Stephen Eikenberry 16 January 2013 AST 2037 Life on Earth - II Stephen Eikenberry 16 January 2013 AST 2037

RNA Single-stranded ribonucleic acid Similar in many ways to DNA Several types of RNA commonly used in life mRNA takes the DNA code “message” to places where proteins are made (“ribosomes”) rRNA actually carries out the protein assembly in ribosomes It appears that some viruses may use RNA for their genetic code

Cells: Basic Units of (most) Life Smallest units of independent life here on Earth

Prokaryotic Cells Cells without nuclei Typically considered “primitive” – i.e. bacterium

Eukaryotic Cells – Animals With nucleus – “Advanced” This one is an animal cell

Eukaryotic Cells – Plants With nucleus – “Advanced” This one is a plant cell Note: Cell Wall Chloroplasts

Multi-cellular Life More than one cell But, not so many you can’t count them easily!

Complex plants

Complex animals

Complex animals

Summary Tremendous commonality amongst a huge range of life on Earth Under the microscope, hard to really tell one human cell from a jellyfish cell from a bacterium from a tree – basic features are the same Also, chemical makeup (all DNA; all L-Alanine even) Suggests a common origin …