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The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day ...
Sep 19, 2022 · Earth is about 4.5 billion years old. Scientists think that by 4.3 billion years ago, Earth may have developed conditions suitable to support life. The oldest known fossils, however, are only 3.7 billion years old. During that 600 million-year window, life may have emerged repeatedly, only to be snuffed out by catastrophic collisions with ...
Aug 2, 2024 · Life - Evolution, History, Earth: The evidence is overwhelming that all life on Earth has evolved from common ancestors in an unbroken chain since its origin. Darwin’s principle of evolution is summarized by the following facts. All life tends to increase: more organisms are conceived, born, hatched, germinated from seed, sprouted from spores, or produced by cell division (or other means ...
The timeline of the evolutionary history of life represents the current scientific theory outlining the major events during the development of life on planet Earth.Dates in this article are consensus estimates based on scientific evidence, mainly fossils.
- In The Beginning
- An Oxygen Atmosphere
- Multicellular Life
- The First Animals
- Ediacaran Biota
- The End-Ediacaran Extinction
- The Cambrian Explosion
Today we take for granted that we live among diverse communities of animals that feed on each other. Our ecosystems are structured by feeding relationships like killer whales eating seals, which eat squid, which feed on krill. These and other animals require oxygen to extract energy from their food. But that’s not how life on Earth used to be. With...
When cyanobacteria evolved at least 2.4 billion years ago, they set the stage for a remarkable transformation. They became Earth’s first photo-synthesizers, making food using water and the Sun’s energy, and releasing oxygen as a result. This catalyzed a sudden, dramatic rise in oxygen, making the environment less hospitable for other microbes that ...
However, other innovations were occurring. While they can process lots of chemicals, microbes did not have the specialized cells that are needed for complex bodies. Animal bodies have various cells – skin, blood, bone – which contain organelles, each doing a distinct job. Microbes are just single cells with no organelles and no nuclei to package th...
These clusters of specialized, cooperating cells eventually became the first animals, which DNA evidence suggests evolved around 800 million years ago. Spongeswere among the earliest animals. While chemical compounds from sponges are preserved in rocks as old as 700 million years, molecular evidence points to sponges developing even earlier. Oxygen...
By about 580 million years ago (the Ediacaran Period) there was a proliferation of other organisms, in addition to sponges. These varied seafloor creatures - with bodies shaped like fronds, ribbons, and even quilts - lived alongside sponges for 80 million years. Their fossil evidence can be found in sedimentary rocks around the world. However, the ...
However, about 541 million years ago, most of the Ediacaran creatures disappeared, signaling a major environmental change that Douglas Erwin and other scientists are still working to understand. Evolving animal body plans, feeding relationships, and environmental engineering may have played a role. Burrows found in the fossil record, dating to the ...
The Cambrian Period (541-485 million years ago) witnessed a wild explosion of new life forms. Along with new burrowing lifestyles came hard body parts like shells and spines. Hard body parts allowed animals to more drastically engineer their environments, such as digging burrows. A shift also occurred towards more active animals, with defined heads...
Jul 14, 2009 · Life Timeline: The evolution of life. The story of evolution spans over 3 billion years and shows how microscopic single-celled organisms transformed Earth and gave rise to complex organisms like ...
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Mar 8, 2024 · 2. Brought to Earth by outer space. Amino acids, as well as some of the other key building blocks of life such as carbon and water, may have been brought to early Earth from outer space, according ...
