In one to two billion years the sun will be so hot that all ice on earth will melt again, forming boiling oceans and an atmosphere composed mostly of water vapor. As the sun becomes even hotter in two billion years all water on earth will eventually evaporate and lost into space forever. The surface will become a dry desert, too hot and unhabitable for life.
The interior of earth, now completely solidified and inactive, will become too cold to provide energy or nutrients for the last existing life forms hidden underground. This is a BETA experience. You may opt-out by clicking here. More From Forbes. Jul 23, , am EDT. Jul 15, , am EDT. Jul 8, , am EDT. Jul 1, , am EDT. Jul 20, , am EDT. Microbes are just single cells with no organelles and no nuclei to package their DNA. Something revolutionary happened as microbes began living inside other microbes, functioning as organelles for them.
Mitochondria, the organelles that process food into energy, evolved from these mutually beneficial relationships. Also, for the first time, DNA became packaged in nuclei.
Cells also began living together, probably because certain benefits could be obtained. Groups of cells might be able to feed more efficiently or gain protection from simply being bigger. Living collectively, cells began to support the needs of the group by each cell doing a specific job. Some cells were tasked with making junctions to hold the group together, while other cells made digestive enzymes that could break down food. These clusters of specialized, cooperating cells eventually became the first animals , which DNA evidence suggests evolved around million years ago.
Sponges were among the earliest animals. While chemical compounds from sponges are preserved in rocks as old as million years, molecular evidence points to sponges developing even earlier. Oxygen levels in the ocean were still low compared to today, but sponges are able to tolerate conditions of low oxygen.
They feed while sitting still by extracting food particles from water that is pumped through their bodies by specialized cells. The simple body plan of a sponge consists of layers of cells around water-filled cavities, supported by hard skeletal parts. The evolution of ever more complex and diverse body plans would eventually lead to distinct groups of animals.
Some genes act like orchestra conductors, controlling the expression of many other genes at specific places and times to correctly assemble the components. While they were not played out immediately, there is evidence that parts of instructions for complex bodies were present even in the earliest animals.
Thanks to their hard skeletons, sponges became the first reef builders on Earth. Klaus Ruetzler are working to understand the evolution of the thousands of sponge species living on Earth today.
By about 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 body plans of most Ediacaran animals did not look like modern groups. Douglas Erwin , using comparative developmental evidence, has examined whether any of the fossilized Ediacaran animals were related to modern animals. By the end of the Ediacaran, oxygen levels rose, approaching levels sufficient to sustain oxygen-based life. The early sponges may actually have helped boost oxygen by eating bacteria, removing them from the decomposition process. Tracks of an organism named Dickinsonia costata suggest that it may have been moved along the sea bottom, presumably feasting on mats of microbes.
They calculated that Earth's habitable-zone lifetime is as long as 7. Earth is estimated to be about 4. Meanwhile, the other planets had habitable-zone lifetimes ranging from 1 billion years to While other models have been developed for Earth, they are not suitable for other planets, he added.
Original article published on LiveScience. Live Science.
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