1. scientists believe that ancient ancestors of all animals were (1 point)
a) single-celled prokaryotes that reproduced asexually.
b) single-celled eukaryotes that sometimes grew in colonies.
c) multicellular organisms that were probably autotrophic.
d) multicellular organisms with an alternation of generations lifecycle.

2. the cambrian explosion resulted in the evolution of the first (1 point)
a) dinosaurs and mammals.
b) representatives of most animal phyla.
c) bacteria.
d) land animals.