Beginning of Life
Exploring how life began on Earth and what it means to actually be a living thing.Chapters:
- Animal & Human Development
- How Did Life Begin?
Life on Earth is thought to have started as simple, one celled organisms approximately 4 billion years ago. For about 3 billion years, only single celled microorganisms existed, but once cells with a true nucleus developed about a billion years ago, multicellular organisms evolved.
- Was There Always Oxygen on Earth?
Describe how organisms on Earth contributed to the big change in how much oxygen there was in Earth's early atmosphere.