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And yet infinity does play a major role in some important views of the natural world. One need only recall that one of the most crucial transformations from the old to the new science was described as a turn from a closed world to an infinite universe. 1 The story of the role this transformation played in the scientific revolution (in the 16th and 17th centuries), as well as its impact on ...
- In The Beginning
- Phanerozoic Diversity of Life
- Further Reading and Resources
Conditions for first life
No one can say exactly when and where life began on Earth, but it is certain that the origin of life is one of the most critical, planet-changing events ever to occur. Based on scientific observation and reasoning, theories have been developed to explain the ideal conditions that allowed life to start. Conventional scientific thought suggests that extreme heat from formational, early meteoritebombardment of Earth during the Hadean would have made conditions at the surface too harsh for life t...
The prokaryotic pioneers
So the first life forms on Earth were likely sulfur-reducing bacteria, which are prokaryotes. Prokaryotes are structurally rather simple–they are single-celled, small in size (0.1 – 10.0 μm), and have no nucleus or other organelles. Make no mistake though, these simple organisms have changed the trajectory of Earth’s history in major ways. To quote Shakespeare, “Though she be but little, she is fierce!” Two of the three Domains of life, Archaea and Bacteria, are prokaryotes. The third Domain,...
Eukaryotes: one small step for cells, one giant leap for life
A consistent pattern that we see in the rock record is that life modifies Earth systems, and Earth systems, in turn, modify life. The accumulation of oxygen in the atmosphere due to prokaryotic photosynthesis ultimately created a new resource that life could exploit as a source of energy. Around 1.8 billion years ago (Paleoproterozoic), definitive eukaryotes appear in the fossil record, armed with a new method of making energy for cellular function–aerobic respiration. Aerobic respiration req...
Before and after: the exoskeleton appears
One of the most fascinating aspects of Earth history is the diversification of life through time. There are many ways to graphically represent this diversification. The “tree of life” diagram is one way to broadly represent phylogenetic relationships of the three major Domains of life, including the Archaea, Bacteria, and Eukarya. Within each of these main stems, further distinctions can be made as organisms are grouped with others that share similar physical traits, as discussed in the cladi...
Here come the plants: landward, ho!
As human animals, we tend to focus on the parts of Earth history that tell our story; however, animals are not the only life form that moved to land during the Paleozoic, and in fact, plantsbeat our ancestors to the punch. The first multicellular plants are marine green and red algaes that were likely derived from photosynthetic cyanobacteria during the Neoproterozoic. The first land plants evolved around the early Ordovician, when fossil evidence of the first bryophytes are found. Bryophytes...
Next up: invertebrate animals invade terrestrial environments
Invertebrate groups diversified significantly throughout the Paleozoic oceans (see diversity section below), increasing the competition for resources. As time went by, there was an increase in ecological tiering above and below the seafloor, as animals evolved forms that allow for deeper burrowing and higher extension away from the sediment-water interface. It was only a matter of time until life found a way to exploit the vast expanse of geographic space on land. This transition to land is t...
Buatois, L.A. and Buatois, L.A. 2016. “Ediacaran Ecosystems and the Dawn of Animals,” in Mángano, M.G. and Buatois, L.A. (eds.) The Trace-Fossil Record of Major Evolutionary Events.Topics in Geobi...Wei-Hass, M. 2018. “World’s Oldest Fossils May Just Be Pretty Rocks,” National Geographic.Knoll, A. H. 2015. Life on a Young Planet: The First Three Billion Years of Evolution on Earth. Princeton University Press.The Gaia hypothesis (/ ˈ ɡ aɪ. ə /), also known as the Gaia theory, Gaia paradigm, or the Gaia principle, proposes that living organisms interact with their inorganic surroundings on Earth to form a synergistic and self-regulating complex system that helps to maintain and perpetuate the conditions for life on the planet.
- Lisa Bartee, Walter Shriner, Catherine Creech
- 2017
- Order. Organisms are highly organized, coordinated structures that consist of one or more cells. Even very simple, single-celled organisms are remarkably complex: inside each cell, atoms make up molecules; these in turn make up cell organelles and other cellular inclusions.
- Sensitivity or Response to Stimuli. Organisms respond to diverse stimuli. For example, plants can bend toward a source of light, climb on fences and walls, or respond to touch (Figure 2).
- Reproduction. Single-celled organisms reproduce by first duplicating their DNA, and then dividing it equally as the cell prepares to divide to form two new cells.
- Growth and Development. All living things increase in size and/or change over their lifespan. For example, a human grows from a baby into an adult and goes through developmental processes such as puberty.
For him, organism referred to an organizational principle rather than a particularily biological sort of stuff: “Organism, that is to say order and artifice, is something essential to matter, produced and arranged by the sovereign wisdom.” (Leibniz, Philosophical Letters, vol III, ed C.I. Gerhardt, p.340). Living beings were thus subjected to a particular variety of mechanism, which ...
Organisms are able to maintain internal conditions within a narrow range almost constantly, despite environmental changes, through homeostasis (literally, “steady state”)—the ability of an organism to maintain constant internal conditions. For example, an organism needs to regulate body temperature through a process known as thermoregulation.
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Feb 28, 2021 · Energy Processing. Contributors and Attributions. All living organisms share several key characteristics or functions: order, sensitivity or response to the environment, reproduction, growth and development, regulation, homeostasis, and energy processing. When viewed together, these characteristics serve to define life.
