exercise

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Unit 1 — Scientific Study

Variables, measurement, SI units, unit-wise analysis, and the principle of homogeneity.

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A. MCQ

11 Questions

⚡

B. Very Short

10 Questions

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C. Short Answer

14 Questions

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D. Long Answer

4 Questions

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Interactive Quiz

Test yourself!

1Which of the following is the characteristic of a scientific study?

iObjectivity

iiCreativity

✓Reproducibility

ivAccuracy

💡 A scientific study should yield the same results if repeated under the same conditions. This quality is called reproducibility — one of the most important characteristics of scientific study.

2What is true about independent variables?

iIn research, there are many independent variables.

iiIndependent variables are measured during the research.

✓Independent variables vary at a known rate.

ivIndependent variables are also called 'y' variables.

💡 The researcher deliberately changes the independent variable at a known, controlled rate. There should be only one; it is plotted along the X-axis (not y).

3Identify the alternative name of dependent variable from the following.

iConstant variable

iiManipulated variable

✓Responding variable

ivHorizontal variable

💡 Dependent variable is also known as responding variable, target variable, outcome variable, measured variable or test variable. 'Manipulated variable' refers to the independent variable.

4In the research for 'finding effect of catalyst in the rate of chemical reaction', which is the correct order of independent, dependent and controlled variables?

✓Catalyst, Rate of reaction, Type of reactants

iiRate of reaction, Catalyst, Type of reactants

iiiType of reactants, Rate of reaction, Catalyst

ivRate of reaction, Type of reactants, Surface area

💡 Catalyst = independent (deliberately changed). Rate of reaction = dependent (measured effect). Type of reactants = controlled (kept constant).

5A student's table shows: Independent = Height of plant; Dependent = Amount of sunlight. What is wrong?

iThe student has correctly identified all variables.

✓The dependent and independent variables should be exchanged.

iiiThe independent variable should be the type of soil.

ivThe controlled variables are incorrect.

💡 Amount of sunlight is the cause (independent). Height of plant is the effect (dependent). The student has swapped them.

6Statement: A variable kept constant is called controlled variable. Argument 1: It reduces cost. Argument 2: It minimizes variations in outcome.

iStatement correct but both arguments incorrect.

iiStatement and argument 1 correct but argument 2 incorrect.

✓Statement and argument 2 correct but argument 1 incorrect.

ivStatement and both arguments correct.

💡 Controlled variables DO minimize variations (Arg 2 ✓), but reducing cost is NOT mentioned as their purpose in the text (Arg 1 ✗).

7Identify the fundamental unit.

iNewton

iiWatt

iiiJoule

✓Candela

💡 Candela (cd) is the SI fundamental unit of luminous intensity. Newton, Watt, and Joule are all derived units.

8Which of the following units is also known as Joule?

iKg·m/s

iiKg·m²/s

✓Kg·m²/s²

ivKg·m/s²

💡 Work (Joule) = Force × Displacement = (kg·m/s²) × m = kg·m²/s².

9Match: Work(a), Force(b), Electric Charge(c), Power(d) with Coulomb(i), Watt(ii), Newton(iii), Joule(iv).

✓(a)→(iv), (b)→(iii), (c)→(i), (d)→(ii)

ii(a)→(i), (b)→(iii), (c)→(ii), (d)→(iv)

iii(a)→(ii), (b)→(iv), (c)→(i), (d)→(iii)

iv(a)→(iii), (b)→(ii), (c)→(iv), (d)→(i)

💡 Work→Joule | Force→Newton | Electric Charge→Coulomb | Power→Watt.

10How many fundamental quantities are there?

ii6

✓7

iv8

💡 There are 7 fundamental quantities: Length, Mass, Time, Temperature, Electric Current, Amount of Substance, and Luminous Intensity.

11Which indicates a unit-wise correct equation?

✓Base units involved on either side of the equation are same.

iiNumerical coefficients on both sides are same.

iiiPhysical quantities on both sides are same.

ivBoth sides have same physical constants.

💡 Principle of Homogeneity: an equation is unit-wise correct if the units of all terms on both sides are the same.

1aDefine: Scientific Study

Scientific study is the systematic investigation based on observation, experimentation, and evidence to understand and explain natural phenomena.

1bDefine: Variable

A variable is any factor, condition, trait or characteristic that can change or vary in an experiment or research study.

1cDefine: Controlled Variable

The variables which are kept constant during an experiment are called controlled variables (also called fixed variables).

1dDefine: Measurement

Measurement is the process of knowing the unknown quantity by comparing it with a known standard quantity of the same type.

1eDefine: Fundamental Quantity

Fundamental quantities are physical quantities whose units are independent and do not depend on any other units. There are 7 fundamental quantities in the SI system.

1fDefine: Unit

The standard amount of a physical quantity chosen to measure the physical quantity of the same kind is called a unit.

1gDefine: Unit-wise Analysis of an Equation

The process of checking the correctness of a scientific equation by comparing the units of all terms on both sides is known as unit-wise analysis of an equation.

2Which variable is measured as the result of an experiment?

The dependent variable is measured as the result of an experiment.

3Which variable is willfully changed by the researcher?

The independent variable is willfully changed by the researcher.

4Name a variable that you would control during an experiment to measure 'heat absorbing capacity of various colours'.

Variables to control: type and thickness of material used for each colour, intensity and distance of the light/heat source, duration of exposure, and the initial temperature of each material.

5What helps us to quantify matter?

Measurement helps us to quantify matter. It allows us to express physical quantities in numerical form using standard units.

6How many fundamental units are there in the SI system?

There are seven (7) fundamental units: metre, kilogram, second, Kelvin, Ampere, mole, and candela.

7What is done to ensure the consistency of measurement across the world?

Internationally accepted and precisely defined standard units (the SI system) are used worldwide, ensuring consistency of measurement across the world.

8Give an example of a unit that depends upon other units.

Newton (N) — Newton = kg·m/s², derived from three fundamental units: kilogram, metre, and second.

9When is a scientific equation said to have uniformity?

A scientific equation has uniformity when the units of all terms on both sides are the same — the condition of the Principle of Homogeneity.

10State the principle of homogeneity of an equation.

According to the Principle of Homogeneity, an equation is unit-wise correct if the units of all the terms on both sides are the same. When satisfied, the equation has uniformity — it is accurate, valid, and applicable under the given conditions.

1Differentiate between the following:

(a) Independent and Dependent Variables:

Independent Variable	Dependent Variable
Deliberately changed by the researcher.	Measured/observed by the researcher.
Represents the 'cause'.	Represents the 'effect'.
Not affected by other variables.	Changes in response to the independent variable.
Plotted along the X-axis.	Plotted along the Y-axis.
Also called: manipulated/input/predictor variable.	Also called: responding/outcome/measured variable.

(b) Dependent and Controlled Variables:

Dependent Variable	Controlled Variable
Changes during the experiment (measured).	Remains constant throughout the experiment.
Represents the effect of the independent variable.	Prevents other factors from influencing the result.
There is only one dependent variable.	There can be many controlled variables.
It is the result/outcome of the experiment.	Fixed to ensure fairness and accuracy.

Fundamental Quantity	Derived Quantity
Independent; does not depend on other quantities.	Derived from combinations of fundamental quantities.
Only 7 fundamental quantities in SI.	A large number of derived quantities exist.
Examples: Length, Mass, Time, Temperature.	Examples: Force, Speed, Volume, Power.

(d) Unit of Length and Unit of Speed:

Unit of Length	Unit of Speed
Metre (m) — a fundamental unit.	Metre per second (m/s) — a derived unit.
Measures distance/length.	Measures the rate of change of position.
Does not depend on other units.	Derived from length (m) and time (s).

2Give reasons for the following:

(a) The independent variable is also called x or horizontal variable:

In a graph, the independent variable (cause) is plotted along the X-axis, which is the horizontal axis.

(b) The dependent variable is important in scientific research:

It is the outcome/result of the experiment. Without observing the dependent variable, we cannot determine the effect of changing the independent variable, making it central to all scientific research.

If variables are not controlled, we cannot be sure which factor is responsible for the change in results. Controlled variables ensure the result truly reflects the relationship between the independent and dependent variables, making the experiment fair, reliable, and scientifically valid.

(d) There are more derived quantities than fundamental quantities:

Derived quantities are formed by combining fundamental quantities in many ways. Since there are many possible combinations of the 7 fundamental quantities, a very large number of derived quantities can be formed — just as countless words can be formed from 26 letters.

(e) 'Kilogram' is a fundamental unit:

Kilogram (kg) is the unit of mass — one of the seven fundamental quantities in SI. It is independent; it does not depend on any other unit. Therefore, it is a fundamental unit.

(f) Unit of volume is a derived unit:

Volume = Length × Breadth × Height. So unit of volume = m × m × m = m³. Since it is derived from the fundamental unit of length (metre), it is a derived unit.

(g) It is important to perform unit-wise analysis of an equation:

Unit-wise analysis: (i) checks the correctness of a physical relation; (ii) helps derive relationships between physical quantities; (iii) converts values between different systems of units; (iv) verifies whether an equation is physically meaningful and applicable.

(h) Different physical quantities cannot be added or subtracted:

Only quantities having the same composition of fundamental units can be added or subtracted. Adding quantities with different units is physically meaningless — e.g., 5 kg + 3 m has no meaning.

3Why is scientific study done?

Scientific study is done to systematically investigate, understand, and explain natural phenomena through observation, experimentation, and evidence. It allows us to find the actual causes of events, discover relationships between factors, test hypotheses, and draw reliable, reproducible conclusions. For example, Goma conducted a scientific study to find the actual cause of stunted plant growth rather than guessing. Scientific study also forms the basis for technological development, medicine, and advancement of human knowledge.

4What are the characteristics of independent variables?

It is changed or controlled deliberately by the researcher.
It represents the 'cause' in the cause-effect relationship.
It is not affected or influenced by other variables.
It is plotted along the X-axis (horizontal axis) in graphs.
There should be only one independent variable in a scientific experiment.
Also known as: manipulated variable, input variable, explanatory variable, or predictor variable.

5What are the characteristics of dependent variables?

It is measured or observed by the researcher to determine the effect of the independent variable.
It represents the 'effect' in the cause-effect relationship.
It changes in response to changes made in the independent variable.
It is plotted along the Y-axis (vertical axis) in graphs.
There should be only one dependent variable in an experiment.
Also known as: responding variable, target variable, outcome variable, or measured variable.
It cannot be manipulated directly; to change it, the independent variable must be changed first.

6Research was conducted to find how applied force affects acceleration of a body. (Refer to the Force vs. Acceleration graph.)

i. Which is the dependent variable?

Acceleration is the dependent variable, because it changes as a result of the applied force — it is measured and observed as the effect/outcome of the experiment.

ii. Why is force plotted along the X-axis?

Force is the independent variable — it is the factor deliberately changed by the researcher (the cause). Independent variables are plotted along the X-axis (horizontal axis). Therefore, force is plotted along the X-axis.

7Write the importance of controlled variables.

They ensure that the result truly reflects the relationship between the independent and dependent variables.
They minimize variations in experimental results, making the data more reliable.
They enhance the reproducibility of the experiment.
They make the experiment fair, reliable, accurate, and scientifically valid.
They allow the researcher to see the true effect of the independent variable without interference.

8Rama conducted an experiment to measure the distance traveled by a paper aeroplane made from papers of different areas. Prepare a graph to represent the relationship.

Area (cm²)	200	300	500	750
Flight distance (m)	2.4	3.1	3.9	4.6

Independent variable: Area of paper (X-axis). Dependent variable: Flight distance (Y-axis). The graph shows a positive/linear upward trend — as paper area increases, flight distance increases.

9Justify with an example that measurement is a process of comparing known and unknown quantity.

Measurement is a comparison between a known (standard) quantity and an unknown quantity of the same type.
Example: When measuring the length of a pencil, we place it alongside a ruler. The ruler has known, standardised markings (cm and mm). We compare the pencil length against these known markings and read off the value (e.g., 14.5 cm). The known standard (ruler) is compared with the unknown (pencil length) — this is the essence of measurement.

10Write the characteristics of a standard unit.

It should be well-defined and unambiguous.
It should be universally accepted across the world.
It should be invariable — it should not change with time, place, or conditions.
It should be reproducible — it should be possible to make exact copies of it.
It should be indestructible and not easily affected by physical or chemical changes.
It should be convenient in size — neither too large nor too small for practical use.

11Show that unit of force is a derived unit.

Force = Mass × Acceleration Unit of Force = kg × m/s² = kg·m/s² = Newton (N) Newton involves kg, m, and s (three fundamental units) ∴ Newton is a DERIVED unit. ✓

12Ampere is coulomb per unit time, yet it is fundamental — while coulomb is derived. Explain.

Ampere (A) is a fundamental unit because it is independently measurable directly through the electromagnetic force between two parallel current-carrying conductors.
Coulomb (C): Coulomb = Ampere × Second (C = A·s). Since Coulomb is derived from Ampere and Second, it is a derived unit.

13Find the fundamental units involved in the following derived units:

Derived Unit	Expression	Fundamental Units
Newton (N)	kg × m/s²	kg, m, s
Pascal (Pa)	kg/(m·s²)	kg, m, s
Joule (J)	kg·m²/s²	kg, m, s
Watt (W)	kg·m²/s³	kg, m, s
Coulomb (C)	A × s	A, s

14Perform unit-wise analysis of the following equations to test their homogeneity:

a) S = ut + ½at²

LHS: S → m RHS: ut=(m/s)×s=m; ½at²=(m/s²)×s²=m m+m=m LHS=RHS=m ✓ CORRECT (Homogeneous)

b) v² = u² + 2aS

LHS: v² → m²/s² RHS: u²=m²/s²; 2aS=(m/s²)×m=m²/s² m²/s²+m²/s²=m²/s² LHS=RHS=m²/s² ✓ CORRECT (Homogeneous)

c) V = IR

LHS: V → kg·m²/(A·s³) RHS: I×R = A × kg·m²/(A²·s³) = kg·m²/(A·s³) LHS=RHS ✓ CORRECT (Homogeneous)

d) P = IV

LHS: P (Power) → kg·m²/s³ RHS: I×V = A × kg·m²/(A·s³) = kg·m²/s³ LHS=RHS ✓ CORRECT (Homogeneous)

1In a classroom activity, Anu connects 1, 2, then 3 batteries to a torch bulb. Identify with reasons the dependent, independent, and controlled variables.

Variable	What it is	Reason
Independent	Number of batteries connected	Anu deliberately changes the number — it is the cause factor.
Dependent	Brightness of the torch bulb	Brightness is observed as the effect; she cannot directly control it — to change brightness, she must first change the number of batteries.
Controlled	Type of bulb, battery brand, connection method, ambient light, position of observer	All kept constant so that only battery number affects brightness — ensures fair, reliable, reproducible results.

2Prove that the unit of electrical resistance, Ohm (Ω) = kgm²/(A²s³). Also: Ritesh wants to find how the size of a parachute affects the time it takes to reach the ground. How can he conduct the experiment?

R = V/I (Ohm's Law) V = Work/Charge = kg·m²/s² ÷ A·s = kg·m²/(A·s³) Ω = V/I = kg·m²/(A·s³) ÷ A = kg·m²/(A²·s³) PROVED ✓

Variable	What it is	Reason
Independent	Size (area) of the parachute	Ritesh deliberately uses three different sizes — the cause factor.
Dependent	Time taken to reach the ground	Measured as the effect of changing parachute size.
Controlled	Height, mass attached, dropping technique, wind conditions	Kept constant so that only size affects falling time.

Procedure & Conclusion: Drop each parachute from the same height and record time with a stopwatch. Repeat 3 times for accuracy. The largest parachute takes the longest time to reach the ground (more air resistance), confirming the relationship between size and descent time.

3Clarify the rules to be followed during unit-wise analysis of an equation with examples.

Rule 1: Only quantities having the same composition of fundamental units can be added or subtracted. (e.g., m + m = m ✓; but m/s + m ✗).
Rule 2: Quantities with different units can be multiplied or divided, giving a meaningful derived unit. (e.g., kg × m/s² = kg·m/s² = Newton).
Rule 3: Pure numbers, coefficients, and dimensionless constants (like 2, π, ½, etc.) are ignored in unit-wise analysis.
Rule 4: An equation is homogeneous (unit-wise correct) only if LHS units = RHS units after applying all above rules.

4Hari says v=u+at is correct; Hina says v=u+at² is correct. Who is right?

Testing Hari's: v = u + at LHS: m/s RHS: u=m/s; at=(m/s²)×s=m/s m/s+m/s=m/s ✓ LHS=RHS CORRECT Testing Hina's: v = u + at² LHS: m/s RHS: u=m/s; at²=(m/s²)×s²=m m/s+m=✗ (cannot add m/s and m)

🏆 HARI IS RIGHT! v = u + at is unit-wise correct. Hina's equation v = u + at² is not homogeneous and is physically invalid.

🔬 Chapter 1 — Fun Zone

Scientific Study Quiz

Flip cards to recall key terms, then challenge yourself!

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Independent Variable

Tap to reveal

The variable deliberately changed by the researcher — the CAUSE. Plotted on X-axis.

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Dependent Variable

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Measured/observed as the result — the EFFECT. Plotted on Y-axis.

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Controlled Variable

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Kept constant throughout the experiment to ensure fair, reliable results.

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7 SI Fundamental Units

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Metre, Kilogram, Second, Kelvin, Ampere, Mole, Candela

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Joule (J)

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Unit of Work = kg·m²/s² (Force × Displacement)

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Reproducibility

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A study gives the same results when repeated under the same conditions.

Question 1 / 5Score: 0

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Unit 2 — Classification of Living Beings

Five kingdoms, plant divisions, vertebrates, invertebrates, and taxonomic classification.

🅰️

A. MCQ

11 Questions

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B. Very Short

10 Questions

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C. Short Answer

13 Questions

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D. Long Answer

3 Questions

🎮

Interactive Quiz

Test yourself!

1What are the main features of organisms under kingdom Animalia?

iEukaryotic cell, cell with cell wall, heterotrophs

✓Eukaryotic cell, cell without cell wall, heterotrophs

iiiEukaryotic cell, cell without cell wall, autotrophs

ivEukaryotic cell, cell with cell wall, autotroph

💡 Animals have eukaryotic cells WITHOUT cell wall and are heterotrophs (cannot make their own food).

2Which class of vertebrates has feathers and pneumatic bones?

iReptilia

iiMammalia

✓Aves

ivAmphibia

💡 Aves (birds) have feathers and hollow pneumatic bones that make their bodies light for flying. These features are unique to birds.

3In the evolutionary sequence of plants, which group represents the transition from aquatic to terrestrial life?

iAlgae

✓Bryophytes

iiiGymnosperms

ivAngiosperms

💡 Bryophytes are called 'amphibians of the plant kingdom' — the first to colonise land but still need water for reproduction.

4What is the distinguishing feature of animals of the phylum Porifera?

iPresence of true tissues

✓Water canal system

iiiBilateral symmetry

ivPresence of organs

💡 Porifera (sponges) have a water canal system — water enters through pores (ostia) and exits through the osculum. They do NOT have true tissues, true organs, or bilateral symmetry.

5What is unique about mammals among all the vertebrates?

iFour-chambered heart

✓Presence of mammary glands

iiiHomeothermic nature

ivInternal fertilization

💡 Mammary glands (which produce milk to nurse young) are the defining feature exclusive to class Mammalia. Birds also have 4-chambered hearts; homeothermic nature is shared with birds; internal fertilization is found in reptiles and birds too.

6Which of the following evolutionary developments is seen in mammals but not in reptiles?

iFour-chambered heart

iiInternal fertilization

✓Mammary glands

ivVertebral column

💡 Mammary glands are found exclusively in mammals. Internal fertilization and vertebral column are present in reptiles too.

7Which character is common to reptiles and birds?

iFeathers

iiMammary glands

✓Amniotic egg

ivHomeothermic nature

💡 Both reptiles and birds lay eggs with protective membranes (amniotic eggs) on land, with internal fertilization. Feathers are exclusive to birds; mammary glands to mammals; homeothermic nature is exclusive to birds (reptiles are cold-blooded).

8Which characteristic distinguishes tracheophytes from other classes of plants?

iPresence of flowers

✓Presence of vascular tissue

iiiPresence of seeds

ivPresence of fruits

💡 Tracheophytes are defined by the presence of vascular tissue (xylem and phloem). Not all tracheophytes have flowers, seeds, or fruits.

9Which feature is unique to gymnosperms among seed plants?

iPresence of seeds

✓Naked seeds

iiiPresence of vascular tissue

ivPresence of leaves

💡 Gymnosperms have seeds that are 'naked' (not enclosed in a fruit). The ovary is absent in gymnosperms. Both gymnosperms and angiosperms have seeds and vascular tissue.

10Based on evolution, which of the following groups of organisms are closely related?

✓Porifera, Coelenterata, Annelida

iiPorifera, Arthropoda, Chordata

iiiCoelenterata, Arthropoda, Chordata

ivPlatyhelminthes, Chordata, Annelida

💡 Porifera, Coelenterata, and Annelida are all invertebrate phyla that appear consecutively in the evolutionary sequence, sharing simpler body organisation. They are more closely related to each other than to more advanced phyla.

11A student observes: soft body, muscular foot for locomotion, and a hard calcium carbonate shell. It belongs to which phylum?

iArthropoda

iiAnnelida

✓Mollusca

ivEchinodermata

💡 Phylum Mollusca: soft-bodied animals with muscular feet for locomotion and an exoskeleton of calcium carbonate. All three features are hallmarks of Mollusca.

1Define taxonomy.

Taxonomy is the branch of biology concerned with the identification, naming, and classification of organisms based on their similarities and differences. It is the science of grouping living beings into systematic categories (taxa) such as kingdoms, phyla, classes, orders, families, genera, and species.

2What is the main function of xylem in tracheophytes?

The main function of xylem is to conduct water and dissolved minerals from the roots upward to the leaves and other parts of the plant. It also provides structural support to the plant body.

3Differentiate between parallel venation and reticulate venation.

Parallel venation: Veins run parallel to each other from base to tip. Found in monocotyledon plants (e.g., maize, rice, sugarcane).
Reticulate venation: Veins form a network (net-like pattern). Found in dicotyledon plants (e.g., mango, pea, rose).

4State a reason why fish are classified under class Pisces.

Fish possess an elongated, streamlined body covered by scales; breathe through gills on the lateral side of the head; and have fins for locomotion in water — all defining characteristics of class Pisces.

5Why are gymnosperms described as plants with 'naked seeds'?

Gymnosperms are plants with 'naked seeds' because their ovules (seeds) are not enclosed within an ovary. Since there is no ovary, no fruit is formed. The seeds lie exposed (naked) on the scales of their cones, unlike angiosperms where seeds are enclosed inside fruits.

6You observe an animal with jointed appendages and a chitinous exoskeleton. Name its phylum.

The animal belongs to phylum Arthropoda. Their body is externally covered by a dry exoskeleton made of chitin, and they have jointed appendages — the defining features of Arthropoda (the largest phylum in the animal kingdom).

7Arrange these groups in ascending evolutionary order: Amphibia, Pisces, Mammalia, Reptilia.

Pisces → Amphibia → Reptilia → Mammalia

This reflects increasing adaptation to terrestrial life, complexity of heart (2-chambered → 3-chambered → 4-chambered), and advancement in reproduction (external to internal fertilization, oviparous to viviparous).

8Justify why birds are considered more advanced than reptiles, citing one anatomical feature.

Birds (Aves) have a four-chambered heart and are homeothermic (warm-blooded). Reptiles mostly have a three-chambered heart, resulting in mixing of oxygenated and deoxygenated blood and a less efficient circulatory system.

9Compare the circulatory system of amphibians and mammals, highlighting one key difference.

Amphibians: Three-chambered heart (2 auricles + 1 ventricle). Oxygenated and deoxygenated blood mix in the ventricle.
Mammals: Four-chambered heart (2 auricles + 2 ventricles). Oxygenated and deoxygenated blood are completely separated, enabling more efficient oxygen delivery to body tissues.
Key difference: Amphibians have a 3-chambered heart; mammals have a 4-chambered heart.

10Evaluate how the classification of living beings reflects evolutionary relationships.

(i) Classification is based on evolutionary history — organisms sharing more features are placed closer together.
(ii) There is noticeable similarity between the closest divisions or classes, suggesting evolution.
(iii) Some organisms exhibit characteristics of two or more classes, providing evidence for the reality of evolution.
(iv) Different classes sharing common characteristics (e.g., cold-blooded oviparous traits in fish, amphibians, and reptiles) suggest shared evolutionary ancestry.

1Write two differences between monocotyledon and dicotyledon plants.

Monocotyledon	Dicotyledon
One cotyledon present in the seed.	Two cotyledons present in the seed.
Parallel venation in leaves.	Reticulate venation in leaves.
Fibrous root system.	Tap root system.
Flower parts in multiples of 3 (trimerous).	Flower parts in 4 or 5 (tetramerous/pentamerous).
Vascular bundles scattered in stem.	Vascular bundles arranged in a ring in stem.

2Explain why bryophytes require water for reproduction.

Bryophytes require water because their male gametes (sperms) are flagellated and motile — they can only travel to the female gametes (eggs) by swimming through water. Without water as a medium, the male gametes cannot reach the female gamete to achieve fertilisation.

3State two reasons why gymnosperms are adapted to live in cold or dry habitats.

Gymnosperms have elongated, needle-like leaves with a reduced surface area that prevents transpiration and conserves water.
The thick bark insulates the plant in cold/dry environments, protecting the plant's internal tissues from extreme temperatures.

4Differentiate between Bat and Owl.

Feature	Bat	Owl
Class	Mammalia	Aves
Reproduction	Viviparous (live birth)	Oviparous (lays eggs)
Body covering	Hair/fur	Feathers
Mammary glands	Yes; nurses its young	No mammary glands
Navigation	Echolocation (ultrasonic sounds)	Keen eyesight and hearing
Forelimbs	Modified into wings	Forelimbs modified into wings made of feathers
Heart	Four-chambered	Four-chambered

5Write any two differences between moss and club moss.

Moss	Club Moss (Lycopodium)
Belongs to Division Bryophyta (non-vascular plant).	Belongs to Division Tracheophyta, Subdivision Pteridophyta (vascular plant).
Lacks vascular tissue (xylem and phloem).	Has vascular tissue (xylem and phloem) for transport.
Lacks true roots, stems, and leaves; has rhizoids.	Has true roots, stems, and leaves.
Gametophytic generation is dominant.	Sporophytic generation is dominant.
Cannot grow tall.	Can grow taller due to vascular tissue.

6Describe two structural adaptations of Aves for flight.

Forelimbs are modified into wings with a large surface area and aerodynamic shape, generating lift and enabling flight.
They have hollow pneumatic bones. Air sacs inside the body further reduce body weight, making flight efficient.

7A farmer observes plants with needle-like leaves and cones instead of flowers. Identify the sub-division and give two reasons.

Sub-division: Gymnosperm

The plants have needle-like leaves (adapted to reduce transpiration).
The plants bear cones instead of flowers — seeds are naked, not enclosed in fruits.

8An organism has a streamlined body and gills but also an air bladder. Name its class and state the role of the air bladder.

Class: Pisces
The air bladder helps fish control their buoyancy, allowing the fish to maintain its position at different depths in the water without constantly swimming.

9While examining a pond, you find a green filamentous plant without true roots or stems. To which division does it belong and why?

Division: Algae (under Kingdom Plantae)

The plant is found in water (aquatic), is green, and has a filamentous form — characteristic of algae.
It lacks true roots, stems, and leaves — it has a thallus body.
The green colour indicates the presence of chlorophyll for photosynthesis.

10Compare reptiles and amphibians on any two points of respiration and reproduction.

Feature	Reptiles	Amphibians
Respiration	Only through lungs (entirely).	Lungs (adults) + moist skin; tadpoles via gills.
Reproduction	Internal fertilization; lay fertilized eggs on land.	External fertilization; lay unfertilized eggs in water.
Eggs	Laid on land with protective coverings.	Laid in water without hard shells.

11Justify with two arguments how classification supports the study of evolution.

Arg 1 — Reveals evolutionary progression: The system arranges organisms from simple (Monera) to complex (Animalia). Within vertebrates: 2-chambered hearts (Pisces) → 3-chambered (Amphibia, Reptilia) → 4-chambered (Aves, Mammalia).
Arg 2 — Shows common ancestry: All animals share eukaryotic cells without cell walls and heterotrophic nutrition, indicating a common evolutionary origin. More closely related groups share more features (e.g., birds and mammals are both homeothermic with 4-chambered hearts).

12'Mammals are the most advanced vertebrates.' Support this statement with two key characteristics.

Advanced reproduction — viviparity and parental care: Mammals are viviparous — they give birth to live young. They possess mammary glands that produce milk to nourish the young — a uniquely advanced reproductive strategy.
Homeothermic nature and four-chambered heart: Mammals are warm-blooded with a fully 4-chambered heart for highly efficient oxygen delivery to tissues, supporting a high metabolic rate and enabling survival in diverse and extreme environments.

13Plants in the figure look similar but are kept in different divisions. Justify with two reasons.

They look similar but brown algae is kept under Algae and Riccia is kept in Bryophyta.

Brown algae are simple, aquatic, photosynthetic organisms lacking true roots, stems, or leaves — they have a thallus body and live entirely in water.
Riccia (Bryophyta) is a primitive, non-vascular land plant with a slightly more complex cellular organisation that lives on moist land, though it still needs water for reproduction.

1Name the phyla which have the following characteristics:

Characteristic	Phylum	Examples
Tube feet	Echinodermata	Starfish, Sea urchin, Sea cucumber
Chitinous exoskeleton	Arthropoda	Butterfly, Cockroach, Crab, Spider
Muscular feet	Mollusca	Snail, Slug, Octopus
Flattened body and gut without anus	Platyhelminthes (Flatworms)	Tapeworm, Liver fluke, Planaria

2Complete the given chart of Multicellular Organisms.

Multicellular Organisms │ ├── Kingdom Monera (e.g., Cyanobacteria — some are multicellular/filamentous) │ ├── Kingdom Fungi (e.g., Mushroom, Yeast — heterotrophs, absorptive nutrition) │ ├── Kingdom Plantae │ ├── Division Algae (e.g., Spirogyra, Ulothrix) │ ├── Division Bryophyta (e.g., Moss, Marchantia) │ └── Division Tracheophyta │ ├── Subdivision Pteridophyta (e.g., Fern) │ ├── Subdivision Gymnosperm (e.g., Pinus, Cycas) │ └── Subdivision Angiosperm │ ├── Class Monocotyledon (e.g., Rice, Maize) │ └── Class Dicotyledon (e.g., Mango, Pea) │ └── Kingdom Animalia ├── Invertebrates (Porifera, Coelenterata, Platyhelminthes, │ Nemathelminthes, Annelida, Arthropoda, Mollusca, Echinodermata) └── Phylum Chordata └── Sub-phylum Vertebrata ├── Class Pisces (Fish) ├── Class Amphibia (Frog) ├── Class Reptilia (Snake, Lizard) ├── Class Aves (Birds) └── Class Mammalia (Mammals)

3Imagine you have found a new organism in your garden. How will you classify it based on the five-kingdom system? Write four steps.

Determine cell type (Prokaryote or Eukaryote): Examine under microscope. If no true nucleus (prokaryotic) → Kingdom Monera. If true nucleus (eukaryotic) → Step 2.
Determine if unicellular or multicellular: Eukaryotic + unicellular → Kingdom Protista. Multicellular → Step 3.
Check cell wall, chlorophyll, and mode of nutrition: Cell wall + no chlorophyll + absorptive nutrition → Fungi. Cell wall + chlorophyll + photosynthesis → Plantae. No cell wall + heterotrophic → Animalia.
Further classification within the identified kingdom: For Plantae: check vascular tissue, seeds, flowers, cotyledons. For Animalia: check backbone, body symmetry, coelom type to assign correct phylum and class.

🌿 Chapter 2 — Fun Zone

Classification Quiz

Test your knowledge of the living world!

🦠

Kingdom Monera

Tap to reveal

Prokaryotes — no true nucleus. Examples: Bacteria, Cyanobacteria.

🌱

Bryophytes

Tap to reveal

Amphibians of plant kingdom — first land plants; need water for reproduction. No vascular tissue.

🦅

Class Aves

Tap to reveal

Birds: feathers, pneumatic bones, oviparous, 4-chambered heart, warm-blooded (homeothermic).

🐟

Class Pisces

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Fish: 2-chambered heart, cold-blooded, breathe through gills, have air bladder for buoyancy.

🌲

Gymnosperms

Tap to reveal

Naked seeds (not in fruit). Needle-like leaves, bear cones. Adapted to cold/dry habitats.

🐸

Amphibia

Tap to reveal

3-chambered heart. Tadpoles: gills; Adults: lungs + moist skin. External fertilization in water.

Question 1 / 5Score: 0

Quiz Complete!

🐝

Unit 3 — Honey Bee

Bee castes, life cycle, apiculture, pheromones, and colony behaviour.

🅰️

A. MCQ

9 Questions

⚡

B. Very Short

7 Questions

📝

C. Short Answer

7 Questions

📖

D. Long Answer

7 Questions

🎮

Interactive Quiz

Bee an expert!

1Why do worker bees have pollen baskets in the hind legs?

iFor defense

iiFor flight balance

✓To collect and transport pollen

ivTo store honey

💡 Pollen baskets (corbiculae) are specialised structures on the hind legs that hold pollen grains gathered from flowers and carry them back to the hive.

2Why do worker bees provide royal jelly to all the larvae during the first three days?

iGuards larvae against predators

iiTriggers drone production

iiiAids in the secretion of wax

✓Offers a high-protein diet necessary for initial growth

💡 Royal jelly is a highly nutritious, protein-rich secretion essential for the initial development of ALL larvae (worker, drone, or queen) in the first three days.

3Which statement most adequately explains why drones die following mating?

iThey are eaten by the queen.

✓Copulation destroys their reproductive organs.

iiiThey are expelled by workers immediately.

ivThey starve to death because of nectar loss.

💡 During mating, the drone's penis and abdominal parts are expelled along with sperm, physically destroying the organs and causing death.

4If a hive suddenly lacks a queen, what will most probably happen?

iDrones will develop new queens

iiHoneycomb cells will disappear

iiiWorker bees will stop producing honey immediately

✓Workers will start laying unfertilized eggs to produce drones

💡 Without a queen, worker bees may lay unfertilised eggs that develop into drones via parthenogenesis. Workers may also feed royal jelly to larvae to develop a new queen.

5To gather a honey bee specimen safely for examination, what is the most suitable thing to do?

iGrasp a live bee manually

iiTake out wax caps bare hands

iiiEmploy powerful perfume to entice it

✓Look at a naturally dead or chilled bee using gloves

💡 The text's precautions state: 'Do not handle live bees with your bare hands, wear gloves. Use bees that have died naturally or were gently chilled and released afterward.'

6A beekeeper notices slow honey production. What is most suited to be done?

iKill some brood cells

iiIncrease more drones alone

iiiReduce the number of flowers nearby

✓Provide access to diverse flowering plants

💡 Honey is made from nectar collected from flowers. More diverse flowering plants = more nectar sources = more honey production. Drones do not collect nectar.

7Worker bees fanning wings at hive entrances — which activity are they mainly performing?

iAlert predators

iiScatter royal jelly scent

iiiEntice drones for mating

✓Evaporate water from nectar and control hive heat

💡 Fanning evaporates water from nectar (turning it into honey) AND regulates hive temperature during hot weather — both critical colony functions.

8A newly introduced pesticide is killing off pollinators. Which observation would most demonstrate its impact on honey bees?

iQueen size grew

iiHoney sweetness increased

iiiLarval metamorphosis accelerated

✓Sudden drop in worker count and low pollination rates

💡 Worker bees are the primary foragers and pollinators. A pesticide killing pollinators would directly reduce the worker population, resulting in fewer bees visiting flowers and a dramatic drop in pollination rates and crop yields.

9Which stage of life cycle of honey bee is shown in the given figure? (A sealed cell with a white curled structure inside.)

iEgg

✓Larva

iiiPupa

ivAdult

💡 A white curled structure inside a cell indicates the larval stage. Eggs are tiny and upright; pupae have developing body parts visible; adults are fully formed bees.

1Write the scientific name for honey bee commercial rearing.

The commercial rearing (farming) of honey bees is called Apiculture.

2Give the name of food that is supplied to queen larvae alone during development.

Royal jelly is the food supplied exclusively to queen larvae throughout their entire larval development.

3Give one reason why worker bees possess hairs on their legs.

Worker bees possess dense hairs on their legs to collect and hold pollen grains from flowers. The hairy structure effectively traps pollen during flower visits.

4Differentiate between the life of a queen bee and that of a worker bee in one sentence.

The queen bee is the only fertile female in the hive, lives for 2 to 5 years, and her sole function is to lay eggs and regulate the colony through pheromones; whereas the worker bee is an infertile female that lives only 6 weeks to 6 months and performs all the labour of the hive — collecting nectar, building comb, feeding larvae, and protecting the hive.

5If you spot a bee with large compound eyes and no stinger, to which caste does it belong and why?

It belongs to the Drone (male bee) caste. Drones are male bees and do not need a stinger since they do not defend the hive or forage.

6Explain briefly why mating with multiple drones (polyandry) is beneficial for a bee colony.

Polyandry increases genetic diversity within the colony, enhancing colony fitness and survival. Genetically diverse colonies exhibit increased population size, foraging activity, and food supplies, which contribute to the production of new queens and creation of new colonies. Greater genetic diversity also improves resistance to diseases and parasites, making the colony more resilient.

7As you inspect a hive, you notice worker bees oscillating their wings at the entrance. Why do they do this?

To evaporate excess water from the nectar stored in honeycomb cells, concentrating it into honey.
To regulate the temperature inside the hive by circulating fresh air.

1Write any two differences between a worker bee and a drone bee based on structural features.

Worker Bee	Drone Bee
Smallest-sized bee in the colony.	Larger than worker bees, but smaller than the queen.
Has a stinger for defense.	Does not have a stinger.
Has pollen baskets on hind legs.	No pollen baskets.
Has nectar gland, venom gland, and wax glands.	Lacks nectar gland, pollen sac, venom gland, and wax glands.
Infertile female bee.	Male bee — sole function is to fertilise the queen.

2A farmer has a low yield of mustard seeds but healthy plants. In what ways can honey bee management help fix this?

The low mustard seed yield despite healthy plants indicates poor pollination.

Cross-pollination by worker bees leads to seed and fruit development.
Setting up beehives near the mustard field ensures a large population of worker bees actively visiting the flowers, dramatically increasing pollination rates and consequently seed yield.

3During a warm winter, the colonies are active for longer periods. What challenge does this present for storing food?

Increased consumption: Active bees consume honey at a much faster rate than resting bees, depleting stored honey reserves.
Reduced flower availability: Despite the colony being active, winter still means very few flowering plants are available for nectar collection.
Risk of starvation: If the stored honey is depleted before spring (when flowers bloom again), the colony may face starvation and collapse.

4A farmer wants to increase tomato and cucumber yield. Suggest one practical step using honey bees and explain briefly how it will help.

Practical Step: Place beehives near the tomato and cucumber fields during the flowering season.
Tomatoes and cucumbers require cross-pollination to set fruits. Worker bees visiting the flowers transfer pollen from one flower to another, enabling fertilization and fruit set. More bee activity = more pollinated flowers = higher yield.

5Your class plans to observe the external structure of honey bees. Describe a safe procedure to obtain a specimen without harming the bees.

Materials needed:

Gloves, forceps, a soft brush, white paper or a Petri dish, hand lens, notebook.

Procedure:

Wear protective gloves before handling anything.
Do NOT attempt to catch or handle a live, active bee.
Look for a bee that has died naturally.
Alternatively, with a beekeeper's supervision, gently chill a bee to temporarily slow it down.
Using forceps, carefully place the bee on a white sheet of paper or Petri dish.
Use a hand lens to observe and identify the three main body parts (head, thorax, abdomen).
Draw and label the bee in your notebook. Release any live chilled bee outside after observation.

6During a field visit, you find a bee with large compound eyes, no stinger, and a hairy body. Identify the caste and give one reason for your choice.

Caste: Drone Bee (male bee)
The presence of notably large compound eyes and the absence of a stinger is unique to drones among the three castes. Drones do not defend the hive or forage, so they have no stinger. Large compound eyes help locate the queen during mating flights.

7State how the queen's practice of mating with multiple drones (polyandry) benefits the long-term survival of the colony.

1A local farmer notices low mustard seed yield despite healthy flowering plants. Analyse two possible reasons related to honey bee behaviour or colony health, and suggest two practical measures.

Two Possible Reasons:

Insufficient pollinator activity due to low bee population in the area.
Use of insecticides or pesticides toxic to bees, reducing their foraging activity or killing them.

Any Two Practical Measures:

Set up beehives near the mustard field during the flowering season.
Avoid using bee-toxic pesticides during the flowering period.

2'Modern apiculture is more sustainable than traditional wild-hive collection.' Evaluate this statement with two advantages and two potential challenges.

Two Advantages of Modern Apiculture:

Higher and sustained honey production, while traditional wild-hive collection is limited and irregular.
Additional economic products and services such as beeswax, royal jelly, bee venom, and pollination services for agriculture. Traditional collection only yields honey and destroys the hive.

Two Potential Challenges:

Setting up a modern apiary requires high initial investment and specialised knowledge.
Risk of colony collapse disorder from diseases, parasites, and environmental stressors.

3Design a simple school project to demonstrate the four stages of the honey bee life cycle using easily available materials.

Project Title:

Model of the Honey Bee Life Cycle — Complete Metamorphosis.

Materials Required:

Card paper/chart paper (base), cotton wool (larva and pupa models), transparent plastic sheet (honeycomb cells), Fevicol/glue, paints and brushes (white, yellow, brown, black), pencil, scissors, small beads or rolled white paper (egg models), wire (antennae and wings of adult model).

Steps:

Make the honeycomb structure: Cut transparent plastic sheet into hexagonal shapes and assemble into a comb pattern. This forms the background for all stages.
Egg Stage: Make tiny white elongated models using tightly rolled white paper. Place upright inside cells. Label: 'Egg — Duration: 3 days.'
Larva Stage: Shape white cotton wool into small curved, C-shaped forms. Place them inside cells with a yellowish tint to represent royal jelly. Label: 'Larva — Duration: ~5–7 days.'
Pupa Stage: Shape cotton into a bee-like form. Seal the cell with card paper painted brown (wax cap). Label: 'Pupa — Duration: 8–14 days.'
Adult Stage: Craft a small bee model using card paper, wire (wings), and paint (black and yellow stripes, eyes, antennae). Place it emerging from an open cell. Label: 'Adult — Emerges to begin colony duties.'

4A beekeeper finds many drones and only a few workers in a hive. Explain the biological reasons and the effect on honey production.

Biological Reasons for Drone-Heavy Hive:

If the queen bee is absent, dead, or has become infertile, she may only lay unfertilised eggs. Unfertilised eggs develop into drones through parthenogenesis.
In the absence of a functional queen, worker bees may themselves lay unfertilised eggs.
During the breeding season, colonies naturally produce more drones for mating purposes.

Effects on Honey Production:

Honey production will severely decline and may stop entirely.
No nectar collection — drones do not forage.
No comb building — drones do not produce wax.
Increased consumption of stored honey by drones, accelerating depletion.

5Describe the role of pheromones in regulating colony activities. Include at least four specific behaviours or processes influenced by queen pheromones.

Role of Pheromones:

Pheromones regulate behaviour and social cohesion within the hive. Four specific behaviours/processes regulated by queen pheromones:

Suppressing new queen development: Queen pheromones prevent workers from raising additional queens while the current queen is present and healthy.
Attracting drones for mating: During mating flights, queen pheromones attract drones from a wide area.
Swarm cohesion: Pheromones keep the swarm together and guide them to a new nest site during swarming.
Hive location and navigation: Pheromones help bees recognise their own hive and communicate the location of food sources.

6Sketch a well-labelled diagram of the external structure of a honey bee.

🐝

Head: compound eyes, antennae, mandibles, proboscis
Thorax: 3 pairs of legs, 2 pairs of wings
Abdomen: stinger (worker/queen), wax glands (worker), pollen baskets on hind legs

7With a simple sketch, illustrate the four phases of the honey bee life cycle in order and label each phase.

EGG (3 days) → LARVA (5-7 days: white, C-shaped, soft) → PUPA (8-14 days: sealed in cell, body parts develop) → ADULT (emerges to begin colony duties) This is COMPLETE METAMORPHOSIS (Holometabolism). Total duration: Queen 16d | Worker 21d | Drone 24d

🐝 Chapter 3 — Fun Zone

Honey Bee Quiz

Buzz through these questions and test your bee knowledge!

👑

Queen Bee

Tap to reveal

Only fertile female. Lays eggs. Lifespan: 2–5 years. Fed royal jelly throughout life.

👷

Worker Bee

Tap to reveal

Infertile female. Collects nectar, builds comb, feeds larvae, defends hive. Lives 6 weeks–6 months.

🧬

Drone Bee

Tap to reveal

Male bee. No stinger. Sole purpose: mate with queen. Dies after mating (organs expelled).

🥚

Life Cycle

Tap to reveal

Egg → Larva → Pupa → Adult (Complete metamorphosis / Holometabolism)

🍯

Royal Jelly

Tap to reveal

Nutritious secretion by workers. All larvae get it for first 3 days; queen larvae get it lifelong.

🌸

Apiculture

Tap to reveal

Commercial rearing of honey bees for honey, beeswax, royal jelly, venom, and pollination services.

Question 1 / 5Score: 0

Quiz Complete!

🧬

Unit 4 — Heredity

Cell division (mitosis & meiosis), DNA & RNA structure, chromosomes, and sex determination.

🅰️

A. MCQ

7 Questions

⚡

B. Very Short

12 Questions

📝

C. Short Answer

10 Questions

📖

D. Long Answer

10 Questions

🎮

Interactive Quiz

Decode your DNA!

1During cell division, what is the process of cytoplasm division called?

iKaryokinesis

✓Cytokinesis

iiiMitosis

ivMeiosis

💡 Cytokinesis = division of cytoplasm and cell membrane (after Karyokinesis = nuclear division). Glossary: 'Cytokinesis: Division of cytoplasm.'

2Which type of RNA carries genetic code from DNA to ribosomes?

irRNA

✓mRNA

iiitRNA

ivAll types of RNA

💡 mRNA (Messenger RNA) carries genetic code from DNA in the nucleus to ribosomes in the cytoplasm for protein synthesis.

3In human cells, how many pairs of autosomes are present?

i23 pairs

✓22 pairs

iii46 pairs

iv44 pairs

💡 Humans have 44 autosomes (22 pairs). The 23rd pair are sex chromosomes (XX or XY), not autosomes.

4What is the primary function of telomeres in chromosomes?

iTo join chromatids

✓To protect chromosome ends

iiiTo initiate cell division

ivTo store genetic information

💡 Telomeres are the end portions of chromosomes that protect them from damage (like the plastic tips on shoelaces).

5Which statement about sex determination in humans is correct?

iMother's chromosomes determine the sex

iiEnvironmental factors determine the sex

✓Father's sperm determines the sex

ivBoth parents equally determine the sex

💡 The mother always contributes X. The father's X-sperm → daughter (XX); Y-sperm → son (XY). Therefore, the father determines the sex.

6What distinguishes RNA from DNA structurally?

✓RNA has Uracil instead of Thymine

iiRNA has more nucleotides

iiiRNA is always double-stranded

ivRNA has no sugar component

💡 RNA contains Uracil (U) replacing Thymine found in DNA. RNA is also single-stranded and uses Ribose sugar instead of Deoxyribose.

7What is the basic unit of DNA called?

iGene

iiChromosome

✓Nucleotide

ivBase pair

💡 Nucleotides are the basic building blocks of DNA. Each nucleotide = deoxyribose sugar + phosphate group + nitrogen base.

1What is the process by which a cell divides to form new cells called?

The process by which a cell divides to form new cells is called cell division.

2Name the type of cell division that produces gametes.

Meiosis (also called meiotic cell division or reductional division) produces gametes.

3Why is mitosis called equational division?

Mitosis is called equational division because the daughter cells have the same chromosome number (2n) as the parent cell.

4Explain why gametes have half the chromosome number of body cells.

Gametes are produced by meiosis (reductional division), during which the chromosome number is halved (2n → n). This ensures that when two gametes fuse at fertilisation, the original chromosome number (2n) is restored.

5How are chromosomes related to genes and DNA?

Chromosome → contains DNA → which contains Genes → which code for Traits

Chromosomes are thread-like structures made of tightly coiled DNA and proteins (histones). A gene is a specific segment of DNA that controls a particular trait.

6Why are offspring similar but not identical to their parents?

Offspring are similar because they inherit genes from both parents through chromosomes. However, they are not identical because: (a) meiosis produces genetic variation through crossing over, (b) there is random assortment of chromosomes during gamete formation, and (c) fertilization randomly combines genes from both parents, creating unique combinations.

7When a cut on your skin heals, which type of cell division occurs and why?

Mitosis occurs. It produces genetically identical daughter cells with the same chromosome number as the parent cell — essential for replacing and repairing damaged skin tissue. The new cells must match the original cells exactly.

8How does DNA fingerprinting help in criminal investigations or parent identification?

DNA fingerprinting compares unique DNA patterns from biological evidence (blood, hair roots, saliva, skin cells) at a crime scene with DNA samples from suspects. Since every person has a unique DNA sequence, matching patterns identifies the individual. For paternity testing, it confirms biological relationships by comparing inherited DNA patterns between individuals.

9What could happen if chromosomes fail to separate properly during meiosis?

If chromosomes fail to separate properly, the resulting gametes will have either too many or too few chromosomes (non-disjunction). When such gametes fertilize, the offspring may have chromosomal disorders (e.g., Down syndrome from an extra chromosome 21).

10In families, siblings look different even with the same parents. Explain this using meiosis and genes.

During meiosis, crossing over occurs — genetic material is exchanged between homologous chromosomes. Additionally, chromosomes assort randomly into gametes, giving each gamete a unique combination of parental genes. Fertilization further randomizes the combination, resulting in different characteristics despite having the same parents.

11Why is meiosis called reductional division? Explain briefly.

Meiosis is called reductional division because the chromosome number is halved in the daughter cells — from the diploid (2n) parent cell to haploid (n) daughter cells. This reduction is essential for maintaining the chromosome number across generations.

12Why is the father responsible for determining the sex of a child in humans?

Mother (XX) → all eggs carry X chromosome Father (XY) → sperm carry either X or Y X-sperm + X-egg = XX = DAUGHTER 👧 Y-sperm + X-egg = XY = SON 👦 ∴ The FATHER determines the sex of the child.

1Differentiate between mitosis and meiosis in terms of number of daughter cells and chromosome number.

Feature	Mitosis	Meiosis
No. of daughter cells	2	4
Chromosome no. in daughter cells	Same as parent (2n) — equational	Half of parent (n) — reductional
Type of cells formed	Somatic/vegetative cells	Gametes (sperm, egg, pollen)
Function	Growth, repair, asexual reproduction	Sexual reproduction

2Write any two significances of mitosis.

Mitosis produces new cells for growth and development of the organism.
It helps to replace old or damaged cells for tissue repair, maintaining the health and functioning of the body.

3Draw a concept map to show the relationship among DNA, gene, and chromosome with an example.

CHROMOSOME (thread-like structure of coiled DNA + proteins) │ └── contains DNA (Deoxyribonucleic Acid — double helix molecule) │ └── contains GENES (specific segments of DNA) │ └── code for TRAITS (e.g., eye colour, blood group) Example: Chromosome 11 → contains DNA → contains GENE (HBB) → codes for haemoglobin

4Distinguish between autosomes and sex chromosomes.

Autosomes	Sex Chromosomes
Determine somatic (body) characteristics.	Determine the sex of the individual.
Humans have 44 autosomes (22 pairs).	Humans have 2 sex chromosomes (1 pair).
Same in males and females.	Female = XX; Male = XY (also called heterosomes).

5A gardener grows a new plant from a stem cutting. Which type of cell division occurs and what is its importance?

Mitosis cell division occurs. When a gardener cuts a stem, the cells in the cutting must divide to produce new cells and form a complete new plant. Since the new plant must be genetically identical to the parent (a clone), mitosis is appropriate — it produces daughter cells with the same genetic makeup as the parent.

6When a person suffers a deep cut, new skin forms after a few days. Explain the role of cell division in this healing process.

Mitosis plays the key role in healing. When skin is cut, the surrounding healthy cells detect damage and begin mitotic division. These new cells are genetically identical to the original skin cells, ensuring the repaired tissue has the same characteristics and structure. The chromosome number is maintained (2n) throughout, so no mutations occur during normal healing.

7How has the discovery of DNA structure contributed to modern genetic engineering and biotechnology?

The discovery of the double helix structure of DNA by Watson and Crick revealed how DNA stores and transfers genetic information through specific base pairing (A-T, C-G). This knowledge allowed scientists to:

Understand the genetic code and how genes control protein synthesis.
Develop techniques to cut, insert, delete, or substitute specific DNA segments using restriction enzymes and DNA ligase.
Produce genetically modified organisms (GMOs) for improved crop yields, disease resistance, etc.
Create recombinant DNA technology for producing insulin, vaccines, and other pharmaceuticals.
Enable DNA sequencing, gene expression studies, and DNA fingerprinting for forensics and paternity testing.

8Why do organisms grow evenly, even though not all cells divide at the same time?

Not all cells need to divide at the same time for even growth. Cells in different tissues divide at different rates according to the body's needs. Growth factors, hormones, and cell signals coordinate division across different tissues, ensuring that growth is regulated and proportional. For example, skin cells divide faster than bone cells, but both contribute to overall proportional growth.

9How does uncontrolled cell division lead to diseases like cancer?

Normally, mitosis is tightly regulated by the body through cell cycle control proteins.
If gene mutations occur that disable these regulatory controls, cells may begin dividing uncontrollably.
This uncontrolled mitosis produces an abnormal mass of cells called a tumour.
These tumour cells do not perform normal functions and may invade surrounding tissues or spread (metastasize) to other parts of the body — causing cancer.

10What might happen if chromosomes fail to separate properly during cell division?

If chromosomes fail to separate properly during meiosis, daughter cells receive incorrect numbers of chromosomes (non-disjunction). Gametes with extra or missing chromosomes can lead to chromosomal disorders. For example, if an egg with an extra chromosome 21 is fertilized, the offspring may have Down syndrome (trisomy 21).

1Describe the process of mitosis with the help of a neat diagram. Mention its importance in growth and repair.

Definition:

Mitosis is the type of cell division that occurs in somatic (body) cells, producing two genetically identical daughter cells with the same chromosome number as the parent cell. It occurs in two main stages: Karyokinesis (nuclear division) and Cytokinesis (cytoplasm division).

Stages of Karyokinesis:

Prophase: Chromatin fibres condense into visible chromosomes. Nuclear envelope begins to disappear. Spindle fibres start forming.
Metaphase: Chromosomes align along the centre (equatorial plate) of the cell. Spindle fibres attach to the centromere of each chromosome.
Anaphase: Sister chromatids are pulled apart to opposite poles of the cell by spindle fibres.
Telophase: Nuclear envelope reforms around each set of chromosomes. Chromosomes begin to uncoil. Cytokinesis follows: the cytoplasm divides producing two genetically identical daughter cells.

Importance of Mitosis:

The number of chromosomes in each daughter cell is genetically identical with the parent cell.
It helps maintain the proper size of the cell.
It maintains equilibrium in the amount of DNA and RNA contents.
It helps in growth and development of the body of an organism.
It replaces dead and decayed cells by new cells.
It helps in asexual reproduction.

2Explain the structure and function of DNA. How does its structure help in storing hereditary information?

Structure of DNA:

DNA is made of smaller units called nucleotides.
Each nucleotide has three parts: (i) Deoxyribose sugar, (ii) Phosphate group, (iii) Nitrogen base.
Four types of nitrogen bases: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).
Base pairing is specific: A pairs with T (double bond), C pairs with G (triple bond).
Two antiparallel strands twist together to form a double helix.
Sugar-phosphate groups form the backbone (sides of the ladder); base pairs form the rungs.
A nucleoside = nitrogen base + deoxyribose sugar. A nucleotide = nucleoside + phosphate group.

Functions of DNA:

Carries hereditary information via unique nucleotide sequence.
Controls protein synthesis (transcription → translation).
Replicates before cell division to pass identical copies to daughter cells.

The specific sequence of nucleotides varies from person to person, encoding unique genetic information. This sequence forms a genetic code, which undergoes transcription to create mRNA, which carries genetic instructions to ribosomes for protein synthesis.

3Explain the process of sex determination in humans with the help of a diagram. Who determines the sex of the child?

Female (Mother): XX → all eggs carry X chromosome Male (Father): XY → sperm carry X OR Y chromosome Egg(X) + X-sperm = XX = GIRL 👧 Egg(X) + Y-sperm = XY = BOY 👦 Probability: 50% daughter, 50% son

The FATHER determines the sex of the child. The mother always contributes X; the type of sperm from the father (X or Y) determines whether the child is female or male.

Common misconception: blaming the mother for the child's sex is scientifically wrong.
Diet, prayers, or practices cannot alter sex determination — it is genetically fixed at fertilisation.

4When a person suffers a deep cut, new skin forms after a few days, but the colour of the new skin remains the same as before. Explain the role of cell division and DNA in this process.

When skin is cut, the healthy cells around the wound begin mitotic cell division. They divide to produce new cells that replace the damaged tissue. Mitosis ensures that each new cell has exactly the same chromosome number and genetic makeup as the original skin cells.

DNA determines the characteristics of every cell, including skin colour. During mitosis, each daughter cell receives an exact copy of the parent cell's DNA, including the genes that control melanin (skin pigment) production. Since the new cells have the same DNA, they produce the same amount and type of pigment, resulting in skin of the same colour.

5Compare mitosis and meiosis under the following basis: a) Number of divisions b) Number of daughter cells c) Chromosome number in daughter cells d) Role in organism

Basis	Mitosis	Meiosis
a) Number of divisions	One division	Two divisions (Meiosis I and II)
b) Number of daughter cells	2 daughter cells	4 daughter cells
c) Chromosome number	Same as parent (2n) — diploid	Half of parent (n) — haploid
d) Role in organism	Growth, repair, asexual reproduction	Formation of gametes for sexual reproduction

6How does the process of crossing over during meiosis lead to variation among offspring? Why is variation important in living organisms?

During Meiosis I, crossing over occurs — genetic material is exchanged between homologous chromosomes. This exchange of DNA segments creates new combinations of alleles. Each gamete produced then carries a unique combination of genetic material, and when two gametes fuse at fertilization, the resulting offspring has a unique genetic constitution. This explains why siblings born to the same parents look different from each other.

Importance of Variation:

It enables populations to adapt to changing environments — individuals with favourable traits survive better.
It is the raw material for evolution and natural selection.
Variation helps in the development of new species over generations.
It reduces the risk of an entire population being wiped out by a single disease or environmental change.

8Why does each person have unique DNA except identical twins? How can understanding DNA help in preventing genetic diseases?

The order/sequence of nucleotides in DNA varies from person to person. During meiosis, crossing over and random assortment of chromosomes produce unique gametes. Fertilization randomly combines one gamete from each parent, producing a unique combination of alleles in every individual — hence unique DNA. (Identical twins are exceptions because they develop from the same fertilized egg and have identical DNA.)

Understanding DNA Helps Prevent Genetic Diseases by:

Scientists can identify disease-causing genes and develop gene therapies to treat genetic disorders.
DNA testing can reveal whether a person carries genes for hereditary diseases, allowing informed reproductive choices.
Genetic engineering allows scientists to add, delete, or modify specific genes to eliminate disease-causing genes.
Personalised medicine based on an individual's genetic makeup can predict disease risk and allow preventive treatment.

9Observe the given figure and answer:

a. What type of cell division is shown in the figure?

Mitosis is shown in the figure.

b. What happens if this cell division does not occur in the organism?

The organism cannot grow.
Damaged or worn-out tissues cannot be repaired or replaced.
Wounds would not heal.
In unicellular organisms, the species could not reproduce asexually.

c. Write any two significances of this type of cell division.

Mitosis produces new cells for growth and development of the organism.
It helps to replace old or damaged cells for tissue repair, maintaining the health and functioning of the body.

10Given diagram shows sex determination in human:

a. Which parent is responsible for sex determination in the child?

The father is responsible for sex determination. (The father's sperm carries either X or Y chromosome, which determines the child's sex.)

b. What is the probability of giving birth to a daughter from this figure?

The probability of giving birth to a daughter (XX) is 50%.

c. Write any two misconceptions in your society about sex determination.

The mother is responsible for the sex of the child.
Diet, prayers, or certain practices can determine the sex of the child.

🧬 Chapter 4 — Fun Zone

Heredity & Cell Division Quiz

Decode your genetics knowledge!

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Mitosis

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Equational division. 2 identical daughter cells (2n). Growth, repair, asexual reproduction.

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Meiosis

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Reductional division. 4 haploid daughter cells (n). Produces gametes. Involves crossing over.

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DNA Structure

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Double helix. Bases: A-T, C-G. Sugar-phosphate backbone. Made of nucleotides.

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Types of RNA

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mRNA — carries code to ribosomes. tRNA — brings amino acids. rRNA — ribosome structure.

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Telomere

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End portion of chromosomes. Protects chromosomes from damage (like a plastic tip on a shoelace).

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Sex Determination

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Father's sperm decides! X-sperm + egg = XX (girl). Y-sperm + egg = XY (boy). 50% probability each.

Question 1 / 5Score: 0

Quiz Complete!