NCERT Solutions for class 11 Biology

NCERT Solutions for Class 11 Biology Chapter 1 The Living World

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NCERT Solutions for Class 11 Biology Chapter 1 The Living World

These Solutions are part of NCERT Solutions for Class 11 Biology. Here we have given NCERT Solutions for Class 11 Biology Chapter 1 The Living World.

Question 1.
Why are living organisms classified?
Solution:
Classification of living organisms grouped them in special categories, which is based on observable characters. It makes their study easy and convenient. For example, Mammals are those who possess mammary glands, the hair on the body, external pinnae, etc.

Question 2.
Why are classification systems changing every now and then?
Solution:
The classification system changes when more information becomes available about the organisms. Additional information are updated from time to time about different organisms at this stage there is a need arises to make changes in the classification system.

Question 3.
What different criteria would you choose to classify people that you meet often?
Solution:
Classification means the arrangement of organisms into groups on the basis of their affinities or relationships. The branch of biology that deals with the study of principles and procedures of biological classification are called taxonomy. Some fundamental elements of taxonomy are discussed below.

Nomenclature: It is the science of providing distinct and proper names to organisms. It is the determination of the correct name as per established universal practices and rules.

Classification: It deals with the mode of arranging organisms or group^ of organisms into categories according to a systematic plan or ah order. The categories used in the classification of animals are Class, Order, Family, Genus, and Species. Each category is a unit and is also called a taxon (PI. Taxa).

Identification: It is the determination of the correct name and place of an organism in a system of classification. It determines that the particular organism is similar to some other organism of known identity. This implies assigning an organism to a particular taxonomic group. Suppose there are three plants say x, y, z. AH represent different species. Another plant w resembles y. The recognition of the plant was identical to the already known plant y is its identification.
One of the important features of systematics is the naming of living organisms. The organisms have been given two types of names i.e

  • common or vernacular names
  • Scientific names.

Question 4.
What do we learn from the identification of individuals and populations?
Solution:
Identification of individuals and populations determines their exact place or position in the set plan of classification.

Question 5.
Given below is the scientific name of mango. Identify the correctly written name.
(a) Mangifera Indica
(b) Mangifera indica
Solution:
(b) Mangifera indica

Question 6.
Define a taxon. Give some examples of taxa at different hierarchical levels.
Solution:
“Taxon is a unit of classification or a rank or a level of hierarchy in system of classification. The following chart gives taxonomical categories showing a hierarchical arrangement in ascending order.

Kingdom
↑
phylum or Division
Class
↑
Order
↑
Family
↑
Genus
↑
Species

Question 7.
Can you identify the correct sequence of taxonomical categories?
(a) Species → Order → Phylum → Kingdom
(b) Genus → Species → Order → Kingdom
(c) Species → Genus → Order → Phylum
Solution:
(c) Species → Genus → Order → Phylum

Question 8.
Try to collect all the currently accepted meanings for the word ‘species’. Discuss with your teacher the meaning of species in the case of higher plants and animals on one hand and bacteria on the other hand.
Solution:

  1. Species is one of the basic units of biological classification. A species is often defined as a
    group of organisms capable of interbreeding aid in producing fertile offspring.
  2. Sometimes more precise or differing measures such as similarity of DNA, morphology o,^ecological niche are used to define the basis of species.
  3. In case of animals, the name of species is defined by the specific name or the specific epithet. For example, gray wolves belong to the species Canis lupus, golden Jackals to Cam’s aureus etc.
  4. Both of them belong to same genus Canis, but species name varies. But species name of plant is only called species epithet.
  5. The ‘specific name’ in botany is always the combination of genus name and species epithet such as saccharum in Acer saccharum (Sugar maple).
  6. But bacteria are grouped under four categories based on their shape – spherical, rod-shaped, comma and spiral shaped and species of bacteria is according to their shapes. Thus the meaning of species in higher organism and bacteria are different.

Question 9.
Define and understand the following terms:
(i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus
Solution:
(i) Phylum: A phylum is a group of related classes having some common features, e.g., protozoa.
(ii) Class: A class is a group of related orders, for e.g., order Rodentia, Lagomorpha and Carnivora all having hair and milk glands are placed in class Mammalia.
(iii) Family: A family is a group of related genera. The genus Felis of cats and the genus Panthera of lion, tiger and leopard are placed in the family Felidal.
(iv) Order: An order is a group of related families. The family Felidae of cats and the »family Coridal of dogs are assigned to the order Carnivora. Cats and dogs have large canine teeth and are flesh-eaters.
(v) Genus: A genus is a group of species alike in the broad features of their organization but different in detail. As per the rules of binomial nomenclatures, a species can not be named without assigning it to a genus.
NCERT Solutions for Class 11 Biology Chapter 1 The Living World 1

Question 10.
How is key helpful in the identification and classification of organisms?
Solution:
Keys are contrasting pairs of characters (couplet), it represents the choice made between two opposite options. This results in acceptance of only one and rejection of the other. Each statement in the key is called a lead. Separate taxonomic keys are required for each taxonomic category such as family, genus, and species for identification purposes.

Question 11.
Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.
Solution: 
NCERT Solutions for Class 11 Biology Chapter 1 The Living World 2

VERY SHORT ANSWER QUESTIONS

Question 1.
Name the basic Unit of classification.
Solution:
Species.

Question 2.
Who introduced the hierarchy in taxonomy?
Solution:
Linnaeus

Question 3.
Who is the father of taxonomy?
Solution:
Carolus Linnaeus.

Question 4.
What is meant by cytotaxonomy?
Solution:
Classification based on chromosome number.

Question 5.
Who devised the binomial nomenclature?
Solution:
Carolus Linnaeus

Question 6.
What is a type specimen?
Solution:
Establishment of the name of the new species on the basis of the original specimen is called type specimen

Question 7.
In which language binomial nomenclature is written?
Solution:
Latin

Question 8.
What term is used to describe organisms without a well-developed nucleus?
Solution:
Prokaryote

Question 9.
Is inter-specific breeding possible?
Solution:
Yes, both.

Question 10.
What are DNA viruses / RNA viruses?
Solution:
Viruses that possess DNA as the genetic material are called DNA viruses.

Question 11.
What is speciation?
Solution:
Formation of a new species from an existing one by the appearance of mutation.

Question 12.
What are correlated characters?
Solution:
The common features the species have to qualify for inclusion in a genus are called correlated characters

Question 13.
Why classification of plants and animals is necessary?
Solution:
Classification divides millions of plant and animal species into convenient groups that make their study easier

Question 14.
What is cohort or order?
Solution:
The cohort is a unit of classification higher than the 6. family

Question 15.
Give an example of symbiotic bacteria.
Solution:
Rhizobium leguminosarum

Question 16.
Give botanical and zoological names of the following:
(1) Pea
(2) Wheat
(3) Man
(4) Potato
Solution:
(1) Pea → Pisumsatinum
(2) Wheat → Triticumaextivum
(3) Man → Homo sapiens
(4) Potato → Solanum tuberosum

SHORT ANSWER QUESTIONS

Question 1.
Write a note on bacteriophages. (Dharwar. 2004, Belgaum. 04,2005)
Solution:
The viruses that infect bacteria are called bacteriophages. They were discovered by Twort. They are Tadpole shaped. They have DNA as their genetic material. They are distinguished into T – odd phages as well as T – even phages.

Question 2.
What is a taxonomic aid?
Solution:
A taxonomic aid is storage of record of either live or dead specimens of flora or fauna, which helps scientists in taking reference to study classification

Question 3.
Give the classification of man.
Solution:
Common Name – Human
Scientific Name – Homo sapiens
Genera – Homo
Families – Hominidae
Orders – Primata
Classes – Mammalia
Phyla/Division – Chordate

Question 4.
What is a museum? How many kinds of museums are found?
Solution:
Museum in an institution where artistic and educational materials are exhibited to the public. The material available for observation and study is called a collection.
Kinds of Museums:

  • Art Museum
  • History Museum
  • Applied Science Museum
  • Natural Science Museum

Question 5.
Give a reason for the following.
Bacteria are the Natural Scavengers ‘ (D.Kannada 2006)
Solution:
because they bring about the decomposition of organic debris and clean the earth’s surface.

Question 6.
What is the role of characteristics of living beings in classification?
Solution:
A group of common features of living beings are placed under a common category of classification and when uncommon under a different category. It means more systematic a process for further study, research, protection and recording.

Question 7.
What is the significance of a HERBARIUM?
Solution:
HERBARIUM:- A book, case, or room containing an orderly collection of dried plants is called Herbarium. It develops interest in Nature for the activists in it. It can be used to gain knowledge and be updated about plants and their scientific names and even compare various samples. It is a small scale it can be proactive to do. One can make projects too from it for schools, colleges and research institutions.

Question 8.
Explain the role of blue-green algae in soil fertility.
Solution:
Blue-green algae like Nostoc, Anabaena fix atmospheric nitrogen. Heterocyst contains nitrogens enzyme that helps in nitrogen fixation. Nitrogen-fixing blue-green algae are inoculated in the rice field to increase soil fertility.

LONG ANSWER QUESTIONS

Question 1.
Write a short note on Binomial Nomencia? ture and guidelines for Binomial nomenclature.
Solution:
Binomial Nomenclature was introduced by Carolus Linnaeus. In this method every organism is given a scientific name, which has two parts, the first is the name of the genus (generic name) and the second is the name of the species (specific epithet) e.g.: Homo sapiens In the above examples, Homo is a generic name, while sapiens is the name of the species belonging to Homo.

Guidelines:

  • scientific names are generally in Latin or derived from Latin irrespective of their origin
  • The scientific names are written in italics or underlined (when handwritten)
  • The first word denotes the name of the genus and the second word denotes the specific epithet
  • The generic name starts with a capital letter, while the specific name starts with a small letter (If a specific name starts with a capital letter it denotes the name of a person or place)
  • The name of the author is written in an abbreviated form after the specific name. e.g.: Homo sapiens Linn.

Question 2.
What is the difference between living and nonliving?
Solution:
Question 3.
Explain the binomial system of nomenclature.
Solution:
Binomial nomenclature system was developed by Linnaeus. Binomial nomenclature is the system of providing organisms with appropriate and distinct names consisting of two words, first generic and second specific. The first or 4.

  • generic word is also called genus. It is like a noun and its first letter is written in capital form.The second word or specific epithet represents the species.
  • It is like an adjective. Its first letter is written in small form except occasionally when it denotes a person or place. The two word name is appended with the name of the taxonomist who discovered the organism and provided with its scientific name, e.g., Ficus bengalensis L., Mangifera indica Linn, The name of taxonomist can be written in full or in abbreviated form.
  • There are several technical names which have three words, e.g., Homo sapien sapiens, Acacia nilotica indica, Gerilla gorilla. Here the first word is generic, the second specific while the third word represents variety (mostly in botanical literature) or subspecies (mostly in zoological literature).
  • If the same scientific name is to be written time and again, the name of the genus can be abbreviated, e.g., F. bengalensis.

Question 4.
What is the role of zoological parks in wildlife conservation?
Solution:

  • In the early stages, the zoological parks were considered as places of relaxation and enjoyment for public, however, there has been a change in the objective of the purposefulness of these parks.
  • The establishment of zoological parks help in providing knowledge about different native and exotic wild mammals, birds, reptiles, fish and flora to the public in general and school children in particular.
  • Since the key to wildlife conservation lies in the education of the masses and the involvement of voluntary organisations, zoological parks are very useful in spreading knowledge on the wildlife wealth of the country.
  • These are also important centres for organising seminars, training and researches on the management of wildlife species and for study of their social behaviour, breeding and ecological species.

We hope the NCERT Solutions for Class 11 Biology at Work Chapter 1 The Living World, help you. If you have any query regarding NCERT Solutions for Class 11 Biology at Work Chapter 1 The Living World, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 11 Biology Chapter 22 Chemical Coordination and Integration

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NCERT Solutions for Class 11 Biology Chapter 22 Chemical Coordination and Integration

These Solutions are part of NCERT Solutions for Class 11 Biology. Here we have given NCERT Solutions for Class 11 Biology Chapter 22 Chemical Coordination and Integration.

Question 1.
Define the following:
(a) Exocrine glands
(b) Endocrine glands Hormones
Solution:
(a) Glands with duct is known as an exocrine gland. They secrete their secretions through ducts. Eg: Pancreas.
(b) Gland without duct is known as an endocrine gland. They directly secrete their secretions. Eg: Pituitary gland.
(c) Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts. Eg: thyroxine.

Question 2.
Diagrammatically indicate the location of the various endocrine glands in our body.
Solution:
NCERT Solutions for Class 11 Biology Chapter 22 Chemical Coordination and Integration 1

Question 3.
List the hormones secreted by the following.
(a) Hypothalamus
(b) Pituitary
(c) Thyroid
(d) Parathyroid
(e) Adrenal
(f) Pancreas
(g) Testis
(h) Ovary
(i) Thymus
(j) Atrium
(k) Kidney
(l) G-ITract
Solution:
(a) Hypothalamus: Gonadotrophic releasing hormone (GnRH), somatostatin.
(b) Pituitary: Growth hormone, prolactin, thyroid-stimulating hormone, luteinizing hormone and follicle stimulating hormone, oxytocin, vasopressin.
(c) Thyroid: triiodothyronine (T3) and tetraiodothyronine (T4).
(d) Parathyroid: Parathyroid hormone.
(e) Adrenal: Adrenaline or epinephrine and noradrenaline or norepinephrine.
(f) Pancreas: Insulin and glucagon.
(g) Testis: A group of androgens mainly testosterone.
(h) Ovary: Estrogens and progesterone.
(i) Thymus: Thymosins.
(j) Atrium: Atrial Natriuretic factor (ANF)
(k) Kidney: Erythropoietin.
(l) G-I tract: Gastrin, secretin, cholecystokinin (CCK).

Question 4.
Fill in the blanks:
Hormones                      Target gland
(a) Hypothalamic hormones ……………….
(b) Thyrotrophin (TSH) ………………
(c) Corticotrophin (ACTH) ………………
(d) GonadobTjpfains(LH,FSH) ……………….
(e) MeIanotrophin(MSH) ………………..
Solution:
(a) Anterior pituitary and posterior pituitaiy.
(b) Thyroid glands
(c) Adrenal cortex
(d) Gonads (testis and ovary)
(e) Pituitary

Question 5.
Write short notes on the functions of the following hormones:
(a) Parathyroid hormone (PTH)
(b) Thyroid hormones
(c) Thymosins
(d) Androgens
(e) Estrogens
(f) Insulin and Glucagon
Solution:
(a) The secretion of PTH is regulated by the circulating levels of calcium ions. Parathyroid hormone (PTH) increases the Ca2+ levels in the blood. PTH acts on bones and stimulates the process of bone resorption. PTH also stimulates reabsorption of Ca2+ by the renal tubules and increases Ca2+ absorption from the digested food. PTH is a hypercalcemic hormone, i.e., it increases the blood Ca2+ levels. Along with TCT, it plays a significant role in calcium balance in the body.

(b) Thyroid hormones play an important role in the regulation of the basal metabolic rate. These hormones also support the process of red blood cell formation. Thyroid hormones control the metabolism of carbohydrates, proteins, and fats. Maintenance of water and electrolyte balance is also influenced by thyroid hormones. The thyroid gland also secretes the protein hormone thyrocalcitonin (TCH) which regulates blood calcium levels.

(c) Thymosins play a major role in the differentiation of T – lymphocytes, which provide cell-mediated immunity. In addition, thymosins also promote the production of antibodies to provide humoral immunity.

(d) Androgens regulate the development, maturation and functions of the male accessory sex organs like epididymis, vas deferens, seminal vesicles, prostate gland, urethra etc. These hormones stimulate muscular growth, growth of facial and axillary hair, aggressiveness, low pitch of voice etc. Androgens play a major stimulatory role in the process of spermatogenesis and act on the central neural system and influence male sexual behaviour. These hormones produce anabolic effects on protein and carbohydrate metabolism.

(e) Estrogens produce wide-ranging actions such as stimulation of growth and activities of female secondary sex organs, development of growing ovarian follicles, appearance of female secondary sex characters, mammary gland development. Estrogen also regulate female sexual behaviour.

(f) Glucagon is a peptide hormone, and plays an important role in maintaining normal blood glucose levels. Glucagon acts mainly on the liver cells and stimulates glycogenolysis resulting in increased blood sugar. In addition, this hormone stimulates the process of gluconeogenesis which also contributes to hyperglycemia. Glucagon reduces cellular glucose uptake and utilisation. Thus, glucagon is a hyperglycemic hormone.

Insulin is a peptide hormone, which plays a major role in the regulation of glucose homeostasis. Insulin acts mainly on hepatocytes and adipocytes and enhances cellular glucose uptake and utilisation. As a result, there is a rapid movement of glucose from blood to hepatocytes and adipocytes resulting in decreased blood glucose levels (hypoglycemia). Insulin also stimulates conversion of glucose to glycogen in the target cells. The glucose homeostasis in the blood is thus maintained jointly by the two insulin and glucagons.

Question 6.
Give example(s) of:
(a Hyperglycemic hormone and hypoglycemic hormone
(b Hypercalcemic hormone
(c) Gonadotrophic hormones
(d Progestational hormone
(e) Blood pressure lowering hormone
(f) Androgens and estrogens
Solution:
(a) Glucagon and insulin
(b) Parathyroid hormone
(c) LH and FSH
(d) Progesterone
(e) Atrial Natriuretic Factor (ANF)
(f) Testosterone and estradiol

Question 7.
Which hormonal deficiency is responsible for the following:
(a) Diabetes mellitus
(b) Goitre
(c) Cretinism
Solution:
Diabetes mellitus: Insulin deficiency.
Goiter: Deficiency of thyroid hormones due to deficiency of iodine.
Cretinism: Deficiency of thyroid hormones during childhood.

Question 8.
Briefly mention the mechanism of action of FSH.
Solution:
Follicle-stimulating hormone (FSH) and LH Stimulate gonadal activity. In males, FSH and androgens regulate spermatogenesis. In females, FSH is responsible for the growth and development of the ovarian follicles, maturation of egg, and secretion of estrogens

Question 9.
Match the following:
Column I Column II
(a) T4 (i) Hypothalamus
(b) PTH (ii) Thyroid
(c) GnRH (iii) Pituitary
(d) IH (iv) Parathyroid
Solution:
(a) – (ii)
(b) – (iv)
(c) – (i)
(d) – (iii)

VERY SHORT ANSWER QUESTIONS

Question 1.
Give two examples of endocrine glands.
Solution:
Examples of endocrine glands are
(i) pituitary gland
(ii) pineal gland.

Question 2.
Which gland secretes glucagon?
Solution:
Pancreas secretes glucagon.

Question 3.
What is the location of the pituitary gland?
Solution:
The pituitary gland is located in a bony cavity called Sella tursica and is attached to the hypothalamus by a stalk.

Question 4.
Which hormone is secreted by pars intermedia?
Solution:
Pars intermedia secretes melanocyte-stimulating hormone (MSH).

Question 5.
Which hormone is secreted by the pineal gland?
Solution:
Pineal gland secretes melatonin hormone.

Question 6.
Name one disorder caused by hyperfunctioning of the pituitary.
Solution:
Gigantism caused by hyperfunctioning of the pituitary.

Question 7.
How many lobes does the thyroid gland have?
Solution:
The thyroid gland is composed of two lobes which are located on either side of the trachea.

Question 8.
Which gland produces the hormone called thyrocalcitonin (TCT) which regulates the blood calcium levels?
Solution:
Thyroid gland secretes a protein hormone called thyrocalcitonin (TCT) which regulates the blood calcium levels.

Question 9.
Name the organ which secretes progesterone.
Solution:
Ovary secretes progesterone.

Question 10.
Name two hormones of pancreas.
Solution:
Glucagon and insulin are two hormones of pancreas.

Question 11.
Which gland secretes somatostatin?
Solution:
Hypothalamus secretes somatostatin.

Question 12.
Which complex is formed during the binding of hormone to a receptor ?
Solution:
Hormone-receptor complex is formed during the binding of a hormone to a receptor.

Question 13.
Name one hormone secreted by gastro-intestinal tract.
Solution:
Gastrin is secreted by gastro-intestinal tract.

Question 14.
Which hormone is secreted by testes and write the function of hormone also.
Solution:
Testosterone is secreted by testes. It controls growth and development of male secondary
v-sexual characters.

Question 15.
What are membrane bound receptors?
Solution:
Hormone receptors that are present on the cell membrane of the target cells are called membrane bound receptors.

Question 16.
How many types of cells are present in Islets of Langerhans?
Solution:
There are two types of cells present in Islets of Langerhans which are a-cells and P-cells.

Question 17.
Why is oxytocin called as birth hormone ?
Solution:
Oxytocin stimulates the contraction of smooth muscles of uterus and facilitates the child birth.

Question 18.
Why is vasopressin known as antidiuretic hormone?
Solution:
Vasopressin stimulates the reabsorption of water and electrolytes and reduces the loss of water through urine, known as diuresis. Hence it is called as anti-diuretic hormone.

Question 19.
What is cretinism ?
Solution:
Cretinism is reduction in body growth as well as underdevelopment of brain resulting in various structural and functional defects mainly due to deficiency of thyroxine (hypothyroidism) in infants and children.

Question 20.
Which hormone interacts with membrane bound receptor and does not normally enter the target cell?
Solution:
Follicle stimulating hormone interacts with membrane bound receptor and does not normally enter the target cell.

Question 21.
Which hormone opposes parathormone?
Solution:
Thyrocalcitonin opposes parathormone.

Question 22
Which hormone is known as anti-aging hormone?
Solution:
Melatonin, secreted by pineal gland is known as anti-ageing hormone.

SHORT ANSWER QUESTIONS

Question 1.
Discuss the location and function of parathyroid hormone.
Solution:
There are four parathyroid glands present on the back side of thyroid glands, two on each of the lobes of the thyroid gland.
The parathyroid glands secrete parathyroid hormone (PTH), a peptide hormone. Parathyroid hormone (PTH) increases the Ca2+ levels in the blood. PTH acts on bones and stimulates the process of bone resorption (dissolution/ demineralization. PTH also stimulates reabsorption of Ca2+ by the renal tubules and increases Ca2+ absorption from the digested food.

Question 2.
What is progesterone? Name two important functions of progesterone.
Solution:
Progesterone is a steroid hormone secreted by ovary.
Functions of progesterone are as follows:
• It supports pregnancy.
• It acts on mammary glands and stimulates the formation of alveoli (sac-like structures which store milk) and milk secretion.

Question 3.
Name the principal mineralocorticoid secreted by adrenal cortex. Give its any two functions
Solution:
Aldosterone is main mineralocorticoid secreted by adrenal cortex.
Functions of aldosterone are :
• It stimulates reabsorption of Na+ and water.
• It stimulates excretion of K+ and phosphate ions.

Question 4.
What are hormone receptors? What are the modes of their action ?
Solution:
Receptors are specific proteins present on the surface of target cell which bind with hormones and produce physiological changes in cell. Their are two types of hormone receptors which are discussed below:
NCERT Solutions for Class 11 Biology Chapter 22 Chemical Coordination and Integration 2

Question 5.
Name the gland that functions as a biological clock in our body. Where is this gland located ? Name its one secretion.
Solution:
Pineal gland functions as a biological clock in our body.

  • It is located on the dorsal side of the forebrain.
  • It secretes melatonin.

Question 6.
Where is thymus gland located in the human body ? Describe its role.
Solution:
The thymus gland is a lobular structure located on the dorsal side of the heart and the aorta.
– It secretes hormone thymosin, which has a stimulating effect on the immune system.
– Thymosin promotes proliferation and maturation of T-lymphocytes.

Question 7.
How does insulin act on high glucose content in the blood in a normal human body ?
Solution:
• Insulin is a peptide hormone, which plays a major role in the regulation of glucose homeostasis. Insulin acts mainly on hepatocytes and adipocytes (cells of adipose tissue), and enhances cellular glucose uptake and utilisation. As a result, there is a rapid movement of glucose from blood to hepatocytes and adipocytes resulting in decreased blood glucose levels (hypoglycemia)
• Insulin also stimulates conversion of glucose to glycogen (glycogenesis) in the target cells.
• The glucose homeostatasis in blood is thus maintained jointly by the two enzyme insulin and glucagon.

Question 8.
What is corpus luteum ? Name its one secretion.
Solution:
Corpus luteum is the structure formed by the ruptured ovarian follicles after ovulation.
– It mainly secretes the hormone progesterone.

Long ANSWER QUESTIONS

Question 1.
Explain briefly the structure and functions of middle ear.
Solution:
Calcitonin (from thyroid) : Essential for maintaining bone strength as it does not allow calcium mobilisation from bones. It also lowers plasma level of calcium ifthe same is high. Parathormone: Low level of parathormone secretion decreases blood plasma level of calcium, prevents reabsorption from bones and causes tetany. Higher levels of parathormone (PTH) increase plasma level of Ca2+ by withdrawal from bones resulting in (i) Inflammation and tenderness in bones due to dissolution of calcium from bones, formation of cavities which get plugged with fibrous nodes and cysts (osteitis fibrosa cystica) making bones soft deformed and prone to fracture, (ii) Excess plasma calcium gets deposited in various parts of body which often leads of obstruction and death.

Question 2.
Draw a well labelled diagram showing the location of parathyroid gland. Discuss the function/(s) of parathormone and hyperparathyroidism.
Solution:
NCERT Solutions for Class 11 Biology Chapter 22 Chemical Coordination and Integration 3
Function : Parathormone (Collip’s hormone) regulates the metabolism of calcium and phosphate between blood and other tissue.
(i) Hyperparathyroidism : It leads to demineralisation resulting in softing and bending of bones. An excess of parathormone cause osteoporosis and kidney stones.

Question 3.
What are the causes for following disorders?
(a) Acromegaly
(b) Cretinism
(c) Gigantism
(d) Myxoedema
Solution:
Disorders and their causes.
(a) Acromegaly (Acro-extremity, megaly – large) – It is caused by excess secretion of growth hormone after adulthood is reached.
(b) Cretinism : It is caused by deficiency of thyroid hormone in infant.
(c) Gigantism : It is caused by excess of growth hormone from early age.
(d) Myxoedema: It is caused by deficiency of thyroid hormone in adults.

We hope the NCERT Solutions for Class 11 Biology at Work Chapter 22 Chemical Coordination and Integration, help you. If you have any query regarding NCERT Solutions for Class 11 Biology at Work Chapter 22 Chemical Coordination and Integration, drop a comment below and we will get back to you at the earliest.