When did all of the modern animal phyla first appear?
a. about 3.5 billion years ago, following the evolution of photosynthesis, which produced food that forms the basis of food webs.
b. about 540 million years ago, during the adaptive radiation known as the cambrian explosion, due in part to predator-prey coevolution.
c. about 200,000 years ago, following the evolution of homo sapiens in africa.
d. about 475 million years ago, after colonization of land by plants, which newly evolved animals could eat.
e. about 65 million years ago, after the extinction of the dinosaurs, because of the available niches and habitat left vacant by the end-cretaceous extinction event.