Which changes occur in the composition of the earth's layers from the core to the surface?

a.
the material is hotter and denser.

b.
the material is cooler and denser.

c.
the material is cooler and less dense.

d.
the material is hotter and less dense.

Which of the following factors would not contribute to allopatric speciation? a) a population becomes geographically isolated from the parent population.b) the separated population is small, and genetic drift occurs.c) the isolated population is exposed to different selection pressures than the ancestral population.d) different mutations begin to distinguish the gene pools of the separated populations.e) gene flow between the two populations is extensive.