Science
How do harmful chemicals get accumulated progressively at each trophic level in a food chain ?
Answer
Several pesticides and other chemicals are used to protect our crops from diseases and pests. These chemicals are either washed down into the soil or into the water bodies. From the soil, these are absorbed by the plants along with water and minerals, and from the water bodies these are taken up by aquatic plants and animals. This is one of the ways in which they enter the food chain. As these chemicals are not degradable, these get accumulated progressively at each trophic level.
Related Questions
A narrow beam XY of white light is passing through a glass prism ABC as shown in the diagram :
Trace it on your answer sheet and show the path of the emergent beam as observed on the screen PQ.
Name the phenomenon observed and state its cause.
It is observed that the power of an eye to see nearby objects as well as far off objects diminishes with age.
(i) Give reason for the above statement.
(ii) Name the defect that is likely to arise in the eyes in such a condition.
(iii) Draw a labelled ray diagram to show the type of corrective lens used for restoring the vision of such an eye.
(a) Identify the reducing agent in the following reactions :
(i) 4NH3 + 5O2 ⟶ 4NO + 6H2O
(ii) H2O + F2 ⟶ HF + HOF
(iii) Fe2O3 + 3CO ⟶ 2Fe + 3CO2
(iv) 2H2 + O2 ⟶ 2H2O
(b) Define a redox reaction in terms of gain or loss of oxygen.
(a) Suggest one remedial measure each to counteract the change in pH in human beings in following cases :
(i) Production of too much acid in stomach during indigestion
(ii) Stung by a honey bee / nettle leaves
(b) Fresh milk has a pH of 6. When it changes into curd will its pH increase or decrease ? Why ?