Short answers, pulled from the story.
Scientists have compiled at least 123 different definitions of life, yet no single description satisfies every case. These definitions list characteristics like homeostasis, organization, metabolism, growth, adaptation, response to stimuli, and reproduction. Most current biological definitions remain descriptive rather than prescriptive.
Life on Earth has existed for at least 3.5 billion years according to physical traces found in ancient rocks. The oldest evidence includes biogenic graphite discovered in 3.7 billion-year-old metasedimentary rocks from Western Greenland. Molecular clocks place the origin of life around 4.0 billion years ago based on data from the TimeTree public database.
All life forms require core chemical elements including carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. Carbon is the most abundant element in organisms and forms multiple stable covalent bonds. DNA carries most genetic instructions used in growth, development, functioning, and reproduction of known living organisms.
Empedocles argued in 430 BC that everything in the universe consists of four eternal elements: earth, water, air, and fire. Aristotle expressed hylomorphism in 322 BC, asserting that living things embody both form and matter. He proposed three kinds of souls: vegetative for plants, animal for movement and sensation, and rational for consciousness found only in humans.
The biosphere encompasses all ecosystems including soil, hot springs, deep ocean subsurfaces, and atmospheric layers up to 77 kilometers high. Spores of Aspergillus niger have been detected in the mesosphere at altitudes between 48 and 77 kilometers. Expeditions of the International Ocean Discovery Program found unicellular life in sediment reaching 120 degrees Celsius located 1.2 kilometers below the seafloor in the Nankai Trough subduction zone.