NEET AIPMT Biology Chapter Wise Solutions – Solved Paper NEET 2016 (Phase – 1)
The Living World
1. Nomenclature is governed by certain universal rules. Which one of the following is contrary to the rules of nomenclature?
(a) The names are written in Latin and are italicised.
(b) When written by hand the names are to be underlined.
(c) Biological names can be written in any language.
(d) The first word in a biological name represents the genus name and the second is a specific epithet. Biological Classification
2. The primitive prokaryotes responsible for the production of biogas from the dung of ruminant animals, include the
3. Which one of the following statements is wrong?
(a) Eubacteria are also called false bacteria.
(b) Phycomycetes are also called algal fungi.
(c) Cyanobacteria are also called blue-green algae.
(d) Golden algae are also called desmids.
4. Which of the following statements is wrong for viroids?
(a) They cause infections.
(b) Their RNA is of high molecular weight.
(c) They lack a protein coat.
(d) They are smaller than viruses.
5. One of the major components of cell wall of most fungi is
6. Chrysophytes, Euglenoids, Dinoflagellates and Slime moulds are included in the kingdom
7. Select the correct statement.
(a) Sequoia is one of the tallest trees.
(b) The leaves of gymnosperms are not well adapted to extremes of climate.
(c) Gymnosperms are both homosporous and heterosporous.
(d) Salvinia, Ginkgo and Pinus all are gymnosperms.
8. In bryophytes and pteridophytes, transport of male gametes requires
9. Which one of the following characteristics is not shared by birds and mammals?
(b) Warm blooded nature
(c) Ossified endoskeleton
(d) Breathing using lungs
10. Which of the following characteristic features always holds true for the corresponding group of animals?
11. Which of the following features is not present in the Phylum Arthropoda?
(b) Jointed appendages
(c) Chitinous exoskeleton
(d) Metameric segmentation
Morphology of Flowering Plants
12. Which of the following is not a stem modification?
(a) Tendrils of cucumber
(b) Flattened structures of Opuntia
(c) Pitcher of Nepenthes
(d) Thorns of citrus
13. Stems modified into flat green organs performing the functions of leaves are known as
14. Cotyledon of maize grain is called
15. Tricarpellary, syncarpous gynoecium is found in flowers of
16. The standard petal of a papilionaceous corolla is also called
Anatomy of Flowering Plants
17. Specialised epidermal cells surrounding the guard cells are called
(a) bulliform cells
(c) complementary cells
(d) subsidiary cells.
Structural Organisation in Animals
18. Which type of tissue correctly matches with its location?
19. Which of the following features is not present in Periplaneta americana?
(a) Exoskeleton composed of N-acetylglucos- amine
(b) Metamerically segmented body
(c) Schizocoelom as body cavity
(d) Indeterminate and radial cleavage during embryonic development
Cell: The Unit of Life
20. Mitochondria and chloroplast are
(A) semi-autonomous organelles
(B) formed by division of pre-existing organelle! and they contain DNA but lack proteir synthesising machinery.
Which one of the following options is correct?
(a) (A) is true but (B) is false.
(b) Both (A) and (B) are false.
(c) Both (A) and (B) are correct.
(d) (B) is true but (A) is false.
21. Microtubules are the constituents of
(a) centrioles, spindle fibres and chromatin
(b) centrosome, nucleosome and centrioles
(c) cilia, flagella and peroxisomes
(d) spindle fibres, centrioles and cilia.
22. Which one of the following cell organelles is enclosed by a single membrane?
23. A typical fat molecule is made up of
(a) one glycerol and one fatty acid molecule
(b) three glycerol and three fatty acid molecules
(c) three glycerol molecules and one fatty acid molecule
(d) one glycerol and three fatty acid molecules.
24. Which one of the following statements is wrong?
(a) Uracil is a pyrimidine.
(b) Glycine is a sulphur containing amino acid.
(c) Sucrose is a disaccharide.
(d) Cellulose is a polysaccharide.
Cell Cycle and Cell Division
25. Spindle fibres attach on to
(a) centromere of the chromosome
(b) kinetosome of the chromosome
(c) telomere of the chromosome
(d) kinetochore of the chromosome.
26. Which of the following is not a characteristic feature during mitosis in somatic cells?
(a) Chromosome movement
(c) Spindle fibres
(d) Disappearance of nucleolus
27. In meiosis crossing over is initiated at
28. In which of the following all three are macronutrients?
(a) Molybdenum, magnesium, manganese
(b) Nitrogen, nickel, phosphorus
(c) Boron, zinc, manganese
(d) Iron, copper, molybdenum
Photosynthesis in Higher Plants
29. Water vapour comes out from the plant leaf through the stomatal opening. Through the same stomatal opening carbon dioxide diffuses into j the plant during photosynthesis. Reason out the above statements using one of following options.
(a) The above processes happen only during night time.
(b) One process occurs during day time and the other at night.
(c) Both processes cannot happen simultaneously.
(d) Both processes can happen together because the diffusion coefficient of water and CO2 is different.
30. In a chloroplast the highest number of protons are found in
(a) intermembrane space
(b) antennae complex
(d) lumen of thylakoids.
31. Emerson’s enhancement effect and Red drop have been instrumental in the discovery of
(a) photophosphorylation and cyclic electron transport
(b) oxidative phosphorylation
(c) photophosphorylation and non-cyclic electron transport
(d) two photosystems operating simultaneously.
32. A plant in your garden avoids photorespiratory losses, has improved water use efficiency, shows high rates of photosynthesis at high temperatures and has improved efficiency of nitrogen utilisation. In which of the following physiological groups would you assign this plant?
(b) Nitrogen fixer
33. Water soluble pigments found in plant cell vacuoles are
Plant Growth and Development
34. The Avena curvature is used for bioassay of
Digestion and Absorption
35. Which of the following guards the opening of hepatopancreatic duct into the duodenum?
(a) Pyloric sphincter
(b) Sphincter of Oddi
(c) Semilunar valve
(d) Ileocaecal valve
36. In the stomach, gastric acid is secreted by the
(a) peptic cells
(b) acidic cells
(c) gastrin secreting cells
(d) parietal cells.
Breathing and Exchange of Gases
37. Reduction in pH of blood will
(a) decrease the affinity of haemoglobin with oxygen
(b) release bicarbonate ions by the liver
(c) reduce the rate of heart beat
(d) reduce the blood supply to the brain.
38. Name the chronic respiratory disorder caused mainly by cigarette smoking.
(a) Respiratory acidosis
(b) Respiratory alkalosis
39. Asthma may be attributed to
(a) inflammation of the trachea
(b) accumulation of fluid in the lungs
(c) bacterial infection of the lungs
(d) allergic reaction of the mast cells in the lungs.
Body Fluids and Circulation
40. Blood pressure in the pulmonary artery is
(a) more than that in the pulmonary vein
(b) less than that in the venae cavae
(c) same as that in the aorta
(d) more than that in the carotid.
Locomotion and Movement
41. In mammals, which blood vessel would normally carry largest amount of urea?
(a) Hepatic Vein
(b) Hepatic Portal Vein
(c) Renal Vein
(d) Dorsal Aorta
42. Lack of relaxation between successive stimuli in sustained muscle contraction is known as
Neural Control and Coordination
43. Photosensitive compound in human eye is made up of
(a) opsin and retinol
(b) transducin and retinene
(c) guanosine and retinol
(d) opsin and retinal.
Chemical Coordination and Integration
44. Which of the following pairs of hormones are not antagonistic (having opposite effects) to each other?
(a) Aldosterone Atrial Natriuretjc Factor
(b) Relaxin Inhibin
(c) Parathormone Calcitonin
(d) Insulin Glucagon
45. The amino acid tryptophan is the precursor for the synthesis of
(a) estrogen and progesterone
(b) cortisol and cortisone
(c) melatonin and serotoriin
(d) thyroxine and triiodothyronine.
46. The coconut water from tender coconut represents
(a) free nuclear proembryo
(b) free nuclear endosperm
(d) fleshy mesocarp.
47. Which one of the following statements is not true?
(a) Pollen grains of many species cause severe allergies.
(b) Stored pollen in liquid nitrogen can be usee in the crop breeding programmes.
(c) Tapetum helps in the dehiscence of anther.
(d) Exine of pollen grains is made up c sporopollenin.
48. Seed formation without fertilisation in flowering plants involves the process of
(a) somatic hybridisation
49. Which of the following statements is not correct?
(a) Pollen germination and pollen tube growth are regulated by chemical components of pollen interacting with those of the pistil.
(b) Some reptiles have also been reported as pollinators in some plant species.
(c) Pollen grains of many species can germinate on the stigma of a flower, but only one pollen tube of the same species grows into the style.
(d) Insects that consume pollen or nectar without bringing about pollination are called pollen/ nectar robbers.
50. Proximal end of the filament of stamen is attached to the
(b) thalamus or petal
51. Changes in GnRH pulse frequency in females is controlled by circulating levels of
(a) progesterone only
(b) progesterone and inhibin
(c) estrogen and progesterone
(d) estrogen and inhibin.
52. Fertilisation in humans is practically feasible only if
(a) the ovum and sperms are transported simultaneously to ampullary-isthmic junction of the cervix
(b) the sperms are transported into cervix within 48 hrs of release of ovum in uterus
(c) the sperms are transported into vagina just after the release of ovum in Fallopian tube
(d) the ovum and sperms are transported simultaneously to ampullary-isthmic junction of the Fallopian tube.
53. Select the incorrect statement.
(a) LH and FSH decrease gradually during the follicular phase.
(b) LH triggers secretion of androgens from the Leydig cells.
(c) FSH stimulates the sertoli cells which help in spermiogenesis.
(d) LH triggers ovulation in ovary.
54. Identify the correct statement on ‘inhibin’.
(a) Is produced by granulosa cells in ovary and inhibits the secretion of LH
(b) Is produced by nurse cells in testes and inhibits the secretion of LH
(c) Inhibits the secretion of LH, FSH and prolactin
(d) Is produced by granulosa cells in ovary and inhibits the secretion of FSH ,
55. Which of the following approaches does not give the defined action of contraceptive?
56. In context of amniocentesis, which of the following statements is incorrect?
(a) It can be used for detection of Down’s syndrome.
(b) It can be used for detection of cleft palate.
(c) It is usually done when a woman is between 14-16 weeks pregnant.
(d) It is used for prenatal sex determination.
Principles of Inheritance and Variation
57. A cell at telophase stage is observed by a student in a plant brought from the field. He tells his teacher that this cell is not like other cells at telophase stage. There is no formation of cell plate and thus the cell is containing more number of chromosomes as compared to other dividing cells. This would result in
(a) somaclonal variation
58. Pick out the correct statements.
(1) Haemophilia is a sex-linked recessive disease.
(2) Downs syndrome is due to aneuploidy.
(3) Phenylketonuria is an autosomal recessive gene disorder.
(4) Sickle cell anaemia is an X-linked recessive gene disorder.
(a) (1), (3) and (4) are correct.
(b) (1), (2) and (3) are correct.
(c) (1) and (4) are correct.
(d) (2) and (4) are correct.
59. A tall true breeding garden pea plant is crossed with a dwarf true breeding garden pea plant. When the F, plants were selfed thp resulting genotypes were in the ratio of
(a) 3:1:: Tall: Dwarf
(b) 3:1:: Dwarf: Tall
(c) 1:2:1:: Tall homozygous: Tall heterozygous : Dwarf
(d) 1:2:1:: Tall heterozygous: Tall homozygous : Dwarf
60. Match the terms in column I with their description in column II and choose the correct
61. In a test cross involving F, dihybrid flies, more parental-type offspring were produced than the recombinant-type offspring. This indicates
(a) the two genes are linked and present on the same chromosome
(b) both of the characters are controlled by more than one gene
(c) the two genes are located on two different chromosomes
(d) chromosomes failed to separate during j meiosis.
62. Which of the following most appropriately describes haemophilia?
(a) Chromosomal disorder
(b) Dominant gene disorder
(c) Recessive gene disorder
(d) X-linked recessive gene disorder
Molecular Basis of Inheritance
63. Which one of the following is the starter codon?
64. Which of the following is required as inducer (s) for the expression of Lac operon?
(b) Lactose and Galactose
65. A complex of ribosomes attached to a single strand of RNA is known as
(b) okazaki fragment
66. Which of the following structures is homologus to the wing of a bird?
(a) Hindlimb of rabbit
(b) Flipper of whale
(c) Dorsal fin of a shark
(d) Wing of a moth
67. Analogous structures are a result of
(a) shared ancestry
(b) stabilising selection
(c) divergent evolution
(d) convergent evolution.
68. Following are the two statements regarding the origin of life.
(A) The earliest organisms that appeared on the earth were non-green and presumably anaerobes.
(B) The first autotrophic organisms were the chemoautotrophs that never released oxygen.
Of the above statements which one of the following options is correct?
(a) Both (A) and (B) are correct.
(b) Both (A) and (B) are false.
(c) (A) is correct but (B) is false.
(d) (B) is correct but (A) is false.
Human Health and Diseases
69. Antivenom injection contains preformed antibodies while polio drops that are administered into the body contain
(b) attenuated pathogens
(c) activated pathogens
(d) harvested antibodies.
70. Which of the following statements is not true for cancer cells in relation to mutations?
(a) Mutations inactivate the cell control.
(b) Mutations inhibit production of telomerase.
(c) Mutations in proto-oncogenes accelerate the cell cycle.
(d) Mutations destroy telomerase inhibitor.
71. In higher vertebrates, the immune system can distinguish self-cells and non-self. If this property is lost due to genetic abnormality and it attacks self-cells, then it leads to
(a) autoimmune disease
(b) active immunity
(c) allergic response
(d) graft rejection.
Strategies for Enhancement in Food Production
72. A system of rotating crops with legume or grass pasture to improve soil structure and fertility is called
(a) strip farming
(b) shifting agriculture
(c) ley farming
(d) contour farming.
Microbes in Human Welfare
73. Which of the following is wrongly matched in the given table?
Biotechnology : Principles and Processes
74. Which of the following is not a feature of the plasmids?
(c) Independent replication
(d) Circular structure
75. The Taq polymerase enzyme is obtained from
(a) Bacillus subtilis
(b) Pseudomonas putida
(c) Thermus aquaticus
76. Which of the following is a restriction endonuclease?
(a) DNase I
(c) Hind ll
77. Which of the following is not required for any of the techniques of DNA fingerprinting available at present?
(a) Restriction enzymes
(b) DNA-DNA hybridisation
(c) Polymerase chain reaction
(d) Zinc finger analysis
Biotechnology and its Applications
78. The two polypeptides of human insulin are linked together by
(a) covalent bond
(b) disulphide bridges
(c) hydrogen bonds
(d) phosphodiester bond.
79. Which part of the tobacco plant is infected by Meloidogyne incognita?
Organisms and Populations
80. It is much easier for a small animal to run uphill than for a large animal, because
(a) small animals have a lower 02 requirement
(b) the efficiency of muscles in large animals is less than in the small animals
(c) it is easier to carry a small body weight
(d) smaller animals have a higher metabolic rate.
81. When does the growth rate of a’ population following the logistic model equal zero? The logistic model is given as dN/dt = rN(l-N/K)
(a) when N/K equals zero
(b) when death rate is greater than birth rate
(c) when N/K is exactly one
(d) when N nears the carrying capacity of the habitat.
82. Gauses principle of competitive exclusion states that
(a) no two species can occupy the same niche indefinitely for the same limiting resources
(b) larger organisms exclude smaller ones through competition
(c) more abundant species will exclude the less abundant species through competition
(d) competition for the same resources exclude species having different food preferences.
83. Which of the following would appear as the pioneer organisms on bare rocks?
(b) Green algae
84. Which one of the following is a characteristic feature of cropland ecosystem?
(a) Absence of weeds
(b) Ecological succession
(c) Absence of soil organisms
(d) Least genetic diversity
85. The term ecosystem was coined by
(a) E. Haeckel
(c) E.P. Odum
(d) A. G. Tansley.
Biodiversity and Conservation
86. Which is the National Aquatic Animal of India?
(a) Blue whale
(c) Gangetic shark
(d) River dolphin
87. Which of the following is the most important cause of animals and plants being driven to extinction?
(a) Habitat loss and fragmentation
(d) Alien species invasion
88. Depletion of which gas in the atmosphere can lead to an increased incidence of skin cancers?
(c) Nitrous oxide
89. Joint Forest Management Concept was introduced in India during
90. A river with an inflow of domestic sewage rich in organic waste may result in
(a) an increased production of fish due to biodegradable nutrients
(b) death of fish due to lack of oxygen
(c) drying of the river very soon due to algal bloom
(d) increased population of aquatic food web organisms.
Biological names are derived either from Latin language or are latinised. This is because Latin language is a dead language and therefore it will not change in form or spellings with the passage of time.
Methanogens are obligate anaerobes found in oxygen deficient environments such as marshes, swamps, sludge (formed during sewage treatment) and digestive systems of ruminants. Mostly they obtain their energy by reducing carbon dioxide and oxidising hydrogen with the production of methane. Eg., Methanobacillus and Methanothrix.
Eubacteria are also called true bacteria.
RNA of viroid has low molecular weight.
Fungal cell wall contains chitin or fungal cellulose along with other polysaccharides, proteins, lipids and a number of other substances.
Protista is a kingdom of unicellular eukaryotic organisms. Itincludesphotosyntheticprotists(dinoflagellates, chrysophytes and euglenoids), consumer-decomposer protists (slime moulds) and protozoan protists.
Sequoia sempervirens is the tallest gymnosperm. The leaves of gymnosperms are well adapted to extremes of climate. This is the reason for gymnosperm to flourish in cold areas where instead of rain, snow is the source of water. Gymnosperms are heterosporous i.e„ produce two different kinds of spores-microspores and megaspores. Salvinia is an aquatic pteridophyte.
The sperms of bryophytes and pteridophytes are flagellated and hence require an external supply of water to reach archaegonia.
All birds are oviparous while all mammals except Ornithorhyncus (duck billed platypus) and Echidna or Tachyglossus (spiny anteater) are viviparous.
PhylumChordataincludesbothjawlessvertebrates (Agnatha) and jawed vertebrates (Gnathostomata). Crocodile of Class Reptilia has four chambered heart with two auricles and two ventricles. Duck billed platypus and spiny anteater are oviparous mammals.
Parapodia are flattened, fleshy, vertical flap¬like outgrowths of body wall found in annelids on lateral sides of trunk segments. These are hollow structures enclosing coelom which is continuous with that of trunk segments. These serve the dual purpose of locomotion and respiration.
Pitcher of Nepenthes is a modification of leaf. In Nepenthes, the pitchers are meant for catching and digesting insects. The lamina is modified into pitcher. The leaf apex gives rise to a coloured lid for attracting the insects.
Phylloclades are flattened green stems which have taken over the function of photosynthesis while cladodes are only the branches of stem that are modified to take over the function of leaves. Cladodes may not be flattened as in Ruscus aculeatus, cladodes are leaf-like with spiny tip whereas in Asparagus, they are slightly flattened, fleshy, straight or curved pointed structures which develop in clusters in the axil of scale leaves.
Members of Liliaceae possess tricarpellary, syncarpous gynoecium with superior ovary. The ovary is trilocular with two to many ovules in each loculus.
The posterior large bilobed petal of a papilionaceous corolla is called standard or vexillum. It overlaps the two smaller lateral petals known as wings or alae.
The leaf and stem epidermis of plant is covered with pores called stomata. Each stomata is surrounded by a pair of specialised epidermal cells known as guard cells which are in some cases further surrounded by another category of less modified epidermal cells known as subsidiary cells which provide support to the guard cells.
Tip of nose has elastic cartilage. Simple columnar epithelium lines the stomach. Tendon is white fibrous connective tissue. Posterior part of intestine has single unit smooth muscle in which all fibres of muscle contract simultaneously as single unit.
In insect cleavage is superficial.
Both mitochondria and chloroplast are semi- autonomous organelles. They have their own DNA which produces its own, mRNA, fRNA and rRNA. These organelles also possess their own ribosomes and hence are able to synthesise some of their proteins.
Microtubules are unbranched hollow submicroscopic tubules of protein tubulin which develop on specific nucleating regions. It can undergo quick growth or dissolution at their ends by assembly or disassembly of monomers.
They are present in the cytoplasm as well as in specialised structures like centrioles, basal bodies, cilia or flagella, sensory hair, equatorial ring of thrombocytes, spindle apparatus, chromosome fibres, nerve processes, sperm tails, axostyle of parasitic flagellates, fibre system of Stentor, cyto- pharyngeal basket of Nassula, etc.
Lysosomes are small vesicles bounded by a single membrane and contain, hydrolytic enzymes. Nucleus, mitochondria and chloroplasts are double membrane bound cells organelles.
Neutral or true fats are triglycerides which are formed by esterification of three molecules of fatty acids with one molecule of trihydric alcohol, glycerol (glycerine or trihydroxy propane).
Glycine is a neutral amino acid. Cysteine and methionine are sulphur containing amino acid.
Small disc-shaped structures at the surface of the centromeres are called kinetochores. These structures serve as the sites of attachment of spindle fibres to the chromosomes that are moved into position at the centre of the cell.
Synapsis is the process of association of homologous chromosomes. It takes place during zygotene stage of prophase I of meiosis. This stage is not seen during mitosis.
Crossing over is a process of exchange of genetic material or chromatid segments between two homologous chromosomes. It is initiated during pachytene stage of meiosis.
(None of the options are correct.)
Macronutrients are essential elements which are present in easily detectable quantities, 1-10 mg per gram of dry weight. The macro nutrients include carbon, hydrogen, oxygen, nitrogen, phosphorous, sulphur, potassium, calcium and magnesium. Micro nutrients or trace elements, are needed in very small amounts (equal or less than 0.1 mg/ gm of dry matter). These include iron, manganese, copper, molybdenum, zinc, boron, chlorine and nickel.
Emerson et al. (1957) found that if light of shorter wavelengths was provided at the same time as the longer red wavelengths, photosynthesis was even faster than the sum of the two rates with either colour alone. This synergism or enhancement became known as the Emerson enhancement effect. Enhancement can be interpreted as the long red wavelengths helping out the shorter wavelengths, or as the short group helping out the long red wavelengths. The two separate groups of pigments or photosystems cooperate in photosynthesis and that such long red wavelengths are absorbed only by one photosystem, called photosystem I (PS I). The second photosystem, photosystem II (PS II), absorbs wavelengths shorter than 690 nm, and for maximum photosynthesis wavelengths absorbed by both systems must function together. The two photosystems normally cooperate to cause photosynthesis at all wavelengths shorter than 690 nm, because both photosystems absorb those wavelengths. The importance of Emerson’s work is that it suggested the presence of two distinct photosystems.
Anthocyanins are water soluble pigments, which commonly occur in membrane enclosed vacuoles. They are responsible for colour of fruits and flower petals.
Avena curvature test is a test based on the experiments of Went (1928) which can measure auxin upto 300 pg/litre. Indole 3-Acetic Acid (IAA) is a universal natural auxin and Avena curvature test may serve as an accurate bioassay for this plant hormone.
The sphincter of Oddi is a muscular valve that controls the flow of digestive juices (bile and pancreatic j uice) through the hepatopancreatic duct into the duodenum.
Parietal cells are large cells present on the side walls of the gastric glands. They lie against the basement membrane. They secrete hydrochloric acid and Castle’s intrinsic gastric factor that helps in the absorption of vitamin BJ2 in the ileum.
Reduction in pH of blood causes oxygen- haemoglobin dissociation curve to shift to right which indicates dissociation of oxygen from haemoglobin. This decreases affinity of haemoglobin for oxygen.
Emphysema is a chronic obstructive pulmonary disease (COPD) caused due to cigarette smoking. It is an inflation or abnormal distention of the bronchioles or alveolar sacs of the lungs which causes irreversible distension and loss of elasticity of alveoli of the lungs.
Asthma is an allergic condition in which the tissue surrounding the bronchioles of the lungs swell up and compress the bronchioles thus causing difficulty in breathing. This allergy mainly involves IgE antibodies and chemicals like histamine and serotonin from the mast cells.
Hepatic vein carries largest amount of urea. Urea is produced in liver. Hepatic vein transports liver’s deoxygenated blood to heart for oxygenation.
Tetanus refers to continued state of contraction of a muscle resulting from the summation of a series of rapid muscular contractions (twitches) that are induced by repeated stimulation of the muscle.
The rods contain a photosensitive pigment called the rhodopsin. Rhodopsin is composed of opsin and retinene. The opsin is a protein and is called scotopsin in rhodopsin. The retinene is an aldehyde of vitamin A and is called retinal.
Aldosterone is released from adrenal glands which induces distal convoluted tubule to absorb more Na+ and water. ANF inhibits the release of renin from juxtaglomerular apparatus (JGA) and thereby, inhibits NaCl reabsorption by the collecting duct and reduces aldosterone release from the adrenal gland.
Calcitonin is secreted when calcium level is high in the blood. It then lowers the calcium level by suppressing release of calcium ions from the bones. Parathormone is secreted when blood calcium level is too low. Parathyroid gland stops secreting PTH and brings calcium level back to the normal. Thus, calcitonin has an action opposite to that of the parathyroid hormone or parathormone on calcium metabolism.
Insulin lowers blood sugar level and glucagon raises blood sugar level. Relaxin hormone is secreted by ovary and placenta during pregnancy, which relaxes ligaments in pelvis and softens and widens cervix during childbirth. Inhibin secreted by granulosa cells in the ovaries inhibits secretion of FSH by anterior pituitary. Thus, relaxin and inhibin have different functions and are not antagonistic.
Tryptophan is an essential amino acid which is precursor for the synthesis of melatonin and serotonin.
Coconut has multicellular endosperm (called coconut meal) in the outer part and free nuclear as well as vacuolate endosperm (called coconut milk or coconut water) in the centre.
Tapetum is the innermost wall layer of microsporangium that nourishes developing pollen grains.
Apomixis is a reproductive process which does not involve gametic fusion. In apomictic flowering plants there is no fertilisation and embryos develop simply by division of a cell of ovule.
Pollen-pistil interaction is the group of events that occur from the time of pollen deposition over the stigma to the time of pollen tube entry into ovule. It is a safety measure to ensure that illegitimate crossing does not occur. Pollen grains of number of plants may settle over a stigma. The pollens belonging to same species would germinate while other fail to do so but the pollen tube of the compatible pollen will grow through the style to reach the ovule whereas growth of incompatible pollens will be arrested at stigmatic disc or sometimes in the beginning part of style.
GnRH is secreted by the hypothalamus which stimulates the anterior lobe of pituitary gland to secrete luteinising hormone (LH) and FSH. FSH stimulates the growth of the ovarian follicles and stimulates the formation of oestrogens. LFI stimulates the corpus luteum to secrete progesterone. Rising levels of progesterone and estrogen inhibits the release of GnRH, which, in turn, inhibits the production of FSH and LH.
The fusion of a haploid male gamete (sperm) and a haploid female gamete (ovum) to form a diploid zygote is called fertilisation. In human beings, it takes place in the ampullary isthmic junction of the oviduct (Fallopian tube).
During follicular phase FSH secretion increases. Follicular phase (proliferative phase) usually includes cycle days 6-13 or 14 in a 28 days cycle. The follicle stimulating hormone (FSH) secreted by the anterior lobe of the pituitary gland stimulates the ovarian follicle to secrete oestrogens.
Vasectomy is a sterilisation technique for the males in which a small part of the vas deferens is removed or tied up through a small cut on the scrotum to prevent passage of sperms. Spermatogenesis is the series of cell division in the testis that results in the production of spermatozoa or sperms.
Amniocentesis is foetal sex determination and disorder test based on the chromosomal pattern in the amniotic fluid surrounding the developing embryo. It can be used to determine the sex of the infant, to identify some abnormalities in the number of chromosomes and to detect certain biochemicals and enzymatic abnormalities. It is usually done when woman is 14-16 weeks pregnant. Cleft plate can be detected by ultrasound.
Polyploidy is the phenomenon of occurrence of more than two sets of chromosomes in the nucleus of a cell. Polyploidy is more common in plants. Polyploidy arises as a result of total nondisjunction of chromosomes during mitosis or meiosis.
Sickle-cell anaemia is an autosomal recessive genetic disorder. It can be transmitted from parents to the offspring when both the partners are carriers of the gene (or heterozygous).
When a tall true breeding garden pea plant is crossed with a dwarf true breeding garden pea plant and the F, plants were selfed the resulting genotypes were in the ratio of 1 : 2 : 1 i.e., Tall homozygous Tall heterozygous Dwarf
It can be illustrated as given below
If in a dihybrid test cross more parental combinations appear as compared to the recombinants in F2 generation, then it is indicative of involvement of linkage. Linkage is the tendency of two different genes on the same chromosome to remain together during the separation of homologous chromosomes at meiosis. During complete linkage no recombinants are formed whereas in incomplete linkage few recombinants are produced along with parental combinations.
Haemophilia is a sex-linked disease. It is genetically due to the presence of a recessive sex linked gene h, which is carried by X-chromosome.
Polypeptide synthesis is signalled by two initiator codons or start codons i.e., AUG (methionine codon) and rarely by GUG (valine codon).
In Lac operon, lactose is an inducer. It binds with suppressor and inactivates it. It allows RNA polfmers access to the promoter and transcription proceeds.
Homologous organs have same fundamental structure but different function. The wing of a bird and flipper of a whale are structurally forelimbs, which consist of humerus, radio-ulna, carpals, metacarpals and digits but they perform different function. The wings of birds help them to fly while flipper helps the whale to swim.
The organs which have similar functions but are different in their structural details and origin are called analogous organs. The analogous structures are the result of convergent evolution.
The Sabin vaccine or trivalent ‘oral polio vaccine’ consists of attenuated viral strains.
Autoimmunity is a disorder of the body’s defence mechanisms in which an immune response is elicited against its own tissues, which are thereby damaged or destroyed. Auto immunity may be caused due to genetic or environmental factors.
Ley farming is an agricultural system where the field is alternately seeded for grain and left fallow for growing hay or used for pasture. During the fallow/pasture period the soil is filled with roots of grasses and other plants. New ploughing mixes them in the soil and also increases the amount of nitrogen in the soil especially when legume forage are used. It also protects soil from erosion by maintaining constant soil coverage.
Clostridium butylicum helps in the production of butyric acid. Candida lipolytica and Geotrichum candidum help in production of lipases that are added in detergents for removing oily stains from laundry.
Plasmids are extra-chromosomal, self-replicating, usually circular, double-stranded DNA molecules that serve as vectors which carry foreign DNA segment and replicate inside host cell.
Taq polymerase, generally used in PCR is isolated from thermophilic bacterium 7hermus aquaticus.
Hind II is the first restriction endonuclease. It was isolated from Haemophilus influenzae Rd. It always cut DNA at specific position producing blunt ends. DNase I is an endonuclease that cleaves DNA preferentially at phosphodiester linkages adjacent to a pyrimidine nucleotide non-specially. RNAse is a type of nuclease that catalyses the degradation of RNA into smaller components. It can be endoribonuclease or exoribonuclease. A protease is an enzyme that perform proteolysis, i.e., protein catabolism by hydrolysis of the peptide bonds.
Any small, functional, freely folded domain in which coordination of one or more zinc ions is required to stabilise its structure is known as zinc finger. The zinc finger domains are widely dispersed in eukaryotic genomes and are actively involved in sequence specific binding to DNA/ RNA and contribute in protein-protein recognitions.
Human insulin is made up of 51 amino acids arranged in two polypeptide chains. Chain A has 21 amino acids and chain B has 30 amino acids. The two polypeptide chains are interconnected by disulphide bridges or S-S-linkages.
Meloidogyne incognita is a nematode which infects the roots of the tobacco plants and causes a great reduction in the yield.
The small animals have smaller surface area to body volume ratio. They have higher metabolic rates than larger animals. Therefore, it is much easier for small animals to move uphill than large animals.
Gause’s ‘competitive exclusion principle’ states that if resources are limited, then two closely related species competing for the same resource cannot co-exist indefinitely and the competitively inferior one will be eliminated eventually.
The bare rocky habitat is extremely hostile to living beings. There is no water, as the substratum does not absorb rain water. There is no nutrient holding mechanism. Plants cannot grow on these rocks. The first inhabitants or pioneers of such a habitat are usually lichens as they are resistant to desiccation and extreme temperatures.
Cropland ecosystem is an artificial or man-made terrestrial ecosystem which is created and maintained by human beings for their maximum benefits. Therefore, they will have least genetic diversity.
The term ecosystem was coined by A.G. Tansley in 1935.
River dolphin found in holy river Ganga, Brahmputra, Indus and its tributaries is the National aquatic animal of India. Presence of river dolphin in Ganga indicates pure and fresh water.
Destruction of natural habitat causes the most serious threat to the biodiversity. Over-population, urbanisation and industrialisation lead to the destruction or fragmentation of natural habitats to fulfill the requirement of additional land. Loss of habitat results in annihilation of plants, microorganisms and forcing out of animals which in alien lands die out after some time. Fragmentation of habitats results in disruption of complex interactions amongst species, destruction of species in the cleared regions, annihilation of species restricted to deeper undisturbed parts of forests and decreased biodiversity in the habitat fragments.
Ozone layer or shield is present in stratosphere. It functions as a shield against strong UV radiations coming from sun. UV radiations are very harmful and may cause mutations in living organisms. Thinning of ozone layer increases the amount of UV radiations reaching the earth. It would increase occurrence of cataract, skin cancers, dimming of eye sight, photoburning, deficient functioning of immune system, etc.
In India, Joint Forest Management was started in 1980s. Village and tribal communities are being involved in development and protection of degraded forests on share basis.
Domestic sewage is rich in biodegradable organic matter. When sewage is discharged into the river, it stimulates the activity of several decomposer microorganisms. Decomposition of organic matter by these microorganisms requires a lot of oxygen and results in sharp decline in dissolved oxygen content downstream from the point of sewage discharge. This causes death of fish and other aquatic creatures.