CBSE – 7th Standard Science

Chapter 11 – Transportation in Animals and Plants


Transportation in Animals and Plants

  • We have learnt that all organisms need food, water and oxygen for survival
  • They need to transport all these to various parts of their body.image001


  • Animals need to transport wastes to parts from where they can be removed.
  • They function to transport substances and together form the circulatory system.
  • Blood is the fluid which flows in blood vessels.
  • It transports substances like digested food from the small intestine to the other parts of the body.
  • It carries oxygen from the lungs to the cells of the body.
  • It also transports waste for removal from the body.
  • Blood is a liquid, which has cells of various kinds suspended in it.
  • The fluid part of the blood is called plasma.
  • One type of cells are the red blood cells (RBC) which contain a red pigment called haemoglobin.
  • Haemoglobin binds with oxygen and transports it to all the parts of the body and ultimately to all the cells.
  • It will be difficult to provide oxygen efficiently to all the cells of the body without haemoglobin.
  • The presence of haemoglobin makes blood appear red.
  • The blood also has white blood cells (WBC) which fight against germs that may enter our body.
  • The clot is formed because of the presence of another type of cells in the blood, called platelets.
  • There are different types of blood vessels in the body.
  • We know that during inhalation a fresh supply of oxygen fills the lungs.
  • Oxygen has to be transported to the rest of the body.
  • Also, the blood picks up the waste materials including carbon dioxide from the cells.
  • This blood has to go back to the heart for transport to the lungs for removal of carbon dioxide as you have
  • So, two types of blood vessels, arteries and veins are present in the body.
  • Arteries carry oxygen-rich blood from the heart to all parts of the body.
  • Since the blood flow is rapid and at a high pressure, the arteries have thick elastic walls.


  • Veins are the vessels which carry carbon dioxide-rich blood from all parts of the body back to the heart.
  • The veins have thin walls.
  • There are valves present in veins which allow blood to flow only towards the heart.
  • On reaching the tissues, they divide further into extremely thin tubes called capillaries.
  • The capillaries join up to form veins which empty into the heart.
  • The heart is an organ which beats continuously to act as a pump for the transport of blood, which carries other substances with it.
  • Yet our heart works like a pump non-stop


  • . The heart is located in the chest cavity with its lower tip slightly tilted towards the left.
  • The two upper chambers are called the atria (singular: atrium) and the two lower chambers are called the ventricles.
  • The partition between the chambers helps to avoid mixing up of blood rich in oxygen with the blood rich in carbon dioxide.
  • To understand the functioning of the circulatory system, start from the right side of the heart


  • These arrows show the direction of the blood flow from the heart to the lungs and back to the heart from where it is pumped to the rest of the body.
  • The walls of the chambers of the heart are made up of muscles.
  • These muscles contract and relax rhythmically.
  • This rhythmic contraction followed by its relaxation constitute a heartbeat.
  • Remember that heartbeats continue every moment of our life.
  • The doctor feels your heartbeats with the help of an instrument called a stethoscope.
  • A doctor uses the stethoscope as a device to amplify the sound of the heart.
  • It consists of a chest piece that carries a sensitive diaphragm, two ear pieces and a tube joining the parts.
  • Doctors can get clues about the condition of your heart by listening through a stethoscope.
  • Each heart beat generates one pulse in the arteries and the pulse rate per minute indicates the rate of heart beat.
  • The rhythmic beating of the various chambers of the heart maintain circulation of blood and transport of substances to the different parts of the body.
  • The English physician, William Harvey (A.D.1578ñ1657), discovered the circulation of blood.
  • The current opinion in those days was that blood oscillates in the vessels of the body.
  • For his views, Harvey was ridiculed and was called ìcirculatorî.
  • He lost most of his patients.
  • However, before he died, Harveyís idea about circulation was generally accepted as a biological fact.
  • When our cells perform their functions, certain waste products are released.
  • These are toxic and hence need to be removed from the body.
  • The process of removal of wastes produced in the cells of the living organisms is called excretion.
  • The parts involved in excretion forms the excretory system.


  • The waste which is present in the blood has to be removed from the body.
  • A mechanism to filter the blood is required. This is done by the blood capillaries in the kidneys.
  • When the blood reaches the two kidneys, it contains both useful and harmful substances.
  • The useful substances are absorbed back into the blood.
  • The wastes dissolved in water are remove as urine.
  • From the kidneys, the urine goes into the urinary bladder through tube-like ureters.
  • It is stored in the bladder and is passed out through the urinary opening at the end of a muscular tube called
  • The kindeys, ureters, bladder and urethra form the excretory system.
  • An adult human being normally passes about 1ñ1.8 L of urine in 24 hours.
  • The urine consists of 95% water, 2.5% urea and 2.5% other waste products.
  • The way in which waste chemicals are removed from the body of the animal depends on the availability of water.
  • Aquatic animals like fishes, excrete cell waste as ammonia which directly dissolves in water.
  • Some land animals like birds, lizards, snakes excrete a semi-solid, white coloured compound (uric acid).
  • The major excretory product in humans is urea.
  • Sometimes a person’s kidneys may stop working due to infection or injury.
  • As a result of kidney failure, waste products start accumulating in the blood.
  • Such persons cannot survive unless their blood is filtered periodically through an artificial kidney. This process is called dialysis.
  • Plants absorb water and minerals by the roots.
  • The roots have root hair
  • The root hair increase the surface area of the root for the absorption of water and mineral nutrients dissolved in water.
  • The root hair is in contact with the water present between the soil particles.
  • Plants have pipe-like vessels to transport water and nutrients from the soil.


  • The vessels are made of special cells, forming the vascular tissue.
  • A tissue is a group of cells that perform specialised function in an organism.
  • The vascular tissue for the transport of water and nutrients in the plant is called the xylem
  • The xylem forms a continuous network of channels that connects roots to the leaves through the stem and branches and thus transports water to the entire plant.
  • Plants absorb mineral nutrients and water from the soil.
  • Not all the water absorbed is utilised by the plant.


  • The water evaporates through the stomata present on the surface of the leaves by the process of transpiration.image009
  • The evaporation of water from leaves generates a suction pull (the same that you produce when you suck water through a straw) which can pull water to great heights in the tall trees.
  • Transpiration also cools the plant.