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Chapter 5: Life Processes

VIGYAN

Chapter 5: Life Processes

Class X Science

Key Points

Life Processes: The processes essential for growth, repair, and maintenance of the body. The essential life processes are nutrition, respiration, transportation, and excretion.

1. Nutrition

  • Steps: Ingestion, digestion, absorption, assimilation, and egestion.
  • Photosynthesis: The process by which green plants make their own food.
    • Equation: \( 6CO_2 + 12H_2O \xrightarrow{\text{Chlorophyll, Sunlight}} C_6H_{12}O_6 + 6O_2 + 6H_2O \)
    • Steps:
      1. Absorption of light energy by chlorophyll.
      2. Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
      3. Reduction of carbon dioxide to carbohydrates.
  • Heterotrophic Nutrition:
    • Amoeba: Uses pseudopodia to engulf food (Holozoic nutrition). Digestion occurs in the food vacuole.
    • Human Beings: Digestion takes place in the alimentary canal.

2. Respiration

  • Aerobic vs Anaerobic: Aerobic uses oxygen (mitochondria); Anaerobic occurs without oxygen (yeast/muscle cells).
  • Breakdown of Glucose:
    \( \text{Glucose (6-C)} \xrightarrow{\text{Cytoplasm}} \text{Pyruvate (3-C)} + \text{Energy} \)
    • \( \xrightarrow{\text{Absence of } O_2 \text{ (Yeast)}} \text{Ethanol} + CO_2 + \text{Energy} \)
    • \( \xrightarrow{\text{Lack of } O_2 \text{ (Muscle cells)}} \text{Lactic Acid} + \text{Energy} \)
    • \( \xrightarrow{\text{Presence of } O_2 \text{ (Mitochondria)}} CO_2 + H_2O + \text{Energy} \)
  • Human Respiratory System: Nostril \(\rightarrow\) Pharynx \(\rightarrow\) Trachea \(\rightarrow\) Bronchi \(\rightarrow\) Bronchiole \(\rightarrow\) Alveoli (Site of gas exchange).

3. Transportation

  • Human Beings:
    • Heart: Double circulation (Pulmonary and Systemic).
    • Blood Vessels: Arteries (carry blood away from heart, thick-walled), Veins (carry blood towards heart, thin-walled, have valves), Capillaries.
    • Blood & Lymph: Blood transports nutrients, \( O_2 \), waste. Lymph transports digested fat and drains excess fluid.
  • Plants:
    • Xylem: Transports water and minerals. Driven by root pressure and transpiration pull.
    • Phloem: Transports food (Translocation). Uses energy (ATP).

4. Excretion

  • Human Excretory System: Kidneys \(\rightarrow\) Ureters \(\rightarrow\) Urinary Bladder \(\rightarrow\) Urethra.
  • Nephron: The filtration unit of the kidney.
    • Functions: Filtration of blood, salt-water balance (Osmoregulation), Selective reabsorption (glucose, amino acids, salts, water), and tubular secretion.
  • Plants: Transpiration (water), Falling leaves (waste stored in vacuoles), release into soil.

Question Bank

Multiple Choice Questions

  1. Nitrogenous wastes excreted through urine in humans is:
    Ans: (d) Urea
  2. The __________ is a network of tiny blood vessels located at the beginning of a nephron.
    Ans: (d) Glomerulus
  3. Which option correctly shows the transport of oxygen to the cell?
    Ans: (a) Lungs \(\rightarrow\) pulmonary vein \(\rightarrow\) left atrium \(\rightarrow\) left ventricle \(\rightarrow\) aorta \(\rightarrow\) body cells
  4. Which of the equations show correct conversion of \( CO_2 \) and \( H_2O \) into carbohydrates in plants?
    Ans: (c) \( 6CO_2 + 12H_2O \xrightarrow{\text{Chlorophyll, Sunlight}} C_6H_{12}O_6 + 6O_2 + 6H_2O \)
  5. Identify the correct path of blood in a fish.
    Ans: (b) Atria \(\rightarrow\) ventricle \(\rightarrow\) gills \(\rightarrow\) body
  6. How is food transported from the phloem to the tissues according to plants’ needs?
    Ans: (d) Food is transported from the region where it is produced to other parts of the plants.
  7. How does pH change in human alimentary canal?
    Ans: (a) From acidic pH in stomach to basic pH in small intestine.
  8. The fungi (bread moulds) obtain nutrition by:
    Ans: (c) Breaking down the nutrients of bread outside the body and then absorbing them (Saprotrophic).
  9. Human skin cannot function as a respiratory organ because:
    Ans: (d) All of the above (Not permeable to \( O_2/CO_2 \), thick, dry).

Assertion-Reason Questions

(a) Both A & R true, R is correct explanation. (c) A true, R false. (d) A false, R true.

  1. Assertion: One of the end products of anaerobic respiration is alcohol.
    Reason: There is incomplete breakdown of glucose.
    Ans: (a)
  2. Assertion: Bile is essential for digestion of lipids.
    Reason: Bile juice contains enzymes.
    Ans: (c) Assertion is true, Reason is false (Bile does not contain enzymes, it emulsifies fats).
  3. Assertion: The purpose of making urine is to filter out undigested food from intestine.
    Reason: Kidneys filter the waste and produce urine.
    Ans: (d) Assertion is false (Urine filters nitrogenous waste from blood), Reason is true.
  4. Assertion: Arteries are thick-walled in nature.
    Reason: Arteries have to transport blood away from the heart under high pressure.
    Ans: (a) (Note: The provided answer key in source lists 'c', but standard scientific explanation aligns with 'a'. Source text confirms thick walls are due to pressure).

Short Answer Questions

Q1. Photosynthesis converts energy X into energy Y. What are X and Y?
Ans: X is Solar Energy, Y is Chemical Energy.

Q2. How do desert plants perform photosynthesis if their stomata remain closed during the day?
Ans: Carbon dioxide is absorbed during the night when stomata are open and stored as an intermediate (Malic acid). During the day, this stored \( CO_2 \) is used for photosynthesis.

Q3. Comment upon the role of the following in digestion: (a) Bile (b) Salivary Amylase (c) HCl
Ans:
(a) Bile: Emulsification of fats (breaking large fat globules into smaller ones).
(b) Salivary Amylase: Digests starch into sugar (maltose) in the mouth.
(c) HCl: Makes the medium acidic for Pepsin to act and kills bacteria.

Q4. What are the modes of excretion in plants?
Ans:
1. Transpiration (excess water).
2. Release of \( O_2 \) by diffusion.
3. Storing wastes in dead tissues (bark, wood) or falling leaves.
4. Excretion into soil.

Long Answer Questions

Q1. Describe the process of nutrition in Amoeba.
Ans: Amoeba follows Holozoic nutrition.
1. Ingestion: Uses finger-like projections called pseudopodia to engulf food.
2. Digestion: Food is enclosed in a food vacuole where complex substances are broken down.
3. Absorption: Digested food diffuses into the cytoplasm.
4. Assimilation: Food is used for energy and growth.
5. Egestion: Undigested waste is thrown out by rupturing the cell membrane.

Q2. Give reasons: (a) Lungs always contain residual volume. (b) Nostrils are lined with mucus.
Ans:
(a) To ensure there is sufficient time for oxygen to be absorbed and carbon dioxide to be released during the breathing cycle, and to prevent lung collapse.
(b) To filter the inhaled air by trapping dust, germs, and harmful substances.

Case Study: Transport System

Blood is the most commonly used body fluid. Lymph also helps in transport. Double circulation is efficient for higher organisms.

Q1. How is lymph different from blood?
Ans: Lymph is colourless (lacks haemoglobin), contains less protein than blood, and flows only in one direction (tissue to heart).

Q2. Why is double circulation not found in fish?
Ans: Fish have a 2-chambered heart. Blood is pumped to gills for oxygenation and passes directly to the body (Single circulation). They are cold-blooded and do not require high energy for temperature regulation.

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