Exam 25: The History of Life on Earth

Use the following to answer questions: Refer to the diagram below, showing the decay of a radioactive substance. -How long will it take for only 12.5 percent of the substance to remain?

The mass extinction at the end of the Ordovician period was probably caused by

The half-life of carbon-14 is 5,700 years. If 10 percent of the original carbon-14 is left in a structure, that structure is _______ years old.

Which of the following would likely be most conducive to the occurance of fossilization?

Which of the following geological periods is the most recent (closest to the present)?

During which of the following geological times did the most new kinds of body plans appear?

Which of the following statements about the mass extinction at the end of the Cretaceous is false?

The _______ dating method makes use of changes in patterns of Earth's magnetism to date rocks.

The cause of the mass extinction at the end of the Mesozoic era probably was

The sudden disappearance of the dinosaurs some 65 mya may have been the result of

The ratio of ¹⁴C to its stable isotope, carbon-12 (¹²C), is relatively constant in living organisms and their environment; however, this changes once an organism dies. In a fossil less than 50,000 years old, what would the ratio of ¹⁴C to ¹²C be?

Rodents, marsupials, and hoofed animals first appeared in North America during the _______ period.

The first person to put forth the idea that Earth's con-tinents are in continual but slow motion was

Earth's crust

The most severe mass extinction event, linked to the formation of Pangaea and massive volcanic eruptions, occurred at the end of the _______ period.

Life first evolved on Earth _______ years ago.

The Cambrian period is the most ancient period of the _______ era.

Mass extinctions often accompany major _______ in sea level. Such extinctions have been particularly felt among _______ animals.

The most dramatic mass extinctions of organisms are thought to have taken place at the end of the Permian period. What factor(s) likely contributed to these extinctions?

The period of time in which most of the land was divided into two large land masses and in which lizards, several groups of mammals, and flowering plants first appeared was the