1. Which era is the first that shows life on Earth? Cenozoic Archean

The **Archean** is the earliest **eon** that provides evidence of life on Earth. While you mentioned "Archean" as an option, it's important to clarify the geological time scale terminology: - **Eons** are the largest time divisions in Earth's history. The Archean eon spans from about 4.0 to 2.5 billion years ago. - **Eras** are subdivisions within eons. For example, within the Phanerozoic eon (which began around 541 million years ago), there are the Paleozoic, Mesozoic, and Cenozoic eras. **Key Points:** 1. **Archean Eon:** - **Time Frame:** Approximately 4.0 to 2.5 billion years ago. - **Significance:** This is the first eon where we find evidence of life, primarily in the form of simple single-celled organisms like prokaryotes (e.g., bacteria and archaea). - **Geological Activity:** Formation of the Earth's first stable continental crust and the emergence of early oceans. 2. **Cenozoic Era:** - **Time Frame:** Begins around 66 million years ago and continues to the present day. - **Significance:** Known as the "Age of Mammals," this era saw the rise of mammals and birds, as well as significant climatic and geological changes. - **Life Forms:** Diverse and complex life, including humans. **Conclusion:** The **Archean** eon is the first known time period in Earth's history that shows evidence of life. The **Cenozoic** era, on the other hand, is much more recent and pertains to the current phase in Earth's biological and geological development.