We only know life from Earth, which makes it difficult to define objectively. As scientists, we use what we know as a model, e.g. life on Earth. These readings help us understand what life is and how we classify it in the context of the evolution of life on Earth - with an understanding that it could be different elsewhere in the Universe.
- 1.1: What is life, exactly?
- What is life? We have to define it in terms of what we know from Earth.
- 1.2: Phylogenetic Trees
- Phylogenetic trees illustrate the hypothetical evolution of organisms and their relationship to other species.
- 1.3: Limitations of Phylogenetic Trees
- Limitations of phylogenetic trees include the inability to distinguish evolutionary time and relatedness between distinct species.
Thumbnail: Several types of photosynthetic bacteria (Cyanobacteria) that grow in Antarctic lakes and form pinnacles.