Uranium-238 has a half-life of 4.5 billion years. given that scientists estimate earth's age to be 4.6 billion years, what is the most likely percentage of parent to daughter isotopes of this element currently existing on earth?

10 percent
25 percent
50 percent
75 percent

Needed fast 15 points the process of natural selection favors certain characteristics in organisms, while it selects against other characteristics. what would happen if there was zero variation between all of the organisms on earth? a. organisms would evolve to increase variety b. natural selection would operate faster c. less food would be available d. evolution through natural selection would not occur

Using complete sentences, explain the differences between a command economy and a market economy. what type of economic system is created when these two systems are combined? what are the benefits of combining these two systems?

Find a formal factor that connects egypt to africa to europe and to southwest asia