Which is a factor in how a species can change over time?
a.
mutations
b.
cytokinesis
c.
extinction
d.
formation of spindles

Why are fossils not found in igneous rocks? igneous rocks are made from cooling of lava or magma. igneous rocks are found too deep underground. igneous rocks are too dark in color to contain fossils. igneous rocks are too dense to contain fossils.

Which line in the graph above best illustrates an effect of the carbon dioxide level in the blood on breathing rate before, during and after a period of exercise? 1.b,2.c,3.a,4.d

Based on their relative positions in the periodic table, which two elements would have the same number of valence electrons?