7th Basic Qustions
- Towards A Hundredfold Yield
• What are your expectations while planting and nurturing a mango sapling?
◦ Expected outcomes include:
▪ Should get a lot of mangoes.
▪ Must start yielding at the earliest.
▪ Mangoes should be sweet.
• Aren’t our goals the same while cultivating fruits, vegetables or cereals too?
◦ Yes, the goals are:
▪ Should yield quickly.
▪ Must yield plenty.
▪ Yield should have good quality.
• What things are to be taken care of to achieve this? Discuss with your friends and write in your Science Diary.
◦ One key thing to be taken care of is that good seeds/planting materials should be used. The chapter further details other factors such as using high-quality plants and fruits for seed collection, proper selection of seeds, and appropriate cultivation methods.
• Haven’t you heard the proverb, ‘vithu gunam pathu gunam’? What does it mean?
◦ While the source does not explicitly define this proverb, the context implies its meaning: Good quality seeds should be selected for better yield.
• Where are seeds formed? What about fruits?
◦ Seeds are generally formed within fruits, and fruits are produced by plants.
• What factors should be considered while selecting the best seeds?
◦ Factors to consider for selecting the best seeds include: Shape, Size, Weight, and Seed coat. Additionally, the seeds should be collected from ripened fruits produced during the middle of the plant’s lifespan. The plant from which seeds are collected should be healthy and high yielding.
• Which of these plants would you choose to collect seeds from? Why?
◦ One should choose the healthy, high-yielding plant to collect seeds from because good quality seeds should be selected for better yield.
• Are the fruits formed at the initial and final stages of the lifespan of plants ideal for seed collection?
◦ No, fruits formed at the initial and final stages of the plant's lifespan are generally not ideal for seed collection. Seeds should be collected from ripened fruits produced during the middle of the plant’s lifespan.
• Can all these seeds be used for the production of seedlings? How can we select the best seeds from them?
◦ No, not all seeds from a single fruit can be used. The best seeds can be selected based on factors such as shape, size, weight, and seed coat.
• Are new plants formed only from seeds? Observe the pictures given below. From which parts of these plants do saplings form?
◦ No, new plants are not formed only from seeds. Saplings can form from other parts:
▪ Curry leaf plant: From root (implied from example lists).
▪ Ginger plant: From underground stem.
▪ Bryophyllum: From leaf....
▪ Pepper plant: From stem (also from layering).
• Find out examples for plants which reproduce through vegetative propagation and sexual reproduction. Write them in the Science Diary.
◦ Vegetative Propagation:
▪ Root: Bread fruit
▪ Stem: Moringa, Shoe flower, Tapioca, Sweet potato, Guava, Sapota, Java apple, Almond, Fig (through layering), Bougainvillea, Jasmine, Betel, Pepper, Grapes, Chrysanthemum (through serpentine layering).
▪ Leaf: Bryophyllum
▪ Underground stem: Dioscorea
◦ Sexual Reproduction:
▪ Moringa (also reproduces from seeds), and generally all seed-producing plants.
• Can you find more examples of plants which can reproduce both through sexual reproduction and vegetative propagation?
◦ Moringa.
◦ Sheemakonna (Gliricidia).
• Do the plants thus formed possess only the qualities of the mother plant? What if a new plant is formed from stem cutting? Won’t it have the same qualities as the mother plant?
◦ For plants formed from stem cuttings (vegetative propagation), they will have the same qualities as the mother plant. For plants formed through sexual reproduction (seeds), they may not possess only the qualities of the mother plant due to pollination.
• But, can the stem of guava plant sprout? Won’t it take years for the seeds to grow into a tree and yield fruits?
◦ It is difficult for guava to sprout from a stem cutting directly. Yes, it takes years for seeds to grow into a tree and yield fruits.
• Is it possible to make it (a desired mango tree sapling) through layering?
◦ No, it is difficult to induce roots in the stem of a mango tree for layering.
• Which variety (Indigenous or Neelam mango tree) is better in terms of quality of fruits?
◦ The Neelam mango tree is better in terms of fruit quality, as it produces big sized, very sweet mangoes.
• Does indigenous variety have any advantages over Neelam variety?
◦ Yes, the indigenous variety grows well in our soil and doesn’t need special care.
• If a sapling is produced by joining the stem of Neelam mango with the young plant of indigenous variety, what specialities will it have?
◦ It will grow well in our soil and yield mangoes of Neelam variety.
• What are the advantages of producing saplings through grafting? Discuss and write them in the Science Diary.
◦ Advantages include early flowering and fruiting. Grafting also allows combining desirable qualities of different plants, such as good fruit quality from the scion and adaptability to local soil from the rootstock.
• What is the reason for early flowering and fruiting of mango saplings produced through grafting?
◦ The reason is that the scion (stem used for grafting) is taken from a mature, high-yielding tree, so it carries the mature characteristics of the mother plant, leading to earlier fruiting compared to growing from a seed.
• Will it take a longer period for fruiting if the stem selected as scion is not mature enough?
◦ Yes, it would likely take a longer period for fruiting if the scion is not mature enough, as the scion's maturity contributes to early fruiting.
• Haven’t you seen the bud growing beneath the grafted area? Will the quality of the plant be affected if this bud is not removed? Write in the Science Diary.
◦ Yes, the quality of the plant will be affected if the bud growing beneath the grafted area is not removed. These buds originate from the rootstock and would produce fruits with the qualities of the rootstock, which may not be the desired superior quality of the scion.
• Is there any advantage in making a new mango variety by grafting the scion of a mature Moovandan mango tree with the root stock of another Moovandan mango tree?
◦ Yes, there is a merit. Since the scion is from a mature Moovandan mango tree, it is of the same age as the mother plant, and this will help in early fruiting.
• Which should be the root stock? Which would be the scion? Write the reason for this in the Science Diary. (For Malgoa and Gomav, an indigenous variety of mango tree)
◦ The root stock should be Gomav (indigenous variety) because it grows well in the local soil and doesn't need special care.
◦ The scion should be Malgoa to ensure the desired superior quality of fruits.
• What are the advantages of these (budding-produced rubber saplings) over the rubber saplings of native origin?
◦ Advantages include higher productivity, thicker latex, and quality saplings at a reasonable price.
• What are the characteristics of each plant? Write them in the Science Diary. (Chilli plants Variety 1 and Variety 2)
◦ The source prompts the reader to observe and list characteristics (e.g., size, yield, pest resistance, taste) but does not provide them.
• If we can produce a chilli plant which has the qualities of both the varieties, what qualities will it have? Note them in the Science Diary.
◦ The plant would possess a combination of the desirable qualities from both parent varieties. For example, if one variety is high-yielding and another is disease-resistant, the hybrid would be both high-yielding and disease-resistant.
• How can we produce such a sapling? Are the methods that we have learnt so far suitable for this?
◦ The methods learned so far (vegetative propagation like layering, grafting, budding) are for replicating a single parent's qualities. To combine qualities of two different plants, Hybridization is used, which involves producing new seeds with combined qualities.
• Is it in self pollination or cross pollination that the qualities of both the plants are combined? Why?
◦ Cross pollination combines the qualities of both plants. This is because it involves pollen grains from one plant being transferred to the stigma of a different plant of the same species, leading to a combination of genetic traits. Self-pollination, conversely, involves pollen from the same plant, leading to similar qualities.
• What kind of pollination should be carried out to produce a chilli plant that will have the qualities of both the chilli plants?
◦ Cross pollination should be carried out.
• If pollination takes place through insects, can we be sure that it happened between the chilli plants we have selected?
◦ No, if pollination occurs naturally through insects, we cannot be sure that it happened only between the specific chilli plants selected.
• If not, can cross pollination be done artificially?
◦ Yes, cross pollination can be done artificially.
• When should these activities (artificial pollination) be performed? Put a tick () mark. Discuss the reason.
◦ The activities (removing stamens, collecting pollen, depositing pollen, wrapping the flower) should be performed immediately after blooming or after the flower has fully bloomed, but before unintended pollination occurs. This ensures control over the desired cross-pollination.
• Both of them planted the same variety of lady’s finger. Even then the yield from the plant of one child is low. What may be the reason?
◦ Good quality seeds alone are not sufficient for a better yield. Other factors like fertile soil, proper application of fertilizers, pest control, and suitable climate are also crucial.
• Can good quality seeds alone give a better yield? What other things are to be considered for a better yield? Write them in the Science Diary.
◦ No, good quality seeds alone cannot guarantee a better yield. Other things to consider include: Fertile soil, Pest control, and Proper application of fertilizers. Suitable climate is also important.
• Which are the fertilizers commonly used by the farmers of your locality? List them after conducting an interview with farmers of your locality.
◦ Commonly used fertilizers listed in the source are Cow dung (organic) and Urea (chemical). Other examples mentioned include Compost, Bonemeal, NPK mixture, and Chicken manure.
• How can pest infestation be controlled?
◦ Pest infestation can be controlled through various methods:
▪ Biological Control: Using friendly insects like Lady bug and Trichogramma, or animals like Frog, Mabuya, Calotes, and Bug that feed on pests.
▪ Mechanical Control: Manually removing pests or using traps like Pheromone traps.
▪ Pesticides: This includes Chemical pesticides (prepared using chemical substances) and Organic pesticides such as Tobacco decoction, Neem oil emulsion, and Garlic-kanthari (Chilli) mixture.
• How can weeds be controlled? Write in the Science Diary.
◦ Weeds can be controlled through the application of weedicides.
• Which are the methods you have learnt so far to produce saplings?
◦ The methods learned for producing saplings include: Vegetative propagation (from root, stem, leaf, underground stem), Layering, Grafting, Budding, and Sexual reproduction (from seeds), including the production of hybrid seeds through hybridization.
• Let’s Assess (Chapter 1)
◦ 1. Identify the statement which does not suit organic fertilizers.
▪ Answer: c. Destroy soil structure. Organic fertilizers are "Not harmful to soil", whereas excess use of chemical fertilizers can destroy soil structure.
◦ 2. Match the following
▪ The provided options are mismatched in the source. Here are the correct pairings based on the text:
• Apiculture - Rearing of honey bees
• Cuniculture - Rearing of rabbits
• Sericulture - Rearing of silkworm
• Pisciculture - Rearing of fish
◦ 3. You have learned about layering.
▪ a. Identify the type of layering shown in the figure.
• Answer: Serpentine Layering.
▪ b. While layering in this way, at which position should we cut the plant, A, B or C?
• For serpentine layering, new saplings are produced from roots that form along the bent branches. One would cut to separate the rooted sections. If B represents a rooted section, then the cut would be made just below position B to plant the new sapling, as per the general layering instruction to "cut the stem just below the area of layering".
◦ 4. Look at the picture.
▪ a. Identify stock and scion from A and B.
• A: Scion
• B: Root stock
▪ b. What is the advantage of attaching the stem of Malgoa to the local variety of mango tree?
• The advantage is that the sapling will grow well in our soil (from the local variety rootstock) and yield mangoes of the Malgoa variety (from the scion).
▪ c. Is there any merit in attaching the stem of a local variety of mango tree to the same variety?
• Yes, if the scion is from a mature local variety tree, it can help in early fruiting.
◦ 5. List different methods of pest control. Give examples for each type.
▪ Biological Control: Examples include Lady bug, Trichogramma, Frog, Mabuya, Calotes, Bug.
▪ Mechanical Control: Examples include manually removing pests and using Pheromone traps.
▪ Pesticides:
• Chemical pesticides (general term, no specific examples provided in the source).
• Organic pesticides: Examples include Tobacco decoction, Neem oil emulsion, Garlic-kanthari (Chilli) mixture.
- Acids and Bases
• What could be the secret behind the experiment conducted by the teacher in Jinu’s class?
◦ The secret is that the teacher likely added an acidic substance (like vinegar, lemon juice, or tamarind water) to the pink pathimugam water, which acts as a natural indicator and turns yellow in the presence of acids....
• Which among the following did the teacher add to turn the pink liquid into yellow? Put a tick () mark on the appropriate boxes, based on the experiment you have done.
◦ Based on the experiment in the source, the substances that turned pathimugam water yellow are:
▪ Lemon juice ()
▪ Vinegar ()
▪ Tamarind water ()
• Do the substances that turned pathimugam water into yellow have anything common in their taste?
◦ Yes, they all have a sour taste.
• Which liquids turned blue litmus into red?
◦ Liquids that turned blue litmus into red include: Vinegar, Lemon juice, Buttermilk, and Tamarind water.
• Which liquids turned red litmus into blue?
◦ Liquids that turned red litmus into blue include: Soap water, Clear baking soda solution, Clear lime water, and Clear ash suspension.
• Didn’t the colour of the paper (red Hibiscus flower rubbed on paper) change?
◦ Yes, when this paper is dipped in acidic liquids, it turns red.
• Which substances can be used as indicators of acids?
◦ Substances that can be used as indicators of acids include: Blue litmus paper, paper rubbed with Hibiscus flower, and Methyl Orange....
• Which substances can be used as indicators of bases?
◦ Substances that can be used as indicators of bases include: Red litmus paper, Phenolphthalein, and Turmeric (paper or water)....
• How do vinegar, lemon juice, buttermilk and tamarind taste?
◦ They all have a sour taste.
• How does it taste (soap)?
◦ Soap has an alkaline taste and feels slippery.
• Which liquids feel slippery? List them.
◦ Liquids that feel slippery include: Soap water, Baking soda solution, Clear lime water, and Clear ash suspension.
• Which common property of bases did you identify here?
◦ The common property identified is that bases are slippery.
• Which among the following substances can turn blue litmus red? List them.
◦ Substances that can turn blue litmus red (i.e., are acidic) include: Orange juice, Black tea, Bilimbi (Irumban puli) juice, Grape juice, and Tomato juice. All food items with a sour taste contain acids.
• What is the reason for the sour taste of curd?
◦ The sour taste of curd is due to the presence of lactic acid, which is produced when Lactobacillus bacteria nourish themselves with milk.
• What precautions should we take to avoid accidents while handling chemicals?
◦ Precautions include:
▪ Avoid spilling on body parts.
▪ Don't touch with hands.
▪ Don't smell.
▪ Don't taste.
▪ Use a dropper while taking out acid from a bottle.
▪ Use a holder while using a test tube.
• Which acids and bases can be taken (for laboratory experiments)?
◦ Acids: Hydrochloric acid, Nitric acid, Sulphuric acid, Acetic acid.
◦ Bases: Calcium hydroxide (Lime), Sodium hydroxide (Caustic soda), Potassium hydroxide (Caustic potash).
• Which indicators are to be taken (for laboratory experiments)?
◦ Indicators: Methyl Orange, Phenolphthalein, Blue litmus paper, and Red litmus paper.
• What do you feel? (when closing the mouth of a test tube with acid and magnesium ribbon)
◦ You will feel a pushing sensation from the gas being produced.
• Which is the gas that bubbles up and pushes at your thumb?
◦ The gas is hydrogen.
• What do you observe? (when bringing a burning matchstick to the mouth of the test tube with the gas)
◦ The gas will burn up with a pop sound.
• Identify it (the gas produced when acid reacts with metal).
◦ The gas produced is hydrogen.
• Will we get the same result if the experiment is repeated with other metals and acids? Let’s find out. Repeat the experiment with dilute hydrochloric acid and zinc.
◦ Yes, you will get the same observations; hydrogen gas is produced when acids react with metals.
• How many general properties of acids have you identified from the experiments done so far? Record in the Science Diary.
◦ General properties of acids identified:
▪ Has sour taste.
▪ Turn blue litmus red.
▪ React with metals to produce hydrogen.
• Based on this, can you explain the reason for the following situations?
◦ Metal containers are not used to store pickles.
▪ Reason: Pickles are acidic (e.g., vinegar, citric acid). Acids react with metals to produce hydrogen gas, which can contaminate the food and corrode the container.
◦ Earthen vessels are commonly used to cook dishes with curd and buttermilk.
▪ Reason: Curd and buttermilk contain lactic acid. Using earthen vessels (which are non-metallic) prevents the acid from reacting with the container, unlike metal vessels which would react with acids.
• What are the uses of vinegar at home?
◦ Vinegar (acetic acid) is used in pickles.
• Let’s Assess (Chapter 2)
◦ 1. Which among the following can be used as an indicator of acid?
▪ Answer: b. Pathimugam. Pathimugam water turns yellow in the presence of acid.
◦ 2. Which acid is used in automobile batteries?
▪ Answer: c. Sulphuric acid. Sulphuric acid is used in motor vehicle batteries.
◦ 3. Among the liquids in the three beakers placed on the table, the first one is water, the second is an acid and the third is a base. Is it right to identify them by touching, tasting or smelling? Why? Suggest a method to identify each of them.
▪ Is it right to identify them by touching, tasting or smelling? Why?
• No, it is not right. Many chemical substances, especially strong acids and bases, are dangerous and can cause severe burns if spilled on the body, or other harm if tasted or smelled.
▪ Suggest a method to identify each of them.
• The safest method is to use indicators.
◦ Dip blue litmus paper into each liquid. The one that turns it red is the acid.
◦ Dip red litmus paper into the remaining liquids. The one that turns it blue is the base.
◦ The liquid that causes no change in either blue or red litmus paper is water (neutral).
◦ 4. In the laboratory metalic caps are not used for glass bottles containing acids. Explain the reason for this.
▪ The reason is that acids react with metals to produce hydrogen gas. Using metallic caps would lead to corrosion of the cap and potential buildup of pressure inside the bottle.
◦ 5. Examine the statements given below. Classify them on the basis of properties of acids and bases.
▪ a. Has sour taste: Acid
▪ b. Turns to pink when phenolphthalein is added: Base
▪ c. Slippery: Base
▪ d. Turns to pink when methyl orange is added: This specific color change for Methyl Orange (to pink) is not explicitly stated in the provided source for classification. Methyl Orange is an indicator.
▪ e. Turns the colour of Pathimugam water into yellow: Acid
▪ f. Red litmus turns blue: Base
▪ g. Reacts with metals to produce hydrogen: Acid
▪ h. Has alkaline taste: Base
◦ 6. You have learnt about various indicators to identify acids and bases. Complete the table below.
▪ Indicators of acids:
• Natural: Paper rubbed with Hibiscus flower, Pathimugam
• Used in lab: Blue litmus paper, Methyl Orange
▪ Indicators of bases:
• Natural: Turmeric
• Used in lab: Red litmus paper, Phenolphthalein
- The World of Electricity
• What do we usually do to get light when there is a power failure?
◦ When there is a power failure, people usually use candles or an emergency lamp to get light.
• What things are needed to make an emergency lamp?
◦ To make an emergency lamp, the following are needed: 9 V battery, LED module, connector, connecting wires, a plastic bottle, a PVC pipe, and a switch.
• How will we get the electricity to make the emergency lamp work?
◦ Electricity will be obtained from a 9 V battery.
• Don’t we need a bulb to get light?
◦ Yes, an LED module is needed to get light.
• How will we connect each part?
◦ The parts will be connected by making an electric circuit.
• How will we make a stand?
◦ A stand can be constructed using a half-litre plastic bottle filled with sand and a PVC pipe.
• Where does each of these devices get its electricity from? (Referring to clock, remote, mobile, laptop pictures)
◦ Clock/Remote: Get electricity from electric cells (non-rechargeable).
◦ Mobile/Laptop: Get electricity from batteries (rechargeable).
• What is the difference between cells and batteries?
◦ A battery is an arrangement made by connecting more than one cell into a single unit. Electric cells convert chemical energy into electrical energy.
• Do all of them represent the right way for making a battery? Which among them is wrong? Which one will give more electricity?
◦ The source provides diagrams (A, B, C) but does not explicitly state which configuration is wrong or which gives more electricity. This is left for the reader to analyze based on general understanding of cell connections.
• From which source do these two devices get electricity? (Referring to car and solar calculator pictures)
◦ Car: Gets electricity from a battery.
◦ Solar calculator: Gets electricity from solar cells.
• What is the difference between the sources of electricity used in these devices?
◦ A car battery stores electrical energy as chemical energy and is rechargeable. A solar cell, in contrast, directly converts solar energy into electrical energy.
• Classify them and write in your Science Diary. (Rechargeable and Non-rechargeable cells in different devices)
◦ Rechargeable: Mobile phone battery, car battery.
◦ Non-rechargeable: Clock cell, remote control cell.
• What kind of bulbs are used in emergency lamps?
◦ LED (Light Emitting Diode) bulbs are used in emergency lamps.
• What are the advantages of using LED?
◦ LEDs help to save energy considerably and require less energy than CFL bulbs.
• Write down the electric source and electric device used for this (lighting the LED bulb) other than the connecting wire.
◦ Electric source: 9 V battery.
◦ Electric device: LED module.
• Will the bulbs in these circuits glow? Why? Analyse the pictures and record in the Science Diary. (Circuit 1, 2, 3 diagrams)
◦ Circuit 1 (complete path): The bulb will glow. This is a closed circuit, which is required for electric devices to work.
◦ Circuit 2 (broken wire): The bulb will not glow. This is an open circuit because the path for electricity is incomplete.
◦ Circuit 3 (damaged bulb): The bulb will not glow. This is an open circuit because the electric device itself is not forming a complete path.
• Are the following circuits closed or open? Why? Analyse the figures and write down in the Science Diary. (Circuit 1, 2 diagrams with switches)
◦ Circuit 1 (switch on): This is a closed circuit, allowing the electric device to work.
◦ Circuit 2 (switch off): This is an open circuit, as the switch prevents the circuit from being complete.
• Then are the circuits of the bulb and fan closed or open (when we use them)?
◦ When the bulb and fan are working, their circuits are closed.
• How can we make circuits open and closed as required?
◦ Circuits can be made open and closed as required by using a switch.
• How does electricity reach the bulb from the battery?
◦ Electricity reaches the bulb from the battery through conducting wires.
• Do all substances allow electricity to pass through?
◦ No, not all substances allow electricity to pass through them. Some are conductors, and others are insulators.
• Will the LED module glow in this circuit (open circuit with A and B ends)? Why?
◦ No, the LED module will not glow because the circuit is open at ends A and B, preventing the flow of electricity.
• Which of the materials you used made the LED glow? What could be the reason?
◦ Materials that made the LED glow are those that conduct electricity, such as: safety pin, steel scale, charcoal, pencil graphite, metal bangle, wet paper, copper wire, iron nail, silver ornament, gold ornament, aluminium wire, zinc, lead wire, magnesium ribbon, and tin sheet.... The reason is that these materials are electric conductors, allowing electricity to pass through them.
• Which materials conduct electricity?
◦ Materials that conduct electricity include: Safety pin, steel scale, charcoal, pencil graphite, metal bangle, wet paper, copper wire, iron, gold, silver, aluminium, zinc, lead, mercury, and nickel....
• Which materials do not conduct electricity?
◦ Materials that do not conduct electricity include: A piece of wood, paper, plastic bangle, plastic, cloth, and dry wooden block.
• Does the LED glow (when fingers are placed over A and B)? Repeat the experiment with wet fingers. What change did you notice? Give reason.
◦ With dry fingers, the LED generally does not glow (or glows very dimly), as dry human skin is a poor conductor.
◦ With wet fingers, the LED might glow (or glow brighter).
◦ Reason: Water is an electric conductor (especially with dissolved impurities), and the human body contains water. Wet hands reduce electrical resistance, making the body a better conductor and increasing the chance of current flow.
• Do not operate a switch with a wet hand. Find out the reason behind it and write it down in the Science Diary.
◦ The reason is that water is an electric conductor. Operating a switch with wet hands can create a path for electricity to flow through your body, leading to a dangerous electric shock.
• Do all substances conduct electricity? (Referring to metals)
◦ While not all substances conduct electricity, all metals are conductors of electricity.
• Do these substances (metals) have any common characteristics?
◦ Yes, metals are generally lustrous, hard, and strong. Most exist in a solid state at normal temperatures (except mercury). Crucially, all metals are conductors of electricity.
• Which metal do we normally use to transmit electricity through electric lines?
◦ Based on common usage and the mention of "copper wire" in electrical contexts, copper and aluminium are typically used.
• What is the reason for not using copper wire in electric lines? Inquire.
◦ The provided source does not contain information on why copper wire might not be used in all electric lines, or the reasons for using alternatives like aluminum for long-distance transmission.
• Find out the uses of each of the above tools (Cutting pliers, Stripper, Screw driver, Tester) from an electrician.
◦ Cutting pliers: Used for cutting wires.
◦ Stripper: Used for stripping off insulation from wires.
◦ Screw driver: Used for tightening or loosening screws in electrical fittings.
◦ Tester: Used for testing the presence of electric current.
• Identify the parts marked A, B, C and D. (Circuit diagrams)
◦ Circuit 1:
▪ A: Cell
▪ B: An unlit bulb
▪ C: Switch off mode
▪ D: Conducting wire
◦ Circuit 2:
▪ A: Battery
▪ B: A glowing bulb
▪ C: Switch on mode
▪ D: Conducting wire
• What are the differences between the two circuits?
◦ Circuit 1 uses a single cell (A), while Circuit 2 uses a battery (multiple cells) (A).
◦ Circuit 1 shows the switch in the off mode (C), resulting in an unlit bulb (B). Circuit 2 shows the switch in the on mode (C), resulting in a glowing bulb (B).
• What are the things to be assessed (for the emergency lamp)?
◦ The emergency lamp should be assessed based on its efficiency, attractiveness, and durability.
• Will we get an electric shock if we touch the wire connected to the battery (9V)?
◦ Typically, you will not get a severe electric shock from touching a 9V battery wire, as its voltage is low compared to household electricity.
• If, somehow the electricity used at home passes through our body, it can cause electric shock. What is the reason?
◦ The reason is that the electricity used at home is of 230 V, which is a high and dangerous voltage. Our body is an electric conductor because of the water present in its living cells, allowing current to pass through it.
• Find out the situations in which there is a chance for electric shock and put a tick mark (√ ) in the appropriate boxes.
◦ Removing the plug pin without switching off (√)
◦ Changing bulb when the switch is on (√)
◦ Using wires without proper insulation (√)
◦ Turning on a switch with wet hand (√)
◦ Repairing devices while switches are turned on (√)
• What are the precautions to be taken while handling electrical appliances? Write them down in the Science Diary.
◦ Precautions include:
▪ Always switch off devices before removing plugs or attempting repairs.
▪ Ensure electrical wires have proper insulation.
▪ Avoid using switches or appliances with wet hands.
▪ Use devices of good quality.
▪ Use insulating footwear when handling electrical appliances.
• What are the things to be done immediately to save a person who has suffered an electric shock?
◦ Immediate actions include:
▪ Disconnect the electric contact by switching off the power or removing the fuse.
▪ If direct disconnection is not possible, separate the person from the electric circuit using a dry wooden stick or another good insulator.
▪ If heart failure occurs, perform chest compressions.
▪ If breathing stops, give artificial respiration.
▪ Keep the body warm by massaging.
▪ Take the person immediately to a hospital if the shock is severe.
• Why is it used (a generator at school events)?
◦ A generator is used to produce electricity for school events when the regular power supply is insufficient or unavailable.
• Which fuel is used to operate a generator?
◦ Generators are operated using fuels like petrol, kerosene, or diesel.
• Can generators be used regularly to get electricity at home and school? Discuss on the basis of cost of diesel, pollution etc. What is the solution?
◦ No, generators cannot be used regularly due to the high cost of fuels like diesel and the pollution they cause. The solution lies in using alternative, more sustainable energy sources such as hydroelectric power stations, wind power, tidal waves, nuclear energy, or solar energy.
• From where do these lines (metallic wires over tall poles) bring electricity? How this electricity is generated?
◦ These lines bring electricity from large power generation facilities like hydroelectric power stations or thermal/nuclear power stations.
◦ In hydroelectric power stations, electricity is generated by using the energy obtained when water stored in reservoirs falls from a height. The force of falling water rotates turbines, which are connected to generators that produce electricity.
• Discuss the merits of hydroelectric power stations as compared to diesel generators based on cost of fuel, pollution etc.
◦ Hydroelectric Power Stations:
▪ Cost of fuel: Water is essentially free, so fuel cost is minimal.
▪ Pollution: Produce significantly less pollution as they do not burn fossil fuels.
◦ Diesel Generators:
▪ Cost of fuel: High, due to reliance on petrol, kerosene, or diesel.
▪ Pollution: Generate high pollution from burning fossil fuels.
• What message does this poster convey? (Poster: "Don't waste electricity")
◦ The poster conveys the message to prevent wastage of electricity and ensure its judicious use.
• Which are the circumstances in which electricity is wasted? Discuss.
◦ Electricity is wasted when fans and bulbs are left working even when nobody is in the room or classroom.
• Let’s Assess (Chapter 3)
◦ 1. What is the energy change in a battery when it is connected to an emergency lamp?
▪ Answer: c. Chemical energy changes first into electrical energy and then into light energy. A battery converts stored chemical energy into electrical energy, which then powers the lamp to produce light energy.
◦ 2. Of the following, which is in an open circuit?
▪ Answer: b) A damaged bell is switched on. An open circuit is one that is not complete, preventing current flow. If a device is damaged, even with the switch on, the circuit remains open.
◦ 3. From where do the artificial satellites get electricity for its working?
▪ Answer: a) Solar panel. Solar panels (combinations of solar cells) convert solar energy into electrical energy for devices like satellites and solar cars.
◦ 4. Sometimes there is power shortage in Kerala during summer season. Why?
▪ Kerala primarily relies on hydroelectric power stations for electricity. During summer, reduced rainfall can lead to lower water levels in reservoirs, thus limiting the amount of water available to rotate turbines and generate electricity.
◦ 5. A person is standing in water. An electric line breaks and falls into the water. Is the person likely to get an electric shock? Give reason.
▪ Yes, the person is likely to get an electric shock. The reason is that water is an electric conductor. When a live electric line falls into the water, the water becomes electrified, and if the person is in the water, the electric current can pass through their body, causing a shock.
◦ 6. Observe the diagram of an open circuit. Convert it to a closed circuit using appropriate symbols and draw it.
▪ This requires a drawing task. To convert an open circuit to a closed one using symbols, one would need to connect any gaps in the circuit or show the switch in the 'on' position using its respective symbol to complete the electrical path.
- When Light Reflects
• Why did grandma ask the girl to close the curtain when light entered the room through the window?
◦ Grandma asked to close the curtain to prevent the sunlight from entering the room because curtains are opaque objects that do not transmit light.
• What are the things that can be used instead of a curtain to prevent sunlight from entering a room through a glass window? List them.
◦ Things that can be used include other opaque objects like a wooden block, black chart paper, or a mirror.
• What do you observe? Record your observations in the Science Diary. (Torch pointed at different objects)
◦ This is an activity for observation. The general observation would be that some objects (e.g., window glass, pure water) transmit light, some (e.g., butter paper, scratched glass) transmit it partially, and others (e.g., wooden block, coin) do not transmit it at all.
• Didn’t light pass through the butter paper? What about the glass used in spectacles? Do both of these substances transmit light in the same manner? Record it.
◦ Yes, light passes through both. However, they do not transmit light in the same manner. Window glass (similar to spectacle glass) transmits light completely (transparent), while butter paper transmits light partially (translucent).
• Can you change a transparent glass sheet into a translucent or opaque one? How? Discuss. What methods can you suggest? Record them in the Science Diary.
◦ Yes, a transparent glass sheet can be changed into a translucent or opaque one. A suggested method is to soot the glass sheet. Other methods could include painting it or frosting it.
• What change do you observe (when a transparent glass sheet is sooted)?
◦ When a transparent glass sheet is sooted, it becomes translucent or even opaque, depending on the amount of soot.
• What happens to the light transmitting property of transparent glass sheet when it becomes sootier? Do an experiment to find it out.
◦ As the transparent glass sheet becomes sootier, its light transmitting property decreases, meaning it becomes less transparent and more opaque.
• What other methods can be adopted to make the glass sheet translucent or opaque? Write down your suggestions in the Science Diary.
◦ Beyond sooting, other methods could include painting the glass or applying a frosted film/treatment to it.
• What about air? Can we convert pure water and air to translucent? Design an experiment for this.
◦ Yes, pure water and air can be made translucent.
▪ For pure water: Add ink to the water to make it translucent.
▪ For air: Introduce smoke (e.g., from an incense stick) into the air to make it translucent.
• How does the opacity and transparency of objects benefit us?
◦ The transparency, opacity, and translucency of objects are utilized in everyday life for various benefits:
▪ Transparent objects (e.g., refill pen body) allow us to see inside and monitor contents.
▪ Translucent objects (e.g., oil paper) allow partial light transmission, useful for tasks like tracing pictures or maps.
▪ Opaque objects (e.g., house walls and doors) provide privacy and block unwanted light or views.
• What happens when light falls on opaque objects?
◦ When light falls on opaque objects, it can be reflected or absorbed. The experiment shows light reflects.
• What happens to the light? (When a lighted torch is pointed at a mirror)
◦ The light reflects from the mirror and falls on the wall.
• Doesn’t the light that fall on the mirror undergo a regular reflection? What about the light falling on the sandpaper?
◦ Light falling on a mirror undergoes regular reflection.
◦ Light falling on sandpaper undergoes irregular reflection or diffused reflection.
• What do you feel? (When touching surfaces of objects that reflect light very well)
◦ Surfaces that reflect light very well feel smooth.
• What about the surfaces of objects that do not reflect light much?
◦ Surfaces that do not reflect light much feel rough.
• Why is it that rough surfaces cannot reflect light well?
◦ Rough surfaces cannot reflect light well because when light falls on them, it gets scattered in different directions, leading to irregular or diffused reflection.
• Analyse the figures and write the inferences. (Mirror vs. Sandpaper reflection diagrams)
◦ Inferences: A smooth surface like a mirror produces regular reflection, where light rays reflect uniformly and parallel. A rough surface like sandpaper produces diffused reflection, where incident light rays scatter in various directions upon reflection.
• Does it always bounce back in the same manner? (Kicking a ball to a wall)
◦ No, the ball does not always bounce back in the same manner; its rebound depends on the angle of impact and the wall's surface. This analogy leads to understanding the laws of reflection for light.
• Why is it that the child who is sitting first can’t see those sitting at the second and the third positions? Similarly, why can’t the other children see all others through the mirror?
◦ This is due to the laws of reflection: light reflects at specific angles. For an observer to see an image in a mirror, the light reflected from the object to the mirror must then reflect off the mirror and reach the observer's eyes. If the angles do not align, the observer cannot see the image.
• Is there any relation between the angle made by the light ray from the torch with the normal and the angle made by the reflecting light ray with the normal?
◦ Yes, there is a direct relation: The angle of incidence (between the incident ray and the normal) and the angle of reflection (between the reflected ray and the normal) are equal.
• How does light reach the eye so that we see the book?
◦ The process is: Light from the bulb (source of light) -> Falls on the book (object) -> Reflected light -> Reaches our eye -> We see the book.
• Why can’t we see our own face?
◦ We cannot see our own face directly because the light falling on our face does not reflect back to our own eyes to form an image on the retina. We need a reflective surface like a mirror to redirect the light from our face back to our eyes.
• What is the device we use to see our face?
◦ We use a mirror to see our face.
• What are the different surfaces from which light gets reflected and reaches our eyes while seeing our face in the mirror?
◦ Light first originates from a source, then falls on our face (which reflects light diffusely), then reflects from the mirror (which performs regular reflection) to reach our eyes.
• On which surfaces other than the mirror, can you see your face?
◦ You can see your face on other smooth, reflective surfaces such as a smooth tile, a new steel plate, bronze, or stagnant water....
• Stand before a plane mirror and raise your left hand. Which hand of the image is raised?
◦ The right hand of the image will be raised.
• Can you read your name in the mirror?
◦ No, you cannot read your name directly because it appears laterally inverted.
• If so, how should the word BASIC SCIENCE be written on a paper so as to read it on a plane mirror?
◦ The word BASIC SCIENCE should be written in a laterally inverted (mirror-image) way on the paper so that it appears correctly in the plane mirror.
• On which side of the image will a mole on one’s left cheek be seen?
◦ A mole on one's left cheek will be seen on the right side of the image due to lateral inversion.
• What property of the image formed in the plane mirror can be understood here?
◦ The property understood here is Lateral Inversion.
• What would be the reason for writing like this (AMBULANCE written inverted) on the vehicle? Discuss and record it in the Science Diary.
◦ The word is written inverted so that drivers of vehicles in front, when looking in their rear-view mirrors (which act as plane mirrors), can read the word correctly.
• At what distance is your image seen (in front of a plane mirror)?
◦ Your image is seen at a distance equal to the distance between you (the object) and the mirror.
• Is there any relation between the distance to the object from the mirror and the distance to the image from the mirror? Record your inference in the Science Diary.
◦ Inference: The distance between the object and the mirror is equal to the distance between the image and the mirror.
• Do the object and the image have the same size?
◦ Yes, in a plane mirror, the size of the object will be equal to the size of the image.
• How many images will you see if a burning candle is placed in between two parallel plane mirrors? What is your assumption? Write it in the Science Diary.
◦ You will see a large number of images, theoretically an infinite number.
• Why do we see such a large number of images?
◦ We see a large number of images due to multiple reflection of light between the two parallel mirrors.
• Is there any relation between the angle between the mirrors and the number of images formed?
◦ Yes, there is a relation. If the angle between the mirrors is 'x', the number of images (n) is given by the formula: n = (360/x) - 1.
• What happens to the number of images when the angle between the mirrors increases?
◦ When the angle between the mirrors increases, the number of images formed decreases.
• What if the angle decreases?
◦ If the angle between the mirrors decreases, the number of images formed increases.
• Isn’t it the upper view that we get when we look through the lower end of periscope? Why is it so?
◦ Yes, the upper view is obtained. This is because the periscope uses multiple reflections from two mirrors placed at specific angles (typically 45 degrees) to redirect light from an object above or around an obstacle to the observer's eye below.
• By observing the path of light shown in the figure, will you be able to explain how this view is possible?
◦ Yes, the view is possible because light from the object first strikes the top mirror, reflects downwards, then strikes the bottom mirror, and reflects horizontally into the observer's eye, allowing perception of an object not in direct line of sight.
• Discuss how a periscope is useful for the submarines in the Navy and for soldiers observing enemies from trenches in the battle field.
◦ A periscope allows submarines to observe the surface above water without surfacing, maintaining stealth. For soldiers, it enables them to observe enemies from within a trench or behind cover without exposing themselves to direct fire.
• When do owls go out for preying?
◦ Owls generally go out for preying in the dark, at night.
• How does the intense light at night affect them?
◦ Intense artificial light at night is harmful to nocturnal organisms like owls because it disrupts their natural environment and hunting behavior in the dark.
• Are the owls alone affected by the artificial light at night?
◦ No, owls are not alone. Intense artificial illumination at night affects many organisms that hunt in the dark and causes many difficulties for human beings as well.
• Didn’t you realize some problems caused by light pollution? Too much light at night causes many difficulties for human beings as well as animals. Discuss them in the class and record in the Science Diary.
◦ Problems caused by light pollution include:
▪ It is harmful to nocturnal organisms by disrupting their hunting and natural behaviors.
▪ It prevents people from seeing many sky views that are only visible on clear nights.
▪ It can cause various difficulties for human beings, such as sleep disruption.
• Let’s Assess (Chapter 4)
◦ 1. Examine the following table and find the odd one out.
▪ Transparent Objects: Clear water, Air
▪ Translucent Objects: Box filled with smoke, Screen guard of a mobile phone, Turbid water, Fog
▪ Opaque Objects: Soil, Tiles, Stone, Mirror, Hardboard
▪ Answer: Mirror under Opaque Objects. While a mirror is opaque (it does not transmit light), its defining characteristic and primary interaction with light is reflection, especially regular reflection, unlike the other opaque objects listed whose primary interaction is blocking/absorbing light.
◦ 2. Observe the pictures. Which type of reflections do you see here? Explain both views based on the reflection of light.
▪ Picture 1 (Smooth water surface reflecting trees): This shows Regular Reflection. Explanation: Light from the trees falls on the smooth, stagnant surface of the water and reflects back uniformly, forming a clear image.
▪ Picture 2 (Rough water surface with distorted reflection): This shows Diffused Reflection (or irregular reflection). Explanation: Light from the trees falls on the rough, wavy surface of the water and is scattered in many different directions, resulting in a distorted or unclear image.
◦ 3. Observe the following situations. Find out which type of reflection takes place in each.
▪ Ornaments shine: Regular reflection (from polished, smooth surfaces).
▪ We get light inside the home during day time: Primarily Diffused reflection (light entering through windows scatters off internal surfaces like walls and furniture).
▪ A polished furniture shines: Regular reflection.
▪ See reflection of trees on stagnant water: Regular reflection.
◦ 4. Figure with children and threads around a nail/mirror
▪ • Light a torch on to the mirror through the thread held by child A. Where does the reflected light fall?
• The reflected light will fall along the path of the thread held by child D, based on the law that the angle of incidence equals the angle of reflection.
▪ • Similarly, let child D also light the torch on the mirror. Where does the reflected light fall?
• The reflected light will fall along the path of the thread held by child A.
▪ • Let the children B and C repeat the activity. Write down your observations.
• If children B and C are positioned symmetrically, the light from B will reflect to C, and from C to B.
▪ • Where will the reflected light fall, if the torch is lighted on to the mirror from X?
• If X represents light falling along the normal (perpendicular to the mirror), the reflected light will fall back along the same path as X.
- Human Body: A Wonder Digestion and Respiration
• Compile a list of the organisms you have observed, and their respective food. Present it in the class room.
◦ Examples provided:
▪ Cow: Grass
▪ Goat: Leaves
▪ Cat: Mice
▪ Bear: Honey
▪ Human: Cooked rice
▪ Rabbit: (Not provided in text, but generally plants/grass)
• With the help of the list, classify the living organisms into herbivore, carnivore and omnivore. Write it in the Science Diary.
◦ Herbivore: Cow, Goat (and implicitly Rabbit).
◦ Carnivore: Cat.
◦ Omnivore: Bear, Human.
• How is the ingested food utilized by the organisms?
◦ The ingested food is utilized by organisms to obtain the energy necessary for their vital activities.
• What are the changes that occur to food in the mouth?
◦ In the mouth, food mixes with saliva and is masticated (chewed) by teeth.
• What is the role of lips, tongue and teeth in ingestion?
◦ Lips: Aid in taking food into the mouth.
◦ Tongue: Helps to move food inside the mouth for chewing, mixes food with saliva, helps to sense taste, and assists in swallowing.
◦ Teeth: Are used to masticate food, and their structure is suitable for biting, tearing, chewing, and grinding food.
• Do you still have your first set of teeth? Will an infant’s first set of teeth last throughout its life?
◦ No, an infant’s first set of teeth, known as milk teeth, do not last throughout its life; they are replaced by permanent teeth.
• How many teeth does an adult have? Examine the table and write the use and number of each type of tooth in the Science Diary.
◦ An adult typically has 32 permanent teeth.
◦ Incisor: Eight in number (four in upper jaw, four in lower jaw); used to bite and tear food items.
◦ Canine: Four in number (two in upper jaw, two in lower jaw); used to tear and cut food.
◦ Premolar: Eight in number (two on both sides in upper and lower jaws); used to chew and grind food.
◦ Molar: Twelve in number (six in upper jaw, six in lower jaw); used to chew and grind food.
• What change do you observe in the marble piece (after being placed in dilute hydrochloric acid)?
◦ The marble piece is observed to have started to corrode.
• What is the reason for this (sister having dental caries)?
◦ Dental caries (tooth decay) occurs because if the mouth is not cleaned properly after eating, bacteria feed on food particles stuck between teeth, resulting in the production of lactic acid, which damages the tooth enamel.
• Lactic acid is a very weak acid. How does it cause tooth decay?
◦ Even though lactic acid is weak, it causes tooth decay because tooth enamel is a calcium compound, and the lactic acid reacts with this calcium compound, gradually damaging it in the long run.
• Is there anything wrong in it (skipping cleaning after sweets), doctor?
◦ Yes, there is something wrong with it. Skipping cleaning after consuming sweets accelerates bacterial action and lactic acid production, which in turn speeds up tooth damage.
• What are the other functions of the tongue?
◦ Other functions of the tongue include: helping in swallowing, and helping to move food inside the mouth so that teeth can chew it.
• Observe the picture and identify from where it (saliva) is produced.
◦ Saliva is produced from the salivary glands.
• To which part of the digestive system does the chewed food reach next?
◦ The chewed food reaches the oesophagus next.
• To which part of the digestive system does food first reach from the mouth?
◦ From the mouth, food first reaches the oesophagus.
• What is oesophagus?
◦ The oesophagus is a long tube that connects the mouth to the stomach. It is made of muscles, and its wave-like movement (peristalsis) helps food reach the stomach.
• How do the nutrients in the digested food get absorbed into the blood?
◦ Nutrients in the digested food get absorbed into the blood through the villi, which are small finger-like projections present in the wall of the small intestine.
• Complete the flow chart showing the various stages of nutrition.
◦ The stages of nutrition are: Food particle -> Ingestion -> Digestion -> Absorption -> Assimilation -> Egestion.
• Observe the diagrammatic representation of human digestive system. Write in your Science Diary the names and functions of the labelled parts.
◦ Mouth: Site of ingestion, mechanical digestion (chewing) and chemical digestion (mixing with saliva).
◦ Oesophagus: Connects mouth to stomach; food moves through it by peristalsis.
◦ Stomach: Site of partial digestion; food is turned into paste; produces gastric juice and hydrochloric acid for protein digestion and pathogen destruction.
◦ Liver: Produces bile which aids in digestion in the small intestine.
◦ Pancreas: Produces pancreatic juice which aids in digestion in the small intestine.
◦ Small Intestine: Site where digestion is completed and absorption of nutrients into the blood via villi occurs.
◦ Large Intestine: Water and some salts are absorbed from digestive waste.
◦ Rectum: Stores digestive waste before elimination.
◦ Anus: For egestion (removal) of digestive waste from the body.
• Do the digestive system of these animals (Hen, Cat, Cow) have any similarity with our digestive system? Discuss.
◦ Yes, they share the fundamental process of obtaining and utilizing food through a digestive tract, involving stages like ingestion, digestion, absorption, assimilation, and egestion. However, specific structures (like stomachs, teeth, gut length) vary according to their specialized diets.
• Analyze the picture and record in the Science Diary the various stages of nutrition in amoeba.
◦ The stages of nutrition in amoeba are: Ingestion (engulfing food particle with pseudopodia), Digestion (food breakdown in food vacuole), Absorption, Assimilation, and Egestion.
• How long can you hold your breath?
◦ The source implies not even for a minute.
• What are the changes that your body is experiencing? (When taking a deep breath in and out)
◦ You feel air coming in and going out, and your chest expands and contracts.
• When the string attached to the large balloon is pulling down, the two small balloons inside the bottle begin to expand. Why?
◦ When the string is pulled down, the large balloon (representing the diaphragm) moves downwards, increasing the volume inside the bottle (representing the thoracic cavity). This reduces the air pressure inside, causing the smaller balloons (lungs) to expand as atmospheric air rushes in.
• Why do the small balloons shrink when the string attached to the large balloon is released?
◦ When the string is released, the large balloon (diaphragm) returns to its original position, which decreases the volume inside the bottle. This increases the internal air pressure, forcing air out of the small balloons (lungs) and causing them to shrink.
• What happens to the diaphragm during inhalation and exhalation?
◦ During inhalation, the diaphragm contracts and flattens slightly.
◦ During exhalation, the diaphragm relaxes and returns to its previous dome-shaped position.
• When does the thoracic cavity increase in volume- during inhalation or exhalation?
◦ The thoracic cavity increases in volume during inhalation.
• Complete the flowchart of the respiratory tract using the indicators.
◦ Nostrils -> Trachea -> Bronchi -> Bronchioles -> Alveolus.
• Write in the Science Diary the different stages of inhalation and exhalation.
◦ Inhalation:
▪ The diaphragm contracts and flattens slightly.
▪ Rib cage lifts upwards.
▪ The volume of the thoracic cavity increases.
▪ The lungs expand.
▪ Atmospheric air enters the lungs.
◦ Exhalation:
▪ The diaphragm relaxes and returns to the previous state, and the rib cage moves down.
▪ The volume of the thoracic cavity decreases and lungs contract.
▪ The air from the lungs moves out.
• Is the level of all components in inhaled and exhaled air the same?
◦ No, the level of all components in inhaled and exhaled air is not the same.
• Which all components show difference in percentage?
◦ The components that show a difference in percentage are Oxygen, Carbon dioxide, and Moisture.
• Which of the components are in higher level and lower level in exhaled air than in inhaled air?
◦ Higher in exhaled air: Carbon dioxide (4% vs 0.04%) and Moisture (3% vs 0.96%).
◦ Lower in exhaled air: Oxygen (15% vs 21%).
• Analyze your findings and find out which gas is utilized by us in respiration.
◦ Based on the decrease in its percentage in exhaled air, Oxygen is utilized by us in respiration.
• What first aid should be given in such cases of choking on food or breast milk?
◦ First aid for choking:
▪ Ask the person to cough forcefully.
▪ For older children/adults: Keep the person in a slightly bent position and press firmly on their stomach from behind with both hands (Heimlich maneuver).
▪ For babies: Place the baby face down on your forearm, resting on your thigh, and give forceful blows between the shoulder blades with the palm of your other hand.
▪ Provide medical attention if necessary.
• Analyze the picture and find out how gas exchange takes place in a protozoan like paramecium.
◦ In a paramecium, gas exchange takes place by taking in oxygen dissolved in the surrounding water through its cell membrane and giving out carbon dioxide.
• Which gas do plants take in during respiration?
◦ Plants take in oxygen during respiration.
• Name the gas released by plants during respiration?
◦ Plants release carbon dioxide during respiration.
• Where does the gas exchange take place in plants?
◦ Gas exchange in plants takes place through stomata, which are fine pores found in leaves and tender stems.
• Let’s Assess (Chapter 5)
◦ 1. Which of the following combination is correct?
▪ Answer: c. Man, Hen, Monkey, Peacock (Omnivores). While the source explicitly lists only Man and Bear as omnivores, this option is the most biologically accurate among the choices, and Hen is commonly known as an omnivore.
◦ 2. In which of the following organ digestion is completed?
▪ Answer: b. Small intestine. Digestion is completed in the small intestine.
◦ 3. What are the precautionary steps to be taken to prevent tooth decay?
▪ Precautionary steps include:
• Cleaning the mouth properly after having food, especially after consuming sweets.
• Brushing teeth in the morning before breakfast and at night after dinner.
• Always cleaning your mouth whenever you eat something.
◦ 4. Compare the dentition of a six year old child and that of an adult.
▪ Six-year-old child: Will likely have a mix of milk teeth (which total 20) and permanent teeth that are replacing them.
▪ Adult: Will have a full set of permanent teeth, typically numbering 32 (including incisors, canines, premolars, and molars).
◦ 5. A person is lying down and eating food. Do you think the food will reach the stomach? Why?
▪ Yes, the food will reach the stomach. This is because the oesophagus uses wave-like muscular movements called peristalsis to push food down, which is independent of gravity.
