Write a note on economic importance of algae and gymnosperms.
Algae are of immense economic importance. They carry out at least half of the total carbon dioxide fixation on Earth through photosynthesis. Being photosynthetic, they increase the level of dissolved oxygen in their immediate environment.
Algae are of paramount importance as primary producers of energy-rich compounds which form the basis of the food cycles of all aquatic animals. Many species of Porphyra, Laminaria and Sargassum are among the 70 species of marine algae used as food.
Commercially, certain marine brown and red algae produce large amounts of hydrocolloids (water holding substances). Algin (from brown algae) and carrageen (from red algae) are economically important. Agar, obtained from Gelidium and Gracilaria, is used to grow microbes and in preparations of ice-creams and jellies.
Chlorella, a unicellular alga rich in proteins, is used as a food supplement even by space travellers.
Regarding gymnosperms, the provided context does not contain specific information about their economic importance. The context mentions gymnosperms in questions about their classification and characteristics but does not detail their economic uses.
Explanation
The provided context contains detailed information about the economic importance of algae, including their role in carbon dioxide fixation, oxygen production, position as primary producers in aquatic food chains, use as food, commercial products like hydrocolloids (algin, carrageen), agar production, and Chlorella as a protein supplement. However, the context does not include specific information about the economic importance of gymnosperms—it only mentions gymnosperms in relation to classification questions and characteristics. A complete exam answer would typically include information about gymnosperms providing timber, resins, and other products, but this information is not present in the provided context.