Rabbit Holes
Spines

Our World in Pictures (N/A)

DK’s Science as You’ve Never Seen it Before (N/A)
    
https://astrobiology.nasa.gov/news/how-did-multicellular-life-evolve/

https://biologydictionary.net/endosymbiotic-theory/

Book Extensions

• We Go Way Back (ONE OF MY FAVORITES)
• Thirty Trillion Cells: How Your Body Really Works by Isabel Thomas
• The Amoeba Sisters' Cartoon Guide to Biology ch. 10 (advanced)