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Punjab PSEB Matric Science study materials
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Punjab PSEB Matric Science practice questions

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Question 1Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which of the following substances turns blue litmus paper red?

  1. Lime water
  2. Baking soda solution
  3. Lemon juice Correct answer.
  4. Soap solution

Explanation

Acids turn blue litmus paper red. Lemon juice contains citric acid, so it is acidic and produces this colour change. Soap, baking soda and lime water are basic and turn red litmus blue instead.

Question 2Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which metal reacts with cold water and moves rapidly on the water surface while releasing hydrogen?

  1. Copper
  2. Silver
  3. Sodium Correct answer.
  4. Gold

Explanation

Sodium is a very reactive metal that reacts vigorously with cold water to form sodium hydroxide and hydrogen gas. The heat released can melt the sodium, so it moves rapidly on the surface. Copper, silver and gold are much less reactive and do not react with cold water in this way.

Question 3Chemical Substances (acids, bases, salts, metals, carbon compounds)

The chemical formula of common table salt is:

  1. KNO3
  2. NaOH
  3. NaCl Correct answer.
  4. CaCO3

Explanation

Common table salt is sodium chloride, which contains sodium ions and chloride ions in a one-to-one ratio. Its formula is therefore NaCl. KNO3 is potassium nitrate, CaCO3 is calcium carbonate, and NaOH is sodium hydroxide.

Question 4Chemical Substances (acids, bases, salts, metals, carbon compounds)

When hydrochloric acid reacts completely with sodium hydroxide solution, the products are:

  1. sodium chloride and hydrogen
  2. sodium oxide and water
  3. sodium chloride and water Correct answer.
  4. sodium hydroxide and chlorine

Explanation

This is a neutralisation reaction between an acid and a base. Hydrochloric acid and sodium hydroxide react to form the salt sodium chloride and water. No hydrogen or chlorine gas is produced in this reaction.

Question 5Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which formula correctly represents propane, a member of the alkane family?

  1. C3H8 Correct answer.
  2. C3H4
  3. C3H6
  4. C2H6

Explanation

Alkanes are saturated hydrocarbons with the general formula CnH2n+2. For propane, n is 3, so the formula is C3H8. C2H6 is ethane, while C3H6 and C3H4 do not fit the alkane formula.

Question 6Chemical Substances (acids, bases, salts, metals, carbon compounds)

Plaster of Paris is prepared by heating which compound to about 373 K?

  1. Quicklime
  2. Washing soda
  3. Limestone
  4. Gypsum Correct answer.

Explanation

Gypsum is calcium sulphate dihydrate, CaSO4·2H2O. When it is heated carefully to about 373 K, it loses part of its water and forms plaster of Paris, CaSO4·1/2H2O. Limestone, washing soda and quicklime are different compounds and are not used for this preparation.

Question 7Chemical Substances (acids, bases, salts, metals, carbon compounds)

The formula of baking soda is:

  1. NaOH
  2. NaCl
  3. Na2CO3
  4. NaHCO3 Correct answer.

Explanation

Baking soda is sodium hydrogen carbonate, which has the formula NaHCO3. It releases carbon dioxide when heated or when treated with an acid, which helps dough rise. Na2CO3 is washing soda, NaOH is sodium hydroxide, and NaCl is common salt.

Question 8Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which alloy is made mainly of copper and zinc?

  1. Bronze
  2. Steel
  3. Solder
  4. Brass Correct answer.

Explanation

Brass is an alloy whose main components are copper and zinc. Bronze is mainly copper and tin, steel is mainly iron and carbon, and solder is commonly an alloy of tin and lead. The composition of the alloy determines its properties and uses.

Question 9Chemical Substances (acids, bases, salts, metals, carbon compounds)

Solution A has pH 3 and solution B has pH 5. Which statement is correct?

  1. B has more H+ ions than A because its pH is higher.
  2. Both A and B are basic since their pH is below 7.
  3. A has 100 times more H+ ions than B. Correct answer.
  4. A is less acidic than B, so A has more H+ ions.

Explanation

The hydrogen ion concentration is related to pH by [H+] = 10^-pH. A pH of 3 means [H+] = 10^-3 mol/L, while pH 5 means [H+] = 10^-5 mol/L. Therefore solution A is 100 times more acidic than solution B, and both solutions are acidic because their pH values are below 7.

Question 10Chemical Substances (acids, bases, salts, metals, carbon compounds)

Saturated hydrocarbons such as methane react with chlorine in sunlight mainly by:

  1. Substitution Correct answer.
  2. Addition
  3. Polymerisation
  4. Neutralisation

Explanation

Saturated hydrocarbons contain only single bonds between carbon atoms. In sunlight, chlorine atoms replace hydrogen atoms one by one in a substitution reaction. Addition reactions are characteristic of unsaturated hydrocarbons, which contain double or triple bonds.

Question 11Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which acid is the main acid present in vinegar?

  1. Nitric acid
  2. Hydrochloric acid
  3. Sulphuric acid
  4. Ethanoic acid Correct answer.

Explanation

Vinegar is a dilute solution of ethanoic acid, also called acetic acid, which gives it its sour taste. Hydrochloric, sulphuric and nitric acids are strong mineral acids and are not the acid present in edible vinegar.

Question 12Chemical Substances (acids, bases, salts, metals, carbon compounds)

In galvanisation, iron articles are coated with which metal to prevent rusting?

  1. Tin
  2. Aluminium
  3. Copper
  4. Zinc Correct answer.

Explanation

Galvanisation is the coating of iron or steel with a thin layer of zinc to protect it from rusting. Zinc is more reactive than iron and corrodes first, so the iron beneath remains protected.

Question 13Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which of the following is a strong base?

  1. Ammonium hydroxide
  2. Sodium hydroxide Correct answer.
  3. Ethanoic acid
  4. Carbonic acid

Explanation

Sodium hydroxide dissolves in water and ionises completely to give hydroxide ions, so it is a strong base. Ammonium hydroxide is a weak base, while carbonic acid and ethanoic acid are acids, not bases.

Question 14Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which gas is evolved when dilute hydrochloric acid is poured over zinc granules?

  1. Carbon dioxide
  2. Chlorine
  3. Hydrogen Correct answer.
  4. Oxygen

Explanation

Zinc lies above hydrogen in the reactivity series, so it displaces hydrogen from dilute hydrochloric acid. The reaction is Zn + 2HCl → ZnCl2 + H2, and the hydrogen gas burns with a pop sound.

Question 15Chemical Substances (acids, bases, salts, metals, carbon compounds)

A few drops of phenolphthalein are added to an unknown solution and it turns pink. The solution is most likely to be:

  1. Neutral
  2. Basic Correct answer.
  3. Pure water
  4. Acidic

Explanation

Phenolphthalein remains colourless in acidic and neutral solutions but turns pink in a basic solution. A pink colour therefore shows that the unknown solution is basic, not acidic or neutral.

Question 16Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which substance reacts with dilute hydrochloric acid to give copper(II) chloride and water?

  1. SO2
  2. CuO Correct answer.
  3. CO2
  4. Cu

Explanation

Copper(II) oxide is a basic oxide and neutralises dilute hydrochloric acid to form copper(II) chloride and water: CuO + 2HCl → CuCl2 + H2O. Copper metal does not react with dilute acid, and CO2 and SO2 are acidic oxides.

Question 17Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which alloy is made mainly of copper and tin?

  1. Steel
  2. Brass
  3. Solder
  4. Bronze Correct answer.

Explanation

Bronze is an alloy made mainly of copper and tin. Brass contains copper and zinc, solder is mainly lead and tin, and steel is an alloy based on iron.

Question 18Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which functional group is present in ethanoic acid?

  1. -CHO
  2. -CO-
  3. -COOH Correct answer.
  4. -OH

Explanation

Ethanoic acid has the formula CH3COOH and contains the carboxyl group, written -COOH. The -OH group is characteristic of alcohols, -CHO of aldehydes and -CO- of ketones.

Question 19Chemical Substances (acids, bases, salts, metals, carbon compounds)

An aqueous solution of sodium chloride conducts electricity, but an aqueous solution of glucose does not. What is the best explanation?

  1. Sodium chloride is an acid while glucose is a base.
  2. Sodium chloride has a lower melting point than glucose.
  3. Glucose reacts with water to produce a gas.
  4. Sodium chloride furnishes ions in water; glucose does not. Correct answer.

Explanation

Conduction of electricity in solution requires mobile charged particles. Sodium chloride is an ionic compound and furnishes Na+ and Cl- ions in water, whereas glucose is covalent and dissolves as neutral molecules, so its solution has no free ions.

Question 20Chemical Substances (acids, bases, salts, metals, carbon compounds)

An aqueous solution of a salt has pH 7. Which salt is it most likely to be?

  1. Sodium carbonate
  2. Sodium chloride Correct answer.
  3. Ammonium chloride
  4. Sodium hydrogen carbonate

Explanation

Sodium chloride is formed from a strong acid (HCl) and a strong base (NaOH), so its ions do not hydrolyse and the solution remains neutral with pH 7. Ammonium chloride gives an acidic solution, while sodium carbonate and sodium hydrogen carbonate give basic solutions.

Question 21Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which of the following is a mineral acid?

  1. Citric acid
  2. Hydrochloric acid Correct answer.
  3. Acetic acid
  4. Oxalic acid

Explanation

Mineral acids are inorganic acids, and hydrochloric acid is obtained by dissolving hydrogen chloride gas in water. Acetic acid and citric acid are organic acids found in vinegar and citrus fruits respectively. Oxalic acid is also an organic acid occurring in plants such as spinach, so it is not the mineral acid here.

Question 22Chemical Substances (acids, bases, salts, metals, carbon compounds)

The common name of sodium carbonate decahydrate is:

  1. Washing soda Correct answer.
  2. Caustic soda
  3. Quicklime
  4. Baking soda

Explanation

Sodium carbonate decahydrate has the formula Na2CO3·10H2O and is commonly called washing soda. Baking soda is sodium hydrogencarbonate, caustic soda is sodium hydroxide, and quicklime is calcium oxide. These are different compounds with distinct formulae and uses.

Question 23Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which metal is commonly stored in kerosene to prevent it from reacting with air and moisture?

  1. Zinc
  2. Gold
  3. Copper
  4. Sodium Correct answer.

Explanation

Sodium is a very reactive metal that reacts vigorously with oxygen and water, so it is kept under kerosene to cut off contact with air and moisture. Copper, gold and zinc do not require this protection under kerosene. Gold is unreactive, while copper and zinc react much less vigorously than sodium.

Question 24Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which of these metals is placed below hydrogen in the reactivity series?

  1. Zinc
  2. Copper Correct answer.
  3. Magnesium
  4. Iron

Explanation

The reactivity series places metals in order of decreasing reactivity, with hydrogen inserted between the more reactive metals and the less reactive ones. Copper lies below hydrogen, so it cannot displace hydrogen from dilute acids. Magnesium, zinc and iron lie above hydrogen and can displace it from dilute hydrochloric acid.

Question 25Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which oxide is amphoteric in nature?

  1. Sodium oxide
  2. Sulphur dioxide
  3. Aluminium oxide Correct answer.
  4. Calcium oxide

Explanation

An amphoteric oxide reacts with both acids and bases to form salts and water, and aluminium oxide shows this behaviour. Sodium oxide and calcium oxide are basic oxides, while sulphur dioxide is an acidic oxide. Aluminium oxide can therefore act as both a basic oxide and an acidic oxide.

Question 26Chemical Substances (acids, bases, salts, metals, carbon compounds)

When excess carbon dioxide is passed through lime water, the milkiness first produced disappears. The soluble compound formed is:

  1. Calcium chloride
  2. Calcium carbonate
  3. Calcium hydrogencarbonate Correct answer.
  4. Calcium oxide

Explanation

Lime water is calcium hydroxide solution, and carbon dioxide first forms insoluble calcium carbonate, which makes the liquid appear milky. When excess carbon dioxide is passed, calcium carbonate is converted into soluble calcium hydrogencarbonate, so the milkiness disappears. Calcium oxide and calcium chloride are not formed in this reaction.

Question 27Chemical Substances (acids, bases, salts, metals, carbon compounds)

Ethanol vapour passed over heated aluminium oxide at about 623 K gives mainly:

  1. Ethanoic acid
  2. Ethene Correct answer.
  3. Methane
  4. Ethane

Explanation

Heating ethanol with a dehydrating agent such as aluminium oxide removes water from the ethanol molecule and produces ethene. This is a dehydration reaction, not oxidation, so ethanoic acid is not the main product. Ethane and methane are not formed because the carbon skeleton is not broken in this reaction.

Question 28Chemical Substances (acids, bases, salts, metals, carbon compounds)

The total number of covalent bonds in one molecule of ethane, C2H6, is:

  1. 8
  2. 6
  3. 12
  4. 7 Correct answer.

Explanation

Ethane has the structure CH3–CH3. Each carbon atom forms three C–H bonds, giving six C–H bonds, and the two carbon atoms are joined by one C–C bond. The total is therefore 6 + 1 = 7 covalent bonds.

Question 29Chemical Substances (acids, bases, salts, metals, carbon compounds)

The pH of a 0.01 mol per litre solution of hydrochloric acid is:

  1. 2 Correct answer.
  2. 1
  3. 3
  4. 12

Explanation

Hydrochloric acid is a strong monobasic acid, so a 0.01 mol per litre solution gives a hydrogen ion concentration of 1 × 10^-2 mol per litre. pH is the negative logarithm of the hydrogen ion concentration, so pH = −log(10^-2) = 2. A pH of 12 would indicate a strongly basic solution, not this acid.

Question 30Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which pair of aqueous solutions, when mixed, gives a white precipitate of silver chloride?

  1. Silver nitrate and sodium chloride Correct answer.
  2. Sodium chloride and potassium nitrate
  3. Sodium sulphate and barium chloride
  4. Copper sulphate and sodium hydroxide

Explanation

Silver chloride is insoluble and is formed when silver ions meet chloride ions in solution. Silver nitrate supplies Ag+ ions and sodium chloride supplies Cl− ions, so mixing them precipitates silver chloride. The other pairs either give no precipitate or form different precipitates such as barium sulphate or copper(II) hydroxide.

Question 31Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which metal is a liquid at ordinary room temperature (about 25 °C)?

  1. Lead
  2. Mercury Correct answer.
  3. Gallium
  4. Sodium

Explanation

Mercury is the only metal that is liquid at ordinary room temperature; its melting point is about −39 °C. Sodium, gallium and lead are solids under the same conditions, although gallium melts just above 30 °C.

Question 32Chemical Substances (acids, bases, salts, metals, carbon compounds)

Rusting of iron takes place when iron is exposed to:

  1. oxygen and moisture Correct answer.
  2. moisture alone
  3. carbon dioxide and moisture
  4. oxygen alone

Explanation

Rusting requires both oxygen and water (moisture); iron exposed only to dry oxygen or to air-free water does not rust readily. The product formed is hydrated iron(III) oxide, commonly called rust.

Question 33Chemical Substances (acids, bases, salts, metals, carbon compounds)

The chemical formula of baking soda is:

  1. NaOH
  2. Na2CO3
  3. NaCl
  4. NaHCO3 Correct answer.

Explanation

Baking soda is sodium hydrogencarbonate, NaHCO3. It is a mild base used in baking powder and as an antacid.

Question 34Chemical Substances (acids, bases, salts, metals, carbon compounds)

The chemical formula of plaster of Paris is:

  1. CaCO3
  2. CaSO4·1/2H2O Correct answer.
  3. Ca(OH)2
  4. CaSO4·2H2O

Explanation

Plaster of Paris is calcium sulphate hemihydrate, CaSO4·1/2H2O, made by heating gypsum to about 373 K. It sets to a hard mass when mixed with water.

Question 35Chemical Substances (acids, bases, salts, metals, carbon compounds)

The chemical name of bleaching powder is:

  1. calcium oxychloride Correct answer.
  2. calcium sulphate
  3. calcium hydrogencarbonate
  4. calcium chloride

Explanation

Bleaching powder is calcium oxychloride, CaOCl2, prepared by the action of chlorine on dry slaked lime. It is used for bleaching cloth and for disinfecting water.

Question 36Chemical Substances (acids, bases, salts, metals, carbon compounds)

An iron nail is kept in a blue solution of copper sulphate for some time. What is observed?

  1. The blue colour deepens and the nail dissolves completely
  2. The blue colour fades and a brown deposit forms on the nail Correct answer.
  3. The blue colour remains unchanged and a white deposit forms on the nail
  4. The solution turns green and no deposit forms on the nail

Explanation

Iron is more reactive than copper, so it displaces copper from copper sulphate solution. The blue colour due to Cu2+ ions fades and reddish-brown copper is deposited on the nail.

Question 37Chemical Substances (acids, bases, salts, metals, carbon compounds)

Two consecutive members of a homologous series differ by:

  1. CH2 and 14 u Correct answer.
  2. C2H4 and 28 u
  3. CH4 and 16 u
  4. H2O and 18 u

Explanation

Members of a homologous series differ by one CH2 unit, which corresponds to a mass difference of 14 u. They share the same general formula and show similar chemical properties.

Question 38Chemical Substances (acids, bases, salts, metals, carbon compounds)

The scum formed when soap is used with hard water is due to the presence of:

  1. sodium and potassium ions
  2. calcium and magnesium ions Correct answer.
  3. chloride and sulphate ions
  4. hydrogen and hydroxide ions

Explanation

Hard water contains dissolved calcium and magnesium ions. These react with soap to form insoluble calcium and magnesium salts, which appear as scum.

Question 39Chemical Substances (acids, bases, salts, metals, carbon compounds)

In the thermite reaction, aluminium powder is heated with iron(III) oxide. Which statement correctly explains the reaction?

  1. The reaction absorbs a large amount of heat and is used to cool railway tracks
  2. Aluminium is more reactive than iron, so aluminium reduces iron(III) oxide to iron Correct answer.
  3. Iron is more reactive than aluminium, so iron displaces aluminium from its oxide
  4. Iron(III) oxide acts as a reducing agent and is itself oxidised to aluminium oxide during the reaction

Explanation

Aluminium is more reactive than iron, so it reduces iron(III) oxide to iron in a highly exothermic reaction. The large amount of heat produced is used to weld railway tracks.

Question 40Chemical Substances (acids, bases, salts, metals, carbon compounds)

Which pair of compounds are isomers?

  1. Ethanol and dimethyl ether Correct answer.
  2. Methane and methanol
  3. Ethanol and ethanoic acid
  4. Ethane and ethene

Explanation

Isomers have the same molecular formula but different structural formulae. Ethanol (C2H5OH) and dimethyl ether (CH3OCH3) both have the molecular formula C2H6O.

Question 41World of Living (life processes, control and coordination, reproduction, heredity and evolution)

In a leaf, the opening and closing of the stomatal pore is controlled directly by

  1. the number of veins supplying the leaf
  2. the rate of photosynthesis in the mesophyll
  3. changes in the water content of guard cells Correct answer.
  4. the thickness of the waxy cuticle on the leaf

Explanation

Guard cells swell when water moves into them, and this turgor pushes the pore open; when they lose water they become flaccid and the pore closes. Light intensity and carbon dioxide levels influence stomatal behaviour only indirectly, by altering the water balance of these cells. The cuticle, mesophyll and veins do not regulate the aperture.

Question 42World of Living (life processes, control and coordination, reproduction, heredity and evolution)

In human blood, most of the oxygen is transported

  1. attached to the surface of white blood cells
  2. in the form of bicarbonate ions in the plasma
  3. dissolved in the plasma as a gas
  4. combined with haemoglobin inside red blood cells Correct answer.

Explanation

About 97 per cent of the oxygen carried by blood is bound to haemoglobin, forming oxyhaemoglobin inside the red blood cells, while only a small fraction dissolves in the plasma. Bicarbonate is the main transport form of carbon dioxide, not oxygen. White blood cells are concerned with defence and carry no respiratory pigment.

Question 43World of Living (life processes, control and coordination, reproduction, heredity and evolution)

A reflex action such as pulling the hand away from a hot object is completed very quickly because the nerve impulse

  1. is carried only by a motor neuron from the receptor
  2. is routed through the spinal cord, which issues the response Correct answer.
  3. is sent to the cerebellum, which stores memory of the action
  4. passes through the medulla oblongata before the muscles act

Explanation

In a reflex arc the sensory neuron takes the impulse to the spinal cord, where a relay neuron passes it straight to a motor neuron that activates the muscle. The brain is informed of the event but does not have to decide the response, so the pathway is short and the action is automatic and fast.

Question 44World of Living (life processes, control and coordination, reproduction, heredity and evolution)

Which of the following is a function of bile juice in the human small intestine?

  1. converting starch into maltose
  2. breaking down proteins into amino acids
  3. absorbing water and salts from undigested food
  4. emulsifying fats into small droplets Correct answer.

Explanation

Bile is produced by the liver and stored in the gall bladder; its bile salts break large fat globules into many small droplets, greatly increasing the surface area on which lipase can act. Bile also neutralises the acidic chyme coming from the stomach. It contains no digestive enzyme of its own.

Question 45World of Living (life processes, control and coordination, reproduction, heredity and evolution)

In birds and mammals, blood passes through the heart twice in one complete circuit. This double circulation is advantageous mainly because

  1. oxygenated blood is delivered to the body at high pressure Correct answer.
  2. the heart can pump blood without any valves
  3. blood flows more slowly through the lungs
  4. deoxygenated blood is pumped to the body tissues

Explanation

In a double circulation the left ventricle pumps oxygenated blood into the systemic circuit at high pressure, while the right ventricle sends blood to the lungs at a much lower pressure. Keeping the two circuits separate allows these different pressures and prevents mixing of oxygenated and deoxygenated blood, so tissues receive oxygen efficiently.

Question 46World of Living (life processes, control and coordination, reproduction, heredity and evolution)

A potted shoot kept near a window bends towards the light. This happens because auxin

  1. collects on the lit side and stops growth there
  2. is destroyed by light on both sides of the shoot
  3. moves to the shaded side and makes cells elongate Correct answer.
  4. travels upward only through the xylem vessels of the stem

Explanation

Auxin is produced at the shoot tip and moves away from light, so it accumulates on the shaded side of the stem. Cells on that side elongate more than those on the lit side, and the unequal growth makes the shoot curve towards the window. This response is phototropism.

Question 47World of Living (life processes, control and coordination, reproduction, heredity and evolution)

In Mendel's pea experiments a pure tall plant (TT) was crossed with a pure dwarf plant (tt), and the F1 plants were then self-pollinated. The phenotypic ratio of tall to dwarf plants in the F2 generation is

  1. 9 : 7
  2. 3 : 1 Correct answer.
  3. 1 : 1
  4. 1 : 3

Explanation

All F1 plants are heterozygous Tt and appear tall because tallness is dominant. Self-pollination of Tt x Tt gives TT, Tt and tt in the ratio 1 : 2 : 1, so three-quarters of the plants are tall and one-quarter dwarf, a phenotypic ratio of 3 : 1.

Question 48World of Living (life processes, control and coordination, reproduction, heredity and evolution)

In humans, the sex of a child is determined by

  1. the number of X chromosomes in the mother's egg
  2. whether an X-bearing or Y-bearing sperm fertilises the egg Correct answer.
  3. the hormone secreted by the placenta during pregnancy
  4. the age of the mother at the time when fertilisation occurs

Explanation

Every egg produced by the mother carries one X chromosome, whereas the father produces two kinds of sperm, X-bearing and Y-bearing. If an X-bearing sperm fertilises the egg the zygote is XX and a girl develops; if a Y-bearing sperm fuses with the egg the zygote is XY and a boy develops. The father's gamete therefore decides the child's sex.

Question 49World of Living (life processes, control and coordination, reproduction, heredity and evolution)

The forelimbs of a frog, a lizard, a bird and a human differ in appearance and in the work they do, yet all contain the same basic set of bones. Such organs are described as

  1. adaptive organs, showing use and disuse of parts
  2. homologous organs, showing a common ancestry Correct answer.
  3. vestigial organs, showing disuse of parts
  4. analogous organs, showing convergent evolution

Explanation

Homologous organs have the same fundamental structure and developmental origin but are modified for different functions, as in the forelimbs of these vertebrates. They indicate divergent evolution from a shared ancestor. Analogous organs, such as the wings of a bird and an insect, perform similar functions but differ in structure and origin.

Question 50World of Living (life processes, control and coordination, reproduction, heredity and evolution)

After a carbohydrate-rich meal the blood glucose level rises. In a healthy person the normal corrective response is that the

  1. pancreas secretes insulin and liver stores glucose as glycogen Correct answer.
  2. pancreas secretes glucagon, which breaks down glycogen in the liver
  3. kidneys excrete the excess glucose in the urine
  4. the liver releases stored glucose into the blood

Explanation

A rise in blood glucose is detected by the beta cells of the islets of Langerhans in the pancreas, which release insulin. Insulin makes liver and muscle cells absorb glucose and convert it into glycogen, so the blood glucose level falls back to normal. This is an example of negative feedback.