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Life Processes | Class 10 CBSE | Web Notes | Part 4 - Transportation

TRANSPORTATION

It is the process of movement of water and other molecules to the concerned parts of the organism.

TRANSPORTATION IN HUMAN BEINGS

Human Circulatory System: It consists of blood, heart, and blood vessels.

BLOOD

  • Blood is a fluid connective tissue.
  • It consists of a fluid medium called plasma in which blood cells (RBC, WBC, and platelets) are suspended.
  • Plasma transports food, O2, CO2, and nitrogenous wastes.
  • Oxygen is mainly transported by haemoglobin.
  • Normal level of haemoglobin in human beings:
    • In men: 14 to 17 g/100 ml.
    • In women: 12 to 15 g/100 ml.
    • In children: 11 to 16 g/100 ml.
  • The normal level of haemoglobin in animals like buffalo or cow is 10.4 to 16.4 g/100 ml. Haemoglobin content in calves is higher than in male and female animals.
  • Adult men do more work than women and children, so they need more oxygen to get energy. That’s why adult men have more haemoglobin.
  • Haemoglobin level in humans is comparatively higher than in animals like cattle because the human body needs more oxygen for various biological processes.

OUR PUMP – THE HEART

A schematic sectional view of the human heart
  • The heart pumps blood all over the body.
  • It is a muscular organ, approximately the size of a fist.
  • It has four chambers: two upper (right and left atria) and two lower (right and left ventricles).
  • Right chambers carry CO2-rich (deoxygenated) blood. Left chambers carry O2-rich (oxygenated) blood.
  • Deoxygenated blood reaches the lungs to remove CO2. Oxygenated blood from the lungs is brought back to the heart and then pumped to the rest of the body.

PUMPING PROCESS OF HEART

  • Oxygenated blood: From the lungs → left atrium relaxes → blood enters left atrium → left atrium contracts & left ventricle relaxes → blood enters left ventricle → left ventricle contracts → blood is pumped out to the body.
  • Deoxygenated blood: From the body → right atrium relaxes → blood enters right atrium → right atrium contracts & right ventricle dilates → blood transfers to right ventricle → right ventricle contracts → blood is pumped into the lungs for oxygenation.
  • Since ventricles pump blood into various organs, they have thicker muscular walls than atria.
  • The heart has valves to prevent backflow of blood when the atria or ventricles contract.

OXYGEN ENTERS THE BLOOD IN THE LUNGS

Schematic representation of transport and exchange of oxygen and CO2
  • The separation of the right and left sides of the heart prevents mixing of oxygenated and deoxygenated blood, allowing a highly efficient supply of oxygen to the body. This is useful in animals that need high energy (birds and mammals) to maintain body temperature.
  • Animals like amphibians and many reptiles do not use energy to maintain temperature, depending on environmental temperature. They have a 3-chambered heart and tolerate some mixing of oxygenated and deoxygenated blood.
  • Fishes have a 2-chambered heart. Circulation occurs as follows:

    • Deoxygenated blood enters the heart → pumped to gills → blood is oxygenated in gills → blood to rest of the body.

  • In fishes, blood goes only once through the heart during one cycle of passage through the body.
  • In other vertebrates, blood goes through the heart twice during each cycle, known as double circulation.

BLOOD PRESSURE (BP)

  • It is the force that blood exerts against the wall of a vessel. This is much greater in arteries than in veins.
  • Systolic pressure: Blood pressure in the artery during ventricular systole (contraction). It is about 120 mm Hg.
  • Diastolic pressure: Blood pressure in the artery during ventricular diastole (relaxation). It is about 80 mm Hg.
  • Sphygmomanometer: An instrument to measure blood pressure.
  • High BP (hypertension) is caused by the constriction of arterioles, which increases resistance to blood flow. It can lead to the rupture of an artery and internal bleeding.

THE TUBES – BLOOD VESSELS

  • It includes arteries, veins, and capillaries.
  • Arteries: They carry blood from the heart to various body parts. Since blood emerges from the heart under high pressure, arteries have thick, elastic walls.

    • On reaching an organ or tissue, the artery divides into small branches (arterioles) to bring blood in contact with all cells.

  • Veins: They collect blood from different organs and bring it back to the heart. They have no thick walls because the blood is no longer under pressure. Instead, they have valves to ensure blood flows in one direction.
  • Capillaries: The smallest vessels with walls that are one-cell thick. Through this wall, the exchange of materials between blood and surrounding cells takes place.

    • Capillaries join together to form veins that convey blood away from the organ or tissue.

Maintenance by platelets
  • Leakage or loss of blood due to injury leads to a reduction in pressure and efficiency of the circulatory system.
  • Platelet cells plug these leaks to clot the blood at the points of injury.

LYMPH (TISSUE FLUID)

  • Through the pores in capillary walls, some amount of plasma, proteins, and blood cells escape into intercellular spaces in the tissues to form lymph.
  • It is similar to blood plasma but colorless and contains less protein.
  • From intercellular spaces, lymph drains into lymphatic capillaries, which join to large lymph vessels that finally open into larger veins.
  • Lymph carries digested fat from the intestine and drains excess fluid from extracellular spaces back into the blood.

TRANSPORTATION IN PLANTS

  • Soil is the nearest and richest source of raw materials (water and minerals).
  • If the distance between roots and leaves is small, energy and raw materials can easily diffuse to all parts. But if the distance is large, a transportation system is essential.
  • Plants do not move and have numerous dead cells, so they need only low energy and slow transport systems.
  • Plant transport systems include two independently organized conducting tubes:
    • Xylem: Moves water and minerals from the soil.
    • Phloem: Transports products of photosynthesis (energy stores) from leaves to other parts.

TRANSPORT OF WATER

  • In xylem tissue, vessels and tracheids of the roots, stems, and leaves are interconnected to form water-conducting channels reaching all parts.
  • At the roots, cells actively take up ions from the soil, creating a difference in ion concentration between root and soil. Water moves into the root from the soil, resulting in a steady movement of water into the root xylem, creating a column of water pushing upwards.
  • This pressure is not enough to move water over great heights, so plants use another strategy called transpiration.
  • Transpiration is the loss of water vapor from the aerial parts (mainly stomata of leaves) of the plant. It can be demonstrated by the following activity:
    • Take two small, same-sized pots with the same amount of soil. One should have a plant, and the other a stick of the same height as the plant.
    • Cover the soil in both pots with a plastic sheet to prevent moisture escape by evaporation.
    • Cover both sets with plastic sheets and place in bright sunlight for half an hour.
    • In the pot with the plant, water droplets are found on the plastic sheet due to condensation of water vapor released by transpiration. In the other pot, no water droplets are formed.
  • The water lost through the stomata is replaced by water from the xylem vessels in the leaf.
  • Transpiration creates a suction that pulls water from the xylem cells of roots.
  • Thus, transpiration helps in the absorption and upward movement of water and minerals from roots to leaves and aids in temperature regulation.
  • Generally, stomata are closed at night, so plants depend on root pressure for water transport at night.
  • During the day, when stomata are open, the transpiration pull is the major driving force in water transport.

TRANSPORT OF FOOD AND OTHER SUBSTANCES

  • Transport of soluble products of photosynthesis (food) from leaves to other parts is called translocation.
  • It occurs in a vascular tissue called phloem.
  • Phloem also transports amino acids and other substances.
  • These substances are delivered to the storage organs of roots, fruits, and seeds, and to growing organs.
  • Translocation takes place in the sieve tubes with the help of adjacent companion cells in both upward and downward directions.
  • Xylem transport occurs mainly by simple physical forces, but translocation in phloem utilizes energy.
  • Material like sucrose is transferred into phloem using energy from ATP, increasing the osmotic pressure of the tissue, causing water to move into it. This pressure moves the material in the phloem to tissues. E.g., in spring, sugar stored in roots or stems is transported to buds that need energy to grow.

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1. What are Life Processes? 2. Nutrition 3. Respiration 4. Transportation 5. Excretion
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