A pouch-like structure in female marsupials, used to carry and nurse their young.

A measure of the amount of matter in an object, often expressed in kilograms or grams.

Events in Earth’s history when large numbers of species went extinct over a relatively short period of time.

The total number of protons and neutrons in the nucleus of an atom.

A form of artificial selection where individuals with the most desirable traits are selected to reproduce.

An analytical instrument used to measure the mass-to-charge ratio of ions, used in chemistry and biology for identifying and quantifying substances.

The branch of medicine that deals with the study of the breast, its diseases, and treatments.

The act of stimulating one’s own genitals for sexual pleasure.

Relating to or characteristic of mammals.

A scientist who specializes in the study of mammals.