Heredity

Charles Darwin observed that finches on different Galapagos Islands had different beak shapes suited to their food sources. This helped him develop the theory of natural selection.

Extinction occurs when the last member of a species dies. Mass extinctions have occurred several times in Earth's history, the most famous killing the dinosaurs 66 million years ago.

Total magnification is the eyepiece lens multiplied by the objective lens, so a ×10 eyepiece with a ×40 objective gives ×400. Magnification makes an image bigger; resolution decides whether the extra size shows any new detail.

Offspring resemble their parents because they inherit genetic information from both, but no two siblings are identical. Some variation is inherited, some comes from the environment, and most visible traits are a combination of the two.

A pedigree chart shows how a trait passes through generations using squares for males, circles for females, and shading for those showing the trait. A trait that skips a generation is usually recessive.