Class 7 Science Notes Chapter 11 (Transportation in Animals and Plants) – Science Book

Okay, let's focus on the key concepts from NCERT Class 7 Science Chapter 11: Transportation in Animals and Plants, tailored for government exam preparation.

Chapter 11: Transportation in Animals and Plants - Detailed Notes

Introduction:
All living organisms need a transport system to move essential substances (like food, water, oxygen) to all their cells and to remove waste products generated by metabolic activities.

I. Circulatory System in Animals (Focus: Humans)

• Purpose: To transport digested food, water, oxygen to all parts of the body and collect waste materials (like carbon dioxide, urea) for removal.

• Main Components: Blood, Blood Vessels, and Heart.

  • 1. Blood:

    • Nature: Fluid connective tissue.
    • Functions: Transports substances, fights diseases, helps in clotting.
    • Components:
      • Plasma: The fluid part (matrix) of blood, mostly water. Transports digested food, CO2, hormones, waste products (like urea).
      • Red Blood Cells (RBCs or Erythrocytes):
        • Contain a red pigment called Haemoglobin.
        • Function of Haemoglobin: Binds with oxygen and transports it from the lungs to all body cells. (Presence of haemoglobin makes blood red).
        • Exam Note: Deficiency of haemoglobin leads to Anaemia.
      • White Blood Cells (WBCs or Leucocytes):
        • Function: Fight against germs and infections, providing immunity. They engulf or destroy pathogens.
      • Platelets (Thrombocytes):
        • Function: Help in blood clotting at the site of injury, preventing excessive blood loss. A network of threads called fibrin is formed (involving platelets and proteins in plasma).

  • 2. Blood Vessels: Tubes through which blood flows.

    • Arteries:
      • Function: Carry oxygenated blood away from the heart to various body parts.
      • Exception: Pulmonary Artery carries deoxygenated blood from the heart to the lungs.
      • Structure: Have thick, elastic walls because blood flow is rapid and at high pressure.
      • Valves: Generally absent (except at the origin from the heart).
    • Veins:
      • Function: Carry deoxygenated blood towards the heart from various body parts.
      • Exception: Pulmonary Vein carries oxygenated blood from the lungs to the heart.
      • Structure: Have relatively thinner walls compared to arteries as blood pressure is lower.
      • Valves: Present to ensure blood flows only towards the heart and prevent backflow.
    • Capillaries:
      • Function: Extremely thin vessels connecting arteries to veins. Site of exchange of materials (oxygen, food, CO2, waste) between blood and body cells.
      • Structure: Very thin walls (one-cell thick) to facilitate easy diffusion.

  • 3. Heart:

    • Function: A muscular organ that pumps blood continuously throughout the body.
    • Location: Situated in the chest cavity, slightly tilted towards the left.
    • Chambers: Has four chambers in humans:
      • Two upper chambers: Atria (singular: Atrium) - Receive blood. Right atrium receives deoxygenated blood from the body; Left atrium receives oxygenated blood from the lungs (via pulmonary vein).
      • Two lower chambers: Ventricles - Pump blood out. Right ventricle pumps deoxygenated blood to the lungs (via pulmonary artery); Left ventricle pumps oxygenated blood to the rest of the body.
    • Septum: A muscular wall completely separating the right and left sides, preventing the mixing of oxygenated and deoxygenated blood.
    • Heartbeat: The rhythmic contraction (systole) and relaxation (diastole) of the heart muscles constitutes one heartbeat. Average rate: 70-80 beats per minute in a resting adult.
    • Pulse: The throbbing sensation felt in arteries (like the wrist) due to the blood flow forced by each heartbeat. Pulse rate = Heart rate.
    • Stethoscope: Instrument used by doctors to amplify the sound of the heartbeat.

II. Excretion in Animals (Focus: Humans)

• Excretion: The process of removal of metabolic waste products from the body.
• Need: Accumulation of waste products (like urea) is toxic and harmful.
• Human Excretory System Components:
  • Kidneys (2): Bean-shaped organs located in the abdomen.
    • Function: Filter waste products (like urea) from the blood and produce urine. Contain millions of filtering units called nephrons (basic functional unit, though 'nephron' term might not be explicit in Class 7).
  • Ureters (2): Tubes that carry urine from each kidney to the urinary bladder.
  • Urinary Bladder: A muscular sac that stores urine temporarily.
  • Urethra: A short tube through which urine is passed out of the body. (Opening at the end is the urinary opening).
• Urine: Consists mainly of water (about 95%), urea (about 2.5%), and other waste salts (about 2.5%).
• Sweating: Sweat glands release sweat (containing water, salts, and some urea), which helps in removing waste and also in cooling the body through evaporation.
• Excretion in Other Animals:
  • Aquatic animals (like fish): Excrete ammonia, which directly dissolves in water.
  • Birds, lizards, snakes, insects: Excrete uric acid (semi-solid, white paste) to conserve water.
• Dialysis: An artificial process to filter blood when kidneys fail. Uses an 'artificial kidney' machine.

III. Transportation in Plants

• Need: Plants need to transport water and minerals absorbed by roots to the leaves, and food prepared in leaves to other parts.

• Absorption:

  • Roots: Absorb water and dissolved minerals from the soil.
  • Root Hairs: Increase the surface area of roots for efficient absorption.

• Transport Tissues (Vascular Tissues): Form a continuous network throughout the plant.

  • 1. Xylem:
    • Function: Transports water and dissolved minerals absorbed by the roots upwards to the stem and leaves.
    • Direction: Unidirectional (roots to leaves).
    • Mechanism: Works partly due to the 'suction pull' created by transpiration.
  • 2. Phloem:
    • Function: Transports food (sugars) synthesized in the leaves (during photosynthesis) to all other parts of the plant, including roots, fruits, and storage organs. This process is called translocation.
    • Direction: Bidirectional (can move up or down as needed).
  • Vascular Bundles: Xylem and Phloem are usually located close together, forming vascular bundles.

• Transpiration:

  • Definition: The process of loss of water in the form of water vapour from the aerial parts of the plant, mainly through tiny pores called stomata on the surface of leaves.
  • Functions:
    • Creates a transpiration pull (suction force) 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 (similar to how sweating cools our body).

Key Takeaways for Exams:

• Know the components of blood and their specific functions (Haemoglobin/O2, WBC/Immunity, Platelets/Clotting).
• Differentiate clearly between Arteries and Veins (Direction of flow, type of blood - with exceptions, wall thickness, valves).
• Understand the structure (4 chambers) and function (pumping, separation of blood types) of the human heart. Know the pulmonary artery/vein exceptions.
• Define Heartbeat and Pulse, and know their relationship.
• Know the main organs of the human excretory system and their sequence (Kidneys -> Ureters -> Bladder -> Urethra). Understand the primary function of kidneys (filtering blood, producing urine).
• Know the main nitrogenous waste product in humans (Urea).
• Differentiate between Xylem and Phloem (Substance transported, direction of transport).
• Define Transpiration and understand its two main functions (suction pull, cooling).
• Remember root hairs increase the surface area for absorption.

This detailed breakdown covers the essential points from the chapter relevant for competitive government exams, focusing on definitions, functions, key components, and processes. Remember to correlate these points with diagrams from the NCERT book for better visualization and retention.