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Today, scientists agree that all current life descends from earlier life, which has become progressively more complex and diverse through Charles Darwin's mechanism of evolution by natural selection. Darwin wrote to J.D. Hooker on 29 March 1863 stating that "It is mere rubbish, thinking at present of the origin of life; one might as well think ...
The definition of life has long been a challenge for scientists and philosophers. [2] [3] [4] This is partially because life is a process, not a substance. [5] [6] [7] This is complicated by a lack of knowledge of the characteristics of living entities, if any, that may have developed outside Earth.
Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. [1] [2] Modern science is typically divided into two or three major branches: [3] the natural sciences (e.g., physics, chemistry, and biology), which study the physical world; and the social sciences (e.g., economics, psychology, and sociology), which ...
The first English use of the expression "meaning of life" appears in Thomas Carlyle's Sartor Resartus (1833–1834), book II chapter IX, "The Everlasting Yea". [1]Our Life is compassed round with Necessity; yet is the meaning of Life itself no other than Freedom, than Voluntary Force: thus have we a warfare; in the beginning, especially, a hard-fought battle.
Life arose from the Earth's first ocean, which formed some 3.8 billion years ago. [33] Since then, water continues to be the most abundant molecule in every organism. Water is important to life because it is an effective solvent , capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution .
The underlying theme of the essay is the need to teach biological evolution in the context of debate about creation and evolution in public education in the United States. [5] The fact that evolution occurs explains the interrelatedness of the various facts of biology, and so makes biology make sense. [6]
It supports the modern evolutionary synthesis—the current scientific theory that explains how and why life changes over time. Evolutionary biologists document evidence of common descent, all the way back to the last universal common ancestor , by developing testable predictions, testing hypotheses, and constructing theories that illustrate ...
Starting in 1985, researchers proposed that life arose at hydrothermal vents, [237] [238] that spontaneous chemistry in the Earth's crust driven by rock–water interactions at disequilibrium thermodynamically underpinned life's origin [239] [240] and that the founding lineages of the archaea and bacteria were H 2-dependent autotrophs that used ...