WhoAwee.com - Free Online Discovery in Biology for Kids

Microscope lens grinder Anton Van Leeuwenhoek accidentally discovers microorganisms in a drop of water. Using his own microscopes, he observes sperm, bacteria and red blood cells. His observations lay the foundation for the sciences of bacteriology and microbiology.

The Cell Nucleus (1831)

While studying an orchid, botanist Robert Brown identifies a structure within the cells that he terms the "nucleus."

Archaea (1977)

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon. Carl Woese discovers bacteria are not the only simple-celled prokaryotes (unicellular organisms without a nucleus) on Earth.

Cell Division (1879)

Walther Flemming carefully observes that animal cells divide in stages and calls the process mitosis. Eduard Strasburger independently identifies a similar process of cellular division in plant cells.

Sex Cells (1884)

August Weismann identifies that sex cells must have divided differently to end up with only half of a chromosomal set. This very special division of sex cells is called meiosis. Weismann's experiments with reproduction in jellyfish lead him to the conclusion that variations in offspring result from the union of a substance from the parents. He refers to this substance as "germ plasm."

Cell Differentiation (late 19th century)

Several scientists participate in the discovery of cell differentiation, eventually leading to the isolation of human embryonic stem cells.. Cells that are not yet differentiated and have the potential to become any type of cell are called stem cells.

Mitochondria (late 19th century to the present)

Scientists discover mitochondria, the powerhouses of the cell. These small structures within animal cells are responsible for metabolism and convert food into chemicals that cells can use. Originally thought to be part of the cell, scientists now believe they are specialized bacteria with their own DNA.

The Krebs Cycle (1937)

Hans Krebs identifies the many steps the cell takes to convert sugars, fats and proteins into energy. Also known as the citric acid cycle, it is a series of chemical reactions using oxygen as part of cellular respiration. The cycle contributes to the breakdown of carbohydrates, fats and proteins into carbon dioxide and water.

Neurotransmission (late 19th to early 20th century)

Scientists discover neurotransmitters and how they tell the body what to do by passing signals from one nerve cell to another via chemical substances or electrical signals.

Hormones (1903)

William H. Bayliss and Ernest H. Starling give hormones their name and reveal their role as chemical messengers. The team specifically describes secretin, a substance released into the blood from the duodenum (between the stomach and small intestine) that stimulates secretion of pancreatic digestive juice into the intestine.

Photosynthesis (1770s)

Jan Ingenhousz discovers that plants react to sunlight differently than shade. Photosynthesis is a process in which plants, algae and certain bacteria convert the energy of light into chemical energy. In plants, leaves take in carbon dioxide and roots absorb water. Sunlight runs a reaction that yields glucose (food for the plant) and oxygen (a waste product released into the environment). Nearly all living things on Earth are ultimately dependent on this process.

Ecosystem (1935)

Arthur George Tansley coins the term ecosystem and single-handedly bridges the biology in ecology with the physics, chemistry and other fields of science that describe the environment. An ecosystem is defined as a dynamic and complex whole that functions as an ecological unit.

Tropical Biodiversity: (15th century to the present)

On sailing expeditions around the world, early European explorers notice that the tropics host a much greater variety of species. Answering why this is the case allows today's scientists to help protect life on Earth.

Genes Are Located on Chromosomes (1910 – 1920s)

Thomas Hunt Morgan discovers that genes are located on chromosomes.

Genes Control Biochemical Events (1930)

George Beadle and Edward Tatum discover through experiments on neurospora, a bread mold, that genes are responsible for the production of enzymes. Their report is the genesis of the "one gene-one enzyme" concept.

Some Genes Can Jump (1940)

Barbara McClintock discovers transposons — genes that can jump on a chromosome — while seeking to explain color variations in corn.

DNA Is the Genetic Material (1928, 1944, 1952)

Several scientists prove that DNA is the chemical basis of genetic information. Oswald Avery proves that DNA carries genetic information.

DNA Is a Double Helix (1953)

James Watson and Francis Crick describe the DNA molecule. The scientists suggest that the DNA molecule is made of two chains of nucleotides, each in a helix, one going up and the other going down.