Siliceous frustules of diatoms being indestructible, piled up at the bottom of ocean and formed a thick bed over billions of years. Such a thick bed is known as

How many statements are correct with respect to chrysophytes ? (i) They are found in the marine environment , freshwater organisms are very rare. (ii) In diatoms , the cell wall form two thick overlapping shells which fit together as in a soapbox . (iii) The cell membranes of diatoms are embedded with silica and accumulation of them over billions of years is referred to as "diatomaceous earth " (iv) Diatoms are the chief " Producers" In the oceans .

How many statements are correct with respect to chrysophytes ? (i) They are found in the marine environment , freshwater organisms are very rare. (ii) In diatoms , the cell wall form two thick overlapping shells which fit together as in a soapbox . (iii) The cell membranes of diatoms are embedded with silica and accumulation of them over billions of years is referred to as "diatomaceous earth " (iv) Diatoms are the chief " Producers" In the oceans .

The energy which we obtain from the sun is called solar energy or radiant energy. The sun's energy is stored in coal, natural gas, water and wind. Coal, oil, and natural gas are known as fossil fuels. Fossil fuels were formed over millions of years ago when the remains and fossils of prehistoric plants and animals sank to the bottom of swamps and oceans. These animal and plant remain were slowly covered and crushed by layers of rock, mud, sand, and water. The pressure of all those layers caused the plants and animals to break down and change into coal, oil and natural gas. We use the energy in these fossil fuels to make electricity. As of the year 2019, most of the energy we use comes from fossil fuels. However, fossil fuels are known as non-renewable sources of energy. They cannot be used over and over again. This means that one day they will run out! _______ formed over millions of years ago from the remains of prehistoric plants and animals.