Its explain why mitochondria in animals and plastids in plants have its own DNA and double membrane. The theory postulates that this is due to a symbiotic relationship that began with the history of life when protists probably engulfed bacteria (most probably by phagocytosis). The bacteria offered energy while it was sheltered. The relationship evolved to become facultative.
Answer: Hydrosphere is the total mass of water found on the Earth's surface. Atmosphere is the layer of air that envelopes the Earth. Hydrosphere consists of lakes, oceans, rivers, seas, water vapours, underground water and ice sheets of the mountainous regions.
