| # | Statement (Answer in bold) |
|---|---|
| 1 | Auxin causes cell elongation, apical dominance and prevents abscission. |
| 2 | Ethylene is a gaseous hormone involved in abscission of organs and acceleration of fruit ripening. |
| 3 | Abscisic acid (ABA) causes stomatal closure. |
| 4 | Gibberellins induce stem elongation in rosette plants. |
| 5 | The hormone which has negative effect on apical dominance is cytokinin. |
| 6 | Calcium metabolism of the body is controlled by parathormone. |
| 7 | In the islets of Langerhans, beta cells secrete insulin. |
| 8 | The growth and functions of thyroid gland is controlled by thyroid stimulating hormone. |
| 9 | Decreased secretion of thyroid hormones in the children leads to cretinism. |
| 1 | A plant hormone concerned with stimulation of cell division and promotion of nutrient mobilization is cytokinin. - True |
| 2 | Gibberellins cause parthenocarpy in tomato. - True |
| 3 | Ethylene retards senescence of leaves, flowers and fruits. - False |
| 4 | Exopthalmic goiter is due to the over secretion of thyroxine. - True |
| 5 | Pituitary gland is divided into four lobes. - False |
| 6 | Estrogen is secreted by corpus luteum. - False |
Answer: a. Both A and R are true and R is the correct explanation of A.
Answer: a. If both A and R are true and R is correct explanation of A
Answer: a. Both A and R are true and R is the correct explanation of A.
The endocrine glands associated with the kidneys are the adrenal glands, also known as suprarenal glands. These glands are situated on top of each kidney. The adrenal glands are composed of two distinct parts: the outer adrenal cortex and the inner adrenal medulla. The adrenal cortex produces steroid hormones like aldosterone, which regulates salt and water balance, and cortisol, which is involved in stress response and metabolism. The adrenal medulla produces catecholamine hormones, primarily adrenaline (epinephrine) and noradrenaline (norepinephrine), which are crucial for the 'fight or flight' response.
(ii) During water stress and drought conditions ABA causes stomatal closure.
Endocrine glands are ductless glands that secrete their products, hormones, directly into the bloodstream. These hormones are then transported via the blood to distant target organs where they exert their specific effects. Examples of endocrine glands include the thyroid gland, pituitary gland, and adrenal glands. In contrast, exocrine glands possess ducts through which they release their secretions. These secretions, which can be enzymes, mucus, or sweat, are typically released onto body surfaces (like skin) or into body cavities (like the digestive tract) and act locally. Examples of exocrine glands include salivary glands, sweat glands, and the exocrine portion of the pancreas, which secretes digestive enzymes.
Glands that lack ducts and release their secretions directly into the circulatory system are known as endocrine glands. The secretions produced by these glands are called hormones. Hormones are chemical substances that act as messengers, traveling through the bloodstream to target cells or organs in different parts of the body. Once they reach their target, they bind to specific receptors and trigger a particular physiological response, thereby regulating a wide range of bodily functions such as metabolism, growth, and reproduction.
The glands that produce hormones are called endocrine glands. These glands are part of the body's endocrine system, which is responsible for regulating various bodily functions through the secretion of hormones. Hormones are chemical messengers that are released directly into the bloodstream and travel to target organs or tissues, where they exert their specific effects. Examples of endocrine glands include the thyroid gland, which produces thyroid hormones that regulate metabolism; the pituitary gland, which produces a variety of hormones that control other endocrine glands and growth; and the adrenal glands, which produce hormones involved in stress response and metabolism.
Glands that possess ducts to transport their secretions to a specific site are known as exocrine glands. These ducts carry substances such as saliva, digestive enzymes, or sweat to the surface of the body or into body cavities. Examples include salivary glands, sweat glands, and glands in the digestive tract that secrete enzymes.
(a) Vasopressin : In kidney tubules it increases reabsorption of water. It reduces loss of water through urine and hence the name antidiuretic hormone.
(b) Oxytocin helps in the contraction of the smooth muscles of uterus at the time of child birth and milk ejection from the mammary gland after child birth.
The hormone thyroxine, secreted by the thyroid gland, requires iodine as a crucial component for its synthesis. If the intake of iodine in our diet is insufficient, the thyroid gland cannot produce adequate amounts of thyroxine. This deficiency leads to a condition known as hypothyroidism. Hypothyroidism can manifest in several diseases, including Simple Goitre, where the thyroid gland enlarges in an attempt to compensate for the lack of iodine; Cretinism, which results from severe iodine deficiency during fetal development or infancy, leading to stunted physical and mental growth; and Myxoedema, a condition seen in adults characterized by swelling of the skin and a decrease in metabolic rate.
(a) The gaseous plant hormone is Ethylene. Its three significant actions in plants include: Firstly, it promotes the ripening of climacteric fruits, such as bananas and tomatoes, by initiating and accelerating the ripening process. Secondly, it plays a role in senescence, the process of aging in plants, and abscission, the shedding of plant parts like leaves, flowers, and fruits. Thirdly, ethylene can inhibit stem elongation, leading to a characteristic 'triple response' in seedlings when exposed to high concentrations, which involves reduced elongation, thickening of the stem, and horizontal growth. (b) Abscisic acid (ABA) is known as the stress hormone in plants. It earns this name because it plays a critical role in helping plants cope with adverse environmental conditions. ABA induces stomatal closure during periods of water scarcity, thereby reducing transpiration and conserving water. It also promotes seed dormancy, preventing germination under unfavorable conditions, and generally inhibits growth, contributing to increased tolerance against stresses like drought, cold, and salinity.
An experiment demonstrating that a growth-stimulating hormone is produced at the tip of the coleoptile was conducted by Went. First, oat coleoptiles were germinated. In one experimental setup, the tip of the coleoptile was removed, which resulted in the cessation of growth. In another part of the experiment, the removed coleoptile tip was placed on an agar block for about an hour, allowing any growth-promoting substance to diffuse into the agar. Subsequently, this agar block, now containing the diffused substance, was placed back onto the decapitated coleoptile. It was observed that growth resumed in the coleoptile. Furthermore, if the agar block was placed asymmetrically on the cut surface, the coleoptile would bend away from the side where the block was placed, indicating differential growth. This experiment led to the conclusion that a chemical substance, later identified as auxin, is produced at the coleoptile tip, moves downwards, and promotes cell elongation. Asymmetric distribution of this substance causes the coleoptile to curve.
(ii) Treatment of rosette plants with gibberellin induces sudden shoot elongation followed by flowering. This is called bolting.
(iii) Gibberellins promote the production of male flowers in monoecious plants (Cucurbits).
(iv) Gibberellins break dormancy of Potato tubers.
(v) Gibberellins are efficient than auxins in inducing the formation of seedless fruit - Parthenocarpic fruits (Development of fruits without fertilization) E.g: Tomato.
Role of Estrogens in the human body :
(i) It brings about the changes that occur during puberty.
(ii) It initiates the process of oogenesis.
(iii) It stimulates the maturation of ovarian follicles in the ovary.
(iv) It promotes the development of secondary sexual characters (breast development, high pitched voice etc).
Deficiency of ADH reduces reabsorption of water and causes an increase in urine output (polyuria). This deficiency disorder is called Diabetes insipidus.
Insulin - Hormone produced by beta cells of Islets of Langerhans.
The deficiency of insulin causes Diabetes mellitus. It is charactersied by
(i) Increase in blood sugar level (Hyperglycemia).
(ii) Excretion of excess glucose in the urine (Glycosuria).
(iii) Frequent urination (Polyuria).
(iv) Increased thirst (Polydipsia).
(v) Increase in appetite (Polyphagia).
(b) Diabetes insipidus results in increase of urine output.
In the case of diabetes mellitus there is frequent urination (polyuria) and excess of glucose is also secreted along with urine. (Glycosuria).
IX Higher Order Thinking Skills (HOTS)
b. A rotten fruit gets mixed with unripe fruits.
c. When cytokinin is not added to culture medium
a. Gibberellin will cause internodal elongation in rice.
b. The rotten fruit will produce lot of Ethylene and the unripe fruits will begin to ripen quickly.
c. Cytokinin induces cell division. If it is not added to culture medium, division of cells will not occur and the cultured tissue will not show growth.
b. It causes excessive stem and internode elongation by stimulating cell elongation and cell division, producing the spindly plants seen in Bakanae disease.
c. Two functions: (1) Promotes stem elongation (bolting) by increasing cell elongation and division. (2) Breaks dormancy and promotes seed/tuber germination (mobilises food reserves).
Gibberellins (GAs) are plant hormones that play a role in promoting the production of male flowers in certain plants, particularly in monoecious species like cucurbits (e.g., cucumbers, melons). In these plants, which have separate male and female flowers on the same individual, gibberellins can influence the sex determination of flowers, leading to an increase in the number of male flowers, which is important for pollination.
Hormone - Thyroxine (Excess secretion).
This condition occurs due to the body's 'fight or flight' response, typically triggered by stress or fear. When Sanjay perceives the exam as a stressful situation, his sympathetic nervous system is activated. This activation signals the adrenal medulla to rapidly secrete adrenaline, also known as epinephrine. Adrenaline is a hormone that prepares the body for intense physical activity by increasing the heart rate, raising blood pressure, and diverting blood flow to muscles. Simultaneously, the sympathetic nervous system stimulates the sweat glands, leading to increased perspiration, which helps to cool the body down in anticipation of exertion. These physiological changes collectively contribute to the feeling of anxiety and the physical symptoms experienced before a high-stakes event like an exam.
Susan's father is likely suffering from diabetes mellitus, a condition characterized by persistently high blood glucose levels. This can occur due to insufficient production or utilization of insulin, a hormone produced by the beta cells of the pancreas. The fact that he requires daily insulin injections suggests he has insulin-dependent diabetes, also known as Type 1 diabetes, where the pancreatic beta cells may have been destroyed or are not functioning properly. The symptoms of tiredness and frequent urination are classic signs of hyperglycemia (high blood sugar), as the body attempts to excrete excess glucose through urine, leading to dehydration and fatigue. While Type 1 diabetes cannot be definitively prevented, it can be effectively managed through regular insulin therapy, consistent monitoring of blood glucose levels, a carefully balanced diet, regular physical activity, and diligent medical follow-up. Maintaining a healthy body weight, engaging in regular exercise, and controlling sugar intake are also crucial for preventing or managing Type 2 diabetes, a related but distinct condition.
Study Smarter, Score Higher.
Revise this Samacheer Class 10 Science topic, then continue with the Revision Challenge.