variation Having many differences.
Image Sources
(1) http://en.wikipedia.org/wiki/Image:Geologica_time_USGS.png. GNU-FDL.(2) http://www.bnsc.gov.uk/assets/channels/education/ae/Mercury_Surface.jpg.
Crown Copyright.(3) http://commons.wikimedia.org/wiki/Image:Achaltekas.jpg. GNU-FDL.(4) http://commons.wikimedia.org/wiki/Image:Kanadagletscher.jpg. GNU-FDL.(5) http://commons.wikimedia.org/wiki/Image:Animalia_diversity.jpg.
GNU-FDL.(6) http://commons.wikimedia.org/wiki/Image:Arenal_at_night.jpg. GNU-FDL.(7) http://upload.wikimedia.org/wikipedia/commons/d/d4/Moon-craters.jpg.
Public Domain.(8) http://commons.wikimedia.org/wiki/Image:
Simple_photosynthesis_overview.png. GNU-FDL.(9) C.R. O’Dell/Rice University; NASA.
http://upload.wikimedia.org/wikipedia/commons/d/da/M42proplyds.jpg.
Public Domain.(10) ESO/L. Calçada.
http://upload.wikimedia.org/wikipedia/commons/0/0b/Artist%E2%80%99s_
Impression_of_a_Baby_Star_Still_Surrounded_by_a_Protoplanetary_Disc.jpg.
CC-Attribution 3.0 Unported.
(11) http://upload.wikimedia.org/wikipedia/commons/c/cf/Meteor.jpg. Public
Domain.
(12) http://commons.wikimedia.org/wiki/Image:Opabinia_BW.jpg. GNU-FDL.
(13) http://www.aerospaceweb.org/question/astronomy/solar-system/
asteroid-belt.jpg.
(14) http://commons.wikimedia.org/wiki/Image:
643px-Explanation_of_Evolution_v2.1.png. GNU-FDL.
(15) U.S. Geological Survey Department of the Interior, USGS. The Geologic Time Scale..
Public Domain.