Phylum Platyhelminthes

Question 1

Describe the Clade Bilateria

Answer 1

• have bilateral symmetry
• contains a third germ layer (mesoderm)
• first appeared 600 mya

Question 2

What are the three key innovations?

Answer 2

1. the evolution of eukaryotic conditions (membrane-bound organisms)
2. the evolution of metazoans ( multicellular)
3. the evolution of the third germ layer