24. History of Life on Earth

Currently scientists think the early atmosphere probably consisted of __________.

Adaptive radiations are often seen after __________.

Lake Malawi, in the African Rift Valley, is home to more than a hundred species of cichlid fishes, each with slightly different diets and habits. All these species probably evolved from a common ancestor, making them an example of __________.

Why is the four-stage hypothesis for the abiotic origin of life useful?

Prior to the Cambrian explosion, most animals were small and soft-bodied. What development appears to have spurred adaptations such as sharp spines, claws, and body armor (shells)?

Mutations in what class of genes have probably been responsible for many of the changes leading to the great diversity of life existing today?

The correct order of the geologic eras, from most ancient to most recent, is __________.

Plants colonized land in the company of __________; their symbiotic relationships still exist today.

A radioactive isotope has a half-life of 1.2 billion years. As measured by the presence of the isotope and its stable decay product, a rock originally contained 10 grams of the radioactive isotope and now contains 1.25 grams. Approximately how many years old is the rock?

If the feathers of extant flying birds originally arose as thermoregulatory devices in ancestral reptiles, then flight feathers could be accurately described as __________.

Ancient cyanobacteria were very important in the history of life because they __________.

Which of the following best describes how the breakup of Pangaea affected evolution?

The early atmosphere may not have been as reducing as originally postulated by Haldane, Oparin, Miller, and Urey. In light of current thinking about the composition of the early atmosphere, what is regarded as a likely place for the abiotic synthesis of organic molecules to have occurred?