Cambrian Explosion Flashcards
Why is the Cambrian explosion significant
It was when most of the major animal groups first appeared in the fossil record.
Why is their little fossil evidence before the Cambrian period
Most organisms were soft bodied so few fossils are present
What period came before the Cambrian period
Ediacaran period
What is a stem group
A paraphyletic group consisting of an ancestor and all its descendants, excluding the living representatives
What is a crown group
The smallest monophyletic group to contain the last common ancestor and all of its descendants
What is punctuated equilibrium
Morphological stability followed by rare bursts of speciation
What caused the rapid divergence of animal phyla in the Cambrian period
A sharp change in selection pressures acting on pre-existing genetic diversity
What are the main triggers of the Cambrian explosion
Ecological: emergence of predators
Genetic: pre-Cambrian expansion of genetic diversity
Environmental: raise in oxygen levels and seawater composition. End of global glaciation
