Stomata :- are tiny pores present in the leaves through which exchange of gases takes place. Each stoma has a pair of guard cells which controls the opening and closing of the stomatal pore. When water enters the guard cells, it swells and the pore opens and when the guard cells lose water, it shrinks and the pore closes.
Activity to show that chlorophyll is necessary for
- Take a potted plant having variegated leaves (croton plant). Keep it in a dark room for three days so that all the starch is used up. Then keep it in sunlight for 6 hours. Then take a leaf from the plant and mark the green areas of the leaf on a sheet of paper. Then dip the leaf in boiling water to make it soft. Then dip the leaf in alcohol and heat it in a water bath to decolourise it and remove the chlorophyll. Then wash the leaf in water and dip it in dilute iodine solution. It will be seen that only the green parts of the leaf turns blue black. This shows that chlorophyll is necessary for photosynthesis.
Activity to show that carbon dioxide is necessary for
- Take two potted plants of the same size and keep them in a dark room for three days so that all the starch is used up. Then keep the plants on separate glass plates. Keep a watch glass containing some potassium hydroxide near one plant to absorb carbon dioxide. Cover both the plants with bell jars and seal the bottom of the jars with vaseline to make it air tight. Keep the plants in sunlight for three hours. Then take a leaf from each plant and test for starch. The leaf of the plant kept in the jar containing potassium hydroxide does not show the presence of starch. This shows that carbon dioxide is necessary for photosynthesis.
Nutrition in animals :-
- a) Nutrition in amoeba :-
- Amoeba is a unicellular animal living in water. It takes in food by forming finger like projections called pseudopodia and forms a food vacuole. Inside the food vacuole the food is digested and absorbed. The undigested food is then sent out through the surface of the cell.
Nutrition in Human beings :-
- Nutrition in human beings takes place in the digestive system. It consists of the alimentary canal and glands which produce enzymes which breaks down food into smaller molecules.
- The main organs of the digestive system are mouth, oesophagus, stomach, small intestine, large intestine, and anus. The main glands are salivary glands, gastric glands, liver, pancreas and intestinal glands.
- In the mouth :- the food is broken down into smaller particles by the teeth and mixed with saliva from the salivary glands. Saliva contains the enzyme salivary amylase which converts starch into sugar. Then the food passes through the oesophagus into the stomach.
- In the stomach :- the gastric glands produce gastric juice which contains the enzyme pepsin, hydrochloric acid and mucous. Pepsin breaks down proteins. Hydrochloric acid makes the medium acidic and helps in the action of pepsin. Mucous protects the walls of the stomach from the action of the acid. Then the food passes into the small intestine.
- In the upper part of the small intestine called duodenum :- the food is mixed with bile from liver and pancreatic juice from the pancreas. Bile breaks down fats into smaller globules. Pancreatic juice contains the enzymes trypsin and lipase. Trypsin breaks down proteins and lipase breaks down fats.
- In the small intestine :- the glands the walls of the small intestine produces intestinal juice. The enzymes of the intestinal juice coverts carbohydrates into glucose, fats into fatty acids and glycerol and proteins into amino acids. The walls of the small intestine has several finger like projections called villi having blood vessels. It helps to increase the surface area for the absorption of digested food. The digested food is absorbed by the blood and transported to all cells in the body. Then the undigested food passes into the large intestine.
- In the large intestine :- water is absorbed and the waste material is removed through the anus.
- Respiration is the process by which food is burnt in the cells of the body with the help of oxygen to release energy. It takes place in the mitochondria of the cells.
- The energy released during respiration is used to make ATP molecules (Adenosine tri phosphate) from ADP molecules (Adenosine di phosphate) and inorganic phosphate.
- ADP + Phosphate ATP
- from respiration
- Energy is stored in the cells in the form of ATP molecules. When the cells need energy, ATP is broken down in the presence of water to form ADP and energy is released.
- ATP ADP + Energy
b) Types of respiration :-
- There are two main types of respiration. They are aerobic and anaerobic respiration.
- i) Aerobic respiration :- takes place in the presence of oxygen. It produces more energy. The end products are carbon dioxide, water and energy. It takes place in most organisms.
- In aerobic respiration glucose is converted into pyruvate in the cytoplasm in the presence of oxygen and then in the presence of oxygen, pyruvate is converted into carbon dioxide, water and energy in the mitochondria.
- presence of oxygen presence of oxygen
- Glucose Pyruvate CO2 + H2O + Energy
- in cytoplasm in mitochondria
- ii) Anaerobic respiration :- takes place in the absence of oxygen. It produces less energy. The end products are lactic acid or ethanol, carbon dioxide, and energy. It takes place in muscle cells and yeast.
- In anaerobic respiration in muscle cells, glucose is converted into pyruvate and in the absence of oxygen pyruvate is converted into lactic acid and energy.
- presence of oxygen absence of oxygen
- Glucose Pyruvate Lactic acid + Energy
- in cytoplasm in muscle cells
- In anaerobic respiration in yeast, glucose is converted into pyruvate and in the absence of oxygen pyruvate is converted into ethanol, carbondioxide and energy. This process is called fermentation.
- presence of oxygen absence of oxygen
- Glucose Pyruvate Ethanol + CO2 + Energy
- in cytoplasm in yeast