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mammal
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polar bear and cubs okapi faunal realms goat herding Steller's sea cow bottlenose dolphins journey of a fertilized egg embryonic development leopard Yellowstone wolf pack
For Students
polar bear and cubs
mammal summary
Quizzes
vulture. An adult bearded vulture at a raptor recovery center. The Gypaetus barbatus also known as the Lammergeier or Lammergeyer, is a bird of prey and considered an Old World vulture.
Animal Factoids
Giraffe standing in grass, Kenya.
Know Your Mammals Quiz
Nine-Banded Armadillo.
A Is for Animal Quiz
Dromedary camels (Camelus dromedarius). Animals, mammals.
Ultimate Animals Quiz
Sea otter (Enhydra lutris), also called great sea otter, rare, completely marine otter of the northern Pacific, usually found in kelp beds. Floats on back. Looks like sea otter laughing. saltwater otters
Animal Group Names
Related Questions
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animal. Amphibian. Frog. Anura. Ranidae. Frog in grass.
Abundant Animals: The Most Numerous Organisms in the World
sea turtle (reptile). Green turtle (Chelonia mydas) (C. mydas) off the Hawaii Islands, Pacific Islands. Green sea turtle, chelonian. Homepage blog 2011, science and technology, animal
5 Vertebrate Groups
cat. orange and white persian cat with long hair, snarl, growl, teeth
7 Questions About Mammals Answered
Platypus (Ornithorhynchus anatinus) swimming on the surface of a creek. Water Australia mammal monotreme
Why Is the Platypus a Mammal?
Ruminant. Deer. Red deer. Cervus elaphus. Buck. Stag. Antlers.
9 of the World’s Deadliest Mammals
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Artist interpretation of a Space meteoroid impact. Meteor impact. Asteroid, End of the world, danger, destruction, dinosaur extinct, Judgement Day, Planet Earth, Doomsday Predictions, comet
10 Failed Doomsday Predictions
Periodical Cicada, Adult, Magicicada spp. Requires 17 years to complete development. Nymph splits its skin, and transforms into an adult. Feeds on sap of tree roots. Northern Illinois Brood. This brood is the largest emergence of cicadas anywhere
Why Do Some Cicadas Appear Only Every 17 Years?
Still from the film Deliverance, 1919. The story of Helen Keller and Anne Sullivan. View shows Keller in the cockpit/front seat of an airplane.
How Did Helen Keller Fly a Plane?
In this aerial photo, structures are damaged and destroyed October 15, 2005 in Balakot, Pakistan. It is estimated that 90% of the city of Balakot was leveled by the earthquake. The death toll in the 7.6 magnitude earthquake that struck northern Pakistan on October 8, 2005 is believed to be 38,000 with at least 1,300 more dead in Indian Kashmir. SEE CONTENT NOTES.
6 of the World’s Deadliest Natural Disasters
Two chicks near an egg with a white background (poultry, chick, chickens, birds).
What Do Eggs Have to Do with Easter?
Albert Einstein in Washington, D.C. c. 1921-1923. Physicist
The Solar Eclipse That Made Albert Einstein a Science Celebrity
United States Electoral College votes by state
How Many Electoral College Votes Does Each U.S. State Have?

In mammals, as in birds, the right and left ventricles of the heart are completely separated, so that pulmonary (lung) and systemic (body) circulations are completely independent. Oxygenated blood arrives in the left atrium from the lungs and passes to the left ventricle, whence it is forced through the aorta to the systemic circulation. Deoxygenated blood from the tissues returns to the right atrium via a large vein, the vena cava, and is pumped to the pulmonary capillary bed through the pulmonary artery. Among vertebrates contraction of the heart is myogenic, or generated by muscle; rhythm is inherent in all ...(100 of 10772 words)

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