Animal life on earth

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How did animal life on earth begin? Fossils found in Canada may have answers

Animal Life on Earth. Get details here…

Friday, 30th July 2021

Fossils found in the rugged and mountainous terrain of northwestern Canada may give us a glimpse of the dawn of animal life in the Earth’s sponges, which inhabited primitive coral reefs built by bacteria about 890 million years ago.

A Canadian researcher said on Wednesday that these fossils dating back to the Neoproterozoic period seem to show the unique microstructure of the body of a marine sponge, similar in structure to a species called Mediterranean bath sponge or sponge living today.

If this explanation is correct, it will be the oldest animal fossil about 300 million years old.

"The earliest evolutionary animal may be furry. Considering that sponges are the most basic animal type in the fossil record today, this is not surprising," said Elizabeth Turner, a geologist at Laurentian University in Canada. This research was published in the journal Nature.

The earth was formed more than 4.5 billion years ago. The first life forms were single-celled marine organisms that resemble bacteria that appeared hundreds of millions of years later. Complex life evolved relatively late in earth's history.

The time and form of the first appearance of primitive animals have always been a controversial subject. A mysterious ribbed pancake-like creature called Dickinsonia, known from fossils about 575 million years ago, is considered a candidate to be the oldest known animal.

"The existence of a long-term history is not surprising, but for some researchers, its duration of hundreds of millions of years can be a bit unexpected," said Turner.

When people think of animals, they may not immediately think of sponges. But sponge aquatic invertebrates are one of the most successful groups of animals that fixate on the seafloor and have soft, porous internal bodies and bones.

"They lack nerves, digestion, and circulatory systems. They have an amazing pump, produced by specialized cells, and they use it to move seawater through their bodies to filter food," Turner said.

The skeleton of some sponges is made of microscopic rods of quartz or calcite. Other people’s bones are made of a tough protein called a sponge, forming a complex three-dimensional network that supports the animal’s soft tissues. Canadian fossils represent the latter type and are called horny sponges.

"This is the remnant structure of the 3D mesh sponge skeleton. It has been preserved and is so unique," Turner said.

This structure visible under the microscope consists of small tubes that bifurcate and reconnect to form a network. The main size of the sponge is approximately one-tenth of an inch (1 cm). Turner said these sponges appear to live in caves and shallow depressions below the surface of the coral reef.

If these fossils actually show a sponge, their age would indicate that the first animals on Earth evolved before a couple of iconic events that are generally considered to predate animal life. One of them is the second of two events in Earth's history, when the oxygen content in the atmosphere increased dramatically, sometime between 830 and 540 million years ago. The other is a very cold period in which the earth may be frozen or at least partially frozen, sometime between 720 and 635 million years.

These fossils are about 350 million years older than the oldest known sponge fossils. Turner noted that genetic studies have shown that sponges first appeared around the age of these fossils.


The News Talkie Bureau



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