Q1. The kidneys in human beings are a part of the system for:

(a) nutrition
(b) respiration
(c) excretion
(d) transportation

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Answer: (c) excretion

Explanation:

• Kidneys remove nitrogenous wastes such as urea, uric acid and excess salts from the blood.

• They filter blood and form urine, which is then expelled from the body.

• This process is called excretion, handled by the excretory system.

Therefore, kidneys belong to the excretory system.

Q2. The xylem in plants are responsible for:

(a) transport of water
(b) transport of food
(c) transport of amino acids
(d) transport of oxygen

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Answer: (a) transport of water

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Explanation:

• Xylem is a conducting tissue in plants responsible for the upward transport of water and minerals from the roots to different parts of the plant.

• Phloem transports food (such as sugars) prepared by leaves during photosynthesis to other parts of the plant.

Q3. The autotrophic mode of nutrition requires

(a) carbon dioxide and water
(b) chlorophyll
(c) sunlight
(d) all of the above

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Answer: (d) all of the above

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Explanation:

Autotrophic nutrition is the process by which green plants prepare their own food through photosynthesis.

Q4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in

(a) cytoplasm
(b) mitochondria
(c) chloroplast
(d) nucleus

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Answer: (b) mitochondria

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Explanation:

After glycolysis in the cytoplasm, pyruvate enters the mitochondria, where it is broken down in the presence of oxygen (aerobic respiration).

$$\text{Pyruvate}+O_2\to C{O}_2+H_{2}O+\text{Energy (ATP)}$$

Q5. How are fats digested in our bodies? Where does this process take place?

Answer:

• Fats are digested in the small intestine.

• The liver secretes bile, which is stored in the gall bladder and released into the small intestine.

• Bile breaks large fat globules into tiny droplets (emulsification), making digestion easier.

• Pancreatic lipase enzyme then converts emulsified fats into fatty acids and glycerol.

Reaction summary:

$$\text{Fat}\stackrel{\text{bile}}{\to }\text{small droplets}\stackrel{\text{lipase}}{\to }\text{fatty acids + glycerol}$$

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Q6. What is the role of saliva in the digestion of food?

Answer:

Saliva plays two important roles:

1. Moistens and softens food to make it easy to swallow.

2. Contains an enzyme called salivary amylase which breaks down starch (carbohydrate) into simple sugar (maltose).

Equation:

$$\text{Starch}\stackrel{\text{amylase}}{\to }\text{maltose}$$

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Q7. What are the necessary conditions for autotrophic nutrition and what are its by-products?

Answer:

Necessary conditions for autotrophic nutrition:

• Sunlight

• Chlorophyll

• Carbon dioxide

• Water

By-products:

$$\text{Glucose (food)}\text{and}\text{Oxygen}$$

Photosynthesis reaction:

$$6C{O}_2+6H_{2}O\stackrel{\text{sunlight, chlorophyll}}{\to }{C}_6{H}_{12}{O}_6+6O_2$$

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Q8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.

Answer:

Examples of organisms using anaerobic respiration:

• Yeast

• Certain bacteria

• Muscle cells in humans (during vigorous exercise)

Equation examples:

$$\text{Glucose}\to \text{Ethanol}+C{O}_2+\text{Energy (yeast)}$$
$$\text{Glucose}\to \text{Lactic acid}+\text{Energy (muscle cells)}$$

Q9. How are the alveoli designed to maximise the exchange of gases?

Answer:

Alveoli are designed to maximise gas exchange because:

• They are very small and numerous (millions in number), providing a very large surface area.

• They have thin walls (one cell thick) which allow faster diffusion of gases.

• They are surrounded by a network of capillaries with rich blood supply.

• They remain moist, helping gases dissolve and diffuse easily.

Result:

Oxygen diffuses into the blood, and carbon dioxide diffuses out rapidly.

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Q10. What would be the consequences of a deficiency of haemoglobin in our bodies?

Answer:

Haemoglobin carries oxygen in the blood.
If haemoglobin is deficient:

• Less oxygen will be transported to body cells.

• The person becomes tired, weak and pale.

• Severe deficiency causes anaemia.

• In extreme cases, tissues can be permanently damaged due to lack of oxygen.

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Q11. Describe double circulation of blood in human beings. Why is it necessary?

Answer:

Double circulation means that blood flows through the heart twice during one complete cycle.

Two circuits involved:

1. Pulmonary circulation

   • From heart → lungs → heart

   • Carries deoxygenated blood to lungs and returns oxygenated blood.

2. Systemic circulation

   • From heart → body → heart

   • Carries oxygenated blood to body and returns deoxygenated blood.

Why is it necessary?

• To separate oxygenated and deoxygenated blood

• For maintaining efficient supply of oxygen

• To release large amounts of energy needed by warm-blooded organisms like humans

• For proper functioning of organs

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Q12. What are the differences between the transport of materials in xylem and phloem?

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Q13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

Conclusion

Both alveoli and nephrons:

• Provide large surface area

• Have thin membranes

• Are highly vascular (rich blood supply)

PAGE 81 – QUESTIONS & ANSWERS

Q1. Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?

Answer:

Diffusion is insufficient in multicellular organisms because:

• Their bodies are large and complex, made up of millions of cells.

• All cells are not directly in contact with the environment.

• Diffusion is a slow process, and oxygen cannot reach each cell quickly or efficiently through diffusion alone.

• Therefore, they need a specialised respiratory and circulatory system to transport oxygen to all parts of the body.

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Q2. What criteria do we use to decide whether something is alive?

Answer:

We decide something is alive if it shows life processes such as:

• Nutrition

• Respiration

• Growth

• Excretion

• Movement (visible or molecular)

• Reproduction
  Even if motion is not visible, molecular movements inside the body show the organism is alive.

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Q3. What are outside raw materials used for by an organism?

Answer:

Outside raw materials are used for:

• Energy production (e.g., glucose breakdown)

• Growth and repair of body tissues

• Maintaining life processes
  Examples: oxygen, water, minerals, and food.

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Q4. What processes would you consider essential for maintaining life?

Answer:

Essential processes for maintaining life are:

• Nutrition

• Respiration

• Transportation

• Excretion

These processes supply energy, distribute useful materials, and remove wastes to maintain life.

PAGE 87 – QUESTIONS & ANSWERS

Q1. What are the differences between autotrophic nutrition and heterotrophic nutrition?

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Q2. Where do plants get each of the raw materials required for photosynthesis?

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Q3. What is the role of the acid in our stomach?

Answer:

• Creates an acidic medium for enzymes like pepsin to work.

• Kills harmful bacteria present in food.

• Helps in digestion of proteins.

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Q4. What is the function of digestive enzymes?

Answer:

Digestive enzymes break down complex food molecules into simpler, absorbable forms:

• Proteins → amino acids

• Carbohydrates → glucose

• Fats → fatty acids & glycerol

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Q5. How is the small intestine designed to absorb digested food?

Answer:

• It has villi – finger-like projections increasing surface area for absorption.

• Villi contain blood vessels, carrying absorbed food across the body.

• Walls are one cell thick, enabling easy diffusion.

• Long and coiled tube provides maximum time for food absorption.

PAGE NO. 91 – QUESTIONS & ANSWERS

Q1. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?

Answer:

Terrestrial organisms obtain oxygen directly from air, which contains more oxygen than water.
Aquatic organisms obtain dissolved oxygen from water, which is present in much lower concentration, so they need to take in large amounts of water to get sufficient oxygen.

Therefore, terrestrial organisms require less energy for breathing than aquatic organisms.

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Q2. What are the different ways in which glucose is oxidised to provide energy in various organisms?

Answer:

Main reaction:

$$\text{Glucose}\to \text{Pyruvate}$$

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Q3. How is oxygen and carbon dioxide transported in human beings?

Answer:

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Q4. How are the lungs designed in human beings to maximise the area for exchange of gases?

Answer:

Lungs contain millions of tiny air sacs called alveoli, which:

• Greatly increase surface area for gas exchange

• Have thin walls and rich blood supply

• Provide large surface for diffusion of gases

PAGE NO. 96 – QUESTIONS & ANSWERS

Q1. What are the components of the transport system in human beings?

Answer:

Components of the transport system:

• Heart

• Blood (plasma, RBC, WBC, platelets)

• Blood vessels (arteries, veins, capillaries)

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Q2. What are the functions of the components of the transport system in human beings?

Answer:

• Heart – pumps blood

• Arteries – carry blood away from the heart

• Veins – carry blood toward the heart

• Capillaries – allow exchange of gases and nutrients

• Blood – transports oxygen, CO₂, nutrients, hormones, waste

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Q3. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?

Answer:

Separation allows efficient oxygen supply to body tissues and maintains high energy level needed for a warm-bloodedlifestyle.
Mixing would reduce the oxygen-carrying efficiency.

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Q4. What are the components of the transport system in highly organised plants?

Answer:

• Xylem – transports water and minerals

• Phloem – transports food (sugar)

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Q5. How are water and minerals transported in plants?

Answer:

• Absorbed by root hairs

• Move upward through xylem

• Driven by transpiration pull, root pressure and capillary action

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Q6. How is food transported in plants?

Answer:

Food is transported by phloem through a process called translocation, using energy from ATP, from leaves (source) to storage organs (sink).

PAGE NO. 98 – QUESTIONS & ANSWERS

Q1. Describe the structure and function of nephrons.

Answer:

Nephron is the functional unit of the kidney.

Structure Components

• Bowman’s capsule

• Glomerulus

• Tubules

• Collecting duct

Functions

• Filtration of blood

• Removal of nitrogenous wastes (urea, uric acid)

• Reabsorption of useful substances

• Formation of urine

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Q2. What are the methods used by plants to get rid of excretory products?

Answer:

Plants remove waste by:

• Diffusion through stomata and lenticels

• Transpiration

• Storing waste in leaves, bark, fruits

• Gums, resins, latex production

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Q3. How is the amount of urine produced regulated?

Answer:

Urine production depends on:

• Amount of water in the body

• ADH (Antidiuretic hormone) regulating water reabsorption

• Salts present in the blood

• Body’s hydration level and temperature

If more water in body → more urine
If less water → concentrated urine