1.Cyanobacteria

2. Fossils are the preserved remains of plants and animals whose bodies were buried in sediments, such as sand and mud, under ancient seas, lakes and rivers. Fossils also include any preserved trace of life that is typically more than 10 000 years old.

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The first photosynthetic organisms that grew well on Earth are believed to be cyanobacteria, also known as blue-green algae. These organisms were some of the first to produce oxygen through photosynthesis, which changed the Earth's atmosphere and paved the way for the evolution of more complex life forms.

The remains of living organisms used in understanding the history of life on Earth are called fossils. These can be imprints, casts, or remnants of organisms that lived in the past, preserved in rocks, sediment, or other geological materials. Through the study of fossils, scientists can learn about the diversity, evolution, and extinction of species, as well as the geological and environmental conditions of the past.