Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

Many cells function properly and divide mitotically even though they do not have

  • plasma membrane

  • cytoskeleton

  • mitochondria

  • plastids


D.

plastids

The presence of plastid is a feature of plant cells but animal cells are devoid of them. Even then they function properly and divide mitotically similar to plant cells.


2.

Which one of the following four glands is correctly matched with the accompanying description ?

  • Thyroid - hyperactivity in young children causes cretinism

  • Thymus - starts undergoing atrophy after puberty

  • Parathyroid - secretes parathormone which promotes movement of calcium ions from blood into bones during calcification

  • Pancreas - Delta cells of the Islets of Langerhans secrete a hormone which stimulates glycolysis in liver


B.

Thymus - starts undergoing atrophy after puberty

The thymus gland is located behind the sternum and between lungs. It is only active until puberty. After puberty, the thymus starts to shrink slowly and become replaced by fat.

The thyroid gland is a vital hormone gland. It plays an important role in the metabolism growth and development of the human body. It helps to regulate many body functions by constantly releasing a steady amount of thyroid hormones into the bloodstream. Cretinism is a type of mental retardation and bodily malformation caused by severe, uncorrected thyroid deficiency.

The major function of parathyroid gland is to maintain the body's calcium and phosphate levels within a very narrow range, so that the nervous and muscular systems can function properly. It secretes parathyroid hormone. It also enhances the excretion of phosphate by the kidneys and its uptake by the cells.

Pancreas is an organ present in abdomen. It plays an essential role in converting the food we eat into fuel for the body's cells. Delta cells is a type of cell found in Islets of Langerhans in pancreas. They form somatostatin, a hormone that inhibits the release of numerous hormones in the body.


3.

Formation of non-functional methaemoglobin causes blue-baby syndrome. This is due to

  • excess of arsenic concentration in drinking water

  • excess of nitrates in drinking water

  • deficiency of iron in food

  • increased methane content in the atmosphere


B.

excess of nitrates in drinking water

Blue baby syndrome is a blood related condition mostly found in babies due to nitrate poisoning. It particularly limits blood's ability to carry oxygen thereby causing baby to look blue and hence known as metheamoglobanemia. It is a serious illness in infants which is caused when nitrate is converted into nitrite in the infant's body. Nitrite interferes with the oxygen carrying capacity of the child's blood and therby replaces the oxygen on the red blood cells. It is an acute disease and symptoms develop in infants.


4.

When synapsis is complete all along the chromosome, the cell is said to have entered a stage called

  • zygotene

  • pachytene

  • diplotene

  • diakinesis


B.

pachytene

Prophase I consists of 5 stages:

(i) Leptotene- Chromosomes become gradually visible.

(ii) Zygotene- Synapsis, pairing of homlogous chromosomes takes place. It results in the formation of bivalents. Also, formation of special proteinaceous structure called synaptonemal complex occur.

(iii) Pachytene- Cells that eneterd this phase results in spiralling, shortening and thickening of the bivalents.

(iv) Diplotene- Dissolution of synaptonemal complex takes place. Also, recombined homologous chromosomes of the bivalents seperate.

(v) Diakinesis- Terminalisation of chiasmata occur in this phase.


5.

Two of the body parts which do not appear in MRI may be

  • molar teeth and eye lens

  • scapula and canines

  • ligaments and ribs

  • tendons and premolars


B.

scapula and canines

MRI is a non-invasive technique which uses strong magnetic field for generating resonance and low radio frequency in protons present in body. Most common protons are H nuclei of H2O molecules. Scapula and canine are osteocytic structures with negligible H2O content. Also, in MRI we can only see soft tissues, fluids, nerves, vessels, fat and CSF, spinal fluids, brain and eyes.


6.

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?

  • Morphallaxis - Regeneration of two transversely cut equal pieces of a Hydra into two small Hydras

  • Epimorphosis - Replacement of old and dead erythrocytes by the new ones

  • Morphallaxis - Healing up of a wound in the skin

  • Epimorphosis - Regeneration of crushed and filtered out pieces of a Planaria into as many new Planarians


A.

Morphallaxis - Regeneration of two transversely cut equal pieces of a Hydra into two small Hydras

Morphallaxis is the type of regeneration in which lost body parts are replaced by the remodelling of the remaining tissue. In this type, little or no cellular proliferation takes place. Eg, Hydra.

When a Hydra is cut into two pieces, two Hydra will be regenerated, both smaller than the parental Hydra. Once regeneration is completed, the two Hydra can continue to grow and reach the size of their original parent.

Epimorphosis require active cellular proliferation prior to the replacement of the lost body part. Eg, Planarian are flatworms, regenerate using a mechanism in which pre- existing cells, known as neoblasts, begin to proliferate and migrate to the injured site in response to injury. These cells later form mass of proliferating cells known as regenration blastema. These further differentiate into specialized cells. 


7.

Which one of the following four secretions is correctly matched with its source, target and nature of action?

  • Secretion Source Target Action
    Gastrin Stomach lining Oxyntic cells Production of HCl
  • Inhibin Sertoli cells Hypothalamus Inhibition of secretion of gonadotropin releasing hormone
  • Enterokinase Duodenum Gall bladder Release of bile juice
  • Atrial Natiuretic Factor (ANF) Sinu atrial node (SAN) M- cells of Atria Juxta- glomerular apparatus (JGA) Inhibition of release of renin

D.

Atrial Natiuretic Factor (ANF) Sinu atrial node (SAN) M- cells of Atria Juxta- glomerular apparatus (JGA) Inhibition of release of renin

Atrial natriuretic factor (ANF) is released by wails of the cardiac atrium in response to high sodium concentration, high extracellular fluid volume, or high blood volume. It then acts via various mechanisms to excrete Na, and to cause vasodilation in the circulatory system. It also decreases Na resorption in the renal distal convoluted tubule and cortical collecting duct. It also inhibits renin secretion.

Gastrin is a polypeptide hormone produced by the enteroendocrinc cells of the stomach. It plays an important role in the control of gastric acid secretion.

Inhibin hormone is secreted from corpus luteum, placenta and testes. It supplements the effect of excess sex hormones for depressing gonadotrophic activity (FSH, LH, ICSH) target of inhibin is anterior lobe of pituitary.

Duodenal enterokinase converts trypsinogcn to activate trypsin which, in turn, activates the other pancreatic enzymes.


8.

The family containing mustard and its main characters are

  • Brassicaceae - Tetramerous flowers, six stamens, bicarpellary gynoecium, siliqua type fruit

  • Brassicaceae - Pentamerous flowers, many stamens, pentacarpellary gynoecium, capsule type fruit

  • Solanaceae - Pentamerous flowers, five stamens, bicarpellary gynoecium, berry type fruit

  • Poaceae - Trimerous flowers, three stamens, monocarpellary gynoecium, caryopsis type of fruit.


A.

Brassicaceae - Tetramerous flowers, six stamens, bicarpellary gynoecium, siliqua type fruit

Brassica or mustard belongs to family Brassicaceae. It is characterised by polypetalous 4 petals, polysepalous 4 sepals, six stamens (which are in tetradynamous condition i.e. 4 + 2. Gynoecium is bicarpellary, syncarpous unilocular with parietal placentation. Fruit is usually siliqua (dry dehiscent fruit formed by bicarpellary syncarpous gynoecium with replum) and rarely lomentum.

Solanaceae is commonly called potato family. It is characterised by bisexual flower, 5 sepals, 5 petals. Androceium is epipetalous and Gynoecium is bicarpellary obligately placed. Fruit is berry or capsule.

Poaceae or Gramineae is a large and nearly ubiquitous family of monocotyledonous flowering plants known as grasses. It is characterised by bracteate flower. It has usually 3 stamens, 3 carpels. Fruit is caryopsis or nut or berry.


9.

Which one of the following statements is correct with respect to salt water balance inside the body of living organisms?

  • when water is not available camels do not produce urine but store urea in tissues.

  • Salmon fish excretes lot of stored salt through gill membrane when in fresh water

  • Paramecium discharges concentrated salt solution by contractile vacuoles

  • The body fluids of fresh water animals are generally hypotonic to surrounding water


A.

when water is not available camels do not produce urine but store urea in tissues.

The balance of water and salt is essential in order to maintain the health of an animal or humans. 

Camels, excrete highly concentrated urine to conserve water. They do not sweat till body temperature rises about 55€-60C. Camel can also tolerate desiccation upto 40% cellular content.


10.

Which one of the following statements pertaining to plant structure is correct?

  • Cork lacks stomata, but lenticels carry out transpiration.

  • Passage cells help in transfer of food from cortex to phloem

  • Sieve tube elements possess cytoplasm but no nuclei.

  • The shoot apical meristem has a quiescent centre


C.

Sieve tube elements possess cytoplasm but no nuclei.

Sieve tubes in flowering plants consists of elongated living cells of the phloem. Their main function is to transport sugars and other important molecules necessary for plants. On maturity, these loose nucleus and other cellular organelles.

Mature cork cells are plant cells that form the protective water resistant tissue in the outer covering of stems and trunks. They are genetically programmed not to divide, but instead to remain as they are dead cells. They also possess lenticels. A lenticel is produced beneath a former stomata or stoma of the epidermis. They encloses intercellular space for gaseous exchange.

Passage cells help in transfer of water from cortex. Quiescent centre is present in root apical meristem.