Exam 24: The History of Life on Earth

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

If the Earth's mantle had somewhat less radioactive material, there would be _______ heat generated and likely _______ plate tectonic activity.

The primary reason that dragonflies grew so much larger 300 million years ago than they do today is that

The _______ of an isotope is the time it takes for a fixed fraction of radioactive material to change from one form to another.

The mass extinction responsible for the demise of the nonavian dinosaurs occurred about 65 million years ago at the end of the _______ period.

Which of the following radioactive substances is commonly used to date very ancient (older than the Cenozoic) fossils and events in the history of life?

In undisturbed sedimentary rock, strata from the _______ period are immediately below rocks from the Ordovician period.

The first plants to produce seeds appeared in the _______ period.

Which of the following was not known to eighteenth- and nineteenth-century geologists?

The half-life of ¹⁴C, a radioactive element of carbon, is 5,700 years.The ratio of ¹⁴C to ¹²C in a fossil 28,500 years old would be about _______ that of a living organism today.

Giant insects have not appeared in the fossil record since the end of the _______ period, due at least in part to declines in the concentration of oxygen in the atmosphere that followed the mass death of swamp vegetation around the globe.

Which statement about the Cambrian period is false?

If you could go back in time and walk in a Permian forest, you would not expect to encounter

Refer to the figure. The bands of sediment shown contain iron oxide in sediments dated to an age of 2.25 billion years.Explain the significance of this with respect to the evolution of life on Earth.

Which of the following is not considered evidence that large meteors struck Earth in the past?

For terrestrial animals and plants, the most recent mass extinction event that occurred prior to the evolution of humans took place approximately _______ million years ago.

Which of the following eras in Earth's history is the longest?

Ecologists have coined a new term for the current era.The "Anthropocene" is named after humans because we are currently living in an age of mass _______ brought about by human activity such as overharvesting, habitat destruction, and pollution.

Evidence that meteorites collided with Earth at times of mass extinctions comes from the presence of _______, a metal that is rare on Earth but common in some meteorites.

What do scientists call the long-term average expectations of temperature and precipitation over the various seasons at a given location?