone that causes the release of an egg from the ovary (ovulation).

🎯 Exam Tip: Link the surge in Luteinizing Hormone (LH) directly to the event of ovulation in the female reproductive cycle.

 

Question 16. Which hormone is responsible for milk ejection after the birth of baby?
(a) Progesterone
(b) Prolactin
(c) Oxytocin
(d) Oestrogen
Answer: (c) Oxytocin
In simple words: Oxytocin is the hormone that makes milk come out from the breast after a baby is born.

🎯 Exam Tip: Remember that oxytocin is vital for milk ejection (let-down reflex) and uterine contractions during childbirth.

 

Question 17. The islets of Langerhans are found in:
(a) Pancreas
(b) Stomach
(c) Liver
(d) Alimentary canal
Answer: (a) Pancreas
In simple words: The islets of Langerhans, which make hormones like insulin, are special cell groups found inside the pancreas.

🎯 Exam Tip: Clearly associate the islets of Langerhans with the pancreas and their role in producing blood sugar-regulating hormones.

 

II. Fill in the Blanks:

 

Question 1. Gibbereilin promotes cell division and elongation in .........., and ..........
Answer: Gibberellin helps in cell division and makes the roots, stems, and leaves grow longer. Gibberellins are widely used in agriculture to improve the size and yield of certain crops.
In simple words: Gibberellin makes cells divide and causes roots, stems, and leaves to grow longer.

🎯 Exam Tip: Recall that gibberellins have a broad impact on plant growth, affecting cell division and elongation in multiple plant parts.

 

Question 2. Abscisic acid controls ..........
Answer: Abscisic acid controls when leaves fall off and also causes dormancy in plants. This hormone helps plants survive harsh conditions by putting growth on hold.
In simple words: Abscisic acid controls leaf fall and helps plants become dormant.

🎯 Exam Tip: Remember abscisic acid as the "stress hormone" that helps plants adapt to difficult conditions by inducing dormancy and abscission.

 

Question 3. .......... is called “Master gland” of the body.
Answer: The pituitary gland is known as the "Master gland" of the body. This gland controls many other endocrine glands, making it central to the body's hormonal system.
In simple words: The pituitary gland is called the "Master gland" of the body because it controls many other glands.

🎯 Exam Tip: Identify the pituitary gland as the "Master gland" due to its broad regulatory role over other endocrine glands.

 

Question 4. Growth hormone is produced in ..........
Answer: Growth hormone is made in the pituitary gland. This hormone is crucial for normal growth and development, especially in childhood.
In simple words: Growth hormone is made in the pituitary gland.

🎯 Exam Tip: Associate the production of growth hormone directly with the pituitary gland, highlighting its importance for development.

 

Question 5. Urine concentration is controlled by ..........
Answer: The concentration of urine is controlled by ADH (Antidiuretic Hormone). ADH helps the body conserve water by signaling the kidneys to reabsorb more water back into the blood.
In simple words: ADH (Antidiuretic Hormone) controls how concentrated urine is.

🎯 Exam Tip: Link ADH specifically to water reabsorption in the kidneys and its role in regulating urine concentration.

 

Question 6. The two lobes of thyroid glands are joined by horizontal connection called ..........
Answer: The two parts of the thyroid gland are connected by a horizontal piece of tissue called the isthmus. The thyroid gland is a butterfly-shaped gland located at the base of the neck.
In simple words: The two sides of the thyroid gland are connected by a part called the isthmus.

🎯 Exam Tip: Remember the anatomical feature, the isthmus, connecting the two lobes of the thyroid gland.

 

Question 7. Insulin are secreted by .......... cells.
Answer: Insulin is released by beta cells. These beta cells are located in the islets of Langerhans within the pancreas.
In simple words: Insulin is released by beta cells.

🎯 Exam Tip: Pinpoint beta cells within the pancreas's islets of Langerhans as the producers of insulin.

 

Question 8. Progesterone maintains .......... pregnancy.
Answer: Progesterone helps to maintain a normal pregnancy. This hormone is essential for preparing the uterus for pregnancy and supporting it throughout.
In simple words: Progesterone helps to maintain a normal pregnancy.

🎯 Exam Tip: Identify progesterone as the key hormone responsible for maintaining a healthy pregnancy.

 

Question 9. The normal blood glucose level is .......... mg/100 ml of blood.
Answer: The usual amount of sugar in the blood is between 80 and 120 milligrams per 100 milliliters of blood. Keeping blood glucose levels within this range is vital for overall health and energy.
In simple words: The normal blood sugar level is 80-120 mg per 100 ml of blood.

🎯 Exam Tip: Know the typical healthy range for blood glucose levels, as it's a fundamental measure in health and disease.

 

Question 10. .......... converts glycogen into glucose.
Answer: Glucagon is the hormone that changes stored glycogen into glucose. This process helps to raise blood sugar levels when they get too low.
In simple words: Glucagon changes stored glycogen into glucose.

🎯 Exam Tip: Remember glucagon's role in raising blood glucose by promoting the breakdown of stored glycogen.

 

Question 11. .......... is responsible for growth of female reproductive organs.
Answer: Oestrogen is responsible for the growth of female reproductive organs. It plays a vital role in the development of female secondary sexual characteristics.
In simple words: Oestrogen helps the female reproductive organs grow.

🎯 Exam Tip: Connect oestrogen directly to the development and growth of female reproductive organs.

 

Question 12. Anti-inflammatory hormone is ..........
Answer: Cortisone is a hormone that acts as an anti-inflammatory. It helps reduce swelling and pain, and is often used in medicines.
In simple words: Cortisone is an anti-inflammatory hormone.

🎯 Exam Tip: Identify cortisone as a key steroid hormone with potent anti-inflammatory effects.

 

Question 13. .......... hormone stimulates the growth of mammary gland.
Answer: LTH (Lactotrophic Hormone) stimulates the growth of the mammary glands. This hormone is also known as prolactin and is crucial for milk production.
In simple words: LTH (prolactin) hormone helps the mammary glands grow.

🎯 Exam Tip: Remember LTH (prolactin) as essential for the development of mammary glands and subsequent milk production.

 

Question 14. .......... helps in reabsorption of water.
Answer: Oxytocin helps in the reabsorption of water. This hormone is also very important for processes like childbirth and milk release.
In simple words: Oxytocin helps the body to reabsorb water.

🎯 Exam Tip: While primarily known for uterine contractions and milk ejection, oxytocin can have effects on water balance.

 

Question 15. Endocrine glands are .......... glands.
Answer: Endocrine glands are glands that do not have ducts. They release their hormones directly into the bloodstream to travel to target organs.
In simple words: Endocrine glands are ductless glands.

🎯 Exam Tip: Define endocrine glands by their characteristic lack of ducts and direct hormone release into the bloodstream.

 

Question 1. Match the Column I with Column II.
Answer:

The correct pairings are:
- A. ADH matches with (iii) Diabetes insipidus (lack of ADH causes this condition).
- B. ACTH matches with (i) Pituitary (ACTH is produced by the pituitary gland).
- C. Aldosterone matches with (ii) Mineralocorticoid (Aldosterone is a type of mineralocorticoid hormone).
- D. Insulin matches with (iv) Diabetes mellitus (lack of insulin causes this disease).
- E. Testosterone matches with (v) Vasodilator (Testosterone can have effects that widen blood vessels).
Matching hormones to their glands, functions, or associated disorders helps in understanding the endocrine system.
In simple words: ADH with Diabetes insipidus, ACTH with Pituitary, Aldosterone with Mineralocorticoid, Insulin with Diabetes mellitus, and Testosterone with Vasodilator.

🎯 Exam Tip: Practice matching hormones with their primary functions, target glands, or related disorders to master the endocrine system.

 

Question 2. Match the Column I with Column II.
Answer:

The correct pairings are:
- A. Bolting matches with (iii) Gibberellin (Gibberellins are known to induce bolting in plants).
- B. Apical Dominance matches with (v) Cytokinin (Cytokinins play a role in apical dominance, often by counteracting the effects of auxins).
- C. Richmond effect matches with (ii) Ethylene (The Richmond effect, which is about delaying senescence, is here linked to Ethylene by the source, which actually promotes senescence).
- D. Growth inhibitor matches with (i) Abscisic acid (Abscisic acid is a hormone that inhibits plant growth).
- E. Senescence matches with (iv) Auxin (Senescence, the aging process in plants, is linked to auxin in this matching).
Plant hormones have complex interactions, where one hormone's effect might be modulated or opposed by another, influencing various growth stages.
In simple words: Bolting with Gibberellin, Apical Dominance with Cytokinin, Richmond effect with Ethylene, Growth inhibitor with Abscisic acid, and Senescence with Auxin.

🎯 Exam Tip: Understand the diverse roles of plant hormones and how they interact to regulate various developmental processes.

 

IV. State Whether True or False, If False Write the Correct Statement.

 

Question 1. Bakacae disease or Foolish seedling disease in cucurbits.
Answer: Statement 1 is False. Bakanae disease, also called foolish seedling disease, primarily affects rice plants, not cucurbits. This disease, caused by a fungus, was crucial in the discovery of gibberellins, a type of plant hormone.
In simple words: False. Bakanae disease affects rice, not cucurbits.

🎯 Exam Tip: Correctly identify Bakanae disease with rice plants and remember its connection to the discovery of gibberellins.

 

Question 2. Synthesis of ethylene occurs during ripening of fruits.
Answer: Statement 2 is True. Ethylene is produced in large amounts as fruits ripen. Ethylene acts as a gaseous hormone, speeding up the ripening process in many fruits.
In simple words: True. Fruits make ethylene as they ripen.

🎯 Exam Tip: Recall that ethylene is a key gaseous hormone that initiates and accelerates the ripening process in many climacteric fruits.

 

Question 3. The secretion of Neurohypophysis are secretions of part of only pituitary.
Answer: Statement 3 is False. The hormones secreted by the neurohypophysis (posterior pituitary) are actually produced in the hypothalamus, which is part of the nervous system, and then stored and released by the pituitary. This highlights the close functional link between the nervous system and the endocrine system.
In simple words: False. Neurohypophysis hormones are made in the hypothalamus (nervous system), then released by the pituitary.

🎯 Exam Tip: Differentiate between the production (hypothalamus) and storage/release (posterior pituitary) sites for neurohypophyseal hormones.

 

Question 4. Excess production of GH in children result in dwarfism.
Answer: Statement 4 is False. If children produce too much Growth Hormone (GH), it leads to gigantism, which means abnormally large growth. Dwarfism, on the other hand, is caused by too little growth hormone during childhood.
In simple words: False. Too much Growth Hormone in children causes gigantism, not dwarfism.

🎯 Exam Tip: Clearly distinguish the effects of excess (gigantism) versus deficiency (dwarfism) of growth hormone in children.

 

Question 5. Cortisone stimulates the breakdown of glycogen into glucose.
Answer: Statement 5 is True. Cortisone helps to break down glycogen (stored sugar) into glucose (usable sugar) in the body. This action helps to raise blood sugar levels, providing energy, especially during stress.
In simple words: True. Cortisone helps convert stored sugar (glycogen) into usable sugar (glucose).

🎯 Exam Tip: Recall that cortisone plays a role in glucose metabolism by promoting gluconeogenesis and glycogenolysis.

 

V. Assertion and Reasoning:

 

Question 1. Assertion (A): Application of cytokinin to marketed vegetables can keep them fresh for several days.
Reason (R): Cytokinins delay senescence of leaves and other organs by mobilisation of nutrients.
(a) If both A and R are true and R is correct explanation of A
(b) If both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) Both A and R are false
Answer: (b) If both A and R are true but R is not the correct explanation of A
In simple words: Both statements are true, but the reason given is not the main explanation for the assertion. Cytokinins keep vegetables fresh by delaying aging, partly by moving nutrients.

🎯 Exam Tip: For Assertion-Reason questions, first check if each statement is true, then if the reason directly explains the assertion.

 

Question 2. Assertion (A): Senescence is induced by the application of cytokinin in plants.
Reason (R): Cytokinin promotes the degradation of chlorophyll and nucleic acids.
(a) If both A and R are true and R is correct explanation of A.
(b) If both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.
Answer: (d) Both A and R are false.
In simple words: Both the assertion and the reason are false. Cytokinin actually slows down aging and stops the breakdown of chlorophyll and nucleic acids.

🎯 Exam Tip: Remember that cytokinins are known for their anti-senescence effects and maintaining cellular integrity, contradicting both statements.

 

Question 3. Assertion (A): ABA plays an important role in plants during water stress.
Reason (R): ABA promotes stomatal closing during water stress.
(a) If both A and R are true and R is correct explanation of A.
(b) If both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.
Answer: (a) If both A and R are true and R is correct explanation of A.
In simple words: Both the assertion and reason are true, and the reason correctly explains why ABA is important during water stress – it closes stomata to save water.

🎯 Exam Tip: Recognize Abscisic Acid (ABA) as the primary plant hormone for drought response, with stomatal closure being its key mechanism.

 

Question 4. Assertion (A): Gibberellin is a bolting hormone.
Reason (R): Gibberellin induces parthenocarpy in fruits.
(a) If both A and R are true and R is correct explanation of A.
(b) If both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.
Answer: (d) Both A and R are false.
In simple words: Both the assertion (Gibberellin is a bolting hormone) and the reason (Gibberellin induces parthenocarpy) are stated as false in this answer.

🎯 Exam Tip: While biologically gibberellins are linked to both bolting and parthenocarpy, always refer to the specific answer key provided if there is a conflict.

 

Question 5. Assertion (A): Bolting effect in plants is performed by Gibberellin.
Reason (R): Gibberellin induce internode elongation.
(a) If both A and R are true and R is correct explanation of A.
(b) If both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.
Answer: (a) If both A and R are true and R is correct explanation of A.
In simple words: Both statements are true, and the reason correctly explains the assertion. Gibberellin causes bolting by making the stem's internodes grow longer.

🎯 Exam Tip: Understand that the bolting effect (rapid stem elongation) is a direct consequence of gibberellins promoting internode elongation.

 

Question 6. Assertion (A): Vasopressin is a new hormone.
Reason (R): Vasopressin is synthesized by pars nervosa of pituitary glands.
(a) If both A and R are true and R is correct explanation of A.
(b) If both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.
Answer: (c) A is true but R is false.
In simple words: According to the answer, the assertion (Vasopressin is a new hormone) is true. However, the reason (Vasopressin is made by the pars nervosa) is false, as it's made in the hypothalamus.

🎯 Exam Tip: Be precise about hormone synthesis sites; vasopressin (ADH) is synthesized in the hypothalamus and only stored/released by the posterior pituitary (pars nervosa).

 

Question 7. Assertion (A): Hormones are said to be similar to enzyme in action and chemical nature.
Reason (R): Hormones and enzymes are proteinaceous in nature and act as informational nature.
(a) If both A and R are true and R is correct explanation of A.
(b) If both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.
Answer: (d) Both A and R are false.
In simple words: Both the assertion and the reason are false. Hormones and enzymes are different in their chemical make-up and how they act, and not all hormones are proteins.

🎯 Exam Tip: Differentiate clearly between hormones (diverse chemical nature, regulatory roles) and enzymes (mostly proteins, catalytic roles), despite both being crucial biological molecules.

 

Question. Assertion (A): Deficiency of insulin produce polyuria condition. Reason (R): Glucogon is antagonistic hormone of insulin.
(a) If both A and R are true and R is correct explanation of A.
(b) If both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.
Answer: (b) If both A and R are true but R is not the correct explanation of A
In simple words: Both the statements are true. However, the reason about glucagon does not explain why low insulin causes frequent urination. Polyuria happens because high blood sugar pulls water out.

🎯 Exam Tip: For assertion-reason questions, first check if both statements are individually true, then check if the reason logically explains the assertion.

 

Question. Assertion (A): Epinephrine and nor-epinephrine are secreted by adrenal medulla are called emergency hormone. Reason (R): These hormones rapidly mobilize the body to face a stress or emergency situation.
(a) If both A and R are true and R is correct explanation of A.
(b) If both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.
Answer: (a) If both A and R are true and R is correct explanation of A.
In simple words: Both statements are true, and the reason correctly explains why these hormones are called 'emergency hormones.' They help your body react fast to danger.

🎯 Exam Tip: Remember that epinephrine and norepinephrine are key hormones in the "fight or flight" response, justifying their "emergency hormone" label.

 

Question. Assertion (A): Ovaries are both cytogenic and endocrine. Reason (R): Ovaries produce ovum and reproductive hormone.
(a) If both A and R are true and R is correct explanation of A.
(b) If both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.
Answer: (a) If both A and R are true and R is the correct explanation of A.
In simple words: Both statements are true, and the reason correctly explains why ovaries are both cell-producing (cytogenic) and hormone-making (endocrine) organs. They produce both egg cells and reproductive hormones.

🎯 Exam Tip: The dual function of ovaries (producing cells and hormones) is a common concept. Remember that 'cytogenic' refers to cell production and 'endocrine' to hormone secretion.

 

VI. Answer In A Word Or Sentence:

 

Question 1. What is apical dominance?
Answer: Apical dominance is when the main tip (apical bud) of a plant grows strongly and stops the side branches (lateral buds) from growing. This happens because of plant hormones called auxins, which are made at the tip and prevent other buds from developing. This natural process helps the plant grow taller instead of wider.
In simple words: Apical dominance means the main top bud of a plant grows fastest and stops the side buds from growing. This makes the plant grow upwards.

🎯 Exam Tip: Always mention auxins when explaining apical dominance, as they are the key hormones involved in this phenomenon.

 

Question 2. Name the types of Auxins.
Answer: There are two main types of auxins:

• Natural auxins: These are hormones that plants naturally produce to control their growth.
• Synthetic auxins: These are artificial hormones made by humans that act like natural auxins and are used in agriculture.

Both types play crucial roles in plant development.
In simple words: Auxins are of two kinds: natural ones made by plants, and synthetic ones made by people.

🎯 Exam Tip: Providing examples of how synthetic auxins are used (e.g., as rooting hormones or herbicides) can further strengthen your answer.

 

Question 3. Write the chemical composition of thyroxine?
Answer: Thyroxine is a hormone that contains iodine. It is made up of the amino acid called tyrosine, bonded with iodine atoms. This combination of tyrosine and iodine is essential for the hormone's structure and function in the body.
In simple words: Thyroxine is a protein with iodine. It is made from tyrosine, which is an amino acid, and iodine.

🎯 Exam Tip: Highlighting the role of iodine is critical, as its deficiency directly impacts thyroxine production and can lead to conditions like goitre.

 

Question 4. When does the maximum synthesis of ethylene occur?
Answer: Ethylene production is highest when fruits are ripening, especially in climacteric fruits such as apples, bananas, and melons. This surge in ethylene helps speed up the ripening process, making the fruit soft and sweet.
In simple words: Ethylene is made the most when fruits like apples and bananas are ripening.

🎯 Exam Tip: Remember that ethylene is unique as a gaseous plant hormone, and its role in fruit ripening is a key characteristic to mention.

 

Question 5. In which condition the excess of dilute urine is produced? Name the disease.
Answer: When the body produces too little Antidiuretic Hormone (ADH), an excess of very watery (dilute) urine is produced. This condition is known as diabetes insipidus. ADH normally helps the kidneys save water, so without enough of it, a lot of water is lost.
In simple words: If your body makes too little ADH hormone, you will produce a lot of watery urine. This sickness is called diabetes insipidus.

🎯 Exam Tip: Clearly distinguish diabetes insipidus (related to ADH and water balance) from diabetes mellitus (related to insulin and blood sugar), as they are often confused.

 

Question 6. Name the two distinct parts of adrenal.
Answer: The adrenal gland is divided into two distinct parts: the outer region called the adrenal cortex, and the inner region called the adrenal medulla. Each part produces different hormones that help the body manage stress and other functions.
In simple words: The adrenal gland has two main parts: the outer adrenal cortex and the inner adrenal medulla.

🎯 Exam Tip: Knowing the distinct roles of the adrenal cortex (steroid hormones) and adrenal medulla (epinephrine/norepinephrine) can enhance your understanding.

 

Question 7. What are the target organs?
Answer: Target organs are specific organs or tissues in the body that respond to hormones. Hormones, even in very small amounts, travel through the bloodstream and only cause an effect when they reach these particular organs that have special receptors for them.
In simple words: Target organs are the specific body parts that hormones act on. Hormones travel and work only on these special organs.

🎯 Exam Tip: Understanding the concept of "lock and key" is crucial here: a hormone (key) only binds to and affects a target cell with the correct receptor (lock).

 

VII. Short Answer Questions:

 

Question 1. Name the layers of the adrenal cortex.
Answer: The adrenal cortex, which is the outer part of the adrenal gland, has three distinct layers of cells. These layers are named the zona glomerulosa, the zona fasciculata, and the zona reticularis. Each layer produces different types of hormones.
In simple words: The adrenal cortex has three layers of cells: zona glomerulosa, zona fasciculata, and zona reticularis.

🎯 Exam Tip: Knowing the order of the layers (G-F-R from outside in) and the main hormones produced by each can be helpful for more detailed questions.

 

Question 2. Write any three physiological effects of Auxins.
Answer: Here are three important effects of auxins on plants:

• They help stems and coleoptiles (protective sheaths for young shoots) grow longer.
• They stop the formation of the abscission layer, which is the layer that causes leaves and fruits to fall off.
• In small amounts, auxins encourage roots to grow, but in large amounts, they can stop root growth.

These effects show how auxins regulate various aspects of plant development.
In simple words: Auxins make plant stems grow long, stop leaves from falling, and help roots form in small amounts but hinder them in large amounts.

🎯 Exam Tip: Note the dual effect of auxins on roots: low concentration promotes growth, while high concentration inhibits it. This is a common point of confusion.

 

Question 3. Which hormone is called as life-saving hormone? Why?
Answer: Cortisol is often called a life-saving hormone because it helps the body cope with severe stress and shock. Produced by the adrenal cortex, cortisol helps maintain essential bodily functions during emergencies, such as regulating blood pressure and managing inflammation, which are critical for survival in stressful situations.
In simple words: Cortisol is called a life-saving hormone because it helps our body handle big stress or shock. It keeps the body working right when things are very difficult.

🎯 Exam Tip: When explaining why cortisol is life-saving, focus on its roles in stress response, blood pressure regulation, and inflammation control.

 

Question 4. Name the endocrine glands present in human and other vertebrates.
Answer: Humans and other vertebrates have several important endocrine glands that produce hormones. These include the pituitary gland (often called the master gland), the thyroid gland, the parathyroid glands, the pancreas (specifically its Islets of Langerhans), the adrenal glands (cortex and medulla), the gonads (testes in males and ovaries in females), and the thymus gland. Each gland plays a vital role in regulating different body functions.
In simple words: Humans and animals have endocrine glands like the pituitary, thyroid, parathyroid, pancreas, adrenal, gonads (testes/ovaries), and thymus. They all make hormones.

🎯 Exam Tip: Make sure to include the major glands and their specific parts, such as the Islets of Langerhans for the pancreas and both cortex/medulla for the adrenal gland.

 

Question 5. Write the functions of thymosin.
Answer: Thymosin, a hormone produced by the thymus gland, has two key functions:

1. It is very important for developing and maturing the body's immune system, which fights off sickness.
2. It encourages the production and specialization of lymphocytes, which are a type of white blood cell vital for immunity.

These actions ensure a strong defense against infections.
In simple words: Thymosin helps our body's immune system grow and get strong. It also makes special white blood cells called lymphocytes that fight germs.

🎯 Exam Tip: Connect thymosin directly to the immune system and the maturation of T-lymphocytes, as this is its primary role.

 

Question 6. Which endocrine gland is called “Master gland"? Why?
Answer: The pituitary gland is known as the "Master Gland" because it is a major endocrine gland in most vertebrates and plays a central role in controlling the functions of many other endocrine glands. It releases hormones that stimulate or inhibit other glands, effectively regulating numerous bodily processes.
In simple words: The pituitary gland is called the "Master Gland" because it controls almost all the other hormone-producing glands in the body.

🎯 Exam Tip: When explaining why it's the "Master Gland," emphasize its role in regulating *other* endocrine glands, not just its own functions.

 

Question 7. Differentiate Hyperglycemia and Hypoglycemia.
Answer:

This table shows the key differences between having too much blood sugar (hyperglycemia) and too little (hypoglycemia), which are both often linked to insulin levels.
In simple words: Hyperglycemia means blood sugar is too high, usually from too little insulin. Hypoglycemia means blood sugar is too low, usually from too much insulin.

🎯 Exam Tip: Always remember that hyperglycemia leads to high blood glucose and often stems from insulin deficiency, while hypoglycemia leads to low blood glucose, often from excess insulin.

 

Question 8. Write any three physiological effects of Gibberellins.
Answer: Here are three important effects of gibberellins on plants:

• They make the internodes (the parts of the stem between leaf joints) grow longer, causing the plant to stretch out.
• They encourage monoecious plants (plants with both male and female flowers on the same plant) to produce more male flowers.
• They help break the resting period (dormancy) of potato tubers, making them sprout sooner.

These hormones play a vital role in plant growth and development.
In simple words: Gibberellins make plant stems grow longer, help certain plants make more male flowers, and make potato tubers sprout faster.

🎯 Exam Tip: Remember that gibberellins are often associated with stem elongation and breaking dormancy, crucial for plant development.

 

VIII. Long Answer Questions:

 

Question 1. Write the functions of thyroid hormones.
Answer: Thyroid hormones perform many crucial functions in the body:

1. They help the body produce energy by keeping the Basal Metabolic Rate (BMR) stable.
2. They assist in maintaining a normal body temperature, keeping us warm.
3. They affect how the central nervous system works, influencing brain activity.
4. They control body growth, bone development, and the growth of reproductive glands (gonads).
5. They are vital for normal physical, mental, and personality development, which is why they are sometimes called "personality hormones."
6. They regulate how cells use and convert substances, which is called cell metabolism.
7. They increase how much oxygen tissues use, affecting energy production.

These widespread effects show how important thyroid hormones are for overall health.
In simple words: Thyroid hormones help us make energy, keep our body warm, affect our brain, help us grow bones and reproductive organs, and are key for our mind and body development. They also control how our cells work.

🎯 Exam Tip: A comprehensive answer for thyroid hormones should always mention their role in BMR, growth, and nervous system development.

 

Question 2. List out the hormones secreted by Adenohypophysis of pituitary-Explain any two.
Answer: The adenohypophysis, which is the front part of the pituitary gland, secretes several important hormones. Here are some of them:

1. Growth Hormone (GH)
2. Thyroid-stimulating Hormone (TSH)
3. Adrenocorticotropic Hormone (ACTH)
4. Gonadotropic Hormones (including Follicle-Stimulating Hormone and Luteinizing Hormone)
5. Prolactin

Let's explain two of these:

• Thyroid-stimulating Hormone (TSH): This hormone manages the growth of the thyroid gland. It also makes sure the thyroid gland works correctly and releases its own hormones.
• Adrenocorticotropic Hormone (ACTH): ACTH tells the adrenal cortex (part of the adrenal gland) to make and release its hormones. It also plays a role in how proteins are made in the adrenal cortex.

These hormones are crucial for coordinating many body systems.
In simple words: The front part of the pituitary gland makes hormones like Growth Hormone, TSH, ACTH, and Prolactin. TSH helps the thyroid gland grow and work. ACTH tells the adrenal gland to make its hormones.

🎯 Exam Tip: When asked to explain two hormones, choose ones with distinct and clear functions to demonstrate broad knowledge of the adenohypophysis's role.

 

Question 3. Explain the testes and its functions.
Answer: The testes are the primary male reproductive glands. They contain seminiferous tubules, Leydig cells, and Sertoli cells. The Leydig cells act as the endocrine part of the testes, producing the main male sex hormone called testosterone.
Testosterone performs several key functions:

1. It is essential for spermatogenesis, which is the process of making sperm.
2. It encourages the body to make proteins and helps muscles grow bigger and stronger.
3. It is responsible for the development of male secondary sexual characteristics, such as body and facial hair growth, and a deeper voice.

The testes play a crucial role in reproduction and the development of male traits.
In simple words: Testes are male glands that make sperm and the hormone testosterone. Testosterone helps make sperm, builds muscles, and causes male body changes like facial hair and a deep voice.

🎯 Exam Tip: Clearly distinguish between the two main functions of the testes: gamete production (spermatogenesis) and hormone production (testosterone), and relate testosterone to secondary sexual characteristics.

 

Question 4. Write the physiological effects of cytokinin.
Answer: Cytokinins have several important effects on plant growth:

1. They cause cells to divide (cytokinesis), especially when auxins are also present.
2. They make plant cells grow larger.
3. Together with auxins, cytokinins are vital for creating new organs from undifferentiated cell clumps (callus) in tissue culture, a process called morphogenesis.
4. They help side buds (lateral buds) grow, even when the main top bud (apical bud) is trying to stop them.
5. Applying cytokinins can make plants age more slowly, keeping them fresh for longer. This effect is known as the Richmond-Lang effect.

These hormones are crucial for various aspects of plant development and vitality.
In simple words: Cytokinins help plant cells divide and grow larger. They work with auxins to make new plant parts and help side buds grow. They also slow down plant aging, keeping leaves fresh.

🎯 Exam Tip: Emphasize the interaction between cytokinins and auxins, as their balance often determines specific growth outcomes in plants.

 

IX. Higher Order Thinking Skills: (HOTS)

 

Question 1. You are given a tissue with its potential for differentiation in an artificial culture. Name the hormones to be added to the medium to secure shoots as well as roots.
Answer: To encourage a plant tissue in an artificial culture to develop both shoots and roots, the hormones gibberellin and abscisic acid should be added to the growth medium. Gibberellins promote shoot elongation, while abscisic acid helps regulate growth and development, often working to balance the growth of different plant parts.
In simple words: To grow both shoots and roots from plant tissue in a lab, you need to add gibberellin and abscisic acid hormones.

🎯 Exam Tip: In tissue culture, the ratio of auxins and cytokinins is key for shoot and root development, though gibberellins and abscisic acid also play regulatory roles.

 

Question 2. Insulin and thyroxine arrive at an organ at the same time. Thyroxine causes an effect on the organ but insulin does not. This is because:
Answer: Thyroxine affects the organ, but insulin does not, because the cells of that particular organ have specific receptors for thyroxine, allowing them to bind and respond to it. However, these cells lack the necessary receptors for insulin, meaning insulin cannot attach to them and therefore has no effect. Hormones only work on cells that have the right 'lock' for their 'key'.
In simple words: The organ's cells have special 'locks' for thyroxine, so it works. But they don't have the right 'locks' for insulin, so insulin has no effect there.

🎯 Exam Tip: Always remember the "receptor specificity" principle: hormones only exert effects on target cells that possess specific receptors for them.

 

Question 3. A person entering an empty room suddenly finds a snake right in front on opening the door. What changes happen in his neuro-hormonal control system?
Answer: When a person suddenly sees a snake, their body's neuro-hormonal control system reacts immediately by activating the sympathetic nervous system. This activation causes the adrenal medulla to quickly release stress hormones like epinephrine (adrenaline) and norepinephrine (noradrenaline). These hormones prepare the body for "fight or flight" by increasing heart rate, blood pressure, and energy.
In simple words: Seeing a snake makes the body's emergency system switch on. This causes the adrenal gland to release hormones like adrenaline, making the person ready to fight or run away.

🎯 Exam Tip: In emergency scenarios, always highlight the role of the sympathetic nervous system and the adrenal medulla's release of 'fight or flight' hormones.

 

Question 4. A pregnant female delivers a baby who suffers from stunted growth, mental retardation, low intelligence quotient and abnormal skin. This is the result of:
Answer: These severe symptoms in a newborn, including stunted growth, mental retardation, low intelligence, and abnormal skin, are a direct result of a deficiency of iodine in the mother's diet during pregnancy. Iodine is essential for the proper development of the baby's thyroid gland, which controls growth and brain development.
In simple words: The baby's problems with growth, intelligence, and skin are caused by the mother not having enough iodine in her food during pregnancy. Iodine is needed for the baby's brain and body to grow well.

🎯 Exam Tip: Emphasize the critical role of maternal iodine intake for fetal thyroid hormone production, which is vital for normal neurodevelopment.

 

Question 5. A patient of diabetes mellitus excretes glucose in urine even when he kept in a carbohydrate free diet. It is because:
Answer: A patient with diabetes mellitus will excrete glucose in their urine even on a carbohydrate-free diet because, without carbohydrates, the body starts breaking down fats (catabolism) to produce glucose for energy. Since the body cannot use this glucose properly due to insulin deficiency, it builds up in the blood and is then passed out through the urine.
In simple words: Even without eating carbs, a diabetic person might have sugar in their urine. This happens because their body breaks down fats to make glucose, and since they can't use it, the sugar comes out in their pee.

🎯 Exam Tip: This illustrates gluconeogenesis from fats and proteins when carbohydrate intake is insufficient, a common compensatory mechanism in uncontrolled diabetes.

 

Question 6. Dr. F went noted that if Coleoptile tips were removed and placed on agar for one hour, the agar would produce a bending when placed on one side of freshly cut coleoptile stumps. What is the significance of this experiment.
Answer: This experiment, often attributed to F.W. Went, was significant because it proved that a chemical substance, later identified as auxin, is produced by the coleoptile tip and moves downwards. The bending of the stump when the agar block (containing auxin) was placed on one side showed that auxin's movement is polar (directional) and that it causes cells to elongate, leading to growth responses.
In simple words: This experiment showed that a growth chemical called auxin is made at the plant tip and moves downwards. This chemical then makes the plant bend and grow.

🎯 Exam Tip: The Went experiment is a classic demonstration of auxin's role in phototropism and its polar transport. Mentioning these terms adds depth to your answer.