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Oldest ancestor of all animals

Date: 26 March 2020 Tags: Biodiversity

Issue

A team of geologists have discovered a tiny, wormlike creature, named Ikaria wariootia that is believed to be the first ancestor on the family tree that contains most familiar animals today, including humans.

 

Background

Ikaria wariootia- a wormlike creature is the earliest bilaterian, or organism with a front and back, two symmetrical sides, and openings at either end connected by a gut.

 

Details

  • The development of bilateral symmetry was a critical step in the evolution of animal life, enabling living beings to move intentionally and a simple yet effective approach to organize their bodies.

  • A large number of animals, from worms to insects to dinosaurs to humans, are organized around this same basic bilaterian body plan.

  • Evolutionary biologists considering the genetics of modern animals predicted the oldest ancestor of all bilaterians would have been small and straightforward, with rudimentary sensory organs. Preserving and distinguishing the fossilized remains from such an animal was believed to be troublesome, if certainly feasible.

  • Scientists agreed that fossilized burrows found in 555 million-year-old Ediacaran Period deposits in Nilpena, South Australia, were made by bilaterians. But there was no sign of the animal that made the burrows.

  • Scientists used a three-dimensional laser scanner that revealed the regular, consistent shape of a cylindrical body with a distinct head and tail and faintly grooved musculature.

  • The animal ranged between 2-7 millimeters long and about 1-2.5 millimeters wide, with the largest size and shape of a grain of rice.

  • Ikaria was complex contrasted with different fossils from this period. It burrowed in thin layers of very well-oxygenated sand on the ocean floor looking for organic matter, showing rudicating sensory abilities.

  • The burrows also preserve crosswise, “V”- shaped ridges, suggesting Ikaria moved by contracting muscles across its body like a worm, known as peristaltic locomotion.

  • Evidence of sediment removal in the burrows and signs the organism fed on buried organic matter uncover Ikaria most likely had a mouth, anus, and gut.

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