After first emerging from the primordial soup, life remained primitive and single-celled for billions of years, but some of those cells eventually congregated like clones in a colony. But at some point there was a leap — arguably second in importance only to the appearance of life itself — towards complex organisms with multiple cells.
This transition progressively gave rise to all the plants and animals that have ever existed. The fossils were uncovered in the Yanshan region of Hebei province in China.
Zhu and colleagues said they had found measurable fossils, a third of them in one of four regular shapes — an indication of complexity. The largest measured 30cm by 8cm. Their very existence 1. But how long it took this vital communion to take hold in the evolutionary process is unknown.
As Bengtson points out, whereas red algae are not a direct precursor to plants—that honor belongs to green algal ancestors—they do closely descend from one common ancestor of all plants on Earth today. Assuming the new findings are true, a major question now facing paleobotanists is why it took another billion years for larger, more complex organisms to flourish.
It was not until between million and million years ago that higher plants and animals began evolving. Submarine algae, bobbing amid blankets of microbes, gradually gave way to what we know as plants.
Plants made their way to shore, shaping a new landscape that would come to include complex fungi and, eventually, terrestrial animals. Bengtson hopes to further study early algal populations in order to better pinpoint where and when they arose, and why they lingered in the sea for so long. He graduated from the University of Virginia School of Medicine in Already a subscriber?
Sign in. Thanks for reading Scientific American. These early environmental engineers disturbed and maybe aerated the sediment, disrupting conditions for other Ediacaran animals. As environmental conditions deteriorated for some animals, they improved for others, potentially catalyzing a change-over in species. The Cambrian Period 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 and tails for directional movement to chase prey. Active feeding by well-armored animals like trilobites may have further disrupted the sea floor that the soft Ediacaran creatures had lived on. Unique feeding styles partitioned the environment, making room for more diversification of life.
While Waptia scoured the ocean bottom, priapulid worms burrowed into the sediment, Wiwaxia attached to sponges, and Anomalocaris cruised above. Many of these odd-looking organisms were evolutionary experiments, such as the 5-eyed Opabinia. However, some groups, such as the trilobites, thrived and dominated Earth for hundreds of millions of years but eventually went extinct. Stromatolite reef-building bacteria also declined, and reefs made by organisms called brachiopods arose as conditions on Earth continued to change.
However, despite all the changes that were to come, by the end of the Cambrian nearly all existing animal types, or phyla, mollusks, arthropods, annelids, etc. Skip to main content. Smithsonian Institution. Early Life on Earth — Animal Origins. An Oxygen Atmosphere When cyanobacteria evolved at least 2.
Multicellular Life However, other innovations were occurring. The First Animals These clusters of specialized, cooperating cells eventually became the first animals , which DNA evidence suggests evolved around million years ago. Ediacaran Biota By about million years ago the Ediacaran Period there was a proliferation of other organisms, in addition to sponges.
The End-Ediacaran Extinction However, about 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. The Cambrian Explosion The Cambrian Period million years ago witnessed a wild explosion of new life forms. Related Resources. Video: The Cambrian Explosion of Life. Science Literacy - What Is Biodiversity?
Video: The Oldest Animal Fossils. Science Literacy: Extinction Over Time.
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