Discovery School - 100 Greatest Discoveries - Genetics
1. Rules of Heredity (1850s) Austrian monk and botanist Gregor Mendel discovers how genetic information is passed down through generations. In experiments performed on pea plants, he notices that characteristics of a plant's offspring, such as height, exhibit recessive and dominant behavior. Mendel's findings are ridiculed during his lifetime and he dies never knowing that he would come to be known as the "father of genetics."
2. Genes Are Located on Chromosomes (1910 – 1920s)
Discovery School - 100 Greatest Discoveries - Evolution
1. K-T Asteroid Theory of Dinosaur Extinction (1980) Walter Alvarez postulates that high levels of iridium found in rock core samples around the world provide evidence that an asteroid impact caused the extinction of dinosaurs. Iridium, a common mineral found in asteroids, was discovered in the clay layer at what is known as the K-T boundary. This layer, at 65 million years, lies between the rocks of the Cretaceous and the Tertiary periods and coincides with the mass extinction of dinosaurs.
2. First Dinosaur Fossils Identified (1820s – 1840s)
Discovery School - 100 Greatest Discoveries - Earth Science
1. Earth's Core (1906) Seismologist Richard Oldham determines that earthquake waves move through the central part of the Earth much slower than through the mantle around it. He surmises that the Earth has a core composed of liquid.
2. Earth's Inner Core (1930s) In 1936, Inge Lehmann documents that some seismic waves from deep inside the Earth's core do not pass through, but are reflected back. It becomes clear that the Earth has an inner core consisting of a small, solid iron sphere that is surrounded by a thick outer core composed of liquid iron.
Discovery School - 100 Greatest Discoveries - Chemistry
1. Oxygen (1770s) Joseph Priestley discovers oxygen; later, Antoine Lavoisier clarifies the nature of elements. Priestley produces oxygen in experiments and describes its role in combustion and respiration. Then, by dissolving fixed air in water, he invents carbonated water. Priestley, oblivious to the importance of his discovery, calls the new gas "dephlogisticated air." Lavoisier gives oxygen its name and correctly describes its role in combustion.
