Biotic index is a scale to quantify assemblage of tolerant species present in the environment. It helps to assess the quality of an environment. Tolerant species are indicative organisms that are present in highly polluted environment. Hence, if the biotic index is high that indicate the high pollution. Biotic index is calculated by using the formula: Biotic index = ∑ n = 1 1 ( n i × a i ) N Where n i is the number of individuals of a species, and a i is the level of tolerance of that given species. The sign ∑ (sum of) means for each species its number is multiplied by their tolerance level and this value is added to the next species and so on. N is the total number of individuals collected.

Match the following: Column A Column B 1. Oxygen a. Upper atmosphere 2. Carbon dioxide b. Factory chimneys 3. Water vapour c. Combustion 4. Smoke d. 0.03% 5. Ozone e. Humidity

Oxygen is required for combustion, it helps in buring. It is also responsible for the process of respiration in living things. In our atmosphere composition of carbon dioxide is 0.03%. The gas helps maintain the temperature of earth. The amount of water vapour in air is called humidity. It is present in air because of evaporation of water bodies among other things. Smoke comes out from the factory chimneys and also from vehicles. It is responsible for the air pollution. Ozone forms the uppermost layer of atmosphere. It protects us from harmful ultraviolet radiations of sun. Column A Column B 1. Oxygen a. Combustion 2. Carbon dioxide b. 0.03% 3. Water vapour c. Humidity 4. Smoke d. Factory chimneys 5. Ozone e. Upper atmosphere