Students can download 10th Science Chapter 16 Plant and Animal Hormones Questions and Answers, Notes, Samacheer Kalvi 10th Science Guide Pdf helps you to revise the complete Tamilnadu State Board New Syllabus, helps students complete homework assignments and to score high marks in board exams.

Tamilnadu Samacheer Kalvi 10th Science Solutions Chapter 16 Plant and Animal Hormones

Samacheer Kalvi 10th Science Plant and Animal Hormones Text Book Back Questions and Answers

I. Choose the correct answer:

Question 1.
Gibberellins cause:
(a) Shortening of genetically tall plants
(b) Elongation of dwarf plants
(c) Promotion of rooting
(d) Yellowing of young leaves
Answer:
(b) Elongation of dwarf plants

Question 2.
The hormone which has a positive effect on apical dominance is _____.
(a) Cytokinin
(b) Auxin
(c) Gibberellin
(d) Ethylene.
Answer:
(b) Auxin

Question 3.
Which one of the following hormones is naturally not found in plants:
(a) 2, 4-D
(b) GA3
(c) Gibberellin
(d) IAA
Answer:
(a) 2, 4-D

Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones

Question 4.
Avena coleoptile test was conducted by _____.
(a) Darwin
(b) N. Smit
(c) Paal
(d) F.W. Went.
Answer:
(d) F.W. Went.

Question 5.
To increase the sugar production in sugarcanes they are sprayed with
(a) Auxin
(b) Cytokinin
(c) Gibberellins
(d) Ethylene
Answer:
(d) Ethylene

Question 6.
LH is secreted by _____.
(a) Adrenal gland
(b) Thyroid gland
(c) Anterior pituitary
(d) Hypothalamus.
Answer:
(c) Anterior pituitary

Question 7.
Identify the exocrine gland:
(a) Pituitary gland
(b) Adrenal gland
(c) Salivary gland
(d) Thyroid gland
Answer:
(c) Salivary gland

Question 8.
Which organ acts as both exocrine gland as well as endocrine gland?
(a) Pancreas
(b) Kidney
(c) Liver
(d) Lungs.
Answer:
(a) Pancreas

Question 9.
Which one is referred to as “Master Gland”?
(a) Pineal gland
(b) Pituitary gland
(c) Thyroid gland
(d) Adrenal gland
Answer:
(b) Pituitary gland

II. Fill in the blanks:

  1. ………. causes cell elongation, apical dominance and prevents abscission.
  2. …………. is a gaseous hormone involved in abscission of organs and acceleration of fruit ripening.
  3. ……… causes stomatal closure.
  4. Gibberellins induce stem elongation in ……… plants.
  5. The hormone which has negative effect on apical dominance is ………
  6. Calcium metabolism of the body is controlled by ………
  7. In the islets of Langerhans, beta cells secrete ………
  8. The growth and functions of thyroid gland is controlled by ………..
  9. Decreased secretion of thyroid hormones in the children leads to ………

Answer:

  1. Auxin
  2. Ethylene
  3. Abscisic acid
  4. Rosette
  5. Ethylene
  6. Parathormone
  7. Insulin
  8. Thyroid Stimulating Hormone (TSH)
  9. Cretinism

Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones

III. Match Column I with Columns II and III

Question 1
Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones 1
Answer:
Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones 2

Question 2.
Match the following hormones with their deficiency states.
Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones 3
Answer:
A. (iii)
B. (v)
C. (ii)
D. (i)
E. (iv)

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

  1. A plant hormone concerned with stimulation of cell division and promotion of nutrient mobilization is cytokinin.
  2. Gibberellins cause parthenocarpy in tomato.
  3. Ethylene retards senescence of leaves,flowers and fruits.
  4. Exopthalmic goiter is due to the over secretion of thyroxine.
  5. Pituitary gland is divided into four lobes.
  6. Oestrogen is secreted by corpus luteum.

Answer:

  1. True
  2. True
  3. False – Ascorbic Acid retards senescence of leaves, flowers and fruits.
  4. True
  5. False – Parathyroid gland is divided into four lobes.
  6. False – Oestrogen is produced by the Graffian follicles.

V. Assertion and Reasoning:

Direction: In each of the following questions a statement of assertion (A) is given and a corresponding statement of reason (R) is given just below it. Mark the correct statement as.
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

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

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

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.

Question 2.
Write the name of synthetic auxin.
Answer:
2, 4 D (2, 4 Dichlorophenoxy Acetic acid).

Question 3.
Which hormone induces parthenocarpy in tomatoes?
Answer:
Gibberellin induces parthenocarpy in tomatoes.

Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones

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.

Question 5.
Name the hormones which regulates water and mineral metabolism in man.
Answer:
Mineralocorticoids hormones of Adrenal cortea maintain the water balance and mineral metabolism in man.

Question 6.
Which hormone is secreted during an emergency situation in a man?
Answer:
The hormones of Adrenal medulla,

  • Epinephrine (Adrenaline)
  • Norepinephrine (Noradrenaline) are secreted during an emergency situation in man.

Question 7.
Which gland secretes digestive enzymes and hormones?
Answer:
Pancreas secretes digestive enzymes and hormones.

Question 8.
Name the endocrine glands associated with kidneys.
Answer:
Adrenal gland, which is called suprarenal glands is associated with kidneys.

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

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.

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.

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.

Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones

Question 5.
What are chemical messengers?
Answer:
Endocrine glands control and coordinate the body functions through secreting certain chemical messengers called hormones.

Question 6.
Write the differences between endocrine and exocrine gland.
Answer:
Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones 4

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.

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.

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.

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.

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, eg. 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.

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.
Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones 5
In his first experiment he removed the tips of Avena coleoptiles. The cut tips did not grow indicating that the tips produced something essential for growth.In his second experiment he placed the agar blocks on the decapitated coleoptile tips. The coleoptile tips did not show any response. In his next experiment he placed the detached coleoptile tips on agar blocks. After an hour, he discarded the tips and placed this agar block on the decapitated coleoptile. It grew straight up indicating that some chemical had diffused from the cut coleoptile tips into the agar block which stimulated the growth.

From his experiments went concluded that a chemical diffusing from the tip of coleoptiles was responsible for growth and he named it as “Auxin” meaning “to grow”.

Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones

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

  • Application of gibberellins on plants stimulates extraordinary elongation of internodes. eg. Com and Pea.
  • Treatment of rosette plants with gibberellin induces sudden shoot elongation followed by flowering, called bolting.
  • Gibberellins promote the production of male flowers in monoecious plants like Cucurbits
  • Gibberellins break the dormancy of potato tubers.
  • Gibberellins is inducing the formation of seedless fruit, termed as Parthenocarpic fruits (Development of fruits without fertilization) eg. Tomato.

Question 4.
Where are oestrogens produced? What is the role of oestrogens in the human body?
Answer:
Oestrogen is produced by the Graafian follicles of the ovary.
Functions of oestrogens:

  1. It brings about the changes that occur during puberty.
  2. It initiates the process of oogenesis.
  3. It stimulates the maturation of ovarian follicles in the ovaiy.
  4. It promotes the development of secondary sexual characters (breast development, high pitched voice etc).

Question 5.
What are the conditions which occur due to lack of ADH and insulin? How are the conditions different from one another?
Answer:
Lack of ADH: Deficiency of ADH (Antidiuretic hormone) reduces the reabsorption of water and causes an increase in urine output (polyuria). This deficiency disorder is called Diabetes insipidus.
Lack of insulin: The deficiency of insulin causes Diabetes mellitus. It is characterised by,

  • Increase in blood sugar level (Hyperglycemia).
  • Excretion of excess glucose in the urine (Glycosuria).
  • Frequent Urination (Polyuria).
  • Increased thirst (Polydipsia).
  • Increase in appetite (Polyphagia).

Lack of ADH reduces the reabsorption of water and increases the urine output. Lack of insulin causes the Diabetes mellitus, which increases the blood sugar level and excrete the excess glucose in the urine, causing frequent urination.

Insulin:
Deficiency in insulin causes Diabetes mellitus.
Insulin deficiency increase the blood sugar level (Hyperglycemia), excretion of excess glucose in the urine (Glycosuria), frequent urination (Polyuria) increased thirst (Polydipsia), increase in appetite (Polyphagia).

IX. Higher Order Thinking Skills: (HOTS)

Question 1.
What would be expected to happen if
(a) Gibberellin is applied to rice seedlings.
Answer:
Causes imemodal elongation in rice.

(b) A rotten fruit gets mixed with unripe fruits.
Answer:
If a rotten fruits get mixed with unripe fruit. Then the ethylene produced from the rotten fruit will hasten the ripening of the unripe fruits.

(c) When cytokinin is not added to culture medium.
Answer:
Formation of new organs from the callus in tissue culture (Morphogenesis) will not be formed.

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. Gibberellins
  2. Intermodal elongation
  3. Functions:
    • promotes the production of male flowers in monoecious plants.
    • Gibberellins break the dormancy of potato tubers.

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 gland involved is the thyroid gland. The hormone involved in a thyroid hormone. It is due to excess secretion of thyroid hormones called hyperthyroidism which leads to Graver’s disease.

Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones

Question 4.
Sanjay is sitting in the exam hall. Before the start of the exam, he sweats a lot, with an increased rate of heartbeat. Why does this condition occur?
Answer:
This is due to the secretion of the hormone Adrenaline in Adrenal medulla of Adrenal gland.

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:
A balance between insulin and glucogon production is necessary to maintain blood glucose concentration.
The deficiency of insulin causes Diabetes Mellitus.
Preventive measure:

  1. Take proper or balanced diet.
  2. Exercise regularly
  3. Avoid stress.

Samacheer Kalvi 10th Science Plant and Animal Hormones 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

Question 2.
Plant hormones are;
(a) Growth regulators
(b) Growth promoters
(c) Growth inhibitors
(d) None of the above
Answer:
(a) Growth regulators

Question 3.
Pick out the hormone which maintain mineral metabolism.
(a) Parathormone
(b) Thymosin
(c) Thyroxine
(d) Melatonin
Answer:
(a) Parathormone

Question 4.
Among the following, which one is attached to the hypothalamus.
(a) Pineal
(b) Pituitary
(c) Thymus
(d) Thyroid
Answer:
(b) Pituitary

Question 5.
Stem elongation affected by:
(a) Gibberellin and Florigen
(b) Florigen and Kinn
(c) Kinn and Auxin
(d) Auxin and Gibberellin
Answer:
(d) Auxin and Gibberellin

Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones

Question 6.
Which of the following is not natural occuring plant hormone?
(a) 2, 4-D
(b) Cytokinin
(c) Gibberellin
(d) IAA
Answer:
(a) 2, 4-D

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

Question 8.
Indole acetic add generally inhibits the growth of:
(a) Root
(b) Leaves
(c) Shoots
(d) Plants in general
Answer:
(a) Root

Question 9.
Hormones are chemically:
(a) Amino acid
(b) Protein
(c) Steroid
(d) All
Answer:
(d) All

Question 10.
Pituitary gland is under the control of:
(a) Hypothalamus
(b) Adrenal gland
(c) Pineal gland
(d) Thyroid
Answer:
(a) Hypothalamus

Question 11.
Hypothyroidism in adults causes:
(a) Addison’s disease
(b) Myxoedema
(c) Sterility
(d) Cretinism
Answer:
(b) Myxoedema

Question 12.
Parathormone deficiency in man causes:
(a) Hyper calcaemia
(b) Hypo calcaemia
(c) Goitre
(d) All
Answer:
(b) Hypo calcaemia

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

Question 14.
Adrenalin increases:
(a) Heart beat
(b) Blood pressure
(c) Both (a) and (b)
(d) None
Answer:
(c) Both (a) and (b)

Question 15.
Hormone responsible for ovulation is:
(a) LH
(b) GSH
(c) Progesterone
(d) Testosterone
Answer:
(a) LH

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

Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones

Question 17.
The islets of Langerhans are found in:
(a) Pancreas
(b) Stomach
(c) Liver
(d) Alimentary canal
Answer:
(a) Pancreas

II. Fill in the blanks:

1. Gibbereilin promotes cell division and elongation in ………, ………. and ………
2. Abscisic acid controls ……….
3. ………. is called as ‘Master gland’ of the body.
4. Growth hormone is produced in …………
5. Urine concentration is controlled by …………
6. The two lobes of thyroid glands are joined by horizontal connection called …………
7. Insulin are secreted by ……….. cells.
8. Progesterone maintains ……….. pregnancy.
9. The normal blood glucose level is ………… mg/100 ml of blood.
10. ………… converts glycogen into glucose.
11. ………… is responsible for growth of female reproductive organs.
12. Anti-inflammatory hormone is ……….
13. ……….. hormone stimulates the growth of mammary gland.
14. …….. helps in reabsorption of water.
15. Endocrine glands are ………. glands.
Answer:
1. Roots, stem and leaves
2. Leaf fall and dormancy
3. Pituitary
4. Pituitary
5. ADH
6. isthumus
7. Beta
8. normal
9. 80 – 120
10. Glucogon
11. oestrogen
12. Cortisone
13. LTH
14. Oxytocin
15. duct less

III. Match the following:

Question 1.
Match the Column I with Column II.
Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones 6
Answer:
A. (iii)
B. (i)
C. (ii)
D. (iv)
E. (v)

Question 2.
Match the Column I with Column II.
Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones 7
Answer:
A. (iii)
B. (v)
C. (ii)
D. (i)
E. (iv)

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

  1. Bakacae disease or Foolish seedling disease in cucurbits.
  2. Synthesis of ethylene occurs during ripening of fruits.
  3. The secretion of Neurohypophysis are secretions of part of only pituitary.
  4. Excess production of GH in children result in dwarfism.
  5. Cortisone stimulates the breakdown of glycogen into glucose.

Answer:

  1. False – Bakacae disease or Foolish seedling disease in rice
  2. True
  3. False – The secretion of Neurohypophysis are secretions of part of the nervous system.
  4. False – Excess production of GH in children result in Gigantism.
  5. True

V. Assertion and Reasoning:

Direction: In each of the following questions a statement of assertion (A) is given and a corresponding statement of reason (R) is given just below it. Mark the correct statement as.
Question 1.
Assertion (A): Ethylene is a plant hormone, which can transfer from one plant to another plant.
Reason (R): Ethylene is a gaseous hormones in plants.
(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.

Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones

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.

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.

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.

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.

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.

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.

Question 8.
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.

Question 9.
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.

Question 10.
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.

VI. Answer in a word or sentence:

Question 1.
What is apical dominance?
Answer:
The auxins produced by the apical buds suppress the growth of lateral bud is called apical dominance.

Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones

Question 2.
Name the types of Auxins.
Answer:

  • Natural Auxins – The Auxins produced by plants.
  • Synthetic Auxins – Artificially synthesized auxins.

Question 3.
Write the chemical composition of thyroxine?
Answer:
Thyroxine is an iodinated protein, composed of the amino acid, tyrosine and iodine.

Question 4.
When does the maximum synthesis of ethylene occur?
Answer:
Maximum synthesis of ethylene occurs during the ripening of fruits like apples, bananas and melons.

Question 5.
In which condition the excess of dilute urine is produced? Name the disease.
Answer:
Due to less production of ADH, excess of dilute urine is produced, it causes diabetes insipidus.

Question 6.
Name the two distinct parts of adrenal.
Answer:
Adrenal cortex and adrenal medulla.

Question 7.
What are the target organs?
Answer:
The hormones, which are produced in minute quantities, act on specific organs which are called as target organs.

VII. Short Answer Questions:

Question 1.
Name the layers of the adrenal cortex.
Answer:
The adrenal cortex consists of three layers of cells called zono glomerulosa, zona fasciculata and zona reticularis.

Question 2.
Write any three physiological effects of Auxins.
Answer:

  • Auxins promote the elongation of stems and coleoptiles.
  • Auxins prevent the formation of abscission layer.
  • Auxins induce root formation at low concentration and inhibit it at higher concentration.

Question 3.
Which hormone is called as life-saving hormone? Why?
Answer:
The cortisol hormones is called as life saving hormone. The cortisol hormones of adrenal cortex serves to maintain the body in living condition and recover it from the severe effects of stress reaction. Thus an increased output of cortisol is life saving in shock conditions.

Question 4.
Name the endocrine glands present in human and other vertebrates.
Answer:

  • Pituitary gland
  • Thyroid gland
  • Parathyroid gland
  • Pancreas (Islets of Langerhans)
  • Adrenal gland (Adrenal cortex and Adrenal medulla)
  • Gonads (Testes and Ovary)
  • Thymus gland.

Question 5.
Write the functions of thymosin.
Answer:

  1. It has a stimulatory effect on the immune function.
  2. It stimulates the production and differentiation of lymphocytes.

Question 6.
Which endocrine gland is called “Master gland”? Why?
Answer:
Pituitary gland. The pituitary gland forms the major endocrine gland in most vertebrates. It regulates and controls other endocrine glands and so it is called “Master gland”.

Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones

Question 7.
Differentiate Hyperglycemia and Hypoglycemia.
Answer:
Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones 8

Question 8.
Write any three physiological effects of Gibberellins.
Answer:

  • Elongation of internodes.
  • Promote the production of male flowers in monoecious plants.
  • Break dormancy of potato tubers.

VIII. Long Answer Questions:

Question 1.
Write the functions of thyroid hormones.
Answer:
The functions of thyroid hormones are:

  1. Production of energy by maintaining the Basal Metabolic Rate (BMR) of the body.
  2. Helps to maintain normal body temperature.
  3. Influences the activity of the central nervous system.
  4. Controls growth of the body and bone formation and development of gonads.
  5. Essential for normal physical, mental and personality development. It is also known as personality hormone.
  6. Regulates cell metabolism.
  7. Increases oxygen consumption in tissues.

Question 2.
List out the hormones secreted by Adenohypophysis of pituitary-Explain any two.
Answer:

  1. Growth Hormone
  2. Thyroid-stimulating Hormone
  3. Adrenocorticotropic Hormone
  4. Gonadotropic Hormone which comprises the Follicle Stimulating Hormone and Luteinizing Hormone
  5. Prolactin

Thyroid-stimulating hormone (TSH) : TSH controls the growth of thyroid gland, coordinates its activities and hormone secretion.

Adrenocorticotropic hormone (ACTH) : ACTH stimulates adrenal cortex of the adrenal gland for the production of its hormones. It also influences protein synthesis in the adrenal cortex.

Question 3.
Explain the testes and its functions.
Answer:
Testes are the reproductive glands of the males. They are composed of ‘ seminiferous tubules, leydig cells and sertoli cells. Leydig cells form the endocrine part of the testes. They secrete the male sex hormone called testosterone.
Functions of testosterone:

  1. It influences the process of spermatogenesis.
  2. It stimulates protein synthesis and controls muscular growth.
  3. It is responsible for the development of secondary’ sexual characters (distribution of hair on body and face, deep voice pattern, etc).

Question 4.
Write the physiological effects of cytokinin.
Answer:

  1. Cytokinin induces cell division (cytokinesis) in the presence of auxins.
  2. Cytokinin also causes cell enlargement.
  3. Both auxins and cytokinins are essential for the formation of new organs from the callus in tissue culture (Morphogenesis).
  4. Cytokinins promote the growth of lateral buds even in the presence of apical bud.
  5. Application of cytokinin delays the process of ageing in plants. This is called Richmond Lang effect.

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:
The hormones to be added to the medium are gibberellin and abscisic acid.

Samacheer Kalvi 10th Science Guide Chapter 16 Plant and Animal Hormones

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:
The organ’s cells have receptors for thyroxine but not for insulin.

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:
Sympathetic nervous system is activated releasing epinephrin and norepinephrine from adrenal medulla.

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:
Deficiency of iodine in diet.

Question 5.
A patient of diabetes mellitus excretes glucose in urine even when he kept in a carbohydrate free diet. It is because:
Answer:
Fats are catabolised to form glucose.

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:
The experiment demonstrated the polar movement of Auxin.