Plant And Animal Hormones
Class 10 | Science — Biology | Unit 16
Class 10 Unit 16 Science
UNIT-16
PLANT AND ANIMAL HORMONES
Learning Objectives
At the end of this lesson the students will be able to:
- Define hormone.
- List out plant hormones.
- Classify plant hormones into growth promoters and growth inhibitors.
- Differentiate the physiological effects of various plant hormones.
- Understand how plant hormones control and coordinate various physiological activities in plants.
- Know the various endocrine glands in the human body.
- Identify the location and structure of the endocrine glands in the human body.
- Differentiate exocrine and endocrine glands.
- Know the specific site of action and their functions.
- Identify the disorders which occur due to decreased or increased hormone secretion.
Introduction
The word hormone is derived from the Greek word "hormon" meaning "to excite". The function of control and coordination in plants is performed by chemical substances produced by the plants called plant hormones. In plants several cells are capable of producing hormones. These phytohormones are transported to different parts of the plants to perform various physiological functions. Endocrine glands in vertebrate animals possess a diversified communication system to co-ordinate physiological and metabolic functions by chemical integration. The endocrine system acts through chemical messengers known as hormones which are produced by specialized glands. Physiological processes such as digestion, metabolism, growth, development and reproduction are controlled by hormones.
16.1 Plant Hormones
Plant hormones are organic molecules that are produced at extremely low concentration in plants. These molecules control morphological, physiological and biochemical responses.
Types of Plant Hormones
There are five major classes of plant hormones. They are:
- Auxins
- Cytokinin's
- Gibberellins
- Abscisic Acid (A B A)
- Ethylene
Among all these plant hormones auxins, cytokinin's and gibberellins promote plant growth while abscisic acid and ethylene inhibit plant growth.
16.1.1 Auxins
Auxins (G k. auxin = to grow) were the first plant hormones discovered. The term auxin was introduced by Kogl and Haagen- Smith (1931). Auxins are produced at the tip of stems and roots from where they migrate to the zone of elongation. Charles Darwin in 1880 observed unilateral growth and curvature of canary grass (Phalariscanariensis) coleoptiles. He came to the conclusion that some 'influence' was transmitted from the tip of the coleoptile to the basal region. This 'influence' was later identified as Auxin by Went.
16.1.1.1 Went's Experiment
Frits Warmolt Went (1903 to 1990), a Dutch biologist demonstrated the existence and effect of auxin in plants. He did a series of experiments in Avena coleoptiles. 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".
Types of Auxins:
Auxins are classified into two types, namely natural auxins and synthetic auxins.
Natural Auxins: Auxins produced by the plants are called natural auxins. Example: IAA (Indole – 3 - Acetic Acid)
Synthetic Auxins: Artificially synthesized auxins that have properties like auxins are called as synthetic auxins. Example: 2, 4 D (2,4 Dichloro phenoxy Acetic Acid).
Physiological effects of auxins:
Auxins bring about a variety of physiological effects in different parts of the plant body.
- Auxins promote the elongation of stems and coleoptiles which makes them to grow.
- Auxins induce root formation at low concentration and inhibit it at higher concentration.
- The auxins produced by the apical buds suppress growth of lateral buds. This is called apical dominance.
- Seedless fruits without fertilization are induced by the external application of auxins. (Parthenocarpy). Examples: Watermelon, Grapes, Lime etcetera.
- Auxins prevent the formation of abscission layer.
Do You Know
Phenyl Acetic Acid (P A A) and Indole 3 Acetonitrile (I A N) are natural auxins. Indole 3 Butyric Acid (I B A), Indole-3- Propionic Acid, α-Naphthalene Acetic Acid (N A A), 2, 4, 5-T (2,4,5 Trichloro phenoxy Acetic Acid) are some of the synthetic auxins.
16.1.2 Cytokinin's
Cytokinin's (Cyrtos - cell; kinesis - division) are the plant hormones that promote cell division or cytokinesis in plant cells. It was first isolated from Herring fish sperm. Zeatin was the cytokinin isolated from Zea mays. Cytokinin is found abundantly in liquid endosperm of coconut.
Physiological effects of cytokinin's
- Cytokinin induces cell division(cytokinesis) in the presence of auxins.
- Cytokinin also causes cell enlargement.
- Both auxins and cytokinin's are essential for the formation of new organs from the callus in tissue culture (Morphogenesis).
- Cytokinin's promote the growth of lateral buds even in the presence of apical bud.
- Application of cytokinin delays the process of ageing in plants. This is called Richmond Lang effect.
16.1.3 Gibberellins
Gibberellins are the most abundantly found plant hormones. Kurosawa (1926) observed Bakanae disease or foolish seedling disease in rice crops. This internodal elongation in rice was caused by fungus Gibberellafujikuroi. The active substance was identified as Gibberellic acid.
Physiological effects of gibberellins
- Application of gibberellins on plants stimulate extraordinary elongation of internode. e.g., Corn and Pea.
- Treatment of rosette plants with gibberellin induces sudden shoot elongation followed by flowering. This is called bolting.
- Gibberellins promote the production of male flowers in monoecious plants (Cucurbits).
- Gibberellins break dormancy of potato tubers.
- Gibberellins are efficient than auxins in inducing the formation of seedless fruit - Parthenocarpic fruits (Development of fruits without fertilization) e.g., Tomato.
16.1.4 Abscisic Acid
Abscisic acid (A B A) is a growth inhibitor which regulates abscission and dormancy. It increases tolerance of plants to various kinds of stress. So, it is also called as stress hormone. It is found in the chloroplast of plants.
Physiological effects of abscisic acid
- A B A promotes the process of abscission (separation of leaves, flowers and fruits from the branch).
- During water stress and drought conditions A B A causes stomatal closure.
- A B A promotes senescence in leaves by causing loss of chlorophyll.
- A B A induces bud dormancy towards the approach of winter in trees like birch.
- A B A is a powerful inhibitor of lateral bud growth in tomato.
Activity
Place two or three unripe tomatoes in a brown paper bag with a ripe banana and roll the top closed. In another bag place two or three unripe tomatoes only and roll the top closed, observe what happens to the tomatoes? Why? As the banana continues to ripen in the first bag, it produces ethylene gas. The gas trapped in the bag will cause tomatoes to ripen. The tomatoes remain unripe in the second bag.
16.1.5 Ethylene
Ethylene is a gaseous plant hormone. It is a growth inhibitor. It is mainly concerned with maturation and ripening of fruits. Maximum synthesis of ethylene occurs during ripening of fruits like apples, bananas and melons.
Physiological effects of ethylene
- Ethylene promotes the ripening of fruits. Example. Tomato, Apple, Mango, Banana, etcetera.
- Ethylene inhibits the elongation of stem and root in dicots.
- Ethylene hastens the senescence of leaves and flowers.
- Ethylene stimulates formation of abscission zone in leaves, flowers and fruits. This leads to premature shedding.
- Ethylene breaks the dormancy of buds, seeds and storage organs.
16.2 Human Endocrine Glands
Endocrine glands in animals possess a versatile communication system to coordinate biological functions. Exocrine glands and endocrine glands are two kinds of glands found in animals. Endocrine glands are found in different regions of the body of animals as well as human beings. These glands are called ductless glands. Their secretions are called hormones which are produced in minute quantities. The secretions diffuse into the blood stream and are carried to the distant parts of the body. They act on specific organs which are referred as target organs.
Do you Know
The branch of biology which deals with the study of the endocrine glands and its physiology is known as 'Endocrinology'. Thomas Addison is known as Father of Endocrinology. English physiologists W. M. Bayliss and E. H. Starling introduced the term hormone in 1909. They first discovered the hormone secretin. Exocrine glands have specific ducts to carry their secretions example.salivary glands, mammary glands, sweat glands.
Endocrine glands present in human and other vertebrates are
- Pituitary gland
- Thyroid gland
- Parathyroid gland
- Pancreas (Islets of Langerhans)
- Adrenal gland (Adrenal cortex and Adrenal medulla)
- Gonads (Testes and Ovary)
- Thymus gland
16.2.1 Pituitary Gland
The pituitary gland or hypophysis is a pea shaped compact mass of cells located at the base of the midbrain attached to the hypothalamus by a pituitary stalk. The pituitary gland is anatomically composed of two lobes and perform different functions. They are the anterior lobe (adenohypophysis) and the posterior lobe (neurohypophysis). The intermediate lobe is non-existent in humans.
The pituitary gland forms the major endocrine gland in most vertebrates. It regulates and controls other endocrine glands and so is called as the "Master gland".
Hormones secreted by the anterior lobe (Adenohypophysis) of pituitary
The anterior pituitary is composed of different types of cells and secrete hormones which stimulates the production of hormones by other endocrine glands. The hormones secreted by anterior pituitary are
- Growth Hormone
- Thyroid stimulating Hormone
- Adrenocorticotropic Hormone
- Gonadotropic Hormone which comprises the Follicle Stimulating Hormone and Luteinizing Hormone
- Prolactin
Growth hormone (GH)
GH promotes the development and enlargement of all tissues of the body. It stimulates the growth of muscles, cartilage and long bones. It controls the cell metabolism. The improper secretion of this hormone leads to the following conditions.
Dwarfism: It is caused by decreased secretion of growth hormone in children. The characteristic features are stunted growth, delayed skeletal formation and mental disability.
Gigantism: Over secretion of growth hormone leads to gigantism in children. It is characterised by overgrowth of all body tissues and organs. Individuals attain abnormal increase in height.
Acromegaly: Excess secretion of growth hormone in adults may lead to abnormal enlargement of head, face, hands and feet.
2 Thyroid stimulating hormone (TSH)
TSH controls the growth of thyroid gland, coordinates its activities and hormone secretion.
3 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.
4 Gonadotropic hormones (GTH)
The gonadotropic hormones are follicle stimulating hormone and luteinizing hormone which are essential for the normal development of gonads.
5 Follicle stimulating hormone (FSH)
In male, it stimulates the germinal epithelium of testes for formation of sperms. In female it initiates the growth of ovarian follicles and its development in ovary.
Luteinizing hormone (LH)
In male, it promotes the Leydig cells of the testes to secrete male sex hormone testosterone. In female, it causes ovulation (rupture of mature graafian follicle), responsible for the development of corpus luteum and production of female sex hormones oestrogen and progesterone.
6 Prolactin (PRL)
PRL is also called lactogenic hormone. This hormone initiates development of mammary glands during pregnancy and stimulates the production of milk after childbirth.
More to Know
Melatonin is a hormone produced by the pineal gland. It is known as a 'time messenger'. It signals nighttime information throughout the body. Exposure to light at night, especially short-wavelength light, can decrease melatonin production interrupting sleep. Suppression of melatonin has been implicated in sleep disturbances and related metabolic disorders.
Hormones secreted by the posterior lobe (Neurohypophysis) of pituitary
The hormones secreted by the posterior pituitary are
- Vasopressin or Antidiuretic hormone
- Oxytocin
1 Vasopressin or Antidiuretic hormone (ADH)
In kidney tubules it increases reabsorption of water. It reduces loss of water through urine and hence the name antidiuretic hormone. Deficiency of ADH reduces reabsorption of water and causes an increase in urine output (polyuria). This deficiency disorder is called Diabetes insipidus.
2 Oxytocin
It helps in the contraction of the smooth muscles of uterus at the time of childbirth and milk ejection from the mammary gland after childbirth.
16.2.2 Thyroid Gland
The thyroid gland is composed of two distinct lobes lying one on either side of the trachea. The two lobes are connected by means of a narrow band of tissue known as the isthmus. This gland is composed of glandular follicles and lined by cuboidal epithelium. The follicles are filled with colloid material called thyroglobulin.
An amino acid tyrosine and iodine are involved in the formation of thyroid hormone. The hormones secreted by the thyroid gland are
- Triiodothyronine (T3)
- Tetraiodothyronine or Thyroxine (T4)
Functions of thyroid hormones
- Production of energy by maintaining the Basal Metabolic Rate (BMR) of the body.
- Helps to maintain normal body temperature.
- Influences the activity of central nervous system.
- Controls growth of the body and bone formation.
- Essential for normal physical, mental and personality development. It is also known as personality hormone.
- Regulates cell metabolism.
More to Know
Edward C. Kendal in 1914 first crystallised thyroxine hormone. Charles Harrington and George Barger identified the molecular structure of thyroxine in 1927. Thyroid gland requires "120 μg" of iodine every day for the production of thyroxine.
Thyroid Dysfunction
When the thyroid gland fails to secrete the normal level of hormones, the condition is called thyroid dysfunction. It leads to the following conditions
Hypothyroidism: It is caused due to the decreased secretion of the thyroid hormones. The abnormal conditions are simple goitre, cretinism and myxoedema.
Goitre: It is caused due to the inadequate supply of iodine in our diet. This is commonly prevalent in Himalayan regions due to low level of iodine content in the soil. It leads to the enlargement of thyroid gland which protrudes as a marked swelling in the neck and is called as goitre.
Cretinism: It is caused due to decreased secretion of the thyroid hormones in children. The conditions are stunted growth, mental defect, lack of skeletal development and deformed bones. They are called as cretins.
Myxoedema: It is caused by deficiency of thyroid hormones in adults. They are mentally sluggish, increase in body weight, puffiness of the face and hand, oedematous appearance.
Hyperthyroidism: It is caused due to the excess secretion of the thyroid hormones which leads to Grave's disease. The symptoms are protrusion of the eyeballs (Exophthalmia), increased metabolic rate, high body temperature, profuse sweating, loss of body weight and nervousness.
16.2.3 Parathyroid Gland
The parathyroid glands are four small oval bodies that are situated on the posterior surface of the thyroid lobes. The chief cells of the gland are mainly concerned with secretion of parathormone.
Functions of Parathormone
The parathormone regulates calcium and phosphorus metabolism in the body. They act on bone, kidney and intestine to maintain blood calcium levels.
Parathyroid Dysfunction
The secretion of parathyroid hormone can be altered due to the following conditions.
Removal of parathyroid glands during thyroidectomy (removal of thyroid) causes decreased secretion of parathormone. The conditions are
- Muscle spasm known as Tetany (sustained contraction of muscles in face, larynx, hands and feet).
- Painful cramps of the limb muscles.
16.2.4 Pancreas (Islets of Langerhans)
Pancreas is an elongated, yellowish gland situated in the loop of stomach and duodenum. It is exocrine and endocrine in nature. The exocrine pancreas secretes pancreatic juice which plays a role in digestion while, the endocrine portion is made up of Islets of Langerhans.
Do you Know
Human insulin was first discovered by Fredrick Banting, Charles Best and MacLeod in 1921. Insulin was first used in treatment of diabetes on 11th January 1922.
The Islets of Langerhans consists of two types of cells namely alpha cells and beta cells. The alpha cells secrete glucagon and beta cells secrete insulin.
Functions of Pancreatic hormones
A balance between insulin and glucagon production is necessary to maintain blood glucose concentration.
Insulin:
- Insulin helps in the conversion of glucose into glycogen which is stored in liver and skeletal muscles.
- It promotes the transport of glucose into the cells.
- It decreases the concentration of glucose in blood.
Glucagon:
- Glucagon helps in the breakdown of glycogen to glucose in the liver.
- It increases blood glucose levels.
Diabetes mellitus
The deficiency of insulin causes Diabetes mellitus. It is characterised by
- Increase in blood sugar level (Hyperglycaemia).
- Excretion of excess glucose in the urine (Glycosuria).
- Frequent urination (Polyuria).
- Increased thirst (Polydipsia).
- Increase in appetite (Polyphagia).
16.2.5 Adrenal Gland
The adrenal glands are located above each kidney. They are also called supra renal glands. The outer part is the adrenal cortex, and the inner part is the adrenal medulla. The two distinct parts are structurally and functionally different.
Adrenal Cortex
The adrenal cortex consists of three layers of cells. They are zona glomerulosa, zona fasciculata and zona reticularis
Hormones of Adrenal Cortex
The hormones secreted by the adrenal cortex are corticosteroids. They are classified into
- Glucocorticoids
- Mineralocorticoids
Functions of adrenocortical hormones
Glucocorticoids: The glucocorticoids secreted by the zona fasciculata are cortisol and corticosterone
- They regulate cell metabolism.
- It stimulates the formation of glucose from glycogen in the liver.
- It is an anti-inflammatory and anti-allergic agent.
Mineralocorticoids: The mineralocorticoids secreted by zona glomerulosa is aldosterone
- It helps to reabsorb sodium ions from the renal tubules.
- It causes increased excretion of potassium ions.
- It regulates electrolyte balance, body fluid volume, osmotic pressure and blood pressure.
More to Know
The cortisol hormones of adrenal cortex serve to maintain the body in living condition and recover it from the severe effects of stress reactions. Thus, an increased output of cortisol is "lifesaving" in "shock conditions". It is also known as life-saving hormone.
Adrenal Medulla
The adrenal medulla is composed of chromaffin cells. They are richly supplied with sympathetic and parasympathetic nerves.
Hormones of Adrenal Medulla
It secretes two hormones namely
- Epinephrine (Adrenaline)
- Norepinephrine (Noradrenaline)
They are together called as "Emergency hormones". It is produced during conditions of stress and emotion. Hence it is also referred as "flight, fright and fight hormone".
Functions of adrenal medullary hormones
Epinephrine (Adrenaline):
- It promotes the conversion of glycogen to glucose in liver and muscles.
- It increases heartbeat and blood pressure.
- It increases the rate of respiration by dilation of bronchi and trachea.
- It causes dilation of the pupil in eye.
- It decreases blood flow through the skin.
Norepinephrine (Noradrenalin):
- Most of its actions are similar to those of epinephrine.
16.2.6 Reproductive Glands (Gonads)
The sex glands are of two types of the testes and the ovaries. The testes are present in male, while the ovaries are present in female.
Testes
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:
- It influences the process of spermatogenesis.
- It stimulates protein synthesis and controls muscular growth.
- It is responsible for the development of secondary sexual characters (distribution of hair on body and face, deep voice pattern, etc).
Ovary
The ovaries are the female gonads located in the pelvic cavity of the abdomen. They secrete the female sex hormones
Estrogen is produced by the Graafian follicles of the ovary and progesterone from the corpus luteum that is formed in the ovary from the ruptured follicle during ovulation.
Functions of estrogens:
- It brings about the changes that occur during puberty.
- It initiates the process of oogenesis.
- It stimulates the maturation of ovarian follicles in the ovary.
- It promotes the development of secondary sexual characters (breast development, high pitched voice etc).
Functions of progesterone:
- It is responsible for the premenstrual changes of the uterus.
- It prepares the uterus for the implantation of the embryo.
- It maintains pregnancy.
- It is essential for the formation of placenta
16.2.7 Thymus Gland
Thymus is partly an endocrine gland and partly a lymphoid gland. It is located in the upper part of the chest covering the lower end of trachea. Thymosin is the hormone secreted by thymus.
Functions of Thymosin
- It has a stimulatory effect on the immune function.
- It stimulates the production and differentiation of lymphocytes.
Points to Remember
- Auxins are produced at the tip of stems and roots from where they migrate to the zone of elongation.
- Cytokinin's are the plant hormones that promote cell division or cytokinesis in plant cells.
- Gibberellins induce the formation of seedless fruit and parthenocarpic fruits.
- Abscisic acid is a growth inhibitor which regulates abscission and dormancy. It increases tolerance of plants to various kinds of stress.
- Ethylene is a gaseous plant hormone mainly concerned with maturation and ripening of fruits.
- The pituitary gland regulates and controls other endocrine glands and so is called as the "Master gland".
- The hormones secreted by the thyroid gland are triiodothyronine (T3), and tetraiodothyronine or thyroxine (T4)
- The parathormone act on bone, kidney and intestine to maintain blood calcium levels.
- Pancreas secretes insulin and glucagon. They maintain blood glucose level.
- Adrenal cortex secrete cortisol and aldosterone and adrenal medulla secretes epinephrine and norepinephrine.
- The sex glands are of two types the testes and the ovaries which secrete testosterone and estrogens respectively.
TEXTBOOK EVALUATION
Exercise 1. 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
2. The hormone which has positive effect on apical dominance is:
a. Cytokinin b. Auxin c. Gibberellin d. Ethylene
3. Which one of the following hormones is naturally not found in plants:
a. 2, 4-D b. GA3 c. Gibberellin d. IAA
4. Avena coleoptile test was conducted by
a. Darwin b. N. Smit c. Paal d. F.W. Went
5. LH is secreted by
a. Adrenal gland b. Thyroid gland c. Anterior pituitary d. Hypothalamus.
6. Identify the exocrine gland
a. Pituitary gland b. Adrenal gland c. Salivary gland d. Thyroid gland
7. Which organ acts as both exocrine gland as well as endocrine gland
a. Pancreas b. Kidney c. Liver d. Lungs
8. Which one is referred as "Master Gland"?
a. Pineal gland b. Pituitary gland c. Thyroid gland d. Adrenal gland Exercise 2. 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 .
Exercise 3 (a). Match Column 1 with Columns II and III
| Column 1 | Column II | Column III |
|---|
| Auxin | | |
| Ethylene | | |
| Abscisic acid | | |
| Cytokinin | | |
| Gibberellins | | |
Options for Column II: Gibberella fujikuroi, Coconut milk, Coleoptile tip, Chloroplast, Fruits
Options for Column III: Abscission, Internodal elongation, Apical dominance, Ripening, Cell division
Exercise 3 (b). Match the following hormones with their deficiency states
| Hormones | Disorders |
|---|
| Thyroxine | |
| Insulin | |
| Parathormone | |
| Growth hormone | |
| ADH | |
Options: Acromegaly, Tetany, Simple goitre, Diabetes insipidus, Diabetes mellitus
Exercise 4. 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. Exopthalmicgoiter is due to the over secretion of thyroxine. 5. Pituitary gland is divided into four lobes. 6. Estrogen is secreted by corpus luteum. Exercise 5. 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: Cytokinin's 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
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
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 Exercise 6. Answer in a word or sentence
1. Which hormone promotes the production of male flowers in Cucurbits?
2. Write the name of a synthetic auxin.
3. Which hormone induces parthenocarpy in tomatoes?
4. What is the hormone responsible for the secretion of milk in female after childbirth?
5. Name the hormones which regulates water and mineral metabolism in man.
6. Which hormone is secreted during emergency situation in man?
7. Which gland secretes digestive enzymes and hormones?
8. Name the endocrine glands associated with kidneys.
Exercise 7. Short answer questions
1. What are synthetic auxins? Give examples.
2. What is bolting? How can it be induced artificially?
3. Bring out any two physiological activities of abscisic acid
4. What will you do to prevent leaf fall and fruit drop in plants? Support your answer with reason.
5. What are chemical messengers?
6. Write the differences between endocrine and exocrine gland.
7. What is the role of parathormone?
8. What are the hormones secreted by posterior lobe of the pituitary gland? Mention the tissues on which they exert their effect.
9. Why are thyroid hormones referred as personality hormone?
10. Which hormone requires iodine for its formation? What will happen if intake of iodine in our diet is low?
Exercise 8. Long answer questions
1. Name the gaseous plant hormone. Describe its three different actions in plants.
2. Which hormone is known as stress hormone in plants? Why?
3. Describe an experiment which demonstrates that growth stimulating hormone is produced at the tip of coleoptile.
4. Write the physiological effects of gibberellins.
5. Where are estrogens produced? What is the role of estrogens in the human body?
6. What are the conditions which occur due to lack of A D H and insulin? How are the conditions different from one another?
Exercise 9. Higher Order Thinking Skills (HOTS)
1. What would be expected to happen if Gibberellin is applied to rice seedlings.
2. A rotten fruit gets mixed with unripe fruits.
3. When cytokinin is not added to culture medium
4. 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:
a. Identify the hormone involved in this process.
b. Which property of this hormone causes the disease?
c. Give two functions of this hormone.
5. Senthil has high blood pressure, protruded eyeball and an increased body temperature. Name the endocrine gland involved and hormone secretion responsible for this condition.
6. Sanjay is sitting in the exam hall. Before the start of the exam, he sweats a lot, with increased rate of heartbeat. Why does this condition occur?
7. 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.
UNIT-17
REPRODUCTION IN PLANTS AND ANIMALS
Learning Objectives
At the end of this lesson the students will be able to:
- Differentiate vegetative, asexual and sexual reproduction.
- Describe parts of flower and their functions.
- Understand the types and modes of pollination and their significance.
- Understand the process of double fertilization, steps involved in fertilization (syngamy and triple fusion), embryo development, endosperm development and formation of seed.
- Understand the process of sexual reproduction in human beings.
- Know the structure of testicular and ovarian cells.
- Know the structural details of human sperm and ovum.
- Realize the events of menstrual cycle and fertilization.
- Gain awareness on reproductive health and strategies.
- Gain knowledge on personal and social hygiene.
Introduction
Living organisms cannot survive for an indefinite period on earth. All living organisms have the ability to produce more of its own kind by the process called reproduction. Reproduction is the unfolding of life forms where new individuals are formed. It ensures continuity and survival of the species. This process is to preserve individual species and it is called as self-perpetuation. The time required to reproduce also varies from organism to organism. You may find great variations in period of reproduction in yeast, bacteria, rat, cow, elephant and humans. In sexual reproduction off springs are produced by the union of male and female gametes (sperm and egg). The male and female gametes contain the genetic material or genes present on the chromosomes which transmit the characteristic traits to the next generation. There are three types of reproduction in plants namely Vegetative Asexual Sexual reproduction.
17.1 Vegetative Reproduction
In this type, new plantlets are formed from vegetative (somatic) cells, buds or organs of plant. The vegetative part of plant (root, stem, leaf or bud) gets detached from the parent body and grows into an independent daughter plant. It has only mitotic division, no gametic fusion and daughter plants are genetically similar to the parent plant. Vegetative reproduction may take place through
Leaves:
In Bryophyllum ,small plants grow at the leaf notches
Stems:
In strawberry aerial weak stems touch the ground and give off adventitious roots and buds. When the connections with the parent plant is broken, the offspring becomes independent.
Root:
Tuberous roots (Asparagus and Sweet potato) can be used for vegetative propagation.
Bulbils:
In some plants the flower bud modifies into globose bulb which are called as bulbils, when these falls on the ground they grow into new plants. Example Agave.
Other types of Vegetative Reproduction
Fragmentation: In filamentous algae, breaking of the filament into many fragments is called fragmentation. Each fragment having at least one cell, may give rise to a new filament of the algae by cell division example Spirogyra.
Fission: In this type the parent cell divides into two daughter cells and each cell develops into a new adult organism example Amoeba.
Budding: Formation of a daughter individual from a small projection, the bud, arising on the parent body is called budding. Example Yeast.
Regeneration: The ability of the lost body parts of an individual organism to give rise to a whole new organism is called regeneration. It takes place by specialized mass of cells example Hydra and Planaria.
17.2 Asexual Reproduction
Production of an offspring by a single parent without the formation and fusion of gametes is called asexual reproduction. It involves only mitotic cell divisions and meiosis does not occur. Offspring produced by asexual reproduction are not only identical to parents but are also exact copies of their parent. Asexual reproduction occurs by spore formation. This is the most common method of asexual reproduction in fungi and bacteria. During spore formation a structure called sporangium develops from the fungal hypha. The nucleus divides several times within the sporangium and each nucleus with small amount of cytoplasm develops into a spore. The spores are liberated, and they develop into new hypha after reaching the ground or substratum.
Activity 1
Wet a slice of bread, and keep it in a cool, moist and dark place. Observe the surface of the slice with a magnifying glass. Record your observations for a week.
17.3 Sexual Reproduction in Plants
Sexual reproduction is the process in which two gametes (male and female) are fused to produce offspring of their own kind. In such cases both sexes, male and female sex organs are needed to produce gametes. You have already learnt that the flower is a reproductive organ of a flowering plant. To understand this further we need to study the structure of a flower.
17.3.1 Parts of a Typical Flower
A flower is a modified shoot with limited growth to carry out sexual reproduction. A flower consists of four whorls borne on a thalamus. These whorls are from outside
- Calyx – consisting of sepals
- Corolla – consisting of petals
- Androecium – consisting of stamens
- Gynoecium or pistil – consisting of carpels
Activity 2
Take a shoe flower from a growing plant. Observe the floral parts Calyx, Corolla, Androecium and Gynoecium. Separate the stamens and carpels and observe the parts. Dust the pollen grains on a slide and observe under a microscope.
The two outermost whorls calyx and corolla are non-essential or accessory whorls as they do not directly take part in the reproduction. The other two whorls androecium and gynoecium are known as the essential whorls, because both take part directly in reproduction.
Androecium:
Androecium, the male part of flower is composed of stamens. Each stamen consists of a stalk called the filament and a small bag like structure called anther at the tip. The pollen grains are produced in the anther within the pollen sac.
Pollen grain:
Pollen grains are usually spherical in shape. It has two layered walls. The hard- outer layer is known as exine. It has prominent apertures called germ pore. The inner thin layer is known as intine. It is a thin and continuous layer made up of cellulose and pectin. Mature pollen grains contain two cells, the vegetative and the generative cell. Vegetative cell contains a large nucleus. The generative cell divides mitotically to form two male gametes.
Gynoecium:
Gynoecium is the female part of the flower and is made up of carpels. It has three parts:
The ovary contains the ovules.
17.3.2 Structure of the Ovule
The main part of the ovule is the nucellus which is enclosed by two integuments leaving an opening called as micropyle. The ovule is attached to the ovary wall by a stalk known as funiculus. Chalaza is the basal part.
The embryo sac contains seven cells and the eighth nuclei located within the nucellus. Three cells at the micropylar end form the egg apparatus and the three cells at the chalaza end are the antipodal cells. The remaining two nuclei are called polar nuclei found in the centre. In the egg apparatus one is the egg cell (female gamete), and the remaining two cells are the synergids.
Process of sexual reproduction in flowering plants. It involves:
- Pollination
- Fertilization
17.4 Pollination
The transfer of pollen grains from anther to stigma of a flower is called as pollination
Importance of Pollination
- It results in fertilization which leads to the formation of fruits and seed.
- New varieties of plants are formed through new combination of genes in case of cross pollination.
17.4.1 Types of Pollination
- Self-pollination
- Cross pollination
Self-pollination (Autogamy)
Self-pollination is also known as autogamy. The transfer of pollen grains from the anther to the stigma of same flower or another flower borne on the same plant is known as self- pollination. Example Hibiscus.
Advantages of self-pollination
- Self-pollination is possible in certain bisexual flowers.
- Flowers do not depend on agents for pollination.
- There is no wastage of pollen grains.
Disadvantages of self-pollination
- The seeds are less in numbers.
- The endosperm is minute. Therefore, the seeds produce weak plants.
- New varieties of plants cannot be produced
Cross pollination
Cross-pollination is the transfer of pollen from the anthers of a flower to the stigma of a flower on another plant of the same species e.g., apples, grapes, plum, etc.
Advantages of cross pollination
- The seeds produced as a result of cross pollination, develop and germinate properly and grow into better plants, that is, cross pollination leads to the production of new varieties.
- More viable seeds are produced.
Disadvantages of cross-pollination
- Pollination may fail due to distance barrier.
- More wastage of pollen grains
- It may introduce some unwanted characters
- Flowers depend on the external agencies for pollination
Activity 3
Observe the flowers in a garden. Identify the insects and birds that act as pollinating agents. Maintain a record of pollinating agents and the plants.
17.5 Agents of Cross Pollination
In order to bring about cross pollination, it is necessary that the pollen should be carried from one flower to another of a different plant. This takes place through the agency of animals, insects, wind and water.
Pollination by wind
The pollination with the help of wind is called anemophily. The anemophilous flowers produce enormous amount of pollen grains. The pollen grains are small, smooth, dry and light in weight. Pollen of such plants are blown off at a distance of more than 1,000 km. The stigmas are comparatively large, protruding and sometimes hairy to trap the pollen grains. Example Grasses and some cacti.
Pollination by insects
Pollination with the help of insects like honeybees, flies are called entomophily. To attract insects these flowers are brightly coloured, have smell and nectar. The pollen grains are larger in size, the exine is pitted, spiny etcetera. so they can be adhered firmly on the sticky stigma. Approximately, 80% of the pollination done by the insects is carried by honeybees.
Pollination by water
The pollination with the help of water is called hydrophily. This takes place in aquatic plants. Pollen grains are produced in large numbers. Pollen grains float on surface of water till they land on the stigma of female flowers example Hydrilla, Vallisneria.
Pollination by Animals
When pollination takes place with the help of animals, it is called Zoophily. Flowers of such plants attract animals by their bright colour, size, scent etc. example.sun bird pollinates flowers of Canna, Gladioli etcetera. Squirrels pollinate flowers of silk cotton tree.
17.6 Fertilization in Plants
Pollen grains reach the right stigma and begin to germinate. Pollen grain forms a small tube-like structure called pollen tube which emerges through the germ pore. The contents of the pollen grain move into the tube. Pollen tube grows through the tissues of the stigma and style and finally reaches the ovule through the micropyle. Vegetative cell degenerates and the generative cell divides to form two sperms (or male gametes). Tip of pollen tube bursts and the two sperms enter the embryo sac. One sperm fuse with the egg (syngamy) and forms a diploid zygote. The other sperm fuses with the secondary nucleus (Triple fusion) to form the primary endosperm nucleus which is triploid in nature. Since two types of fusion syngamy and triple fusion take place in an embryo sac the process is termed as double fertilization. After triple fusion, primary endosperm nucleus develops into an endosperm. Endosperm provides food to the developing embryo. Later the synergids and antipodal cells degenerate.
Significance of Fertilization
- It stimulates the ovary to develop into fruit.
- It helps in development of new characters from two different individuals.
Post fertilization changes:
- The ovule develops into a seed.
- The in teguments of the ovule develop into the seed coat.
- The ovary enlarges and develops into a fruit.
- The seed contains the future plant or embryo which develops into a seedling under appropriate conditions.
17.7 Sexual Reproduction in Human
You have studied the structural details of the male and female reproductive system in 9th standard. In human beings the male and female reproductive organs differ anatomically and physiologically. New individuals develop by the fusion of gametes. Sexual reproduction involves the fusion of two haploid gametes (male and the female gametes) to form a diploid individual (zygote).
Organs of the reproductive system are divided into primary and secondary (accessory) sex organs.
Primary reproductive organs include the gonads (Testes in male and Ovaries in female).
Accessory sex organs
Male: Vas deferens, epididymis, seminal vesicle, prostate gland and penis.
Female: Fallopian tubes, uterus, cervix and vagina.
The secondary (accessory) sex organs include those structures which are involved in the
- Process of ovulation
- Fusion of the male and female gametes (fertilization)
- Division of the fertilized egg up to the formation of embryo
- Pregnancy
- Development of foetus
- Childbirth.
Now let's see the cells of the primary reproductive organs in human male and female and their role in reproduction.
17.7.1 Male Reproductive Organ - Structure of Testes
Testes are the reproductive glands of the male that are oval shaped organs which lie outside the abdominal cavity of a man in a sac like structure called scrotum. Now we shall study the various cells which are present in the testes. Each testis is covered with a layer of fibrous tissue called tunica albuginea. Many septa from this layer divide the testes into pyramidal lobules, in which lie seminiferous tubules, cells of Sertoli, and the Leydig cells (interstitial cells). The process of spermatogenesis takes place in the seminiferous tubules. The Sertoli cells are the supporting cells and provide nutrients to the developing sperms. The Leydig cells are polyhedral in shape and lie between the seminiferous tubules and secrete testosterone. It initiates the process of spermatogenesis.
17.7.2. Female Reproductive Organ - Structure of Ovary
The ovaries are located on either side of the lower abdomen composed of two almond shaped bodies, each lying near the lateral end of fallopian tube. Each ovary is a compact structure consisting of an outer cortex and an inner medulla. The cortex is composed of a network of connective tissue called as stroma and is lined by the germinal epithelium. The epithelial cells called the granulosa cells surround each ovum in the ovary together forming the primary follicle. As the egg grows larger, the follicle also enlarges and gets filled with the fluid and is called the Graafian follicle.
Info bits
The number of primordial follicles in newborn female child ranges over 7 million and during reproductive period (at puberty) the number is around 60,000 to 70,000. During a woman's lifetime, she will only ovulate 300 to 400 of the 1-2 million eggs, she was initially born with. On the other side, men will produce over 500 billion sperms in their lifetime.
17.8 Gametogenesis
The formation of the sperm in male and the ovum in female is called gametogenesis. It involves spermatogenesis (formation of spermatozoa) and oogenesis (the formation of ova). Gametes with haploid cells are produced through gametogenesis.
17.8.1 Structure of Human Sperm
The spermatozoan consists of head, a middle piece and tail. The sperm head is elongated and formed by the condensation of nucleus. The anterior portion has a cap like structure called acrosome. It contains hyaluronidase an enzyme that helps the sperm to enter the ovum during fertilization. A short neck connects the head and middle piece which comprises the centrioles. The middle piece contains the mitochondria which provides energy for the movement of tail. It brings about sperm motility which is essential for fertilization.
17.8.2 Structure of Human Ovum
The mature ovum or egg is spherical in shape. The ovum is almost free of yolk. It contains abundant cytoplasm and the nucleus. The ovum is surrounded by three membranes. The plasma membrane is surrounded by inner thin zona pellucida and an outer thick corona radiata. The corona radiata is formed of follicle cells. The membrane forming the surface layer of the ovum is called vitelline membrane. The fluid-filled space between zona pellucida and the surface of the egg is called perivitelline space.
Puberty
The reproductive system in both males and females becomes functional and an increase in sex hormone production resulting in puberty. This phenomenon tends to start earlier in females than in males. Generally, boys attain puberty between the age of 13 to 14 years, while girls reach puberty between 11 to 13 years. In male, the onset of puberty is triggered by the secretion of the hormone testosterone in the testes, in female the secretion of estrogens and progesterone from the ovary. The secretion of both male and female hormones is under the control of the pituitary gonadotropins luteinizing hormone (LH) and follicle stimulating hormone (FSH).
17.9 Menstrual Cycle-Process of Ovulation
The cyclic events that take place in a rhythmic fashion during the reproductive period of a woman's life is called menstrual cycle. In human females the menstrual cycle starts at the age of 11-13 years which marks the onset of puberty and is called menarche and ceases around 48-50 years of age and this stage is termed menopause. The reproductive period is marked by characteristic events repeated almost every month in physiologically normal women (28 days with minor variation) in the form of a menstrual flow. The menstrual cycle consists of 4 phases
- Menstrual or Destructive Phase
- Follicular or Proliferative Phase
- Ovulatory Phase
- Luteal or Secretory Phase
These phases show simultaneous synchrony of events in both ovary and uterus. Changes in the ovary and the uterus are induced by the pituitary hormones (LH and FSH) and ovarian hormones (estrogen and progesterone).
Table 17.1 Events of Menstrual Cycle and the Role of Hormones
| Phase | Days | Changes in Ovary | Changes in Uterus | Hormonal Changes |
|---|
| Menstrual phase | 4–5 days | Development of primary follicles | Breakdown of uterine endometrial lining leads to bleeding | Decrease in progesterone and oestrogen |
| Follicular phase | 6th–13th day | Primary follicles grow to become a fully mature Graafian follicle | Endometrium regenerates through proliferation | FSH and oestrogen increase |
| Ovulatory phase | 14th day | The Graafian follicle ruptures, and releases the ovum(egg) | Increase in endometrial thickness | LH peak |
| Luteal phase | 15 th to 28th day | Emptied Graafian follicle develops into corpus luteum | Endometrium is prepared for implantation if fertilization of egg takes place, if fertilization does not occur, corpus luteum degenerates, uterine wall ruptures, bleeding starts and unfertilized egg is expelled | LH and FSH decrease, Corpusluteum produces progesterone and its level increases followed by a decline, if menstrual bleeding occurs |
Info bit
Menstruation is a periodical phenomenon that continues from puberty to menopause. This will happen if the released ovum is not fertilized by the sperm. Lack of menstruation generally indicates pregnancy.
17.10 Fertilization to Foetal Development
Fertilization
Fertilization in human is internal and occurs in the oviduct of the female genital tract. It takes place usually in the ampulla of the fallopian tube. An oocyte is alive for about 24 hours after it is released from the follicle. Fertilisation must take place within 24 hours. The sperm enters into the ovum and fuses with it, resulting in the formation of a 'zygote'. This process is called fertilization. The zygote is a fertilized ovum.
Cleavage and Formation of Blastula
The first cleavage takes place about 30 hours after fertilization. Cleavage is a series of rapid mitotic divisions of the zygote to form many celled blastula (Blastocyst) which comprises an outer layer of smaller cells and inner mass of larger cells.
Implantation
The blastocyst (fertilized egg) reaches the uterus and gets implanted in the uterus. The process of attachment of the blastocyst to the uterine wall (endometrium) is called implantation. The fertilized egg becomes implanted in about 6 to 7 days after fertilization.
Gastrulation
The transformation of blastula into gastrula and the formation of primary germ layers (ectoderm, mesoderm and endoderm) by rearrangement of the cells is called gastrulation. This takes place after the process of implantation.
Info bits
Normally one egg matures in the ovary each month. Ovulation is the rupture of the follicle releasing the egg or ovum. The uterus prepares itself to receive the fertilized egg every month. The uterine lining becomes thick and spongy for implantation of the fertilized egg.
Events leading to when fertilization occurs and does not occur
If fertilization takes place the corpus luteum persists, continues to secrete progesterone maintains the thickened state of uterine wall and prevents maturation of another follicle till the end of pregnancy.
If fertilization does not occur, corpus luteum degenerates, the egg disintegrates and the uterine lining slowly breaks, discharged as blood and mucus leading to menstrual events.
Organogenesis
The establishment of the germ layers namely ectoderm, mesoderm and endoderm initiate the final phase of embryonic development. During organogenesis the various organs of the foetus are established from the different germ layers attaining a functional state.
Formation of Placenta
The placenta is a disc shaped structure attached to the uterine wall and is a temporary association between the developing embryo and maternal tissues. It allows the exchange of food materials, diffusion of oxygen, excretion of nitrogenous wastes and elimination of carbon dioxide. A cord containing blood vessels that connects the placenta with the foetus is called the umbilical cord.
Pregnancy (Gestation)
It is the time period during which the embryo attains its development in the uterus. Normally gestation period of human last for about 280 days. During pregnancy the uterus expands up to 500 times of its normal size.
Parturition (Childbirth)
Parturition is the expulsion of young one from the mother's uterus at the end of gestation. Oxytocin from the posterior pituitary stimulates the uterine contractions and provides force to expel the baby from the uterus, causing birth.
Do You Know
Sometimes ovaries release two eggs and each is fertilised by a different sperm, resulting in Non-Identical Twins (Fraternal Twins). If single egg is fertilised and then divides into two foetus, Identical Twins develop.
Lactation
The process of milk production after childbirth from mammary glands of the mother is called lactation. The first fluid which is released from the mammary gland after childbirth is called as colostrum. Milk production from alveoli of mammary glands is stimulated by prolactin secreted from the anterior pituitary. The ejection of milk is stimulated by posterior pituitary hormone oxytocin.
Info bits
The milk produced from the breast during the first 2 to 3 days after childbirth is called colostrum. It contains immune substances and provides immunity to the newborn which is essential for the body.
17.11 Reproductive Health
According to World Health Organization (W H O) reproductive health means a total wellbeing in all aspects of reproduction, ability to reproduce and regulate fertility, women's ability to undergo pregnancy and safe childbirth, maternal and infant survival and well-being. Several measures were undertaken by the government to improve the reproductive health of the people by launching National Health Programmes such as the Family Welfare Programme Reproductive and Child Health Care (RCH) Programme
Family welfare programme:
The National Family Welfare Programme is a comprehensive scheme which includes:
- Maternal and child health care (MCH)
- Immunization of mothers, infants and children.
- Nutritional supplement to pregnant women and children.
- Contraception with health education, to motivate couples to accept contraceptive methods and to have small family norms, which improve economic status, living status and the quality of life.
Reproductive and Child Health Care (RCH) Programme:
It has integrated all services which include
- Pregnancy and childbirth
- Postnatal care of the mother and child
- Importance of breast feeding
- Prevention of reproductive tract infections and sexually transmitted diseases.
17.12 Population Explosion and Family Planning
Population explosion defined as the sudden and rapid rise in the size of population, especially human population. Realizing the dangers inherent in population growth, the Government of India has taken several measures to check population growth and introduced family planning. India has been one of the first country in the world to launch the nationwide family planning programme in 1952. Family planning is a way of living that is adopted voluntarily by couples on the basis of knowledge and responsible decisions to promote the health and welfare of the family group and society. The W H O (World Health Organisation) has also stressed the importance of family planning as global strategy health for all.
Do You Know
The inverted red triangle is a symbol of family planning in India for family welfare. It is displayed prominently at all hospitals, primary health clinics and family welfare centres where any help or advice about family planning is available free of cost. The symbol is displayed along with a slogan Small Family, Happy Family.
17.12.1. Contraception
Contraception is one of the best birth control measures. A number of techniques or methods have been developed to prevent pregnancies in women. The devices used for contraception are called contraceptive devices. Common contraceptive methods used to prevent pregnancy are discussed here.
- Barrier methods
- Hormonal methods
- Intra-Uterine Devices (IUD s)
- Surgical methods
Barrier Methods
This method prevents sperms from meeting the ovum. Its entry into the female reproductive tract is prevented by barrier.
Condom: Condom prevents deposition of sperms in the vagina. Condoms are made of thin rubber or latex sheath. Condom also protect against sexually transmitted diseases (STD) like syphilis, AIDS.
Diaphragm (Cervical cap): Vaginal diaphragm fitting into the vagina or a cervical cap fitting over the cervix. This prevents the entry of sperms into the uterus.
Hormonal Methods
Hormonal preparations are in the form of pills or tablets (contraceptive pills). These hormones stop (interfere with ovulation) the release of egg from the ovary.
Intra-Uterine Devices (IUD s)
The intrauterine device (IUD) are contraceptive devices inserted into the uterus. There are two synthetic devices commonly used in India are Lippe's Loop and Copper-T made of copper and plastic (non-irritant). This can remain for a period of 3 years. This reduces the sperm fertilizing capacity and prevents implantation. This also helps to give adequate time interval between pregnancies.
Surgical Methods
Surgical contraception or sterilization techniques are terminal methods to prevent any pregnancy. This procedure in males is vasectomy (ligation of vas deferens) and in females it is tubectomy (ligation of fallopian tube). These are methods of permanent birth control.
17.13 Urinary Tract Infection (UTI)
Many diseases affect both women and men, but a few diseases occur at a higher frequency in woman. Women are susceptible to U T I from the bacteria that are present on skin, rectum or vagina. This will enter the urethra, before moving upwards. The types of U T I are:
1 Cystitis or Bladder infection
Bacteria lodged in the urinary bladder thrive and multiply leading to inflammation. It is most common in the age group of 20 to 50.
2 Kidney Infection
The bacteria can travel from the urinary bladder and upward to ureter and affect one or both the kidneys. It also infects the blood stream and leads to serious life-threatening complications.
3 Asymptomatic Bacteriuria
The bacteria present in the urinary bladder which may not show any symptoms.
17.14 Personal Hygiene
Hygiene is the practice of healthy living and personal cleanliness. Personal hygiene is caring of one's own body and health. Social hygiene is proper care of the surrounding environment. The main aspect of hygiene is body hygiene, food hygiene, sanitary hygiene and hygienic environment.
17.14.1 Body Hygiene
Washing is vital to all age group of people which maintains our personal hygiene. A daily bath regularly keeps skin clean and free of germs. Hair should be kept clean by frequent washing. Mouth wash should be done after every meal. We should wash our hands many times during the day. Cloth towels used to dry our hands or body should be dried after each use and laundered regularly. Clothes, handkerchief, undergarments and socks should be washed daily. Washing prevents body odour, infections and skin irritation.
17.14.2 Toilet Hygiene
The toilet has a lot to do with personal hygiene and general health as it is a place that cannot be avoided and used regularly. Parents should guide and practice their children on how to use the toilets at home, in schools and other public places so that it will protect the children from various contagious infections and diseases. The following measures can ensure toilet hygiene
- The floors of the toilet should be maintained clean and dry. This helps to reduce the bad odour and also infection.
- Toilet flush handles, doorknobs, faucets, paper towel dispensers, light switches and walls should be cleaned with disinfectants to kill harmful germs and bacteria.
- Hands should be washed thoroughly with soap before and after toilet use.
17.14.3 Menstrual and Napkin Hygiene
Women's health depends upon the level of cleanliness to keep them free from skin and genitourinary tract infection.
Menstrual hygiene
Maintaining menstrual hygiene is important for the overall health of women. The basic menstrual hygiene ways are
- Sanitary pads should be changed regularly, to avoid infections due to microbes from vagina and sweat from genitals.
- Use of warm water to clean genitals helps to get rid of menstrual cramps
- Wearing loose clothing rather than tight fitting clothes will ensure the airflow around the genitals and prevent sweating.
More to Know
Every year May 28 is observed as Menstrual Hygiene Day to make girls and women aware of maintaining menstrual hygiene and importance of menstrual hygiene for good health. By way of awareness through films, discussions and campaigns menstrual hygiene has taken quite the centre stage in recent days.
Napkin hygiene
The parents and teachers are to create awareness among the schoolgirls about the use of napkins and their proper disposal. Girls should be educated in the following ways
- The sanitary pad and tampons should be wrapped properly and discarded because they can spread infections.
- Sanitary pad or tampon should not be flushed down the toilet.
- Napkin incinerators are to be used properly for disposal of used napkins.
Info bits
The menstrual hygiene scheme to provide subsidized sanitary napkins was launched by the health ministry in 2011In Tamil Nadu, UNICEF has developed an affordable incinerator that uses firewood to handle sanitary napkin waste at schools and special wells are equipped where sanitary napkins are composted.
Points to Remember
- Many bacteria and protozoa simply divide into two or more daughter cells by fission.
- Organisms such as hydra can regenerate if they are broken into pieces. They can also give out buds which mature into new individuals.
- Reproduction in flowering plants involves transfer of pollen grains from the anther to the stigma which is referred to as pollination. This is followed by fertilization.
- Sexual reproduction involves the fusion of two haploid gametes (male and the female gametes) to form a diploid individual (zygote).
- The formation of the sperm in male and the ovum in female is called gametogenesis. It involves spermatogenesis (formation of spermatozoa) and oogenesis (the formation of ova).
- The cyclic events that take place in a rhythmic manner during the reproductive period of a woman's life is called menstrual cycle.
- The process of attachment of the blastocyst to the uterine wall (endometrium) is called implantation.
- The placenta is a temporary association between the developing embryo and maternal tissues.
- Parturition is the expulsion of young one from the mother's uterus.
- Contraception is one of the best birth control measures. The devices used for contraception are called contraceptive devices.
TEXTBOOK EVALUATION
Exercise 1. Choose the correct answer
1. The plant which propagates with the help of its leaves is
a. Onion b. Neem c. Ginger d. Bryophyllum
2. Asexual reproduction takes place through budding in
a. Amoeba b. Yeast c. Plasmodium d. Bacteria
3. Syngamy results in the formation of
a. Zoospores b. Conidia c. Zygote d. Chlamydospores
4. The essential parts of a flower are
a. Calyx and Corolla b. Calyx and Androecium c. Corolla and Gynoecium d. Androecium and Gynoecium
5. Anemophilous flowers have
a. Sessile stigma b. Small smooth stigma c. Coloured flower d. Large feathery stigma
6. Male gametes in angiosperms are formed by the division of
a. Generative cell b. Vegetative cell c. Microspore mother cell d. Microspore
7. What is true of gametes?
a. They are diploid b. They give rise to gonads c. They produce hormones d. They are formed from gonads
8. A single highly coiled tube where sperms are stored, get concentrated and mature is known as
a. Epididymis b. Vasa efferentia c. Vas deferens d. Seminiferous tubules
9. The large, elongated cells that provide nutrition to developing sperms are
a. Primary germ cells b. Sertoli cells c. Leydig cells d. Spermatogonia
10. Estrogen is secreted by
a. Anterior pituitary b. Primary follicle c. Graffian follicle d. Corpus luteum
11. Which one of the following is an IUCD?
a. Copper T b. Oral pills c. Diaphragm d. Tubectomy Exercise 2. Fill in the blanks
1. The embryo sac in a typical dicot at the time of fertilization is .
2. After fertilization the ovary develops into .
3. Planaria reproduces asexually by .
4. Fertilization is in humans
5. The implantation of the embryo occurs at about day of fertilization
6. is the first secretion from the mammary gland after childbirth
7. Prolactin is a hormone produced by .
Exercise 3 (a). Match the following
| Column1 | Column2 |
|---|
| Fission | |
| Budding | |
| Fragmentation | |
Options: Spirogyra, Amoeba, Yeast
Exercise 3 (b). Match the following terms with their respective meanings
| a) Parturition | |
| b) Gestation | |
| c) Ovulation | |
| d) Implantation | |
1) Duration between pregnancy and birth, 2) Attachment of zygote to endometrium, 3) Delivery of baby from uterus, 4) Release of egg from Graafian follicle
Exercise 4. State whether True or False. Correct the false statement 1. Stalk of the ovule is called pedicle. 2. Seeds are the product of asexual reproduction. 3. Yeast reproduces asexually by means of multiple fission. 4. The part of the pistil which serves as a receptive structure for the pollen is called as style. 5. Insect pollinated flowers are characterized by dry and smooth pollen. 6. Sex organs produce gametes which are diploid. 7. LH is secreted by the posterior pituitary. 8. Menstrual cycle ceases during pregnancy. 9. Surgical methods of contraception prevent gamete formation. 10. The increased level of estrogen and progesterone is responsible for menstruation. Exercise 5. Answer in a word or sentence
1. If one pollen grain produces two male gametes, how many pollen grains are needed to fertilize 10 ovules?
2. In which part of the flower germination of pollen grains takes place?
3. Name two organisms which reproduces through budding.
4. Mention the function of endosperm.
5. Name the hormone responsible for the vigorous contractions of the uterine muscles.
6. What is the enzyme present in acrosome of sperm?
7. When is World Menstrual Hygiene Day observed?
8. What is the need for contraception?
9. Name the part of the human female reproductive system where the following occurs.
a. Fertilization
b. Implantation
Exercise 6. Short answer question
1. What will happen if you cut planaria into small fragments?
2. Why is vegetative propagation practiced for growing some type of plants?
3. How does binary fission differ from multiple fission?
4. Define triple fusion.
5. Write the characteristics of insect pollinated flowers.
6. Name the secondary sex organs in male
7. What is colostrum? How is milk production hormonally regulated?
8. How can menstrual hygiene be maintained during menstrual days?
9. How does developing embryo gets its nourishment inside the mother's body?
10. Identify the parts A, B, C and D
11. Write the events involved in the sexual reproduction of a flowering plant. Discuss the first event and write the types. Mention the advantages and the disadvantages of that event.
12. Why are the human testes located outside the abdominal cavity? Name the pouch in which they are present.
13. Luteal phase of the menstrual cycle is also called the secretory phase. Give reason.
14. Why are family planning methods not adopted by all the people of our country?
Exercise 7. Long answer questions
1. With a neat labelled diagram describe the parts of a typical angiospermic ovule.
2. What are the phases of menstrual cycle? Indicate the changes in the ovary and uterus.
📝 Summary
- Plant and animal hormones are chemical messengers that control and coordinate physiological functions - the word "hormone" comes from Greek "hormon" meaning "to excite"
- There are five major classes of plant hormones: Auxins, Cytokinins, Gibberellins, Abscisic Acid (ABA), and Ethylene - where auxins, cytokinins and gibberellins promote growth while ABA and ethylene inhibit growth
- Auxins were the first plant hormones discovered, with Charles Darwin observing their effects in 1880 and the term "auxin" introduced by Kogl and Haagen-Smith in 1931
- Went's experiments with Avena coleoptiles demonstrated that auxins are produced at stem and root tips and migrate to elongation zones, proving that a chemical substance diffuses from tips to stimulate growth
- Auxins are classified into natural auxins (like IAA - Indole-3-Acetic Acid) produced by plants and synthetic auxins (like 2,4-D) that are artificially synthesized with auxin-like properties