Describe two different hypotheses of the origin of early cell structure

When did life appear on earth?  for many million years the earth was pummeled by asteroids and other celestial objects. temperatures also would have been very high. the earliest evidence of life on earth comes from fossils discovered in western australia that date back about 3.5 million years ago. thank you so much.

An autotrophic protist - they can perform photosynthesis and mainly consist of unicellular algae. they can be divided into number of systematic group according to the shape of their cell and the type of photosynthetic pigments they use.