Photosynthesis More recent studies, reported in March 2018, also suggest that photosynthesis may have begun about 3.4 billion years ago. The main source of oxygen in the Earth's atmosphere derives from oxygenic photosynthesis, and its first appearance is sometimes referred to as the oxygen catastrophe. Geological evidence suggests that oxygenic photosynthesis, such as that in cyanobacteria, became important during the Paleoproterozoic era around 2 billion years ago. Modern photosynthesis in plants and most photosynthetic prokaryotes is oxygenic. Oxygenic photosynthesis uses water as an electron donor, which is oxidized to molecular oxygen () in the photosynthetic reaction center. Several groups of animals
Need for achievement do) assess such things as "creativity" in any general sense. One has always to ask "creativity in relation to what?" So McClelland's measures, originally presented as means of assessing "personality", are best understood as means of measuring competence in ways which break radically with traditional psychometric approaches. Everybody has different goals and needs for achievement based off many factors like past experiences, education, the risks, and the feedback they will receive. Need for achievement Need for achievement (N-Ach) refers to an individual's desire for significant accomplishment, mastering of skills, control, or high standards. The term was first used by Henry