Draw a neat labelled diagram of the longitudinal section of the human heart and show the direction of the flow of blood through the different chambers with arrow marks, and give a brief description of the blood circulation through it.

The heart is pear shaped structure, triangle in outline, wider at the anterior end and narrower at the posterior end. The size of the heart is approximately the size of ones own fist. The heart is covered by two layers of membranes. The membranes are called pericardial membranes. The space between these layers is filled with pericardial fluid, which protects the heart from shocks. The heart is divided into four chambers. The two upper chambers are called the left and right atrium. The two lower chambers are called the left ventricle and right ventricle. The right auricle receives blood from the different parts of the body. The left auricle receives oxygen-rich blood from the lungs. The right ventricle pumps out blood containing waste materials to the lungs. The left ventricle pumps the blood out of the heart to the different parts of the body.

What is photosynthesis? What are the events that takes place during this process? Write how does the plant absorb carbon dioxide.

Plants can prepare their own food with the help of photosynthesis. It is the process by which green leaves make food by using carbon dioxide, water, chlorophyll pigment and sunlight. Oxygen is released out from the plants which are used for breathing. Three events take place during photosynthesis. Following are the events that take place in the photosynthesis process: The first event takes place in the absorption of light energy in the form of chlorophyll. The second event, that takes place during the process of photosynthesis is the transformation of light energy into chemical energy, where the splitting of water molecules takes place. The water molecule is divided into hydrogen and oxygen. The third event in the process of photosynthesis is the reduction of carbon dioxide into carbohydrates. The carbon dioxide is taken from the atmosphere by the stomata and carrying oxygen is considered to be the removal of waste products.

Name the respiratory pigment present in our blood. State its function.

The respiratory pigment present in the blood is called haemoglobin. Haemoglobin provides red colour to the blood. The function of haemoglobin is as follows: Haemoglobin carries oxygen to the cells. This respiratory pigment of the blood transports carbonic anhydride that regulates pH balance. It gives rise to bilirubin and gives the blood its red colour.

What are the components of the transport system in highly organized plants? How are water and minerals transported in plants? What is the role of transpiration in transporting water and minerals in plants?

The components of the transport system of organised plants consist of the xylem and phloem. Xylem: It is a vascular tissue. It transports water and minerals from the root to other parts of the plant. They have tough walls containing a woody material called lignin. Phloem: It transports food from leaves to other parts of the plants. 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. Transpiration is the loss of water from the leaves. It results in pull which thereby increases the rate of absorption of water along with minerals from the soil through roots. It also helps in the transportation of absorbed minerals to all the parts of the plant.

Name the parts of the excretory in humans. Describe the mechanism of urine formation and elimination.

The process of removal of chemical wastes mainly nitrogenous wastes from the body is known as excretion. Organs that are concerned with the formation, storage and elimination of urine constitute the excretory system. Kidneys: These are the primary excretory organs eliminating nitrogenous wastes (chiefly urea) from the blood and throwing it out in the form of urine. Skin: Sweat excreted by the sweat glands of the skin primarily excrete water and sodium chloride, along with small amounts of urea and lactic acid. Lungs: They excrete carbon dioxide from our body through the expired air. The mechanism of urine formation is as follows: Glomerular filtration: It is the process by which the kidneys filter the blood, removing excess wastes and fluids. Reabsorption: The glomerular filtrate entering the renal tubule is not urine. It is an extremely dilute solution containing a lot of useful materials including glucose and some salts such as that sodium. As the filtrate passes down the tubule, much of the water is reabsorbed together with the useful substances. Tubular secretion: Certain substances like potassium are passed into the forming urine in the distal convoluted tubule. This passage involves the activity of the cells of the tubular wall, and hence it is called tubular secretion. The filtrate left after reabsorption and tubular secretion is called urine.