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