Chapter - 11 Transportation in Animals and Plants

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.
• It has cells of various kinds suspended in it. The fluid part of the blood is called plasma. One type of cells is the red blood cells (RBC) which contain a red pigment called hemoglobin.
• Hemoglobin bind 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 hemoglobin. The presence of hemoglobin makes blood appear red.
• The blood also has white blood cells (WBC) which fight against germs that may enter our body.
• Blood 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.
• Arteries: 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.
• Arteries divide into smaller vessels. 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 .It is located in the chest cavity with its lower tip slightly tilted towards the left, the heart has four chambers. 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.
• 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 constitutes a heartbeat.
• The stethoscope is 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.
• Each heart beat generates one pulse in the arteries and the pulse rate per minute indicates the rate of heartbeat. The rhythmic beating of the various chambers of the heart maintains circulation of blood and transport of substances to the different parts of the body.
• Animals such as sponges and Hydra do not possess any circulatory system. The water in which they live brings food and oxygen as it enters their bodies. The water carries away waste materials and carbon dioxide as it moves out. Thus, these animals do not need a circulatory fluid like the blood.

EXCRETION IN ANIMALS

• 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.
• 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 removed as urine. From the kidneys, the urine goes into the urinary bladder through tube-like ureters. It is s stored in the bladder and is passed out through the urinary opening at the end of a muscular tube called urethra. The kidneys, ureters, bladder and urethra form the excretory system. An adult human being normally passes about 1–1.8 L of urine in 24 hours, and 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 in gaseous form (ammonia) which directly dissolves in water. Some land animals like birds, lizards, snakes excrete a semi-solid, white colored compound (uric acid). The major excretory product in humans is urea.
• 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 vascular tissue. A tissue is a group of cells that perform specialized 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.
• Leaves synthesize food. The food has to be transported to all parts of the plant. This is done by the vascular tissue called the phloem. Thus, xylem and phloem transport substances in plants.
• Plants release a lot of water by the process of transpiration. Plants absorb mineral nutrients and water from the soil. Not all the water absorbed is utilized by the plant. The water evaporates through the stomata present on the surface of the leaves by the process of transpiration. 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.