Control and Co-ordination in Animals: Nervous system and endocrine system. In animals, the nervous system and hormonal system are responsible for control and co¬ordination. Receptors: Receptors are the specialized tips of the nerve fibres that collect the information to be conducted by the nerves. Receptors are in the sense organs of the animals. These are classified as follows : Phono-receptors: These are present in inner ear. Functions: The main functions are hearing and balance of the body. Photo-receptors: These are present in the eye. Function: These are responsible for visual stimulus. Thermo-receptors: These are present in skin. Functions: These receptors are responsible for pain, touch and heat stimuli. These receptors are also known as thermoreceptors. Olfactory-receptors: These are present in nose. Functions: These receptors receive smell. Gustatory-receptors: These are present in the tongue. Functions: These helps in taste detection. Nervous System: T...
Chemical Reaction: The transformation of chemical substance into another chemical substance is known as Chemical Reaction. For example: Rusting of iron, the setting of milk into curd, digestion of food, respiration, etc. In a chemical reaction, a new substance is formed which is completely different in properties from the original substance, so in a chemical reaction, a chemical change takes place. Only a rearrangement of atoms takes place in a chemical reaction. The substances which take part in a chemical reaction are called reactants . The new substances produced as a result of a chemical reaction are called products . Example: The burning of magnesium in the air to form magnesium oxide is an example of a chemical reaction. 2Mg(s) + O2(g) △→ 2MgO(s) Before burning in air, the magnesium ribbon is cleaned by rubbing with sandpaper. This is done to remove the protective layer of basic magnesium carbonate from the surface of the magnesium ribbon. Reactant : Substances which take pa...