Samacheer Kalvi 10th Science Solutions Chapter 16 Pdf
Tamilnadu Board Samacheer Kalvi 10th Science Solutions Chapter 16: Tamilnadu State Board Solution Class 10 Science Chapter 16 – Plant and animal Hormones.
Samacheer Kalvi 10th Science Solutions Chapter 16: Overview
Board |
Samacheer Kalvi |
Class |
10 |
Subject |
Science |
Chapter |
16 |
Chapter Name |
Plant and animal Hormones |
Samacheer Kalvi 10th Science Solutions Chapter 16 Plant and animal Hormones
I) choose the correct answer
1.) Gibberellins cause:
a) Shortening of genetically tall plants
b) Elongation of dwarf plants
c) Promotion of rooting
d) Yellowing of young leaves
Ans:c) Promotion of rooting
Because, gibberellins causes promotion of rooting.
2.) The hormone which has positive effect on apical dominance is:
a) Cytokinin
b) Auxin
c) Gibberellin
d) Ethylene
Ans:b) Auxin
Because, the auxin produced by the apical buds suppress growth of lateral buds which is called as apical dominance.
3.) Which one of the following hormones is naturally not found in plants?
a) 2, 4-D
b) GA3
c) Gibberellin
d) IAA
Ans:a) 2, 4-D
Because, 2, 4 – D is the synthetic auxin.
4.) Avena coleoptile test was conducted by
a) Darwin
b) N. Smit
c) Paal
d) F.W. Went
Ans:d) F.W. Went
Because, F. W. Went demonstrated an experiment for the Avena coleoptile test.
5.) To increase the sugar production in sugarcanes they are sprayed with _______
a) Auxin
b) Cytokinin
c) Gibberellins
d) Ethylene
Ans:d) Ethylene
6.) LH is secreted by
a) Adrenal gland
b) Thyroid gland
c) Anterior pituitary
d) Hypothalamus.
Ans:c) Anterior pituitary
Because, LH i.e. luteinizing hormone is secreted by the anterior lobe adenohypophysis of pituitary gland.
7.) Identify the exocrine gland
a) Pituitary gland
b) Adrenal gland
c) Salivary gland
d) Thyroid gland
Ans:c) Salivary gland
Because, salivary gland, mammary gland and sweat glands are exocrine glands.
8.) Which organ acts as both exocrine gland as well as endocrine gland?
a) Pancreas
b) Kidney
c) Liver
d) Lungs
Ans:a) Pancreas
Because. Pancreas is exocrine and endocrine in nature.
9.) Which one is referred as “Master Gland”?
a) Pineal gland
b) Pituitary gland
c) Thyroid gland
d) Adrenal gland
Ans:b) Pituitary gland
Because, pituitary gland regulates and control the other endocrine glands hence it is called as Master Gland.
II Fill in the blanks
1) _________ causes cell elongation, apical dominance and prevents abscission.
Ans:Auxincauses cell elongation, apical dominance and prevents abscission.
2) _________ is a gaseous hormone involved in abscission of organs and acceleration of fruit ripening.
Ans: Ethyleneis a gaseous hormone involved in abscission of organs and acceleration of fruit ripening.
3) _________ causes stomatal closure.
Ans:Abscisic acidcauses stomatal closure.
4) Gibberellins induce stem elongation in _________ plants.
Ans: Gibberellins induce stem elongation inCorn and Pea plants.
5) The hormone which has negative effect on apical dominance is _________.
Ans: The hormone which has negative effect on apical dominance isCytokinin.
6) Calcium metabolism of the body is controlled by _________.
Ans:Calcium metabolism of the body is controlled byParathormone.
7) In the islets of Langerhans, beta cells secrete _________.
Ans:In the islets of Langerhans, beta cells secreteInsulin.
8) The growth and functions of thyroid gland is controlled by _________.
Ans:The growth and functions of thyroid gland is controlled by hormone T3 and T4.
9) Decreased secretion of thyroid hormones in the children leads to _________.
Ans:Decreased secretion of thyroid hormones in the children leads to Cretinism.
III) Match the following.
a) Match the column I with column II and column III
Ans:
a.) Auxin: Coleoptile tip: Apical dominance
b.) Ethylene: Fruits: Ripening
c.) Abscisic acid: Chloroplast: Abscission
d.) Cytokinin: Coconut milk: Cell division
e.) Gibberellins: Gibberellafujikuroi: Intermodal elongation
b) Match the following hormones with their deficiency states.
Ans:
1) Thyroxine: Simple goitre
2) Insulin: Diabetes mellitus
3) Parathormone: Tetany
4) Growth hormone: Acromegaly
5) ADH: Diabetes insipidus
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.
Ans:True
2) Gibberellins cause parthenocarpy in tomato.
Ans:True
3) Ethylene retards senescence of leaves, flowers and fruits.
Ans:False
Correct statement: Ethylene hastens the senescence of leaves, flowers and fruits.
4) Exopthalmic goiter is due to the over secretion of thyroxine.
Ans:True
5) Pituitary gland is divided into four lobes.
Ans:False
Correct statement: The pituitary gland is composed of two lobes.
6) Estrogen is secreted by corpus luteum.
Ans:False
Correct statement: Estrogen is produced by the Graafian follicles of the ovary.
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.
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
1.) Assertion: Application of cytokinin to marketed vegetables can keep them fresh for several days.
Reason: Cytokinins delay senescence of leaves and other organs by mobilisation of nutrients.
Ans:d. Both A and R are false
2.) Assertion (A): Pituitary gland is referred as “Master gland”.
Reason (R): It controls the functioning of other endocrine glands.
Ans:a. if both A and R are true and R is correct explanation of A
3.) Assertion (A): Diabetes mellitus increases the blood sugar levels.
Reason (R): Insulin decreases the blood sugar levels.
Ans: a. if both A and R are true and R is correct explanation of A
- VI) Answer in a word or sentence
1) Which hormone promotes the production of male flowers in Cucurbits?
Ans: Gibberellins promote the production of male flowers in cucurbits.
2) Write the name of a synthetic auxin.
Ans: Artificially synthesized auxins which are having properties like auxins are called as synthetic auxins. 2, 4 Dichlorophenoxy Acetic acid is the example of synthetic auxins.
3) Which hormone induces parthenocarpy in tomatoes?
Ans: Gibberellins are more efficient in inducing the formation of seedless fruits i.e. parthenocarpic fruit in tomatoes.
4) What is the hormone responsible for the secretion of milk in female after child birth?
Ans: Prolactin which is also called as lactogenic hormone initiates the development of mammary glands during pregnancy and stimulates the production of milk after birth of the child.
5) Name the hormones which regulates water and mineral metabolism in man.
Ans:Vasopressin or anti-diuretic hormone regulates the water and mineral metabolism in man.
6) Which hormone is secreted during emergency situation in man?
Ans: Adrenaline and Noradrenaline are the hormones secreted during emergency situation in man.
7) Which gland secretes digestive enzymes and hormones?
Ans: Pancreas is exocrine and endocrine in nature. The exocrine pancreas secretes pancreatic juice which plays a role in digestion while the endocrine portion is made from Islets of Langerhans which secrets hormones.
8) Name the endocrine glands associated with kidneys.
Ans: Adrenal glands are associated with kidney which are located above each kidney.
VII) Short answer questions
1) What are synthetic auxins? Give examples.
Ans:
- Artificially synthesized auxins which are having properties like auxins are called as synthetic auxins.
- For example: 2, 4 Dichlorophenoxy Acetic acid is the synthetic auxin.
2) What is bolting? How can it be induced artificially?
Ans:
When the rosette plants are treated with gibberellins, then it induces sudden shoot elongation which is followed by flowering and this process is called as bolting.
3) Bring out any two physiological activities of abscisic acid
Ans:
Following are the physiological activities of abscisic acid.
- During water stress and draught condition, abscisic acid causes to close the stomata.
- By causing loss of chlorophyll ABA promotes senescene in leaves.
- In the trees like birch ABA induces bud dormancy towards the approach of winter.
- In tomato, ABA acts as a powerful inhibitor of lateral bud growth.
4) What will you do to prevent leaf fall and fruit drop in plants? Support your answer with reason.
Ans:
Auxin prevents the formation of abscission layer that means it prevents the leaf fall and fruit drop in plants.
5) What are chemical messengers?
Ans:
Chemical messengers are the any compounds which serves to transmit a message. The endocrine system acts through the chemical messengers called as hormones which are produced by specialized glands.
6) Write the differences between endocrine and exocrine gland.
Ans:
- Endocrine glands found in different regions of the body of animals as well as in the human beings. These glands are called as ductless glands and their secretion is called as hormones.
- Exocrine glands are having specific ducts to carry their secretions.
- For example: The endocrine glands in human being are pituitary gland, thyroid gland, parathyroid gland etc.
- The exocrine glands secrets juices which plays a role in digestion.
- For example: Salivary glands, mammary glands, sweat glands etc.
7) What is the role of parathormone?
Ans:
- The secretion of parathyroid gland is called as parathormone.
- It regulates calcium and phosphorus metabolism in the body and also by acting on bone, kidney and intestine maintains the blood calcium levels.
8) What are the hormones secreted by posterior lobe of the pituitary gland? Mention the tissues on which they exert their effect.
Ans:
- The hormones secreted by the posterior lobe neurohypophysis of pituitary gland are vasopressin or anti-diuretic hormone and oxytocin.
- In the tubules of kidney, vasopressin increases the reabsorption of water and thereby reduces the loss of water through urine.
- Oxytocin helps in contracting the smooth muscles of uterus at the time of child birth and helps in ejecting milk from mammary gland after child birth.
9) Why are thyroid hormones referred as personality hormone?
Ans:
- Thyroid hormone maintains body temperature, controls body growth and bone formation and also influences the activities of central nervous system.
- Thyroid hormone is essential for physical, mental and personality development.
- Because of these above all reasons, thyroid hormone is also called as personality hormone.
10) Which hormone requires iodine for its formation? What will happen if intake of iodine in our diet is low?
Ans:
- An amino acid tyrosine and iodine are required for the formation of thyroid hormone.
- The hormones secreted by the thyroid gland which requires tyrosine and iodine for their formation are Triiodothyronine, Tetraiodothyronine.
- If the intake of iodine in our diet is low, then it causes goiter. Due to which thyroid gland becomes enlarged and protrude as a marked swelling in the neck which is called as goiter.
VIII.) Long answer questions
1) (a) Name the gaseous plant hormone. Describe its three different actions in plants.
Ans:
- Ethylene is a gaseous plant hormone which inhibits the growth.
- The physiological effects of ethylene are as follows.
- It promotes the ripening of fruits.
- For example: Tomato, Apple, Mango, Banana etc.
- The elongation of stem and root in dicot is inhibited by ethylene.
- The premature shedding caused due to the stimulation by ethylene for the formation of abscission zone in leaves, flowers and fruits.
- The dormancy of buds, seeds and storage organs is broken by ethylene.
(b) Which hormone is known as stress hormone in plants? Why?
Ans:
- Abscisic acid in plants is called as stress hormone because it inhibits the growth which regulates abscission and dormancy.
- Also it increases tolerance of plants to various kinds of stress.
- It is found in the chloroplast of plants, and because of the above all reasons abscisic acid in plants is called as stress hormone.
(2) Describe an experiment which demonstrates that growth stimulating hormone is produced at the tip of coleoptile.
Ans:
- Frits Warmolt Went, a Dutch biologist demonstrated an experiment which concludes that growth stimulating hormone is produced at the tip of coleoptile.
- He did the experiment in Avena coleoptile. In his experiment, he removed the tips of Avena coleoptile indicating that the cutted tips did not grow and hence something is required for tips growth and it is present only at the tips.
- In his next experiment, he placed the agar blocks on the decapitated coleoptile tips and observed that coleoptile tips did not showed any response.
- Then in his next experiment, he placed the detached coleoptile tips on agar blocks and after an hour he removed the tips and placed this agar block on the decapitated coleoptile. And he observed that, the tip grew straight up which shows that there were some chemical which get diffused from cuted coleoptile tips into the agar block and hence stimulated the growth.
- From this experiment, Went concludes that there is a chemical diffusing from tip of the coleoptile which is responsible for growth and he named it as Auxins which means to grow.
- The following figure shows the Went experimental demonstration.
(3) Write the physiological effects of gibberellins.
Ans:
Following are the physiological effects of gibberellins.
- By applying gibberellins on plants, it stimulates the extraordinary elongation of internode.
- For example: Corn and Pea
- When rosette plants are treated with gibberellins then it induces sudden shoot elongation which is followed by flowering. And this process is called bolting.
- Also, gibberellins promotes the production of male flowers in cucurbits.
- The dormancy of potato tuber is broken by gibberellins.
- Gibberellins induces the formation of seedless fruits i.e. parthenocarpic fruits, since gibberellins are more efficient than auxins.
- For example: tomatoes
(4) Where are estrogens produced? What is the role of estrogens in the human body?
Ans:
- Estrogen is the female sex hormone produced by the Graafian follicles of the ovary.
- The role of estrogen in human body is as follows.
- The changes occurring in puberty are brought by the hormone estrogen.
- The process of oogenesis is also initiated by estrogen.
- The maturation of ovarian follicles in the ovary is stimulated by estrogen.
- Development of secondary sexual characters like breast development, high pitched voice is also promoted by estrogen.
(5) What are the conditions which occur due to lack of ADH and insulin? How are the conditions different from one another?
Ans:
- The deficiency of ADH reduces the reabsorption of water and causes an increase in urine output which is called as polyuria. This deficiency is called Diabetes insipidus.
- While insulin is needed for moving blood sugar into the cells throughout the body. The deficiency in insulin causes to leave more sugar in the blood and not provided to the cells for energy and leads to Diabetes mellitus.
IX) Higher Order Thinking Skills (HOTS)
(1) What would be expected to happen if?
Ans:
a) Gibberellin is applied to rice seedlings.
When gibberellin is applied to rice seedlings, the intermodal elongation in rice will be occurs.
b) A rotten fruit gets mixed with unripe fruits.
If a rotten fruit gets mixed with unripe fruits then ethylene created from the rotten fruit may hasten the ripening of unripe fruits.
c) When cytokinin is not added to culture medium
Cytokinin is responsible for cell division, growth and differentiation. If cytokinin is not added to culture medium then cell division, growth and differentiation will not takes place.
2) A plant hormone was first discovered in Japan when rice plants were suffering from Bakanae disease caused by Gibberellafujikoroi. Based on this information answer the following questions:
Ans:
a.) Identify the hormone involved in this process.
The hormone involved in this process is Gibberellins.
b.) Which property of this hormone causes the disease?
The intermodal elongation due to gibberellin causes the disease.
c) Give two functions of this hormone.
It promotes the production of male flowers in cucurbits.
It breaks the dormancy of potato tubers.
3.) Senthil has high blood pressure, protruded eyeball and an increased body temperature. Name the endocrine gland involved and hormone secretion responsible for this condition.
Ans:
- The endocrine gland involved is thyroid gland and the hormones are tetraiodothyronine and triiodothyronine.
- The excess secretion of thyroid hormones T3 and T4 causes Grave’s disease. And the symptoms are protrusion of the eyeballs, increased metabolic rate, high body temperature, profuse sweating, loss of body weight and nervousness.
4) Sanjay is sitting in the exam hall. Before the start of the exam, he sweats a lot, with increased rate of heart beat. Why does this condition occur?
Ans:
- It is caused due to the hormone secretion epinephrine and norepinephrine by the adrenal medulla.
- This hormones are called as emergency hormones because they are produced during the condition of stress and emotion. Hence they are also referred as flight, fright and fight hormones.
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.
Ans:
The deficiency of insulin causes the diabetes mellitus which is due to the increase in blood sugar level. The doctor was advised to take to take injection daily because insulin converts glucose into glycogen and stores in liver. Due to which the sugar level in the blood is regulated.
The preventions for this are exercise regularly, balanced diet daily etc.