Evolution 101

Learn About Evolution

What is a Theory?

A theory is a coherent group of tested general propositions, commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena. (Dictionary.com)

The Theory of Evolution

Charles Darwin configured that the Theory of Evolution supported the idea that all life is related and has descended from a common ancestor. It supports that life developed from non-life.

History of Evolution

4.6 billion years ago: the earth forms and is bombarded by meteorites and comets

3.8 billion years ago: replicating molecules (precursors of DNA) form

3.5 billion years ago: unicellular life evolves; photosynthetic bacteria begin to release oxygen into the atmosphere

500 million years ago: fish-like vertebrae evolve

420 million years ago: land-plants evolve, changing landscape and creating habitats

360 million years ago: four-limbed vertebrates move onto the land as seen plants and large forests appear; vast reef systems

250 million years ago: the super continent Pangea forms; conifer-like forests, reptiles, ancestors of mammals are common

225 million years ago: dinosaurs and mammals evolve; Pangea begins to separate into continents

65 million years ago: a massive asteroid hits the Yucatan Peninsula, and ammonities an non-avian dinosaurs go extinct; birds and mammals are among survivors

4 million years ago: in Africa, an early hominid (Lucy) lives

130 thousand years ago: modern humans evolve

Ways Scientists Date Fossils and Rocks

Relative Dating

  • the configure the order the layers of sediment were deposited
  • if a fossil is found in rock, it gives a good estimate of how old the rock is

Absolute Dating

  • tells exact age
  • carbon dating
  • by studying the proportion of Carbon-14 atoms, compared to the other Carbon atoms, we can find out how old rocks and fossils are


The remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock.


Transitional Fossils

Any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group.


Apes to Humans

Fish to Tetra-pods

Dinosaurs to Birds

Homologous Structures

An example of an organ or bone that appears in different animals, underlining anatomical commonalities demonstrating descent from a common ancestor. In other words, it's when very different animals have bones that appear very similar in form or function and seem to be related.
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Vestigial Structures

Vestigial refers to genetically determined structures or attributes that have apparently lost most or all of their ancestral function in a given species, but have been retained through evolution.
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