Ch. 7 Transportation in Animals and Plants PDF

## Transportation of Materials in Organisms All organisms need oxygen, food, and water to stay alive. The digested food along with oxygen and water need to reach each and every cell of the body to ensure that different organ systems work efficiently. Further, organisms also need to transport wastes...

## Transportation of Materials in Organisms All organisms need oxygen, food, and water to stay alive. The digested food along with oxygen and water need to reach each and every cell of the body to ensure that different organ systems work efficiently. Further, organisms also need to transport wastes to specific parts of the body from where they can be removed. Therefore, an organism has an efficient system to transport substances within it. ### Transportation of Materials in Unicellular Organisms - Unicellular organisms, such as *Amoeba* and *Paramecium*, do not require a separate system to transport substances. - This is because the single cell remains in direct contact with the environment. - Oxygen, nutrients, and waste materials move in and out of the cell by the process of diffusion. - **Diffusion** is the net movement of molecules or atoms from the region of higher concentration to the region of lower concentration - All the materials within the cells are circulated by the streaming movement of the cytoplasm. ### Transportation of Materials in Simple Multicellular Organisms - In simple multicellular organisms, such as *Hydra* and sponges, nutrients and oxygen are transported by water that enters their bodies. - Similarly, waste materials are removed along with the water that moves out. ### Transportation of Materials in Human Beings - Higher animals including human beings have a well-developed transportation system known as the **circulatory system**. - The human circulatory system consists of **blood**, **blood vessels**, and the **heart**. #### Blood - Blood is the fluid that flows in blood vessels. - An average human being has about 5 litres of blood. - Circulating in the body, blood consists of the following components: * **Red Blood Corpuscles (RBCs) or erythrocytes:** These are specialized blood cells that are red in colour as they contain a red pigment called **haemoglobin**. Haemoglobin helps in transporting oxygen to different parts of the body. * **White Blood Corpuscles (WBCs) or leucocytes:** They are specialized blood cells that protect our body against germs, thus they are also called “soldiers of the body.” They are larger than RBCs and are devoid of haemoglobin. * **Platelets or thrombocytes:** Platelets are cellular fragments of bone marrow cells that help in clotting blood at the site of an injury. * **Plasma:** It is the straw-coloured fluid part of the blood that transports nutrients as well as metabolic waste products #### Blood Vessels - Blood flows through our body in a complex network of tubes called **blood vessels**. - There are three types of blood vessels: **arteries**, **veins**, and **capillaries**. * **Arteries:** Arteries have thick elastic walls and are located deep under the skin. The walls of the arteries are thick and elastic to withstand the flow of blood from the heart at high pressure. Arteries carry blood from the heart to various parts of the body. Arteries generally carry oxygenated (oxygen-rich) blood except for the **pulmonary artery**, that carries deoxygenated blood. * **Capillaries:** Arteries divide into a network of extremely thin blood vessels called **capillaries** to penetrate various tissues of the body. The thin walls of the capillaries facilitate easy exchange of nutrients, gases, and waste products between the blood and the surrounding cells, by the process of diffusion. The capillaries join to form veins. * **Veins:** Veins have thin walls. They have valves that prevent backflow of blood thus allowing it to flow only towards the heart. Veins are situated just under the skin. These can be easily seen as greenish-blue tubes on the hands and legs. Veins carry deoxygenated (oxygen-deficient) blood from all parts of the body to the heart except for the **pulmonary vein**, that carries oxygenated blood. | S.No. | Arteries | S.No. | Veins | |:---:|:---:|:---:|:---:| | 1 | The walls of the arteries are thick and elastic. | 1 | Veins have thin walls. | | 2 | The arteries carry blood away from the heart. | 2 | The veins carry blood towards the heart. | | 3 | Blood flows under high pressure inside arteries. | 3 | Blood does not flow under high pressure in veins. | | 4 | There are no valves inside arteries. | 4 | A series of valves in the veins prevents backward flow of blood. | | 5 | Arteries are placed deep under the skin. | 5 | They are superficially placed just under the skin. | | 6 | They generally carry oxygenated blood except for pulmonary artery which carries deoxygenated blood from the heart to the lungs. | 6 | They generally carry deoxygenated blood except for pulmonary veins which carry oxygenated blood from lungs to the heart. | - **Know More:** English physician William Harvey was the first to accurately describe how blood is pumped around the body by the heart. In those days, people believed that blood was formed continuously from digested food and that the main function of the heart was to produce heat. However, before his death Harvey's views about blood circulation were accepted as a biological fact. #### Heart - The heart is a fist-sized muscular organ. - It is centrally placed in the chest cavity but is slightly tilted towards the left (The human heart consists of four chambers Fig. 7.6). - The two upper chambers are called the atria (singular: atrium) and the two lower chambers are called the ventricles. - The right atrium opens into the right ventricle and - the left atrium opens into the left ventricle. - The right side of the heart is completely separated from the left side by a muscular partition called septum - to ensure that deoxygenated blood does not mix with oxygenated blood. **Blood circulation in the body:** - Deoxygenated blood from different parts of the body enters the right atrium) through the superior vena cava and the inferior vena cava and is then pumped into the right ventricle. - From here, the blood is pumped through the pulmonary artery to the lungs for reoxygenation. - In the lungs, this blood gives up carbon dioxide into the alveoli and absorbs oxygen. - This oxygenated blood returns to the left atrium through the pulmonary veins and then enters the left ventricle. - From here the blood is pumped through the aorta to different parts of the body. - As the blood passes through the capillaries, oxygen and other nutrients are delivered to the cells and carbon dioxide and other wastes are picked up by the blood. - This deoxygenated blood again goes back to the right atrium and this cycle is repeated continuously throughout the life of a person (Fig. 7.7). - **Teacher's tip:** You may use a chart of human circulatory system to explain the topic. This will aid in longer retention of the topic. #### Heartbeat - All the muscles of the heart do not contract at the same time. - The two atria contract first, pumping the blood into the ventricles. - A fraction of a second later, the two ventricles contract. - A healthy heart makes a lub-dub sound with each beat. - This sound comes from the closing of the valves in the heart when contractions occur. - This periodic contraction and relaxation of the heart muscles is known as the **heartbeat**. - The heart beats continuously. You can feel the heartbeat if you place your ear against your friend’s chest. - The heart beats on an average of 72 times a minute. - When you go for a checkup, your doctor uses a stethoscope to listen carefully to your heart (Fig. 7.8). ## Excretion in Organisms - Several chemical reactions take place in each cell of an organism. These chemical reactions, collectively called metabolism, convert the food we eat into energy that is needed to carry out various activities. - These metabolic reactions also produce waste materials, such as water, carbon dioxide, urea, and uric acid. - If these waste materials are allowed to accumulate in the body, they can be harmful and thus need to be removed from the body at regular intervals. - The process of removal of metabolic waste produced by the cells of a living organism is called **excretion**. ### Excretion In Animals - In lower organisms, such as Amoeba, Paramecium, and Hydra, there are no specialized excretory organisms. - The waste products, such as ammonia, are removed from the cell by the process of diffusion. - Animals living in water excrete their metabolic waste in the form of ammonia, releasing a large amount of water. These animals are called **ammonotelic animals**. - Some land animals, such as birds, lizards, and snakes excrete a semi-solid white compound called uric acid. Such animals are called **uricotelic animals**. - Land animals including human beings excrete metabolic waste as urea. They are known as **ureotelic animals**. - Higher animals have well-developed excretory organs. ### Excretion in Human Beings - The excretory system in human beings consists of **kidneys**, **ureters**, **urinary bladder**, and **urethra**. * **Kidneys**: In the human body, a pair of kidneys are located in the abdomen, one each on either side of the vertebral column. Each kidney is brick red in colour and bean-shaped. Kidneys filter waste from the blood and eliminate harmful substances in the form of urine. They also maintain the water and mineral balance in the body. * **Ureters**: The ureters are thin-walled, urine-carrying ducts. A single ureter originates from each kidney and is about 25 to 30 cm in length. The ureters run downward and open into the urinary bladder. * **Urinary Bladder**: It is a bag-like structure that stores urine. Its size and position varies with the amount of urine it contains. * **Urethra**: Urethra is the duct that finally discharges urine from the body. #### Mechanisms of Excretion - **Urine formation:** Each kidney has about a million tiny filters called **nephrons**. Nephrons filter excess water, nitrogenous waste, such as urea and salt, from the blood. - The filtered blood is carried towards the heart from the kidneys. - The filtered waste, on the other hand, flows out of the kidneys through the ureters and is collected in the bladder in the form of urine. - Urine is a pale yellow-coloured liquid. - A human being excretes an average of 1.5 to 2.5 litres of urine per day. #### Sweat Formation - **Sweat formation:** Basically, sweating helps regulate our body temperature. - Sweat glands (Fig. 7.13), present in the skin also excrete some amount of metabolic waste along with salts and water. #### Renal Failure or Kidney Failure - Sometimes a person's kidneys may stop working. - An infection in the kidneys, an injury or restricted flow of blood to the kidneys can cause damage. - Complete failure of the kidneys result in the accumulation of urea and other waste products in the blood. - Even the quantity of water is not regulated in the body. - If left untreated, these symptoms may even lead to the death of the patient. - **Dialysis:** An individual with failed kidneys can get their blood filtered or cleaned artificially. - The process used for cleaning the blood of a person with kidney failure by separating waste substances (urea) from it is called **dialysis** and the device is called a dialysis machine or a dialyser. - The best long-term solution for kidney failure is kidney transplantation in which the damaged kidney is replaced with a healthy kidney. ## Transportation of Materials In Plants - Plants are living organisms like animals. They need water, minerals, and food for their survival. - The transport of materials in plants is carried out by two types of conducting tissues called **xylem** and **phloem** which together constitute the vascular tissue system. #### Transport of Water, Minerals, and Food - You know that xylem [Fig. 7.14 (a)] transports water and minerals upwards from the roots to the leaves. - The movement of water and minerals in the xylem is **unidirectional**. - Phloem [Fig. 7.14 (b)] carries the food prepared by the leaves to all parts of the plant including roots. - The movement of materials in the phloem is **bidirectional**. - Thus, xylem and phloem transport various substances in plants. - Plants absorb water and minerals through the roots as shown in Figure 7.15. - The roots have root hairs that are in direct contact with the water molecules present between the soil particles. - Root hairs also increase the surface area for the absorption of water and minerals present in the soil. - The fluid containing water and dissolved minerals in the cells of the root hairs is called **sap**. - The upward movement of fluid through the xylem is called the **ascent of sap**. #### Activities: - Let us do Activities 3 and 4 to understand that xylem conducts sap in a plant. - **Observation:** After one day, we find that the leaves of the first shoot remain normally, but in the second plant, the leaves wilt (Fig. 7.17). - **Conclusion:** This proves that water and minerals are conducted through the xylem. - **Water moves from root hair to the xylem in the root. From the root, it moves up the stem. The movement of water into the roots and up the stem is through osmosis. Osmosis is the process by which molecules of a solvent move from a region of low solute concentration to a solution of high solute concentration across a semipermeable membrane.** #### Translocation - The food prepared in the leaves is transported from the leaves to other parts of the plant through phloem. - This process is called **translocation**. - Figure 7.19 shows a schematic representation of ascent of sap and translocation of food in a plant. - The blue arrows indicate the movement of water and minerals from the root to the leaves and the orange arrows indicate translocation of food from the leaves to all parts of the plant body. ## Excretion in Plants - Plants have no special excretory organs. - Plants produce two gaseous waste products. - These are oxygen (produced during photosynthesis) and carbon dioxide (produced during respiration). - Excretion of gaseous waste in plants takes place through the stomatal pores on leaves. - Excess water is also excreted from the plant body through the stomatal pores by a process called transpiration. - There are some other forms of stored waste products produced by plants. For examples: * Oil produced by orange and eucalyptus plants. * Latex produced by rubber (