O. C. Marsh discovers the first North American pterosaur, from chalk deposits in Kansas. He calculates the wingspan at 20 feet. The following year, he will collect more fossils that confirm this calculation.

Quarry workers in the Valley Forge area discover the Port Kennedy Bone Cave, under roughly the same site where the Continental Army wintered over a century earlier. The site proves rich in Pleistocene plant and animal fossils, but will be accidentally flooded decades later. The site will be lost to science until its rediscovery after the turn of the 21st century.

The rivalry between fossil collectors O. C. Marsh and E. D. Cope turns ugly when Marsh publicly points out Cope's error in reconstructing a fossil marine reptile (putting its head on the tip of its tail). Their rivalry is the public's gain as they try to outdo each other in identifying new dinosaur species — over 130.

Publication of Charles Darwin's Descent of Man, in which the role of sexual selection in evolution is described for the first time.

Lord Kelvin suggests that "the germs of life might have been brought to the Earth by some meteorite," an idea that will enjoy support a century later.

Johann Friedrich Miescher isolates a substance which he calls NUCLEIN from the nuclei of white blood cells. The substance was soluble in alkalis but not in acids and came to be known as nucleic acid.

Lambert Adolphe Jacques Quetelet showed the importance of statistical analysis for biologists and laid the foundation of biometry.

George Johnstone Stoney notes that the wavelengths of three lines in the hydrogen spectrum are found to have simple ratios, and anticipation of Balmer's formula, an important step towards understanding the structure of the atom.

James Clerk Maxwell explains how his statistical theory of heat works by inventing MAXWELL'S DEMON, a mythical creature that can see and handle individual molecules. By opening a gate between two vessels containing a gas only one of fast molecules passing into one, the demon would make heat flow from cold to hot.

Ferdinand Julius Cohn coined the term BACTERIUM and founded the study of bacteriology.

Anton Schneider observed and described the behavior of nuclear filaments (chromosomes) during cell division in his study of the platyhelminth Mesostoma. His account was the first accurate description of the process of mitosis in animal cells.

Francis Galton publishes a paper entitled "Hereditary Improvement" arguing that people "of really good breed" should be encouraged to reproduce while their inferiors should be discouraged from doing so. This, he argues, will improve humanity the way selective breeding improves livestock.

James Clerk Maxwell's Electricity and Magnetism contains the basic laws of electromagnetism and predicts, in great detail, such phenomena as radio waves and pressure caused by light rays.

The Hamburg Tierpark features an "anthropological-zoological" display of Lapps acting out "daily life" with reindeer. The show draws enthusiastic crowds.

The Mütter Museum buys 139 human skulls from Viennese anatomist Joseph Hyrtl. Hyrtl has compiled the collection to show the remarkable variation within European populations, and to debunk the claims of phrenologists. The collection is unusual for the time, when most skull assemblages are aimed at emphasizing differences between ethnic groups.

Irish physicist George J. Stoney estimates the charge of the then unknown electron to be about 10^-20 coulomb, close to the modern value of 1.6021892 x 10^-19. He also introduces the term ELECTRON.

The Cavendish laboratory at Cambridge is completed. Although widely believed to have been named after the 18th-century physicist Henry Cavendish, it is, in fact, named after the entire Cavendish family, because the 19th century steel-making descendent of Henry, William Cavendish, financed the laboratory. The structure of DNA was worked out at the Cavendish many years later by Watson and Crick.

Eduard Strasburger accurately described the processes of mitotic cell division in plants.

Francis Galton demonstrates the usefulness of twin studies for elucidating the relative influence of nature (heredity) and nurture (environment) upon behavioral traits.

Oscar Hertwig concludes from a study on sea urchins that fertilization in both animals and plants consists of the physical union of the two nuclei contributed by the male and female parents.

Paleontologist Roberto Lawley collects a badly eroded Pliocene whale bone near Pisa, Italy, and donates it to the paleontology museum of Florence. In the 21st century, close examination will indicate boreholes of Osedax, mouthless, gutless marine worms (nicknamed zombie worms) that extract nutrients by drilling into bones.

Charles Doolittle Walcott becomes the first to successfully find and describe elusive trilobite legs, ending speculation about how the animals moved.

Eugen Goldstein shows that the radiation in a vacuum tube produced when an electric current is forced through the tube starts at the cathode. Goldstein introduces the term CATHODE RAY to describe the light emitted.

Hermann Fol reports watching the spermatozoan of a starfish penetrate the egg. He was able to see the transfer of the intact nucleus of the sperm into the egg, where it became the male pronucleus.

A new Archaeopteryx fossil is discovered in Solnhofen, complete with a toothy jaw. This well-preserved fossil, which will become known as the Berlin Archaeopteryx, supports Huxley's previous observations about its reptilian affinities.

Comparative anatomy professor François Louis Paul Gervais undertakes thin-section microscopy studies of fossil eggs. His work will be largely forgotten until Roy Chapman Andrews discovers dinosaur eggs in Mongolia in the 1920s.

Germ Theory of Disease: Louis Pasteur presented his Germ Theory of disease. Joseph Lister went on to initiate the practice of insuring that surgeons were clean before they conducted surgery.

Wilhelm Friedrich Kühne proposed the term ENZYME (meaning "in yeast") and distinguished enzymes from the micro-organisms that produce them.

Charlotte Hill collects a well-preserved fossil butterfly, later named Prodryas persephone, from the Florissant Formation in Colorado. The fossil is about 35 million years old.

Entire skeletons of Iguanodon are discovered in Belgium, enabling a more accurate reconstruction of this dinosaur than those of Owen and Waterhouse Hawkins in the 1850s. Engineer-turned-paleontologist Louis Dollo will publish the first of several papers on these fossils in 1882.

From 1879 through 1882, Walther Flemming describes and names CHROMATIN, MITOSIS, and the SPIREME. He makes the first accurate counts of chromosome numbers and accurately drew the "longitudinal splitting" of chromosomes.

Eight-year-old Maria de Sautuola finds a Paleolithic cave drawing of bison on her father's property in Spain. It is the oldest artwork yet discovered, but it will be dismissed as a forgery for years, considered too beautiful to be the work of prehistoric savages.

Charles Lapworth resolves a priority dispute between Adam Sedgwick and Roderick Murchison by assigning older rocks to the Cambrian (named by Sedgwick), younger rocks to the Silurian (named by Murchison), and naming the Ordivician System in between.

The United States Geological Survey is formed.