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(1) the colorado river carved out a deep canyon in the habitat of an abert’s squirrel population. this is an example of which stage of speciation?

a) the populations become adapted to different environments and eventually become so different that they cannot interbreed to produce fertile offspring.
b) the populations are isolated and thus do not interbreed.
c) the populations become totally separated from one another.
d) the populations successfully interbreed.

(2) the formation of the canyon acted as a barrier that prevented any mating between the separated populations. this is an example of which stage of speciation?

a) the populations become adapted to different environments and eventually become so different that they cannot interbreed to produce fertile offspring.
b) the populations are isolated and thus do not interbreed.
c) the populations become totally separated from one another.
d) the populations successfully interbreed.

On a recent expedition to a remote region of northern canada, scientists uncovered skeletal remains from about 100,000 years ago. surprisingly, all the skeletal remains, which included many species from differing biological families and spanned about two thousand years, showed evidence of experiencing temperatures in excess of 1000 degrees fahrenheit (or 538 degrees celsius). which of the following, if true, best explains the apparent paradox between the cold environment and the evidence of the bones experiencing hot temperatures? (a) chemical changes that naturally occur during the process of decay in only one north canadian species produce the same evidence of the species' skeletons being exposed to hot temperatures as the expedition scientists found. (b) a little over 103,000 years ago, a large fire is known to have occurred in northern canada. (c) strong evidence exists that as early as 70,000 years ago, homo sapiens around the world relied heavily on fire to cook animals. (d) in the same expedition and in roughly the same layer of excavation, scientists found rudimentary wood cutting and hunting tools used by early humans.

The unique structure of the neuron is dedicated to the efficient and rapid transmission of neural signals. the relationship between neurons, the spinal cord, and the brain constitutes an elaborate communication system throughout the human body. all but one of the functions listed below are a result of this interaction.

For this question look at the hydropic diagram water that is heated by the sun evaporates. select the number that represents it.