The ability to understand evolutionary tree graphics and use them to organize one’s knowledge of biodiversity.

Part of the process of decoding an RNA molecule composed of nucleotide bases into a protein composed of amino acids.

Fossils or organisms that show the transformation from an ancestral form to descendant species’ form. For example, there is a well-documented fossil record of transitional forms for the evolution of whales from their amphibious ancestor. For a more detailed explanation, see our resource on transitional forms.

An internal tube that carries air into the body of an animal for breathing. For example, in humans, a trachea carries air to the lungs; in insects, a network of tracheae carries air directly to tissues throughout the body. (plural = tracheae)

The repeated deformation of a body (for example, a moon) due to tides from another body (for example, a planet), which leads to heating of the former’s interior. Tidal forces arise due to variations in the gravitational forces between bodies. For example, tidal forces from the Moon cause tides in the Earth’s oceans of course, but they also very slightly deform the Earth itself. Tidal heating may have resulted in a water ocean under the ice covering Jupiter’s moon Europa.

In animals with three body regions, the middle body region, usually between the head and abdomen.

A broad explanation for a wide range of phenomena. Theories are concise, coherent, systematic, predictive, and broadly applicable. They usually integrate many individual hypotheses. A scientific theory must be testable with evidence from the natural world. If a theory can’t be tested with experimental results, observation, or some other means, then it is not a scientific theory.

The animal clade containing vertebrates with sturdy legs (as opposed to fins).

A clade, species, or lineage that appears at the tip of a phylogenetic tree. Terminal taxa may be extant or extinct.

(taxa — pl.) Any named group of organisms (e.g., the reptiles, Felidae, beetles, Homo sapiens), whether or not it forms a clade.

The process of building an RNA molecule using DNA as a template. In this process, complimentary RNA bases are matched to their DNA counterparts so that the strand of RNA that is produced carries the “imprint” of one strand of the DNA molecule.

In evolution, a situation in which undergoing natural selection improving performance in one arena (e.g., attracting a mate with an extra-long tail) means simultaneously decreasing performance in another arena (e.g., avoiding predation). For more details, read about trade-offs in Evolution 101.

Trilobites are an extinct group of arthropods, distinguished by the following characters:

• a body built from a cephalon, thorax, and pygidium
• a body divided into three lobes, running from head to tail
• one pair of antennae

The last trilobites went extinct about 245 million years ago, but they are well represented by the fossil record.