Explain how the scales on some fishes can be used to estimate the age of those fishes

If a set of instructions that determines all of the charactersitics of an organism is comparedto a book, and a chromosme is compared to chaper in the book, then what might be compared to a paragraph in the book?

Awater molecule is polar because there is an uneven distribution of these between the oxygen and hydrogen atoms.

What do isotopes of uranium have the same number of? what do they have a different number of? a) same number of protons; different number of electrons b) same number of protons; different number of neutrons c) same number of electrons; different number of protons d) same number of neutrons; different number of protons