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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?

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)?

What is bioinformatics?

A pea pod is formed from _____. A pea inside the pod is formed from _____.

Selection that acts over evolutionary time to preserve traits that increase an individual’s ability to mate is known as _____.

Antibiotic resistance in bacteria is an example of which of the following?

Which of the following is the most common type of homeowners policy? 

Which example below is evidence provided by living gymnosperms of an evolutionary transition between seedless and seed plants?

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

Directions: From the options below, choose the letter corresponding to the plant clade that evolved approximately at the time indicated by the question mark (?) on the timeline.