write a note on economic importance of algae and gymnosperms.
Answer to your question is available in chapter 3, lesson 1 and lesson 4. Kindly go through these lesson to find answer yourself.
Due to paucity of time we will not be attend all your queries as we have to answer queries of thousands of other students also.
Kindly read the lessons first and try to answer questions yourself. It seems that you are intelligent student so, i think you will definitely find answers to your questions yourself once you have gone through the chapter. If doubt still persists then do get back to us.