CBSE Class 10 Term 2: Science 3 Marks Important Questions

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CBSE 10th Science Term-2 2022: 3 Marks Important Questions With Solution

This article contains 3 marks important questions of science from class 10th. These questions are suggested by me and the my experts team for the upcoming board exam Term 2 2022.

Every Students must practice all these questions to improve their preparation so that they can score good marks in their final Science board exam Term 2 2022. CBSE Class 10 Science 3 marks important Questions are provided here from all chapters which are provided below.

CBSE Class 10 Science Term 2
CBSE Class 10 Science Term 2


Carbon and its Compounds

Que-1: What is a Homologous Series Of Compounds? List Any Two Characteristics of a Homologous Series.

Ans : A series of compounds having similar structural formulae, same functional group and hence similar chemical properties are called homologous series of compounds.

Characteristics of homologous series:

1. The members of a homologous series have similar chemical properties.

2. Any two adjacent members of a homologous series differ by a CH2 unit in their molecular formulae.

Que-2: Give reasons for the following:

(a) Element carbon forms compounds mainly by covalent bonding. 

(b) Diamond has a high melting point.

(c) Graphite is a good conductor of electricity.

Ans : (a) elements of carbon forms compounds mainly by covalent bonds because it has 4 electrons in its outermost shell and can be the gain electrons not give electrons so it forms covalent bonds by sharing of electrons.

(b) Diamond has a high melting point because the forces of attraction between the molecules of diamond is very large and a large amount of heat is in the form of energy of heat is required to break that bonds between the Diamond molecules.

(c) graphite is a good conductor of electricity because it contains free molecules which contains electrons which helps in conduction of electricity.

Que-3: Give reason why carbon can neither form C4+ cations nor C4- anions but forms covalent compounds are bad conductors of electricity and have low melting and boiling points?

Ans : ACarbon cannot form C4+ cation because of removal of 4 elections from a carbon atom would require a large amount of energy.b Carbon cannot form C4- anion because it would be difficult for the nucleus with 6 protons to hold on to 10 electrons.c Hence carbon atoms share electrons forming covalent compounds.d Covalent compounds do not form ions/ charged particles and therefore do not conduct electricity.e Inter molecular forces of attraction are weak hence low melting and boiling points.

Que-4: Two carbon atoms cannot be linked to each other by more than three covalent bond. Why?

Ans : A carbon atom has atomic number 6. It’s electronic configuration is 2,4 To become stable it shares it’s 4 electrons. Two carbon atoms when linked together share 1 electron.After it now 3 electrons are left. Then these 3 electrons link by covalent bond to other atoms.So only 3 covalent bonds can be formed

Q.5. What are the two properties of carbon which lead to the formation of a large number of carbon compounds?

Ans. Catenation (self linking of carbon atoms to form long chains) and Tetravalency are the two properties of carbon which lead to the formation of a large number of carbon compounds.

Chapter 5

Periodic Classification of Elements

Que-1: Given below are some elements of the modern periodic table :

4Be, 9F, 14Si, 19K, 20Ca.

(a) Select the element that has one electron in the outermost shell and write its electronic configuration.

(b) Select two elements that belong to the same group. give reason for your answer.

(c) Select two elements that belong to the same period. Which one of the two has bigger atomic size?

Ans. (a) 19K (Potassium) is the element that has one electron in the outermost shell. Electronic configuration = 2,8,8,1

(b) (ii) 4Be (Beryllium) and 20Ca (Calcium) belong to the same group because they have same number of valence electrons. Be=2,2 and Ca = 2,8,8,2

(c) Beryllium (Be) and Fluorine (F) have the same period i.e., a second period which has 2 shells (K and L) whereas Potassium (K) and Calcium (Ca) also belong to same period i.e., the fourth period which has 4 shells (K, L, M and N).

Que-2: (a) The modern periodic table has been evolved through the early attempts of Dobereiner, Newland and Mendeleev. List one advantage and one limitation of all the three attempts.

(b) Write the Modern Periodic law.

Ans. (a) Dobereiner Periodic Table

Advantage: To predict the atomic mass of middle element in each triad. 

Limitation: Dobereiner could identify only three triads. 

Newland Periodic table 

Advantage: Every eighth element had properties similar to that of first/co-related the properties of elements with their atomic mass.

Limitation: It was only applicable up to Calcium/only 56 elements and no future element. 

Mendeleev’s Periodic Table 

Advantage: Elements with similar properties could be grouped / He predicted the existence of new elements that had not been discovered at that time. 

Limitation: No fixed position for hydrogen/position of isotopes/ Atomic masses do not increase in a regular manner.

(b) The modern periodic law states that the physical and chemical properties of the elements are the periodic function of the atomic numbers. The various elements with similar properties repeat after certain regular intervals. This repetition occurs when you arrange the elements in order of their increasing atomic numbers.

Que-3: What is periodicity in properties of elements with reference to the Modern Periodic Table ? Why do all the elements of the same group have similar properties ? How does the tendency of elements to gain electrons change as we move from left to right in a period ? State the reason of this change.

Ans. The occurance of the elements with similar properties after certain regular intervals when they are arranged in increasing order of atomic number is called periodicity. The periodic repetition of the properties is due to the recurrence of similar valence shell configuration after regular interval.
The element in a group have same valence electrons thus similar properties. In a period, tendency to gain electrons increases from left to right. This tendency increases because the hold of nucleus on the outermost electrons becomes weak thus it becomes easy to eject the electrons.

Que-4: Write the electronic configuration of two elements X and Y whose atomic numbers are 20 and 17 respectively. Write the molecular formula of the compound formed when element X reacts with element Y. Draw electron-dot structure of the product and also state the nature of the bond formed between both the elements.

Ans. Electronic configuration of X = 2,8,8,2
Electronic configuration of Y = 2,8,7
Molecular formula : x+2 + 2y-1 = xy2

X has two extra electrons hence X has +2 valency Y needs 1 electron to be stable hence Y has -1 valency. Type of bond – Ionic Bond


Que-5 The electronic configuration of an element is 2, 8, 4. State its,

(a) Group and period in the Modern Periodic Table.

(b) Name and write its one physical property.

Ans. (a)  Group – 14, Period – 3

(b) Name of element: Silicon
It is a metalloid because it exhibits properties of both metals and non-metals.

Chapter 8

How Do Organisms Reproduce?

Que-1: What is Placenta? Write two functions of Placenta.

Ans. The placenta is an organ which is responsible for now rising and protecting a fetus dwing pregnancy

It is a temperature organ (also unique). Its growth takes place dwing for period of pregnancy among with the fetus

Two function of placenta are:

1  It allows gas exchange so that the fetus gets enough of oxygen and also helps it to get sufficient nuterition.

2  Placenta removes the waste from the fetus for processing by the mother’s body, also helps in filteration of microbes that cold was infection.

Que-2: What is the importance of variation?

Ans. Variation help in survival of the organism by many different ways-

(i)It helps a species to survive

(ii)It also helps organisms to adapt to their environment as well as to changes which do occur in the environment.

(iii)It also helps a species to emerge strong if favoured by natural selection.

(iv)Variation helps a species to be resistant to diseases.

Que-3: Why is vegetative propagation practiced for growing some types of plants?

Ans. Vegetative propagation is practiced because:

1. It is more rapid and easier method.

2. It can help plant to grow in regions where germination failed.

3. It is useful for propagating those plants that do not produce viable seeds or produce less number of seeds.

4. It is quick method of producing several plants in short period of time..

5. Example- Tuber of potato, the rhizome of ginger.

Que-4: Differentiate between bisexual and unisexual flowers.

Ans. In flowering plants, flowers are the reproductive organs. Some flower like Rose and Sweet pea contain both male and female reproductive organs. They are hermaphrodites and are known as complete (or bisexual) flowers. Complete flower have stamens, pistil, petals and sepals. Other flowers like Com and Papaya contain only male or female reproductive organ. They are known as incomplete (or unisexual) flowers. 

Que-5: What is tissue culture?

Ans. Tissue culture is a technique in which fragments of plants are cultured and grown in a laboratory. Many times the organs are also used for tissue culture. The media used for the growth of the culture is broth and agar.

This technique is also known as micropropagation. It has proved beneficial for the production of disease-free plants and increase plant yield in developing countries. It only requires a sterile workplace, greenhouse, trained manpower, and a nursery.

Que-6: Explain the process of fertilisation in flowering plants.

Ans. Fertilization in flowering plants happens through a process called pollination. Pollination occurs when pollen grains from the anther land on a stigma. Fertilization occurs when one of the sperm cells fuses with the egg inside of an ovule. After fertilization occurs, each ovule develops into a seed.

Que-7: Name the different constituents of semen. 

Ans. Semen, also known as seminal fluid, is an organic fluid that may contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize female ova. In humans, seminal fluid contains several components besides spermatozoa: proteolytic and other enzymes as well as fructose are elements of seminal fluid which promote the survival of spermatozoa, and provide a medium through which they can move or “swim”. Semen is produced and originates from the seminal vesicle, which is located in the pelvis.

Que-8: Draw a labelled diagram of male reproductive system.

Ans. The human male reproductive system consists of a scrotum, testes, testicular lobules, seminiferous tubules, urethra, and penis. The scrotum is a pouch of deeply pigmented skin divided into two separate sacs. Each sac contains one testis. Testes are the primary sex organs of the man. Each testicular lobules consists of 2-3 seminiferous tubules, blood vessels, nerves, and connective tissue. The male urethra is a common pathway for both semen and urine. The penis is the male copulatory organ and for conducting urine from the body.


Que-9: What is pre-natal sex determination? Why is it banned?

Ans. Pre-natal sex determination is the process of determining the sex of a child before it is born. It is banned because people use it to find and abort the birth of a girl child as they are considered burdens to the family.

Que-10: Draw a labelled diagram of the longitudinal section of a flower.

Ans.  A flower is made up of both reproductive and non-reproductive parts. The given diagram represents the longitudinal section of a flower. 

1.1. Reproductive parts:

Female reproductive parts

(i) Pistil or carpel is the female reproductive part of the flower.

(ii) Each carpel is made up of stigma, style, and ovary. 

Male reproductive parts

(i) Stamens are the male reproductive parts of the flower.

(ii) Each stamen consists of anther and filament.

2.2. Non-reproductive parts:

(i) The calyx is the outermost whorl of modified leaves called sepals.

(ii) Corolla is the whorl inner to the calyx and mostly comprises brightly coloured petals.


Chapter 9

Heredity and Evolution

Que-1: Distinguish between homologous and analogous organs with example.

Ans. HOMOLOGOUS ORGANS ANALOGOUS ORGANS 1. They differ morphologically. 1. They show a superficial resemblance. 2. They have a similar internal structure. 2. Their internal structure is quite different. 3. They develop in related organisms. 3. They develop in unrelated organisms. 4. Stages in the development are similar. 4. Stages in the development are different. 5. They perform different functions. 5. They have similar functions. 6. They have a similar developmental pattern. 6. They have the dissimilar developmental pattern. 7. Homologous organs show adaptive radiation (divergent evolution). 7. Analogous organs show convergent evolution. 8. For example, The arm of a human, the wing of a bird or a bat, the leg of a dog and the flipper of a dolphin or whale are homologous structure. 9. For example, analogous structures range from wings in flying animals like bats, birds, and insects, to fins in animals like penguins and fish.

Que-2: Variation is beneficial to the species but not necessarily for the individual. Give three reasons to justify it.

Ans. The variation is important and beneficial for species as it allows a species to adapt to a changing environment.

For example, climate change can force a species to shift its range to poleward or to higher altitudes.

Only those who adopt the changes can survive in harsher conditions by adapting to the changes.

For an individual, the variation doesn’t matter in most of the conditions.

Take the example of we humans, if a climate change happens, we can shed our clothes and our body will help us control the temperature, and if the environment gets colder, we can wear more clothes to protect us.

However, in conditions like any new virus or bacteria attack which is harmful to humans, our body has to adapt according to this scenario or we will perish.

Que-3: The human hand, cat paw and horse foot, when studied in detail show the same structure of bones and point towards a common origin.

(a) What do you conclude from this?

(b) What is the term given to such structure?

Ans. (a) Same basic structure of human hand, cat paw and the horse foot indicate that these structures have same embryonic origin. These structures show divergence which occurs when same basic organ modifies itself according to different environmental conditions it is facing.

(b)Such structures are called homologous structures. The same basic organ becomes specialised to perform different functions and give rise to homologous organs.

Que-4: What is genetic drift. Explain with examples

Ans. Genetic drift is the change in the frequency of an existing gene variant in a population due to random sampling of organisms. The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces. Examples of genetic drift are more evident in smaller populations of organisms. 2. A population of rabbits can have brown fur and white fur with brown fur being the dominant allele. By random chance, the offspring may all be brown and this could reduce or eliminate the allele for white fur.

Que-5: Write a short note on

(a) gene flow

(b) Natural selection

Ans. (a)Gene flow is also called gene migration. Gene flow is the transfer of genetic material from one population to another. Gene flow can take place between two populations of the same species through migration, and is mediated by reproduction and vertical gene transfer from parent to offspring.

(b) Natural selection is the process through which populations of living organisms adapt and change. Individuals in a population are naturally variable, meaning that they are all different in some ways. This variation means that some individuals have traits better suited to the environment than others.

Que-6: Distinguish between autosomes and sex chromosomes.



Sex chromosomes

  • Autosomes control the somatic characters of the body.
  • Example: eye colour, height, etc.
  • Out of 23 pairs 22 pairs of chromosomes are autosomes.
  • Sex chromosomes determine sex of the organism and they govern the sex linked traits of an organism.
  • Example: baldness, colour blindness.
  • Out of 23 pairs one pair is of sex chromosomes. XX in females and XY in males.

Que-7: Distinguish between inherited traits and acquired traits giving one example of each. Give reason why the traits acquired by an individual during the life time are not inherited.

Ans. The changes in germ cells of the reproductive tissue of a sexually reproducing organism, which can be passed on to the next generation are called inherited traits. For example colour of the eye.
The changes in non-reproductive tissue of an organism, which cannot be passed on to the progeny, because they do not involve any change in the DNA of germ cells, are called acquired traits. For example reduction in weight due to starvation, These are the traits acquired during the lifetime of an individual and are not inherited because of lack of change in germ cells that participate in the reproduction process.

Que-8: A cross was carried out between a pure bred tall pea plant and a pure bred dwarf pea plant and F1 progeny was obtained. Later, the F1 progeny was selfed to obtain F2 progeny. Answer the following questions : 

(i) What is the phenotype of the F1 progeny and why ? 

(ii) Give the phenotypic ratio of the F2 progeny. 

(iii) Why is the F2 progeny different from the F1 progeny ?

Ans. (i) The phenotype of F1 progeny is Tt because F1 or hybrid plants were not intermediate between the two alternate forms of a character. They resembled only one parent. In a cross between tall and dwarf of pea plants, the F1 plants were all tall. 

(ii) The phenotypic ratio of F2 progeny is 3: 1. 

(iii) F1 progeny resembled only one parent which is dominant in nature but in F2 progeny phenotypically three plants are tall and one plant is dwarf. But according to genotype ratio, one plant is pure tall, two are hybrid tall and one plant is a pure dwarf.

Chapter 12


Que-1: Find a relationship between P, I and V.

Ans. (i) Power can stream either as immediate or substituting flow and is utilized in homes to control electrical appliances. The National Grid disperses power all through the country.

(ii) The amount of energy transferred each second (power) between the energy stores can be calculated by:

Power = Potential difference × current


Where P is the power and S.I unit of power is Watt (W), V is the potential difference and the unit of potential difference is Volts (V), and I is the current and unit is ampere.

Que-2: State Ohm’s law. Derive relation between I, V and R. Draw the graph between V and I

Ans. Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the two points.
The relationship between voltage, current, and resistance is described by Ohm’s law. This equation, i = v/r, tells us that the current, i, flowing through a circuit is directly proportional to the voltage, v, and inversely proportional to the resistance, r. In other words, if we increase the voltage, then the current will increase. But, if we increase the resistance, then the current will decrease. We saw these concepts in action with the garden hose. Increasing the pressure caused the flow to increase, but getting a kink in the hose increased the resistance, which caused the flow to decrease.

Que-3: What is Joule’s heating effect of current P? Derive its expression.

Ans. Hence the heating effect produced by an electric current, I through a conductor of resistance, R for a time, t is given by H = I2Rt. Joule’s law states the amount of heat production in a conductor is : Directly proportional to the square of electric current flowing through it.

Que-4: What would be new resistance if length of conductor is doubled and thickness is halved?

Ans. New resistance is 8 times the old resistance. If the length is double then the resistance would increase by 8 times. Since R = P*L/A (Resistivity constant) length becomes 2L and area becomes 1/4th. So, almost the new resistance increase by 4 times.

Que-5: Find the effective resistance between A and B


Ans. Top Most Picture

three 1 Ω  Resistance in Parallel

so Net resistance of three 1 Ω  Resistance in Parallel =  1/(1/1 + 1/1  + 1/1)  = 1/3

Resistance between A & B = 1/3 + 1 + 1/3  = 5/3 Ω

Middle Picture

3 Ω & 3 Ω are in series = 6Ω

Then 6Ω &  6Ω are in Parallel

so Resistance between A & B = 1/(1/6 + 1/6)  = 6/2 = 

Bottom one Picture

2 Ω & 2 Ω are in Parallel = 1/(1/2 + 1/2)  = 1Ω

so Resistance between A & B = 1 + 1 + 2 = 4Ω

Que-6: Which is the better way to connect lights and other appliances in domestic wiring and why ?

Ans. A parallel arrangement will be a simpler way to connect lights and other electrical appliances in house wiring because there is low resistance to the parallel arrangement. Even if there is a short circuit in one device, many electrical appliances tend to be unaffected.

Que-7: Show how would you join three resistors, each of resistance 9 Ω so that the equivalent resistance of the combination is

(i) 13.5 Ω,

(ii) 6 Ω?

Ans. (i) Two resistors in parallel and then one is series

1/R = 1/R+ 1/R= 1/9 + 1/9 = 2/9/2

R = 9/2 = 4.5Ω

R’ = R + R3  


=4.5 + 9 = 13.5Ω

(ii) Two resistors in series and one in Parallel 

R = R+ R= 9 + 9 = 18Ω

1/R’ = 1/R + 1/R= 1/18 + 1/9 = 1 + 2/18 = 3/18

R’ = 18/3 = 6Ω 


Que-8: (a) Write Joule’s law of heating.

(b) Two lamps, one rated 100 W; 220 V, and the other 60 W; 220 V, are connected in parallel to electric mains supply. Find the current drawn by two bulbs from the line, if the supply voltage is 220 V.

Ans. (a) Joule’s law of heating states that, when a current ‘i ‘ passes through a conductor of resistance ‘r’ for time ‘t’ then the heat developed in the conductor is equal to the product of the square of the current, the resistance and time.

(b)From Joule’s Law of heating,

P = V2/R

For first lamp, 

R1​ = 2202/100

For second lamp, 

R​= 2202/60

When they are connected in parallel,


I = 0.73 A

Que-9: (a) List the factors on which the resistance of a conductor in the shape of a wire depends.

(b) Why are metals good conductors of electricity whereas glass is a bad conductor of electricity?

(c) Why are alloys commonly used in electrical heating devices?

Ans. (a) Resistance of a conductor depends on the following factor :

(i) Resistance of a conductor is directly proportional to length (l) of the conductor.

(ii) Resistance of a conductor is inversely proportional to area of cross-section of the conductor

(iii) Resistance also depends on a material of conductor (ρ)

(iv) Resistance and resistivity also depends on temperature.

(b) Metals have more free electrons than glass to carry currents. That’s why glass is bad conductor and metals are good conductors

(c) Every metals have fixed conductivity and melting point. but, in electrical heating devices, We required different types of wires like; it can be good conductor with high/ law melting points or Bad conductors with low/ high melting points. To serve this purpose we need to take allows wire.

Chapter 13

Magnetic Effects of Current

Que-1: A charged particle enters at right angle into a uniform magnetic field. What is the nature of charge particle if it experiences a force in a direction pointing vertically out of page.


Ans. According to the Fleming’s left-hand rule, the charged particle should be a positively charged in order to experience the force in the direction out of the page after interaction with the magnetic field.

Que-2: Write the three ways to produce magnetic field.

Ans. Three different ways of producing magnetic fields are

1) A loop or solenoid carrying current.

2) A magnetic bar, round magnet or horse-shoe magnet.

3) A coil which carries current.

Que-3: What is solenoid ? Where the magnetic field is uniform in solenoid?

Ans. A solenoid is a tightly wound helical coil of wire whose diameter is small compared to its length. The magnetic field generated in the centre, or core, of a current carrying solenoid is essentially uniform, and is directed along the axis of the solenoid.

Que-4: Draw the pattern of magnetic field lines due to current carrying straight conductor.



The Magnetic field lines around a straight conductor carrying current are concentric circles whose centres lie on the wire. The direction of magnetic field lines can be determined using Right-Hand Thumb Rule.

Que-5: (a) Draw a diagram to show the pattern of magnetic field lines through and around a current carrying solenoid

(b) List two factors on which the strength of the magnetic field produced by the solenoid depends.

(c) What is the effect of placing an iron core in a solenoid?

Ans. (a)


Magnetic field pattern inside the solenoid indicates that the magnetic field is same at all points inside the solenoid.

(b) The strength of magnetic field produced by a current-carrying solenoid depends on:

1. The strength of current in the solenoid: Large the current passed through solenoid; stronger will be the magnetic field produced.

2. The number of turns in the solenoid; Larger the number of turns in the solenoid, greater will be the magnetic field produced.

(c) By placing a core inside of a coil the strength of the magnetic field can be increased. By putting a ferrous (iron) core inside a solenoid, the field lines are concentrated. This has the effect of strengthening the field.

Que-6: A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is

(a) pushed into the coil,

(b) withdrawn from inside the coil,

(c) held stationary inside the coil?

Ans. (a) When a bar magnet is pushed into the coil of insulated copper wire connected to a galvanometer, an induced current is set-up in the coil due to change of magnetic field through it. As a result, galvanometer gives a deflection (say towards left).

(b)  When the bar magnet is withdrawn from inside the coil, again an induced current is set­up in the coil due to change of magnetic field through it. As a result galvanometer gives a deflection in the reverse direction. (say towards right).

(c)  If the bar magnet is held stationary inside the coil, then there is no induced current in the coil, because there is no change in magnetic field through it. As a result, galvanometer does not show any deflection. 

Que-7: (a) Mention the factors on which the direction of force experienced by a current-carrying conductor placed in a magnetic field depend.

(b) Under what condition is the force experienced by a current-carrying conductor placed in a magnetic field maximum?

(c) A proton beam is moving along the direction of a magnetic field. What force is acting on proton beam?

Ans. (a) The direction of force experienced by the current-carrying conductor depends on:  (i) direction of current and  (ii)direction of magnetic field. 

(b) When the direction of current is at right angle to the direction of magnetic field, the force is maximum. 

(c) No force is experienced by the proton beam. As proton beam is moving along the direction of magnetic field.

Chapter 15

Our Environment

Que-1: Why only 10% energy is transferred to the next trophic level?

Ans. The amount of energy at each trophic level decreases as it moves through an ecosystem. As little as 10 percent of the energy at any trophic level is transferred to the next level; the rest is lost largely through metabolic processes as heat.

Que-2: Why is ozone layer important for the existence of life on earth?

Ans. The ultra violet radiations coming from the sun are harmful for living beings. This layer absorbs these radiations coming from the sun and does not allow them to reach the earth’s surface. Therefore ozone layer is essentials for the existance of life on earth.

Que-3: What is the role of decomposers in ecosystem?

Ans. Various roles played by decomposers in the ecosystem are:

→ They decompose biodegradable substances into useful substances.

→ They release nutrients into the soil by decomposing dead and decaying matter, thus making the soil fertile.

→ They maintain the nutrient pool by returning back the nutrients in the pool.

Que-4: Draw an energy pyramid showing different trophic levels.



Que-5: How ozone molecule is formed in the atmosphere?

Ans. Ozone is formed throughout the atmosphere in multistep chemical processes that require sunlight. In the stratosphere, the process begins with an oxygen molecule (O2 ) being broken apart by ultraviolet radiation from the Sun. In the lower atmosphere (troposphere), ozone is formed in a different set of chemical reactions involving hydrocarbons and nitrogen-containing gases.

Que-6: Why natural ecosystem is more stable than artificial ecosystem?

Ans. Artificial ecosystem that consists of plants and species outside their natural habitat. Natural ecosystems contain more naturalfactors and organisms. The relationships between organisms, each other and the environment in this ecosystem are morecomplex than that of artificial ecosystems.

Que-7: Why some materials are not decomposed by the action of micro-organisms?

Ans. Some materials are not decomposed by the organism because the individual units join together with the carbon-carbon bond which was not recognisable by the bacteria and this lead to the non degradation of the matter. Decomposition is a process carried out by micro organisms to breakdown the organic matter contains the peptide bond. The organism decomposes them and releases the nutrients back to the soil. Plastics and other related polymer didn’t get decomposed by the action of microorganisms. Most plastics and other polymer are made up of propylene, a simple chemical compound made up of petroleum.

Que-8: Give any two ways in which non-biodegradable wastes would affect the environment.

Ans. 1. Non-Biodegradable substances are complex compounds that cannot be decomposed into simpler substances by the degrading action of bacteria, fungi and other saprophytes. It leads to pollution and it affects the fertility of the soil.

2. Non-Biodegradable substances lead to pollution and contaminate soil and water because these do not get decomposed.

Que-9: What is a food web? Explain with example

Ans. Food chain only follows just one path as animals find food. eg: A hawk eats a snake, which has eaten a frog, which has eaten a grasshopper, which has eaten grass. A food web shows the many different paths plants and animals are connected. eg: A hawk might also eat a mouse, a squirrel, a frog or some other animal.

Que-10: How the components of an ecosystem are dependent on each other?

Ans. All living organisms interact with each other and their growth, reproduction and other activities are affected by the temperature, water, humidity, etc., which constitute the abiotic components. Hence, biotic and abiotic components are dependent on each other.

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