MCQ | GROWTH REGENERATION AGEINGFlame Institute

Histones are synthesised during [CBSE PMT 1992]

(a) Mitosis (b) S phase

Multiplicative growth is not found in

(a) Higher vertebrate (b) Crab

Allometric growth is [MP PMT 1994]

(a) Increase in the number of cells with growth of individual cells

(b) Growth due to multiplication of constituent cells at constant rate

(d) Growth due to special reserve cells of the body

Growth occurs when

(a) Anabolism is higher than catabolism

(b) Catabolism is higher than anabolism

(d) Apoplasmatic synthesis is more than protoplasmic synthesis

Rate of growth can be expressed by

(a) (b)

Growth in most warm blooded vertebrates is [MP PMT 1995]

(a) Determinate (b) Indeterminate

The process of series of changes from larva to adult after embryonic development is called [CBSE PMT 1999]

(a) Growth (b) Ageing

Growth in living being is called [Kerala CET 2002]

(a) Accretion (b) Intussusception

Willfully seperation of body parts by an animal is called

(a) Autotomy (b) Reparative regeneration

The ability of animals to regenerate the lost parts of the body was reported by [MP PMT 1995]

(a) Carlson (b) Trembley

In old age memory

(a) Increases

(b) Impaired

(d) None of the above

Which of the following protein plays an important role in ageing

(a) Elastin (b) Collagen

B–cells and T–cells become less active in old age. They secrete ……. respectively

(a) Lymphocytes only

(b) RBC and antibodies

(d) Antibodies and lymphocytes

Ageing is characterised by

(a) Nuclear pyknosis

(b) Changes in collagen of extracellular fluid

(d) All the above

Blood volume

(a) Increases with age

(b) Decreases in old age

(d) Least in diseased man

In animals Chalones are substances responsible for

[MP PMT 2002]

(a) Regeneration (b) Ageing

1	b	2	d	3	c	4	a	5	a
6	a	7	d	8	a	9	a	10	b
11	b	12	b	13	d	14	d	15	b
16	b

(b) S–phase is also known as synthesis phase.
(d) In tunicates, auxetic growth is present instead of multiplicative growth.
(a) Growth occurs when the anabolic (Constructive activities) exceed the catabolic activities (destructive activities).
(d) In embryology metamorphosis is defined as transformation of larva into adult during which many structural as well as physiological changes take place.
(a) Autotomy is the power of shedding certain body parts in self defence e.g., limbs in prawns, arms in starfish, tail in wall lizard.
(b) Among animals, power of regeneration was first discovered in Hydra by Trembley, an Englishman, in 1744.
(b) Collagen is the most abundant extracellular protein which with ageing becomes less permeable, less flexible and insoluble. These changes interfere the normal functioning of the cells (decreased inflow of nutritive substances and oxygen into cells and also decreased loss of nitrogenous waste and CO₂ from the body cells) and induce ageing.

Morphallaxis is

(a) Reconstruction of the whole body

(b) Growth of lost limb

(d) Regeneration with the help of blastema

Compensatory hypertrophy is referred to the phenomenon when

(a) An organ redevelops

(b) A small piece of body produces complete animal

(d) An organ is automatically shed

Postembryonic growth is

(a) Accretionary (b) Auxetic

In human beings, growth stops completely at the age of

(a) 18 years (b) 22–23 years

The developing embryo shows

(a) No growth (b) Auxetic growth

Cell growth occurs during

(a) Interphase

(b) Mitotic phase

(d) Interphase and postmitotic phase

Accretionary growth is due to

(a) Reserve cells (b) Meristematic cells

Growth in the first 10–13 years of age is controlled by

(a) Somatotrophic hormone (b) Thyroxine

Substances synthesised during growth are

(a) Protoplasmic

(b) Apoplasmic

(d) Nucleic acids

Absolute increase is the term which means

(a) Total growth in life time

(b) Total growth in one year

(d) Difference between initial weight and final weight of the body during specific time interval irrespective of other factors

In animals, growth rate is

(a) Uniform (b) Linear

Multiplicative growth is found in

(a) Old age (b) Adulthood

A new born sheep grows ……. times faster than a new born human being

(a) 10 (b) 24

Auxetic growth was defined by

(a) Huxley in 1932 (b) Needham in 1942

Growth curve shows

(a) Increase in the length of the animal with age

(b) Increase in the mass of the animal with time

(d) Increase in the mass of the animal with temperature

The nearest approach to pure exponential growth is found in

(a) Rod shaped bacteria

(b) Multicellular organisms

(d) All the above

Absolute increase is

(a) Increase taken as a difference between the final and initial length of an organism for any period of time

(b) Increase taken as a difference between the final and initial age of an organism for any period of time

(d) Total increase in number of a population

The portion of sigmoid growth curve where it represents almost a horizontal line indicates that growth rate

(a) Slows down (lag phase)

(b) Increases very fast (Exponential phase)

(d) Reduces and becomes constant (Steady phase)

Growth controlling factors are

(a) Constitutional factors (b) Temperature

Degrowth is seen during

(a) Regeneration (b) Autotomy

Nucleoprotein ratio increases during

(a) Phase of wound healing

(b) Dedifferentiation

(d) Phase of redifferentiation

Replacement of cells of skin takes place in

(a) 1–2 days (b) 2– 8 days

The turnover time for intestinal cells is

(a) 1–2 days (b) 2– 3 days

Growth curve of higher animals is

(a) J–shaped (b) R–shaped

Thymosine hormone secreted from the thymus gland

(a) In the early stages it enhances in later stages it decreases growth

(b) Enhances growth

(d) Does not show any effect

Juvenile stage extends from

(a) Birth to 10 months of age

(b) 10 months to 4 or 5 years of age

(d) 14 years to 20 or 22 years of age

Growth abnormalities such as gigantism and dwarfism are due to

(a) Hormonal factors (b) Genetic factors

If one kidney of a man is lost, the other kidney enlarges to take over the function of the missing kidney and is called

(a) Restorative regeneration

(b) Reparative regeneration

(d) Compensatory hypertrophy

During regeneration, in destructive metabolism respiratory quotient (R.Q.) in the tissue

(a) Increases

(b) Decreases

(d) First increases then decreases

When volume of body increases due to increase in the volume of cells, not in the number of cells, then it is called ‘auxetic growth‘. Such growth is found in [MP PMT 1996]

(a) Lizards (b) Men

At cellular level, GH affects growth by controlling the production of [MP PMT 1997]

(a) rRNA (b) tRNA

Growth is an irreversible process seen at all organizational levels. It consists of [MP PMT 2002]

(a) Organ growth (b) Subcellular growth

Damage to thymus in a child may lead to [CBSE PMT 2005]

(a) A reduction in haemoglobin content of blood

(b) A reduction in stem cell production

(d) Loss cell mediated immunity

Pennatal growth in higher vertebrate is [AMU 2005]

(a) Auxetic (b) Accretionary

In an experiment freshly hatched larvae of an insect (Khapra beetle) were reared on a basal diet without increasing amounts of cholesterol. Results obtained are shown in the graph given in the table [AIIMS 2005]

(a) Cholesterol is an essential dietary requirement of khapra beetle

(b) Growth of khapra beetle is directly proportional to cholesterol concentration.

(d) Growth of khapra beetle is inhibited when cholesterol concentration exceeds diet.

Which pair is essential for the growth of the fish in water

[BHU 2005]

(a) Calcium and Phosphorus

(b) Phosphates and carbonates

(d) Nitrates and sulphates

Repair and Regeneration

In echinodermata, the following organs can be regenerated

(a) Arms and disc (b) Digestive system

The damaged leg is not regenerated in

(a) Salamander (b) Frog’s tadpole

Blastema formation takes place in

(a) Epimorphosis type of regeneration

(b) Morphallaxis type of regeneration

(d) Deaccelerating growth

The repair by cell division in the damaged tissue is

(a) Epimorphosis regeneration

(b) Morphallaxis regeneration

(d) Deaccelerating growth

Restorative regeneration is

(a) A regular process in which the dead and worn out cells of some organs are continuously replaced by new cells

(b) Formation of a new organism from a piece of the body of the parent

(d) All the above

Healing of cuts and wounds is

(a) Repair (b) Regeneration

Regeneration of a limb or tail is an example of [BVP 2000]

(a) Compensatory hypertrophy

(b) Epimorphosis

(d) Autotomy

The steps involved in cellular growth is/are

(a) Cell division

(b) Cell enlargement

(d) All of the above

During constructive metabolism or regeneration

(a) pH becomes normal (b) R.Q. increases

Which of the following is not case of epimorphosis

[CPMT 2004]

(a) Formation of sperms from small clumps of cells

(b) Regeneration of tail in a lizard

(d) Replacement of limb in salamander

Based on cellular mechanisms there are two major types of regeneration found in the animals. which one of the following is the correct example of the type mentioned

[AIIMS 2005]

(a) Morphallaxis – Regeneration of two transversely cut equal pieces of a Hydra into two small Hydras.

(b) Epimorphosis – Regeneration of old and dead erythrocytes by the new ones.

(d) Epimorphosis – Regeneration of curshed and filtered out pieces of a planaria into as many new planarians.

Ageing and Death

Degenerative changes occur during [CBSE PMT 1991]

(a) Metamorphosis only

(b) Parthenogenesis

(d) Both in metamorphosis and ageing

Which of the following is the environmental theory of ageing

(a) The radiation affects the gene mutation resulting in the DNA transcription in somatic cells.

(b) The rate of ageing and age is controlled by the ageing gene

(d) Metabolic rate affects the ageing

Errors are accumulated due to translation of genetic code affecting the ageing. The theory is

(a) Mutation theory

(b) Error catastrophe theory

(d) Gene theory

Thymus and brain are the main factors in the ageing

(a) Stress theory (b) Gene theory

In old age the activity of collagen protein is badly affected. This is

(a) Permeability which becomes very slow

(b) Permeability which becomes very high

(d) Diffusion which becomes very high

The science of ageing is called or The study of degenerative changes is called

[MP PMT 1993, 96, 2002; Kerala CET 2002]

(a) Chronology (b) Odontology

Ageing in many mammals including man may be due to

[MP PMT 1993]

(a) Adverse changes in the environment

(b) Interaction between hereditary factors (genes) and the environment

(d) All of the above

Who described ageing first

(a) Gagenbaur (b) Mendebaur

Which is called “Clock of ageing”

(a) Thymus (b) Thyroid

Ageing is the result of

(a) Cellular changes (b) Extracellular changes

Ageing is characterised by

(a) Decline in metabolic activity

(b) Increased metabolic activity

(d) Increased consumption

During ageing, collagen present in intercellular spaces becomes [MP PMT 2001]

(a) Destroyed

(b) Impermeable and rigid

(d) All the above

Human body regularly loses cells in the region of

(a) Skin surface (b) Lining layer of gut

Generally decline in hearing power begins after the age of

(a) 50 years (b) 30 years

According to which theory, the resistance of body decreases with the increase in age

(a) Immunity theory (b) Collagen theory

Which theory holds that accumulation of specific waste products causes ageing

(a) Waste product theory (b) Metabolic theory

The parts of the lung affected by ageing are

(a) Alveoli (b) Pulmonary arteries

By which age, the number of uriniferous tubules is reduced to half in man

(a) 40 years (b) 50 years

Intercellular depositions occurs during

(a) Growth (b) Repair

The efficiency of heart decreases with age so heart pumps about …… blood per minute in comparison to young age

(a) 20% (b) 40%

With advancing age in the liver cells there is increased inactivity of

(a) Lipase enzyme (b) Ptyalin enzyme

In old age there is decrease in amount of urine output and difficulty in micturitions it is due to

(a) Increase in number of nephrons

(b) Increase in glomerular filtration

(d) (a) and (b) both

Ageing is a process programmed by the action of on–off–switches was postulated by

(a) Orgel (1963) (b) Holliday (1974)

Immune system of the body is impaired in old age which

(a) Decreases memory

(b) Makes skin loose and wrinkled

(d) Decreases chances of infection

Ageing substances are

(a) Pigments (b) Lipofuchsin

In old age problems like indigestion constipation and gases are caused because of

(a) Number of taste buds are decreased

(b) Amount of digestive juices decreases

(d) All the above

In old age bones become

(a) Elastic

(b) Long

(d) Hollow

Genetic clock was propounded by

(a) V.N. Naik (b) Dr. Singh

Error catastrophe theory was propounded by

(a) B. Pal (b) Orgel

Ageing is process which takes place in

(a) Non-living (b) Dead

Which one of the following is true during ageing

[MP PMT 1997]

(a) Decrease in blood urea and GFR

(b) Increase in calcium content of arteries and cartilage

(d) Decrease in calcium content of arteries and cartilage

The theory of ageing holds that ageing is due to

[MP PMT 2001]

(a) Random mutation in D.N.A. of somatic cells

(b) Increased cross-linkage of collagen & other proteins

(d) All of these

Maximum life span of dog in years is [AFMC 2004]

(a) 5 (b) 10

Which of the following glands control the growth

(a) Anterior pituitary only

(b) Thyroxin only

(d) Anterior pituitary and Thyroxin

Auxetic growth is one in which there is [CBSE PMT 1994]

(a) Increase in the fatty tissue only

(b) Increase in the cell volume only

(d) Increase in the volume of the body due to the decrease in the inter-cellular material

The following cells cannot be grown under tissue culture conditions [MP PMT 1994]

(a) Hela cells (b) Leucocytes

Morphallaxis is reported in

(a) Porifers

(b) Coelentrates and flatworms

(d) All the above

Degrowth takes place when

(a) Anabolism is higher than catabolism

(b) Catabolism is higher than anabolism

(d) Apoplasmatic synthesis is more than protoplasmic synthesis

Maximum growth in human foetus occurs at the age of

(a) Four months (b) Two months

In human beings, which part shows, the minimum increase in weight from birth to adulthood

(a) Muscles (b) Skeleton

Exponential growth of cell population is defined by the expression

(a) (b)

Ageing is caused by disappearance of

Which one of the following is gradually reduced and degenerated in aging according to immunity theory

[CBSE PMT 1996; CPMT 2001; Pb PMT 2004]

(a) Thyroid (b) Parathyroids

When growth takes place only by increase in volume of existing cells it is called as

(a) Auxetic growth (b) Multiplicative growth

Which of these possesses good regenerating power

[MP PMT 2001]

(a) Brain (b) Kidney

Replacement of dead RBCs by new RBCs formed from the erythroblasts of the bone marrow by the process of erythropoeisis is an example of

(a) Growth (b) Degrowth

As a person becomes old, a degenerative process sets in the body which causes [AIIMS 1992]

(a) A gradual alteration in the connective tissue components only

(b) Increase in the collagen content of the connective tissues only

(d) (a) and (b) both are correct

The symptoms of ageing at the organismic level include decrease in the efficiency of

(a) Heart (b) Lungs

Which of the following is the cause of death

(a) Metabotic rate is affected

(b) Sudden check in blood circulation to brain and lungs

(d) All of the above

The bones of old persons become brittle due to accumulation of

(a) Calcium (b) Magnesium

Percentage of nerve cells deteriorated till the age of 70 years is

(a) 10 (b) 20

With increasing age, cell volume

(a) Increases (b) Decreases

Read the assertion and reason carefully to mark the correct option out of the options given below :

(a) If both the assertion and the reason are true and the reason is a correct explanation of the assertion

(b) If both the assertion and reason are true but the reason is not a correct explanation of the assertion

(c) If the assertion is true but the reason is false

(d) If both the assertion and reason are false

(e) If the assertion is false but reason is true

Assertion : Autotomy is the mechanism of self-amputation of certain body parts in self-defence.

Reason : Autotomy is found in legs of prawn, tail of wall lizard and arms of starfish.

Assertion : Birds and mammals show isometric growth.

Reason : Fishes and insects show allometric growth.

Assertion : Growth involves the synthesis of protoplasmic as well as a protoplasmic materials.

Reason : During growth, catabolic activities are faster than anabolic activities.

Assertion : During late childhood period, the body parts show rapid growth rate.

Reason : Thyroxine and STH both become functional in addition to thymosine hormone.

Assertion : Nematodes and tunicates show auxetic growth.

Reason : In these animals, growth occurs only by increases in size of cells and not number of cells.

Assertion : Coelenterates and flatworms show morphollaxis regeneration.

Reason : In both of these, a body fragment can develop into complete organism.

Assertion : In human being, growth is differential.

Reason : Growth is rapid during pre-natal and puberty period, while it is slow during juvenile and post-adolescent period.

Assertion : Growth curve of higher animals is sigmoid.

Reason : Absolute growth is difference between initial and final weight/size of an organism.

Assertion : Growth of different body parts is differential.

Reason : During human growth, muscles show minimum growth, while brain shows maximum growth.

Assertion : In ageing, power of intake of useful material and expelling of harmful materials out of the cells both decrease.

Reason : With age, elastin protein of connective tissue becomes less flexible, less permeable and insoluble.

Assertion : Death is an essential and inescapable biological phenomenon.

Reason : Death maintains ecological homeostasis and justifies the need of reproduction.

Assertion : Nerve supply to a cut part is essential for initiation and completion of regeneration.

Reason : Nerve secretes epidermal growth factor and neurotrophic factor for regeneration.

Assertion : In mammals, liver and kidneys have high power of restorative regeneration.

Reason : Liver increases in size than the normal size when a part of liver is removed.

Assertion : With age, resistance power to diseases is lowered.

Reason : With age, there is gradual degeneration of thymus gland.

Assertion : A regenerated tail of wall lizard shows heteromorphosis.

Reason : Newly formed tail is different from original tail in being without vertebrae.

Assertion : Liver and kidney of man show compensatory hypertrophy.

Reason : Both of these organs grow larger than their normal size when a part is lost.

Assertion : Regeneration blastema is a bud-like structure formed during regeneration of limb in salamander.

Reason : Formation of regeneration blastema involves dedifferentiation.

Assertion : Death is one of the important regulatory process on earth.

Reason : It avoids over-crowding caused by continuous reproduction. [AIIMS 2002]

Assertion : The number of cells in a multicellular organism is inversely proportional to size of body.

Reason : All cells of biological world are alive.

[AIIMS 2002]

Assertion : Smaller the organism higher is the rate of metabolism per gram weight.

Reason : The heart rate of a six month old baby is much higher than that of an old person.

[AIIMS 2003]

Assertion : Old age is not an illness. It is a continuation of life with decreasing capacity for adaptation.

Reason : Cessation of mitosis is normal genetically programmed event. [AIIMS 2003

Growth

1	c	2	d	3	c	4	b	5	a
6	a	7	b	8	c	9	c	10	d
11	a	12	c	13	a	14	b	15	d
16	d	17	a	18	c	19	c	20	d
21	c	22	c	23	c	24	b	25	b
26	c	27	c	28	d	29	d	30	c
31	b	32	c	33	b	34	d	35	b
36	c	37	d	38	d	39	b	40	d
41	c	42	d	43	d	44	d	45	a
46	a

Repair and Regeneration

1	a	2	c	3	a	4	a	5	a
6	a	7	b	8	d	9	d	10	a
11	a

Ageing and Death

1	d	2	a	3	b	4	c	5	a
6	d	7	d	8	c	9	a	10	d
11	a	12	b	13	d	14	d	15	a
16	a	17	d	18	d	19	d	20	c
21	d	22	c	23	c	24	c	25	d
26	b	27	c	28	c	29	b	30	c
31	b	32	d	33	d

Critical Thinking Questions

1	d	2	b	3	d	4	d	5	b
6	a	7	d	8	c	9	c	10	a
11	d	12	c	13	d	14	d	15	d
16	a	17	a	18	b

Assertion and Reason

1	b	2	d	3	c	4	a	5	a
6	a	7	a	8	b	9	c	10	c
11	a	12	d	13	c	14	a	15	a
16	d	17	b	18	a	19	d	20	a
21	c

Growth

(c) In G₂ phase the cell grows further synthesizing more protein and RNAs and doubling the organ cells such as centrioles, mitochondria, golgi apparatus. The G₂ phase prepares the cell for its division.
(d) Growth curve of higher animals including man is ‘S’ shaped and is called sigmoid growth curve.
(c) Accretionary growth due to mitotic multiplication of some specials cells type of reserve cells (condriocytes, osteocytes and mesenchyme) occurring in specific location of the body, e.g. post embryonic growth of animals.
(b) Growth curve is the mathematical expression of the pattern of the growth and can be prepared by plotting the weights of an individual taken at different time intervals (in years). It is generally a sigmoid curve (`S’ shaped).
(a) As proteins form components of cytoplasm, so they help in growth and repair of injured tissues. Proteins are infact the main building blocks of the body.
(c) A few days after the healing of the cut, the undifferentiated cells accumulate inside the epidermis. Due to this cellular aggregation, a stumpy out growth or bulge is formed. This is known a regeneration bud or blastema.
(c) Growth at the end of childhood and during puberty is controlled by thyroxin and somatotropic hormone.
(d) Growth may be defined as increase in size weight and synthesis of new protoplasm.
(a) Morphallaxis is reconstitution of the whole body from a small fragment e.g. Hydra.
(d) During this type of growth, number of cells increase involving cell growth and cell multiplication. The average size of body cells remains nearly constant.
(d) Post mitotic phase includes the interphase consisting of growth₁ phase (G₁) synthetic phase and growth₂ phase (G₂).
(a) Because some special cells present at specific positions of a multicellular organism remain constantly undifferentiated and act as reserve cells.
(c) It is secreted by thymus gland and inhibits growth before the onset of puberty.
(c) Growth takes place by addition of new substances, both protoplasmic and apoplasmic.
(c) Because growth rate is different at different periods of life.
(c) In multiplicative growth the number of cells increase by mitosis division. The average size of cell remain almost same, e.g. growth in embryo.
(b) Growth curve is mathematical expression of growth of a living organism. It can be prepared by plotting the weight (mass) of an organism against the time intervals.
(c) The miniature frog produced at the end of metamorphosis, is lighter and smaller than the mature tadpole. This reduction of body mass is called degrowth.
(b) Dedifferentiation is reversion of the specialised cells back to a more generalised (embryonic) actively dividing state.
(c) The skin cells and epithelial cells lining the respiratory and digestive tracts are rapidly replaced. The turn-over time for skin cells is 1-2 weeks and for intestinal cells is only 2 or 3 days.
(c) Juvenile stage extends from 4 or 5 years to about 14 years of age, i.e. upto the time of puberty.
(b) Due to incomplete oxidation in tissue R.Q. decreases. Mitochondrial number is reduced causing incomplete oxidation.
(d) In auxetic growth the volume of the body increases due to growth of cells not number of cells e.g. nematodes and urochordates.
(d) At the time of birth, Thymus is a prominent atrophics. This gland secretes thymosin hormone, thymic humoral factor, thymic factor and thymopoietin. Proliferation of lymphocytes and differentiation of these lymphocytes and differentiation of these lymphocytes into a variety of clones are induced by these factors. These clones are differentially specialized to destroy different specific category of antigens and pathogens. Thus thymus gland brings T-lymphocytes for cell mediated immunity.

Repair and Regeneration

(c) In adult frog power of regeneration of complete appendage is totally absent.
(a) Epimorphosis is the proliferation of the new tissue cells from the surface of wound e.g. limbs and tail of salamander and lizzard.
(a) Healing the cuts and wounds is repair. The worn out cells, tissue, organs etc can be repaired by the body.
(a) Epimorphosis is a form of development in segmented animals in which body segmentation is completed before hatching. Formation of sperm from small clumps of cells can not be a case of epimorphosis.

Ageing and Death

4. (c) Immunological (Thymus) & neuroendocrine (Brain) control theories of ageing are collectively called a pace-maker theory of ageing.
(a) Collagen in young age groups is permeable, flexible and soluble so there is easy exchange material between the cell cytoplasm and interstitial fluid through semipermeable cell membrane. But with advancing age the collagen protein becomes less flexible, less permeable and insoluble.
(d) Gerentology is the branch of science that deals with ageing. Ageing is also called as senescence.
(a) Burnet suggested that degeneration of thymus gland is a programmed event by the late middle age in man. He stated that thymus is the biological clock of ageing in man.
(a) Due to decreased number of mitochondria with advancing age.
(d) Decline in hearing power beings after the age of 10 years. It declines steadily upto 50 years of age after which the rate of decline is much slower.
(a) According to waste product theory. The accumulation of waste products are considered to poison the cell gradually, resulting in their ageing and death.
(d) Due to the reduction in urine formation, the number of glomeruli undergo degeneration.
(c) The efficiency of heart decreases with age so heart pumps about 65% blood per minute in comparison to young age (30 years). So the blood supply to various organs is also decreased e.g. 80%, to brain and 40–42% to the kidney.
(d) Increased inactivity of aldolase enzyme in the liver cells with advancing age.
(c) The number nephrons in kidneys in old age decreases to 56%, rate of glomerular filtration falls to 69%, so there is decrease in amount of urin output and difficulty in micturition.
(c) The immune system of the body is gradually impaired with advancing age. This increase the chances of infection in old age. Many old persons die of infectious disease.
(d) Accumulation of exhaustion pigments like lipofuscin and yellow pigment etc, formed by incomplete oxidation of unsaturated fats and failure of some excretory mechanism.
(b) The secretion of digestive juices also decreases with old age. This may result in indigestion, loss appetite, dyspepsia, constipation and gas formation.
(c) In old age, mineral deposition increases making bones hard and brittle.
(c) Genetic clock theory was proposed by B. Pal (1975). It is also known as genetic time table theory. Every organism has ageing genes and thus its maximum life span.

Critical Thinking Questions

(d) Anterior pituitary or pars distalis controls growth by increasing rate of cell division through secretion of growth hormone somatotrophin and thyroid regulates growth by secretion of thyroxine hormone which besides increasing rate of cell division is also essential for cell differentiation.
(b) It is a rare type of growth and is found in a few nematodes (Ascaris), rotifers, tunicates (Herdmania) etc.
(b) Degrowth takes place when catabolism (Break down process) is higher than anabolism (constructive process)
(d) In human beings muscles show maximum growth while brain shows minimum growth.
(c) ‘P’ is the size of the population of cells and ’n’ is the number of cycles of cell reproduction.
(c) It has role in growth and disappear after age of 22 while other endocrine glands have role throughout the life.
(d) In mammals liver has extensive power of regeneration. If a part of liver is surgically removed the cells of the remaining part undergo repeated division until the original volume of this vital organ restored
(c) In repairative regeneration the power of repairing only some body cells e.g., skin layer, gut lining RBCs of blood etc.
(b) The cells showing ageing exhibit hypertrophy or decrease in cell volume.

Assertion and Reason

(b) Autotomy power in some non chordates e.g., crustaceans and all echinoderms. Number of vertebrates also have power of autotomy e.g., limbs of ambystoma, tail of wall lizard.
(d) In allometric growth different body organ shows different rate found in birds and mammals, while isometric growth body form and size remain proportional found in fishes and insects.
(c) Growth may be defined as “The increase in size and weight of an organism due to synthesis of new protoplasm”. Growth occurs when the anabolic activities exceed the catabolic activities.
(a) Growth is rapid in pre-natal and puberty period (14-18 years). It is slow in juvenile (5-14 years) and post-adolescent (18-22 years) but is almost nil after the post-adolescent period. During the late childhood period, growth rate becomes faster as long with thymosine, two more hormones start operating – Thyroxin hormone of thyroid gland and somatotrophic hormone (STH) or Growth hormone of anterior pituitary.
(a) In Auxetic category of growth, the volume of the body increases due to growth of body cells in their size with out any change in the number of cells. It involves only cell growth and no cell reproduction. It is rare type of growth and is found in a few nematodes (Ascaris), rotifers, tunicates (Herdmania) etc.
(a) Hydra (coelentrates) is cut transversely into two or more parts. Then they can grew into complete organism of smaller size and planaria (flatworms) can also develop into a complete animal though of smaller size than the parental animal by morphollactic regeneration as in Hydra.
(a) The growth rate is not uniform but is different at different periods of life, so the growth is differential. Growth is rapid in the pre-natal and puberty period (14-18 years). It is slow in the juvenile (5-14 years) and post-adolescent period as there is no addition of living matter in this period.
(b) Growth curve is the mathematical expression of the growth of a living organism. Growth curve of higher animals, including man, is S-shaped and is called sigmoid growth curve. The difference between the initial and final weight (or size) of an individual in a given period of time is called absolute growth.
(c) The growth rate is not uniforms but is different at different period of life. So the growth is differential. In human beings, the muscles show maximum growth (from 0.8 Kg in newly born bady to 30 Kg in adult) while brain shows minimum growth (from 0.4 Kg in newly born bady to 1 Kg in adult) from birth to adult hood.
(c) Collagen forms about 40% of total protein contents of the body collagen in young age-groups, is permeable, flexible and soluble so there is easy exchange of materials between the cell cytoplasm and interstitial fluid through semipermeable cell membrane. But with advancing age, the collagen protein becomes less flexible less permeable and insoluble. Due to these changes, there is a decreased inflow of nutritive substances and oxygen into the cells and also decreased loss of nitrogenous wastes and CO₂ from the body cells. This causes decreased efficiency body cells and induces ageing in the body cell finally in the whole body.
(a) Death is an essential and inescapable biological phenomenon which helps in maintaining ecological balance or homeostasis in nature. It prevents overcrowding of the members of a specific species and justifies the continuity of life on earth.
(d) Regeneration has been shown that if a limb is first denervated and then amputated, or if nerves are by any means blocked from penetrating the epidermis, no regenerative blastema is formed. But if the amputated limb is denervated after the initiation of blastema formation, regenerative process continues and new limb is formed. This confirmed that nerve supply is required for the initiation of regeneration but not for its completion.

The epithelium stimulates the secretion of certain proteinous growth factor like epidermal growth factor (EGF). EGF stimulates the mitotic division and neurons secrete some trophic factor which are essential for the regeneration of amphibian limb.

(c) In fishes, birds and mammals regeneration power is very restricted. In fishes only part of fins can be regenerated; only part of beak can be regenerated in birds while mammals can show only tissue regeneration which is equivalent wound healing. But the liver and kidney of mammals have very high repairative regeneration. Maximum repairative regeneration is found in the liver of mammals. If a part of liver is surgically removed, then the cells of remaining part undergo repeated maintained.
(a) According to the immunity theory – The resistance of body decreases with the increase in age. According to one of the theories of ageing, the decline and disappearance of thymus gland by late middle age is the primary cause of ageing.
(a) Wall lizard can regenerate its lost tail when severed in autotomy but the regenerated tail differs from the original one in shape, lack of vertebrae and the type of scales covering it (heteromorphosis).
(d) Maximum repairative regeneration is found in the liver of mammals. If a part of liver is surgically removed, then the cells of the remaining part undergo repeated mitotic divisions and original volume of the liver is maintained. Similarly if one kidney of man is lost, the other kidney enlarges to take over the function of the missing kidney and is called compensatory regeneration.
(b) Formation of a conical bulge called regeneration blastema or bud below the newly formed epidermal cover so that the epidermis starts bulging during the regeneration of limb of salamander. A number of evidence have supported that the mitotically proliferating cell in a regenerating limb are derived by a regressive process called transformation of dedifferentiation of specialized or fully differentiated cells of the skin, muscles, bones etc.
(a) Death is most important regulatory process on earth. It regulates population and avoids over-crowding on earth.
(d) The number of cells in an organism are directly proportional to size of body cells, vary greatly in size, form and function.
(a) In smaller organism the rate of metabolism is higher in comparison to adult one. For example the average heart rate per minute in new born boby is 130 while in 75 year and above aged persons it is only 75.
(c) Old age is not illness. It includes progressive deterioration of the structure and functions of cells, tissue, organs and organs systems. With increasing age, the efficiency of heat decreases and consequently, the blood going the brain and kidney is reduced to 80% and 42% respectively. Arthritis, weak eyesight, less secretion of digestive juices etc. are some degenerative diseases. Cessation of mitosis is not a genetically programmed event.

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