When did life on Earth first appear?
Life on Earth ignited over 3.7 billion years ago, emerging from the planet's first oceans in a process that remains one of science's greatest mysteries.
Common questions about Biology
Short answers, pulled from the story.
Who discovered the cell and when was cell theory established?
Anton van Leeuwenhoek improved the microscope in the 17th century to reveal microscopic life, and Matthias Schleiden and Theodor Schwann proposed the cell is the basic unit of all organisms by 1838. Robert Remak and Rudolf Virchow proved that cells arise only from other cells in the 1860s, making cell theory universally accepted.
When was the structure of DNA discovered and who discovered it?
James Watson and Francis Crick discovered the double-helical structure of DNA in 1953, marking the transition to the era of molecular genetics. This discovery built upon Gregor Mendel's work from 1865, which outlined the principles of biological inheritance.
When was Charles Darwin's theory of natural selection published?
Charles Darwin published his theory of natural selection in 1859, providing the unifying framework for understanding how life changes over time. Alfred Russel Wallace independently reached similar conclusions, and the modern synthesis of the early 20th century reconciled Darwinian evolution with classical genetics.
What percentage of all living mass is made of chemical elements?
Oxygen, carbon, hydrogen, and nitrogen account for 96 percent of all living mass. These simple chemical elements combined to form water and organic compounds that could arise spontaneously under early Earth conditions.