THE CAMBRIAN EXPLOSION
Fill in the blank spaces using the word list below.
aquatic, species, ozone layer, superposition, strata, fossil record,
periods, older, UV, terrestrial, phanerozoic.
Prior to the formation of the ___________ ______________, terrestrial
environments were subjected to lethal levels of ______________ radiation.
Organisms are thought to have evolved from ______________ to
________________ environments around 500 mya.
The Cambrian Explosion marks a period of time noted for the evolution of
many new ______________ .
Changes occurring to living things over time can be seen in the
______________ _________________. Most fossils are located within
sedimentry rock layers called _______________. Generally, the deeper a
fossil is located in rock strata, the _________________ it is thought to be. This
concept is referred to as the Law Of _______________________.
This basic principle has allowed geologists to divide up the current
________________ eon into several smaller eras and _________________.