Earth Science

Life on Earth

Evolution of Eukaryotes to Multicellular Life

Study Tip
To remember the difference between eukaryotes and prokaryotes, remember that you are a eukaryote. Humans are large, complex organisms whose eukaryotic cells have nuclei.

Evolution of Eukaryotic Cells

  • Several different specialized prokaryotes began to live together in a symbiotic relationship. These cell types took on specialized functions, and became organelles in a larger cell.
  • A eukaryote is a cell that contains a separate nucleus to hold its DNA and RNA.
Study Tip
To remember the difference between eukaryotes and prokaryotes, remember that you are a eukaryote. Humans are large, complex organisms whose eukaryotic cells have nuclei.

Multicellular Life

  • Prokaryotes and Eukaryotes can both be multicellular.
  • Multicellular life may have evolved several times throughout Earth’s history.

Why It Took So Long

  • Evolutionary processes are generally slow
  • No evolutionary advantage to being larger and more complex
  • Harsh conditions during Earth’s earlier years
  • Limited atmospheric oxygen
  • Planet was too cold for complex life
  • Extinction due to global glaciations
Eukaryotic cell
Eukaryotic cells formed as simpler, specialized
prokaryotes began working together in cells.
Concept Check
  • What are the differences between eukaryotes and prokaryotes?
  • How did one evolve into the other?
  • Why did complex life take so long to evolve?