2 James Watson
James Watson is a geneticist, molecular biologist, and zoologist. He is credited with co-authoring the academic paper that propounded the double helix structure of nucleic acids such as DNA for which he was awarded the Nobel Prize in 1962. In 1977, he was honored with the Presidential Medal of Freedom. In 1997, he was awarded the National Medal of Science.
3 Terri Irwin
American–Australian naturalist Terri Irwin is best known as the co-host of The Crocodile Hunter, along with her husband, the late animal expert Steve Irwin. She has also been part of shows such as Croc Files and Crikey! It's the Irwins, and helped in the development of Australia Zoo.
4 Thomas Hunt Morgan
Thomas Hunt Morgan was an evolutionary biologist, geneticist, and embryologist. He won the Nobel Prize in Physiology or Medicine in 1933. He worked extensively on the role that the chromosome plays in heredity and demonstrated that genes are carried on chromosomes. In his later career, he established the division of biology at the California Institute of Technology.
5 Louis Agassiz
Louis Agassiz was a biologist and geologist. He was famous as a scholar of Earth's natural history. Born in Switzerland, he completed his education in Europe and emigrated to USA. He was appointed a professor of zoology and geology at Harvard University. He later founded the Museum of Comparative Zoology at the Lawrence Scientific School.
6 Walter Reed

7 Paul R. Ehrlich

Paul R. Ehrlich is a biologist best known for the 1968 book The Population Bomb, which he co-authored with his wife, Anne. He kindled controversy for his views on the consequences of population growth in a world with limited resources. He has been called an "irrepressible doomster” by his critics, while his supporters credit him for spreading concern about overpopulation.
8 Jim Fowler

9 Ernest Everett Just
Ernest Everett Just was an African-American biologist and academic. He is credited with recognizing the fundamental role of the cell surface in the development of organisms. As a black boy growing up in the late 19th century, he had to face enormous challenges before he could establish himself in his career. He co-founded the Omega Psi Phi Fraternity, Inc.
10 David Starr Jordan

Remembered as the first president of the Leland Stanford Junior University, now known as Stanford University, David Starr Jordan was a reputed ichthyologist. An anti-war activist, too, who opposed America’s participation in World War I, he spent his later years as the chief director of the World Peace Foundation.
11 Mary J Rathbun

12 Karl Patterson Schmidt

Karl Patterson Schmidt was a herpetologist. He studied biology and geology at Cornell University and realized his keen interest in herpetology. He later worked as a scientific assistant in herpetology at the American Museum of Natural History. He undertook many collecting expeditions for the Field Museum of Natural History in Chicago. He died after being bitten by a boomslang snake.
13 PZ Myers

PZ Myers is a biologist known for founding the Pharyngula science blog. His blog is one of the top-ranked blogs by a scientist. A "science geek" from an early age, he obtained a Ph.D. in biology from the University of Oregon. As an academician, he has taught at the University of Oregon, the University of Utah, and Temple University.
14 Jim Cronin

15 Dixie Lee Ray

16 Martin William Kratt

17 Robert T. Paine

18 Charles Henry Turner

19 Roger Tory Peterson

20 Edmund Beecher Wilson

Edmund Beecher Wilson was an American geneticist and zoologist. He is credited with writing a textbook titled The Cell which is widely regarded as one of the most influential and important books in modern biology. Regarded as America's first cell biologist, Wilson is also credited with discovering the XY sex-determination system which is used to classify several mammals, including humans.
21 James Dwight Dana

22 Spencer Fullerton Baird

23 Clinton Hart Merriam

24 Willy Burgdorfer

25 Thomas Say

26 Elliott Coues

Renowned ornithologist Elliott Coues, known for his pathbreaking written works such as Key to North American Birds, had established the American Ornithological Union. He had also previously worked as an army surgeon and later taught anatomy. He was also briefly part of the Theosophical Society, though he later lost interest.
27 Libbie Hyman

28 Ross Granville Harrison

29 Victor Ernest Shelford

30 Theophilus Painter

Zoologist Theophilus Painter made some groundbreaking studies on chromosomes, with special focus on the X and Y chromosomes and chromosomes of the salivary glands of the Drosophila fly. The Yale alumnus was associated with the University of Texas, where he eventually became the president.
31 Warder Clyde Allee

32 Frank Rattray Lillie

33 James Hall

Best known for his contribution to the geosynclinal theory of mountain building, paleontologist and geologist James Hall had also taught at the Rensselaer Polytechnic Institute and worked at the Geological Survey of New York. The National Academy of Sciences member had also penned works such as The Paleontology of New York.
34 Addison Emery Verrill

35 Orator F. Cook

36 Edwin Conklin

37 Alpheus Hyatt

Alpheus Hyatt was an American paleontologist and zoologist. He is credited with co-founding a scientific journal named The American Naturalist for which he served as the editor between 1867 and 1870. He also served as the professor of zoology and paleontology at the Massachusetts Institute of Technology where he taught for 18 years.
38 John Henry Comstock

39 Clarence Erwin McClung

40 Herbert Spencer Jennings

Renowned zoologist and geneticist Herbert Spencer Jennings is best known for his research on microorganisms and the genetic processes in single-celled organisms. The Harvard alumnus had also penned valuable texts such as Behaviour of the Lower Organisms and Life and Death: Heredity and Evolution in Unicellular Organisms.
41 Cornelia Clapp

42 Marston Bates

43 E. Newton Harvey

44 Oliver Perry Hay

Initially a professor of geology and biology at Butler University, Oliver Perry Hay later contributed immensely to catalogs on North American fossil vertebrates. He had also served as the associate curator of New York’s American Museum of Natural History. His son, too, grew up to be a zoologist.
45 Peter Marler

46 Geoffrey H. Bourne

Geoffrey H. Bourne was an Australian-American primatologist and anatomist. He is best remembered for his pioneering work in histochemistry. From 1962 to 1978, Bourne served as the director of Emory University's Yerkes National Primate Research Center. He also taught physiology and histology at Oxford University and the University of London respectively.
47 John Bachman

Lutheran minister and naturalist John Bachman is best known for his collaboration with John James Audubon to create a text on North American birds and mammals. His The Unity of the Human Race stated all humas arise from a single species. He preached to all, including African-American slaves.
48 Elwyn L. Simons

Regarded widely as the father of modern primate paleontology, Elwyn L. Simons, is best remembered for his discovery of the Aegyptopithecus, the earliest common forebear of man, apes, and monkeys. An enthusiastic wildlife conservationist, too, he worked for the preservation of rare primates such as lemurs and lorises.
49 William Keith Brooks

50 Charles Manning Child
