Class 7 Science Notes Chapter 11 (Chapter 11) – Examplar Problems Book

Detailed Notes with MCQs of Chapter 11: Transportation in Animals and Plants from your Science Exemplar book. This is a crucial chapter, not just for your class exams, but also forms the basis for many questions in competitive government exams. Pay close attention to the details.

Chapter 11: Transportation in Animals and Plants - Detailed Notes

1. Introduction: Why Transportation is Necessary

• All living organisms need nutrients, water, and oxygen to survive.
• Waste products generated during metabolic activities need to be removed.
• Multicellular organisms have specialized systems to transport these substances to and from all cells efficiently.

2. Transportation in Animals (Focus: Humans)

A. Circulatory System: The system responsible for transporting substances like digested food, oxygen, water, and waste materials within the body.

• Components:
  * Blood: A fluid connective tissue.
  • Plasma: The fluid matrix (about 55% of blood). Contains water, proteins, salts, hormones, digested food, waste products (like urea, carbon dioxide).
  • Blood Cells (Formed Elements): Suspended in plasma.
    • Red Blood Cells (RBCs or Erythrocytes):
      • Contain Haemoglobin, a red pigment that binds with oxygen and transports it to all body cells.
      • Presence of haemoglobin gives blood its red colour.
      • Lack nucleus in mature mammals (including humans) to accommodate more haemoglobin.
      • Produced in the bone marrow.
    • White Blood Cells (WBCs or Leucocytes):
      • Fight against germs and infections (provide immunity).
      • Can change shape and squeeze through blood vessel walls.
      • Several types exist (e.g., neutrophils, lymphocytes).
    • Platelets (Thrombocytes):
      • Cell fragments involved in blood clotting.
      • Form a clot at the site of injury to prevent excessive blood loss.

  *   **Blood Vessels:** Tubes through which blood flows.
      *   **Arteries:**
          *   Carry **oxygenated blood** (rich in oxygen) **away** from the heart to various body parts.
          *   *Exception:* **Pulmonary Artery** carries deoxygenated blood from the heart to the lungs.
          *   Have thick, elastic walls because blood flows under high pressure from the heart's pumping action.
          *   Do not have valves (except at the origin from the heart).
      *   **Veins:**
          *   Carry **deoxygenated blood** (rich in carbon dioxide) **towards** the heart from various body parts.
          *   *Exception:* **Pulmonary Vein** carries oxygenated blood from the lungs to the heart.
          *   Have thinner walls compared to arteries as blood pressure is lower.
          *   Contain **valves** to prevent the backflow of blood, ensuring it flows only towards the heart.
      *   **Capillaries:**
          *   Extremely thin blood vessels connecting arteries to veins.
          *   Walls are only one-cell thick.
          *   Site of exchange of gases (O₂, CO₂), nutrients, and waste products between blood and body cells.

  *   **Heart:** A muscular organ that pumps blood throughout the body.
      *   Located in the chest cavity, slightly tilted towards the left.
      *   Protected by the rib cage.
      *   Has **four chambers:**
          *   Two upper chambers: **Atria** (singular: Atrium) - Receive blood. Right atrium receives deoxygenated blood from the body; Left atrium receives oxygenated blood from the lungs.
          *   Two lower chambers: **Ventricles** - Pump blood out. Right ventricle pumps deoxygenated blood to the lungs; Left ventricle pumps oxygenated blood to the rest of the body.
      *   **Septum:** A muscular wall completely separating the right and left sides of the heart, preventing the mixing of oxygenated and deoxygenated blood.
      *   **Valves:** Present between atria and ventricles, and where major arteries leave the ventricles, ensuring unidirectional blood flow.
      *   **Heartbeat:** The rhythmic contraction (systole) and relaxation (diastole) of the heart muscles. A healthy adult human heart beats about 70-80 times per minute at rest.
      *   **Pulse:** The rhythmic throbbing felt in arteries (like the wrist) due to the blood being forced into them by each heartbeat. Pulse rate equals the heartbeat rate.
      *   **Stethoscope:** Instrument used to amplify the sound of the heart.

B. Excretory System: The system responsible for removing metabolic waste products from the body.

• Excretion: The process of removal of waste products produced in the cells of living organisms.
• Waste Products in Humans: Primarily Urea (formed from protein breakdown), excess salts, water, carbon dioxide.
• Organs:
  * Kidneys (Pair): Bean-shaped organs located in the abdomen. Filter waste products from the blood to form urine. Contain millions of filtering units called nephrons (though nephron structure isn't detailed in Class 7).
  * Ureters (Pair): Tubes that carry urine from each kidney to the urinary bladder.
  * Urinary Bladder: A muscular sac that stores urine temporarily.
  * Urethra: A tube through which urine is passed out of the body. The opening is called the urinary opening.
• Urine Composition: Mostly water (about 95%), urea (about 2.5%), and other waste salts (about 2.5%).
• Other Modes of Excretion:
  * Sweat: Produced by sweat glands in the skin. Contains water, salts, and some urea. Evaporation of sweat helps cool the body.
  * Lungs: Excrete carbon dioxide during exhalation.
• Dialysis (Artificial Kidney): A process used to filter the blood of patients whose kidneys have failed. Blood is passed through a machine (dialyser) that removes urea and other wastes before returning the cleaned blood to the body.

3. Transportation in Plants

• Plants absorb water and minerals from the soil through their roots and transport them to the leaves.

• Leaves synthesize food (glucose) through photosynthesis, which needs to be transported to all other parts of the plant.

• Vascular Tissues: Specialized tissues for transport.
  * Xylem:

  • Transports water and dissolved minerals absorbed by the roots upwards to the stem and leaves.
  • Forms a continuous network of channels from roots to leaves.
  • Movement is primarily unidirectional (upwards).
  • Mechanism: Transpiration Pull.

  *   **Phloem:**
      *   Transports **food (sugars produced during photosynthesis)** from the leaves to other parts of the plant like roots, fruits, stems, and storage organs.
      *   This transport of food is called **Translocation**.
      *   Movement can be bidirectional (upwards or downwards) depending on the plant's needs.

• Absorption by Roots:
  * Root Hairs: Extensions of epidermal cells of the root. Increase the surface area for absorption of water and minerals dissolved in water from the soil. Water enters root hairs by osmosis.

• Transpiration:
  * The loss of water in the form of water vapour from the aerial parts of the plant, mainly through tiny pores on the leaf surface called stomata.
  * Importance:

  • Creates a suction pull (Transpiration Pull) which helps in the absorption and upward movement of water and minerals from roots to great heights in tall trees.
  • Helps in cooling the plant surface.

  *   Excessive transpiration can lead to wilting if water absorption by roots does not keep pace.

Key Points for Exams:

• Know the functions of all blood components (RBC, WBC, Platelets, Plasma).
• Remember the role of Haemoglobin.
• Clearly distinguish between Arteries and Veins (direction of flow, type of blood - with exceptions, wall thickness, presence of valves).
• Understand the structure (4 chambers) and function of the heart, including the role of the septum and valves.
• Define Heartbeat and Pulse, and know the instrument used (Stethoscope).
• Know the main organs of the human excretory system and their functions.
• Understand what urine is composed of and the need for dialysis.
• Differentiate between Xylem and Phloem based on substance transported and direction of transport.
• Explain the role of root hairs in absorption.
• Define Transpiration, explain its mechanism (stomata), and list its importance (transpiration pull, cooling effect).

Multiple Choice Questions (MCQs)

1. Which component of blood is responsible for transporting oxygen?
   a) Plasma
   b) White Blood Cells
   c) Platelets
   d) Red Blood Cells

2. Blood vessels that carry deoxygenated blood from the body towards the heart are called:
   a) Arteries
   b) Veins
   c) Capillaries
   d) Pulmonary Veins

3. The rhythmic expansion and contraction of arteries each time blood is forced into them is known as:
   a) Heartbeat
   b) Blood Pressure
   c) Pulse
   d) Clotting

4. Which chamber of the human heart receives oxygenated blood from the lungs?
   a) Right Atrium
   b) Right Ventricle
   c) Left Atrium
   d) Left Ventricle

5. The process of removal of metabolic waste products from the body is called:
   a) Respiration
   b) Circulation
   c) Excretion
   d) Digestion

6. The main nitrogenous waste product present in human urine is:
   a) Ammonia
   b) Uric Acid
   c) Urea
   d) Carbon Dioxide

7. In plants, water and minerals are transported upwards from the roots primarily through:
   a) Phloem
   b) Stomata
   c) Xylem
   d) Root Hairs

8. The loss of water vapour from the leaves of plants is termed:
   a) Translocation
   b) Photosynthesis
   c) Respiration
   d) Transpiration

9. What is the primary function of platelets in the blood?
   a) Transporting oxygen
   b) Fighting infection
   c) Helping in blood clotting
   d) Transporting carbon dioxide

10. The structure in plants that increases the surface area for water absorption from the soil is:
    a) Stomata
    b) Root Hairs
    c) Xylem vessels
    d) Phloem tubes

Answer Key for MCQs:

1. d) Red Blood Cells
2. b) Veins
3. c) Pulse
4. c) Left Atrium
5. c) Excretion
6. c) Urea
7. c) Xylem
8. d) Transpiration
9. c) Helping in blood clotting
10. b) Root Hairs

Study these notes thoroughly. Remember to correlate the functions with the structures in both animals and plants. Understanding the 'why' behind each process, like why arteries have thick walls or why transpiration occurs, will help you remember the facts better for your exams. Good luck!