If a radioactive nuclide has a half-life of 1.3 billion years, and it is determined that a rock contains 50% of its original amount of this nuclide, about how old is the rock?

The salinity of an ocean will in crasr when a fresh water source flows into it

What type of protein controls what goes in and out of cells? APEX

Differences among individuals of a species are referred to as

How does a toxin cause mutations in humans? A. It alters the sequence of human DNA B. It increases susceptibility to viral infections C. It inhibits the production of white blood cells D. It produces antibodies

Which of the following are examples of insects which have chewing mouthparts? A. Mosquitoes and whiteflies B. Horses and blowflies C. Beatles and Catapillars D. Butterflies and Moths

A) What are the bases of mRNA coded for by this section of DNA before the mutation? Hint in RNA A pairs with U.

How does secondary succession differ from primary succession? It begins where no plants have grown. It begins on bare rock or land. Soil nutrients are already in place. Lichens and mosses form soil first.

True of False? The structure of the cell membrane is what allows water and other molecules to move in and out of cells.

Dolphins and fish have similar body shapes. isthis feature more likely a homologous or analogoustrait?

Which of the following is not a phase of gastric secretion? A. cephalic B. gastric C. intestinal D. enterogastric