Measurements indicate that a fossilized skull you unearthed has a carbon-14: carbon-12 ratio about 1/16th that of the skulls of present-day animals. What is the approximate age of the fossil? (The half-life of carbon-14 is 5,730 years.)

SCIENTIFIC THINKING Cetaceans are fully aquatic mammals that evolved from terrestrial ancestors. Gather information about the respiratory system of cetaceans and describe how it illustrates the statement made in that 'Evolution is limited by historical constraints.'

The vast majority of animals that ever existed are now extinct, but Tereza Jezkova and John Wiens wondered which variables were most important in driving the diversification of species that exist today. Why are there so many species in some phyla, such as Cnidaria (see photo), but so few in others, such as Ctenophora?A sample of Jekova and Wiens' results is shown here. The R2 value represents the strength of the correlation (where 0.00 is lowest and 1.00 is highest). The P value represents the statistical significance. Which five traits look most important?

Which traits do not correlate strongly with diversification rate within phyla, but are likely to have been important in the original diversification of animal phyla during the Cambrian? Select True or False for each trait.T/F presence of a headT/F mobile lifestyleT/F terrestrial lifestyleT/F bilateral symmetry

Advocates of 'scientific creationism' and 'intelligent design' lobby school districts for such things as a ban on teaching evolution, equal time in science classes to teach alternative versions of the origin and history of life, or disclaimers in textbooks stating that evolution is 'just a theory.' They argue that it is only fair to let students evaluate both evolution and the idea that all species were created by God as the Bible relates or that, because organisms are so complex and well adapted, they must have been created by an intelligent designer. Do you think that alternative views of evolution should be taught in science courses? Why or why not?

The vast majority of animals that ever existed are now extinct, but Tereza Jezkova and John Wiens wondered which variables were most important in driving the diversification of species that exist today. Why are there so many species in some phyla, such as Cnidaria (see photo), but so few in others, such as Ctenophora?The researchers know that correlation does not equal causation. However, can the absence of a correlation enable you to reject a hypothesis of causation? How would the R2 values be different in a scenario where a single trait was important to diversification in many phyla versus a scenario where different traits were important to diversification in different phyla?

SCIENTIFIC THINKING When Stanley Miller's experiment was published in 1953, his results made global headlines. The general public thought Miller had answered the question of how life on Earth began by creating life in a test tube. However, scientists understood that Miller's experiment was neither a final answer nor a recipe for life. Rather, it was the first test of a long-standing hypothesis about the origin of life. Write an essay describing how the process of science progresses over time toward understanding how nature works.

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

The early atmosphere on Earth is thought to have lacked which of the following gases?