[33] During the Permian period, synapsids, including the ancestors of mammals, dominated the land,[34] but most of this group became extinct in the Permian–Triassic extinction event 252 Ma. this.value = this.value.trim();
[20] The evolution of photosynthesis, around 3.5 Ga, eventually led to a buildup of its waste product, oxygen, in the atmosphere, leading to the great oxygenation event, beginning around 2.4 Ga.[21] The earliest evidence of eukaryotes (complex cells with organelles) dates from 1.85 Ga,[22][23] and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism.
e.preventDefault(); tooltip.className = '_error'; [49][53] While there is no direct evidence of conditions on Earth 4 to 3.8 Ga, there is no reason to think that the Earth was not also affected by this late heavy bombardment. var elem = allInputs[i]; Furthermore, if, as some physicists say, our universe is just one of many, and each universe contained a billion billion planets, then it's nearly a certainty that life will arise on at least one of them. var remove_tooltip = function(elem) { } [175][189], In aquatic algae, almost all cells are capable of photosynthesis and are nearly independent. [194][195] Its air-breathing, terrestrial nature is evidenced by the presence of spiracles, the openings to tracheal systems. The planet was molten hot and bombarded with incoming objects from space. var expireTime = time + 1000 * 60 * 60 * 24 * 365; [142] Another early multicellular fossil, Qingshania, dated to 1.7 Ga, appears to consist of virtually identical cells. window.cfields = []; Dissolving sugar in water2. [134] The hypotheses discussed above all depend on the possible beneficial effects of random genetic variation produced by genetic recombination. Land plants were so successful that they are thought to have contributed to the Late Devonian extinction event. if (no_error && /date_field/.test(elem.className)) {
who created us? err.parentNode.removeChild(err) : false; For nearly 4.5 billion years the story of earth goes. Simple algae and bacteria were thought to be the only organisms to live there.
script.charset = 'utf-8'; [220], While the archosaurs and dinosaurs were becoming more dominant in the Triassic, the mammaliaform successors of the therapsids evolved into small, mainly nocturnal insectivores. It is not to be confused with, "Prehistoric life" redirects here. tooltip.innerHTML = text; selected = false;
var regexStr = '[\?&]' + name + '=([^&#]*)'; Most of the steps required temperatures of about 100 °C (212 °F) and moderate pressures, although one stage required 250 °C (482 °F) and a pressure equivalent to that found under 7 kilometres (4.3 mi) of rock. elem.className = elem.className + ' _has_error'; Variant organisms will leave offspring like themselves. if (!no_error) { [170][171][172] Although the earliest good evidence of land plants and animals dates back to the Ordovician period (488 to 444 Ma), and a number of microorganism lineages made it onto land much earlier,[173][174] modern land ecosystems only appeared in the Late Devonian, about 385 to 359 Ma. func.apply(this, arguments);
var wrapper = document.createElement('div'); if (fieldVal) { } script.charset = 'utf-8'; tooltips.push(new_tooltip); // Site tracking URL to use after inline form submission. var elem = allInputs[i]; Some question whether life began on Earth at all, asserting instead that it came from a distant world or the heart of a fallen comet or asteroid. } if (!tooltips[i].no_arrow) resize_tooltip(tooltips[i]); As all of this was unfolding in the animal kingdom, plant species across the world were diversifying rapidly. } They retained aquatic, fry-like tadpoles, a system still seen in modern amphibians.
} addEvent(window, 'scroll', resize_tooltips); [7 Theories on the Origin of Life]. oldFunc.apply(this, arguments); return new_tooltip; if (typeof window._form_callback !== 'undefined') window._form_callback(id); e.preventDefault(); var elems = form_to_submit.elements[elem.name], found = false, err = []; for (var i = 0, len = allInputs.length; i < len; i++) { Soon after, the first vertebrates appear. } inner.innerHTML = text; var input = allInputs[i]; Tarnishing of Silver coated jewelry4. [79] The earliest "ribozymes" may have been formed of simpler nucleic acids such as PNA, TNA or GNA, which would have been replaced later by RNA. if (elem.tagName.toLowerCase() !== "select") { © return el.name == 'email' || el.getAttribute('required') !== null;
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