David Fleetham / Silhouette of a Green Sea Turtle (Chelonia mydas) passes overhead. West Maui, Hawaii.

Denis-Huot / Masai giraffe (Giraffa camelopardalis tippelskirchi) two silhouetted at sunrise, Maasai Mara Game Reserve, Kenya.

Will Burrard-Lucas / Three Ethiopian wolf (Canis simensis) pups waiting for their parents to return, Ethiopia.

John Cancalosi / Cross-Section of Utah Septarian Nodule, Utah. A type of geode, Utah Septarian Nodules are found about 15 miles east of Zion National park. They were formed in an ancient sea floor during the Cretaceou...

Andy Rouse / Silhouetted Grizzly Bear (Ursus arctos horribilis) walking. Katmai, Alaska, USA, September.

Bence Mate / Silhouette of an African leopard (Panthera pardus pardus) snarling, Mkuze, South Africa. September. 'White Fang' - this leopard bared its fangs to the hyenas threatening his prey. Eventually the leopa...

Ingo Arndt / Aerial view of Hardy Reef, Great Barrier Reef, Queensland, Australia, December 2010.

Erlend Haarberg / Mountain hare (Lepus timidus) breath backlit during cold night, Vauldalen, Norway May

Loic Poidevin / Red deer (Cervus elaphus) male stag silhouetted at dusk, rut season, Jura, Scotland, UK, September

Tony Wu / Giant frogfish (Antennarius commersoni) silhouetted against sea surface from below, Ambon, Indonesia.

Franco Banfi / Giant manta ray (Manta birostris) seen from above, Revillagigedo Archipelago Biosphere Reserve, Socorro Islands, Western Mexico

Paul D Stewart / The history of life, proposed by Swiss-American naturalist Louis Agassiz. Agassiz would disagree strongly with Darwin's theory of evolution. This diagram from 1855 shows how he understood biological...