Explain in brief about the alternate methods to be followed to prevent the harmful effects of over usage of pesticides.
(OR)
Mention any four effective methods of controlling pests, which are less harmful on environment based on biological principles.

Read the passage and answer the following. The prevention of pregnancy in woman by preventing ferilisation is called contraception.Any device or chemical which prevents pregnancy is called a contraceptive.Physical device like condoms in males and diaphragm (cap) for woman are used. Pills for male and female are available which prevent pregnancy.Intra uterine device called copper-t,loopetc., also very effective in preventing pregnancy.Surgical method of birth control fo males nd females are vasectomy and tubectomy. What is the intra uterine device used in womens?

Atmosphere, hydrosphere, lithosphere and biosphere are the four main segments of the environment. Atmosphere is a cover of gases that extends to a height of about 1600 km above the surface of the earth and protects the life on the earth from harmful radiations coming from the sun or the outer space. Atmosphere is further divided into four regions such as troposphere, stratosphere, mesosphere and thermosphere. Hydrosphere forms that part of the environment which contains water. Lithosphere is the solid component of the earth consisting of soil, rocks, mountains etc. Biosphere is that part of the above segments where living organisms interact with these parts and live together. Hydrogen and Helium are found in which of the following regions ?

Atmosphere, hydrosphere, lithosphere and biosphere are the four main segments of the environment. Atmosphere is a cover of gases that extends to a height of about 1600 km above the surface of the earth and protects the life on the earth from harmful radiations coming from the sun or the outer space. Atmosphere is further divided into four regions such as troposphere, stratosphere, mesosphere and thermosphere. Hydrosphere forms that part of the environment which contains water. Lithosphere is the solid component of the earth consisting of soil, rocks, mountains etc. Biosphere is that part of the above segments where living organisms interact with these parts and live together. Which of the following is the coldest region ?

Read the passage and answer the following. The prevention of pregnancy in woman by preventing ferilisation is called contraception.Any device or chemical which prevents pregnancy is called a contraceptive.Physical device like condoms in males diaphragm (cap) for woman are used.Pills for male and female are available which prevent pregnancy.Intra uterine device called copper-t,loopetc., also very effective in preventing pregnancy.Surgical method of birth control for males and females are vasectomy and tubectomy. What is the purpose of contraception?

To explain the nature of radiation, James Clark Maxwell in 1864 put forward .Electromagnetic wave theory.. This theory could explain the phenomena of interference and diffraction but could not explain phenomena of black body radiation and photoelectric effect. Also, after the advent of electromagnetic wave theory, Rutherford.s model of atom suffered a serious drawback. To explain the phenomena of black body radiation and photoelectric effect, Max planck in 1900 put forward Planck.s quantum theory. BAsed on this theory, Neils Bohr in 1913 put forward Bohr.s model of atom which could overcome the drawback of Rutherford.s model and also explain the line spectral elements, especially the line spectra of hydrogen and hydrogen-like particles. Which of the following statements is incorrect about electromagnetic wave theory ?