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  Genetic variation _____. A) is created by the direct action of natural selection B) arises in response to changes in the environment C) must be present in a population before natural selection can act upon the population D) tends to be reduced by when diploid organisms produce gametes  

How many electrons are in nitrogen ion, N3-?

As Wallace traveled the Malay Archipelago, he noticed that western islands had placental mammals, like monkeys. Eastern islands had marsupial mammals, like kangaroos. How did Wallace explain this distribution?   A.   The western islands were once connected to Asia and the eastern islands had been connected to Australia. The islands had never been connected to each other. B.    God specially created monkeys on one set of islands and kangaroos on the other. C.    Marsupial and placental mammals live in different habitats. Monkeys could only survive in the western islands and kangaroos in the eastern islands. D.   Monkeys and tree kangaroos compete against one another and cannot live together.

Chemical changes are accompanied by changes in the total mass of the substances involved.

Perform the following calculation of measured numbers and express your result as a scientific notation with correct number of significant figures. 3.4 + 2.86 – 6.8 =

In liquids and gases particles are close to each other.

Both solids and liquids have definite volume.

Classify each of the following as element, compound, or mixture.

Physical change is change in shape or change in state of a substance.

What is the empirical formula for C6H12O6?