PSEB 10th Science – Chapter 5 Life Processes

Textbook Exercise Questions

1. The kidneys in human beings are a part of the system for:
   (c) excretion
   (Explanation: The kidneys filter waste products from the blood to create urine.)

2. The xylem in plants are responsible for:
   (a) transport of water
   (Explanation: Xylem acts like a pipeline to carry water and minerals from the roots to the rest of the plant.)

3. The autotrophic mode of nutrition requires:
   (d) All of the above
   (Explanation: Plants need carbon dioxide, water, chlorophyll, and sunlight to make their own food.)

4. The breakdown of pyruvate to give CO₂, water and energy takes place in:
   (b) mitochondria
   (Explanation: The mitochondria are the powerhouses of the cell where the final steps of aerobic respiration happen.)

5. How are fats digested in our bodies? Where does the process take place?
   Fat digestion mainly happens in the small intestine. First, bile juice from the liver breaks down large fat globules into smaller ones. Then, an enzyme called lipase (from the pancreas) acts on these smaller globules, breaking them down into fatty acids and glycerol, which can be easily absorbed by the body.

6. What is the role of saliva in the digestion of food?
   Saliva has two main roles:

   • It contains an enzyme called salivary amylase, which starts the digestion of starch (a complex carbohydrate) into simpler sugars right in the mouth.

   • It also moistens the food, making it easier to chew and swallow.

1. What are the necessary conditions for autotrophic nutrition and what are its byproducts?
   The necessary conditions are:

   • Sunlight

   • Chlorophyll (the green pigment in plants)

   • Carbon Dioxide (CO₂)

   • Water
     The byproducts of this process (photosynthesis) are:

   • Glucose (the food for the plant)

   • Oxygen (which is released into the air)

   • Water

2. What are the differences between aerobic respiration and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
   | Aerobic Respiration | Anaerobic Respiration |
   | :— | :— |
   | Happens in the presence of oxygen. | Happens in the absence of oxygen. |
   | Produces a large amount of energy. | Produces a very small amount of energy. |
   | The final products are CO₂ and water. | The final products can be ethanol and CO₂ (in yeast) or lactic acid (in muscle cells). |

   Organisms that use anaerobic respiration include yeast and some types of bacteria. Our own muscle cells also use it temporarily during intense exercise.

3. How are alveoli designed to maximise the exchange of gases?
   Alveoli are designed perfectly for gas exchange in three ways:

   • Large Surface Area: There are millions of these tiny, balloon-like sacs in the lungs, which together create a very large surface area for oxygen to pass into the blood.

   • Thin Walls: Their walls are extremely thin (only one cell thick), making it very easy for gases to pass through.

   • Rich Blood Supply: They are covered in a dense network of tiny blood vessels (capillaries), which quickly carry oxygen away and bring carbon dioxide to be released.

1. What would be the consequences of a deficiency of haemoglobin in our bodies?
   Hemoglobin is the protein in red blood cells that carries oxygen. If there is a deficiency of hemoglobin, the blood cannot carry enough oxygen to all the body’s cells. This would lead to a lack of energy, constant tiredness, weakness, and shortness of breath. This condition is called anemia.

2. Describe double circulation in human beings. Why is it necessary?
   Double circulation means that blood flows through the heart twice for each complete circuit of the body.

   • First circuit: The heart pumps deoxygenated blood to the lungs to pick up oxygen.

   • Second circuit: The now oxygenated blood returns to the heart, which then pumps it to the rest of the body.
     It is necessary because it keeps oxygen-rich blood completely separate from oxygen-poor blood. This ensures a very efficient supply of oxygen to the body’s cells, which is needed to produce the large amount of energy that mammals and birds require to maintain a constant body temperature.

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

1. Transports water and minerals.
2. Movement is only upwards, from roots to leaves.
3. Transport is driven by a physical force (transpiration).

             Phloem

1. Transports food (sugars).
2. Movement can be upwards or downwards, wherever food is needed.
3. Transport requires energy (in the form of ATP).

1. Compare the functioning of alveoli in the lungs and nephrons in the kidneys.
   Both alveoli and nephrons are the basic functional units of their organs and share some similarities, but they perform different jobs.

   • Similarities: Both have very thin walls and are surrounded by a rich network of blood capillaries to allow for easy transfer of substances.

   • Differences:

     • Alveoli are involved in gas exchange. They allow oxygen to move from the lungs into the blood and carbon dioxide to move from the blood into the lungs.

     • Nephrons are involved in filtration and excretion. They filter waste products like urea from the blood to form urine, while also reabsorbing useful substances like water and glucose back into the blood.

InText Questions

1. Why is diffusion insufficient to meet the energy requirements of multicellular organisms like humans?
   Diffusion is a very slow process. In large multicellular organisms like humans, most cells are far away from the surface of the body. Diffusion would take far too long to deliver oxygen and nutrients to all these internal cells, so a more active transport system (the circulatory system) is needed.

2. What criteria do we use to decide whether something is alive?
   We use several criteria. The most obvious are visible movements like walking, breathing, or growing. However, the most fundamental characteristic is the presence of molecular movement inside the cells and the carrying out of essential life processes like nutrition, respiration, transport, and excretion.

3. What are outside raw materials used by a living organism?
   The raw materials depend on the organism:

   • For plants (autotrophs): Carbon dioxide, water, and minerals from the soil.

   • For animals (heterotrophs): Food (from other organisms), oxygen, and water.

4. What processes would you consider essential for maintaining life?
   The essential life processes are:

   • Nutrition: Getting food for energy.

   • Respiration: Breaking down food to release energy.

   • Transportation: Moving substances around the body.

   • Excretion: Getting rid of waste.

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

   • Autotrophic nutrition: Organisms make their own food from simple inorganic materials (like plants using sunlight). “Auto” means self.

   • Heterotrophic nutrition: Organisms get their food by eating other living things (like animals eating plants or other animals). “Hetero” means other.

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

   • Carbon Dioxide: From the air, taken in through pores on the leaves called stomata.

   • Water: From the soil, absorbed through the roots.

   • Sunlight (Energy): From the sun, captured by chlorophyll in the leaves.

7. What is the role of acid in our stomach?
   The hydrochloric acid in our stomach has two main jobs:

   • It creates an acidic environment that is necessary for the protein-digesting enzyme, pepsin, to work.

   • It kills most of the harmful bacteria that enter the body along with food.

8. What is the function of digestive enzymes?
   Digestive enzymes act like biological scissors. Their function is to break down large, complex food molecules (like starches, proteins, and fats) into small, simple molecules that are easy for the body to absorb into the bloodstream.

9. How is the small intestine designed to absorb digested food?
   The inner lining of the small intestine is covered with millions of tiny, finger-like projections called villi. These villi dramatically increase the surface area of the intestine, providing a much larger area for the absorption of digested food into the blood.

10. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
    Air contains a much higher concentration of oxygen compared to water. This means land (terrestrial) animals can get the oxygen they need much more easily and with less effort than aquatic animals, who have to breathe much faster to get the same amount of oxygen from water.

11. What are the different ways in which glucose is oxidised to provide energy in various organisms?
    There are three main pathways:

    1. Aerobic Respiration: In the presence of oxygen, glucose is completely broken down in the mitochondria to produce carbon dioxide, water, and a large amount of energy.

    2. Anaerobic Respiration (in yeast): Without oxygen, glucose is broken down into ethanol, carbon dioxide, and a small amount of energy. This is called fermentation.

    3. Anaerobic Respiration (in muscle cells): During heavy exercise when oxygen is low, glucose is broken down into lactic acid and a small amount of energy.

12. How is oxygen and CO₂ transported in human beings?

    • Oxygen: It is mostly carried by the pigment hemoglobin found inside red blood cells.

    • Carbon Dioxide: It is mostly transported in its dissolved form in the blood plasma because it is more soluble in water than oxygen is.

13. How are lungs designed in human beings to maximise the area for exchange of gases?
    The lungs are designed like a branching tree. The main windpipe (trachea) divides into smaller and smaller tubes, which finally end in millions of tiny, balloon-like air sacs called alveoli. This structure creates a massive internal surface area, allowing a large amount of gas to be exchanged quickly and efficiently.

14. What are the components of the transport system in human beings? What are the functions of these components?
    The three main components are:

    1. The Heart: A muscular organ that acts as a pump to push blood throughout the body.

    2. Blood: A fluid that carries oxygen, nutrients, hormones, and collects waste products.

    3. Blood Vessels (Arteries, Veins, Capillaries): A network of tubes that carries the blood. Arteries carry blood away from the heart, veins carry it back, and capillaries connect them.

15. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
    It is necessary to provide a highly efficient supply of oxygen to the body. Mammals and birds are warm-blooded and need a lot of energy to maintain a constant body temperature. By keeping the two types of blood separate, they can ensure their cells get the maximum amount of oxygen needed for this high energy production.

16. What are the components of the transport system in highly organised plants?
    The transport system in plants consists of two main tissues:

    1. Xylem: Transports water and minerals.

    2. Phloem: Transports food.

17. How are water and minerals transported in plants?
    Water and minerals are transported by the xylem. They are absorbed from the soil by the roots and then pulled upwards through the stem to the leaves. This upward pull is mainly caused by a process called transpiration, which is the evaporation of water from the surface of the leaves.

18. How is food transported in plants?
    Food (in the form of sugars) is transported by the phloem. This process is called translocation. It moves the sugars made in the leaves to other parts of the plant that need energy, such as the roots, fruits, or growing buds. This process requires energy.

19. Describe the structure and functioning of a nephron.
    A nephron is the tiny filtering unit of the kidney.

    • Structure: It consists of a cup-shaped part called Bowman’s capsule, which contains a bundle of capillaries called the glomerulus, and a long, coiled tubule.

    • Functioning: Blood enters the glomerulus under pressure, and small molecules like water, glucose, salts, and urea are filtered out into the Bowman’s capsule. As this filtrate travels along the tubule, essential substances (like most of the water, glucose, and salts) are reabsorbed back into the blood. The leftover fluid containing waste like urea is collected as urine.

1. What are the methods used by plants to get rid of excretory products?
   Plants use several methods:

   • They release gaseous waste (oxygen) through stomata.

   • They get rid of excess water through transpiration.

   • They can store some waste products in their leaves, which then fall off.

   • They also excrete some waste substances into the soil around them or store them as gums and resins.

2. How is the amount of urine produced regulated?
   The amount of urine produced is regulated by how much water is reabsorbed by the nephron tubules. This depends on two main factors:

   • How much excess water is in the body. (If you drink a lot of water, you produce more urine).

   • How much dissolved waste needs to be excreted from the body.
     This process is controlled by hormones to maintain the correct water balance in the body.

Chapter 1 – Chemical Equations and Reactions