In unicellular organisms, the intake of food, water, oxygen and removal of waste material occur across the cell surface by the process of diffusion. Plants and animals are multicellular. They have a specific organ to perform specific functions. To perform these functions, every cell in the plant and animal body require useful substances such as nutrients, oxygen and water. Plants and animals have a transport system to carry useful substance to every cell of the body and for the removal of waste material produced by the body.
In animals, the transportation system is called the circulatory system and in plants, the transportation takes place through pipeline connection called vascular bundles.
Transportation of substances in humans:
Diffusion in higher multicellular organisms like humans is too slow to transport substances to all the cells. Hence, a fluid medium called blood always circulates throughout the body within a narrow tube channel called blood vessels. The heart, blood and blood vessels together make up the circulatory system in humans.
Blood
Blood is red-coloured fluid that transport respiratory gases, nutrients, secretions as well as waste material from one part of our body to another.
Blood consists of a pale yellow liquid called Plasma in which red blood cells (RBCs), white blood cells (WBCs) and blood platelets float. Functions of Blood:
Blood perform several functions:
It transport digested food from the small intestine to the other parts of the body.
It carries oxygen from the lungs to the cells and carbon dioxide from the cells to the lungs.
It protects the body against infection by destroying disease causing germs.
It clot blood when there is an injury or cut, preventing excess loss of blood.
It also carries waste products from the cell to the kidney for removal from the body.
Blood Vessels
The blood in our body moves through tube-like structures called blood vessels. Blood vessels are of three types: artery veins and capillaries.
The heart
The heart is a fist-sized muscular organ found in the chest cavity towards the left lungs. It pumps blood to all parts of the body. It beats 60-80 times a minute throughout our life.
The heart is made up of four chambers. The Upper two chambers are called right atrium and left atrium. The two lower chambers are called right ventricle and left ventricle.
A muscular wall called septum separates the right and left side of the heart, preventing the mixing of oxygenated blood with the deoxygenated blood and have valves. Valves allow the blood to flow in only one direction.
The blood rich in carbon dioxide flows through the right side of the heart, while the blood rich in oxygen flows through the left side of the heart.
The arteries and veins in the heart connect to other parts of the body. The blood vessels that enter or leave the heart are: Vena cava: It is a large vein that collect blood rich in carbon dioxide from all parts of the body through smaller veins and empties the blood from the right atrium. Pulmonary artery: It carries blood rich in carbon dioxide from the right ventricle of the heart to the lungs. Pulmonary vein: It brings oxygenated blood from the lungs to the left atrium of the heart. Aorta: It is the largest artery which receives blood rich in oxygen from the left ventricle. The oxygenated blood is then circulated to different parts of the body.
Working of heart:
The heart functions as a double pump. Impure (deoxygenated) blood from the veins flows into the right Atrium of the heart.
From here, the blood enters the right ventricle through an opening.
The impure blood is transported from the right ventricle to the lungs by the Pulmonary artery.
Gaseous exchange takes place in the lungs.
The blood gives off carbon dioxide and takes in oxygen.
Oxygen-rich blood is carried to the left Atrium by the Pulmonary vein.
From here, the blood flows through an opening into the left ventricle.
The left ventricle pumps oxygen rich blood to every part of the body through the aorta.
The oxygen is then used by the cells and the cell produces carbon dioxide.
The blood takes in carbon dioxide and returns to the right ventricle of the heart.
Heartbeat and pulse:
The heart works by contracting and relaxing its muscles. The contraction and relaxation follows a rhythm called heartbeat. Pulse is the throbbing sensation of an artery at each beat of the heart. A Doctor uses an instrument called the Stethoscope to listen to your heartbeat. The number of beats per minute is called the pulse rate.
Lymphatic system of the human body
The lymphatic system is made up of lymph vessels and lymph nodes.
As the blood flows through the capillary some of the plasma oozes out of the walls. Most of the fluid enters the lymph vessels and is drained back into the blood vessels.
Before this blood is returned to the circulatory system, it is filtered through lymph nodes. lymph nodes contain special types of cells called Lymphocytes which protect the human body from disease causing organisms and harmful substances.
Transportation of substances in plants
Transportation of water
Like animals, plants also need to transport water minerals and nutrients to all their parts.
Once the water and minerals are absorbed from the soil by the roots through root hair, they move up the stem and leaves through tube-like tissues called the xylem.
Absorption and transportation of water is a continuous process which occurs with the help of transpiration.
Transpiration is the process in which plants lose water through the stomata in the form of water vapour. This results in water loss in the cells of the leaves and creates pressure. The pressure helps to pull the water from the roots through the xylem of the stem to reach all the way to the leaves.
The upward movement of sap is called the ascent of sap.
Transportation of food
The food manufactured in the leaves during photosynthesis reaches all parts of the plant through another tube- like tissues called the phloem. This process is called translocation.
Excretory system
Besides carbon dioxide gas, the human body produces several other kinds of waste materials which mix into the blood. Waste products are often toxic and need to be removed from the body. The process by which metabolic waste products are removed from the body is called excretion.
Excretion in animals:
In unicellular organisms like Amoeba, Paramecium and lower animals like Hydra and sponges, waste products are excreted by the process of diffusion through their body surface. Large animals have special organs for excretion.
Human excretory system:
The human excretory system is made up of Kidneys, ureter, urinary bladder and urethra.
A Human being has two Kidneys, located in the abdominal cavity.
Each kidney consists of a large number of coiled tubes called nephrons. The nephrons filter out waste products from the blood. The end product of this process is urine. Urine contains wastes such as urea, ammonia and uric acid.
The urine flows through two long tubes called ureters and collects in the urinary bladder.
Urinary bladder is the storage sac for the urine. The urine ultimately is drained out of the body through the urethra.
Sometimes due to infection, genetic conditions or injury, the kidneys may stop functioning which results in the accumulation of waste substances within the body. In such cases, blood is passed through an artificial kidney machine to remove waste products from the body. This process is known as dialysis. Kidney transplant is another option to treat a failed kidney.
Excretion in plants:
Plants excrete waste products from their body. They get rid of their waste product in the following ways:
Oxygen and Carbon dioxide are given out during the process of photosynthesis and respiration.
The excess water is lost by the plants through transpiration.
Some plants excrete their waste product in the form of gums, resins and latex. The substances are of great use as adhesive, paints, varnishes and rubber.
