life

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Ability to grow, reproduce, and respond to such stimuli as light, heat, and sound. Life on Earth may have begun about 4 billion years ago when a chemical reaction produced the first organic substance. Over time, life has evolved from primitive single-celled organisms to complex multicellular ones. There are now some 10 million different species of plants and animals living on the Earth. The earliest fossil evidence of life is threadlike chains of cells discovered in 1980 in deposits in northwestern Australia; these ‘stromatolites’ have been dated as being 3.5 billion years old.

Biology is the study of living organisms – their evolution, structure, functioning, classification, and distribution – while biochemistry is the study of the chemistry of living organisms. Biochemistry is especially concerned with the function of the chemical components of organisms such as proteins, carbohydrates, lipids, and nucleic acids.

Life probably originated in the primitive oceans. The original atmosphere, 4 billion years ago, consisted of carbon dioxide, nitrogen, and water. Laboratory experiments have shown that more complex organic molecules, such as amino acids and nucleotides, can be produced from these ingredients by passing electric sparks through a mixture. The climate of the early atmosphere was probably very violent, with lightning a common feature, and these conditions could have resulted in the oceans becoming rich in organic molecules, producing the so-called ‘primeval soup’. These molecules may then have organized themselves into clusters capable of reproducing and eventually developing into simple cells. Soon after life developed, photosynthesis would have become the primary source of energy for life. By this process, life would have substantially affected the chemistry of the atmosphere and, in turn, that of its own environment. Once the atmosphere had changed to its present composition, life could only be created by the replication of living organisms (a process called biogenesis).

Blue symbolizes hope, the clear sky, and the streams of the south. Yellow stands for the sun and the Sahara Desert. Red represents unity, prosperity, and national sacrifice. Effective date: 6 November 1959. >>