Subscribe to our free daily newsletters
. Earth Science News .




Subscribe to our free daily newsletters



EARLY EARTH
Evolution: In the beginning there was the sponge
by Staff Writers
Munich, Germany (SPX) Dec 05, 2017


Cup-shaped demosponge, Maldives. Source: G. Worheide

Which group of animals evolved first? This problem has become a bone of contention among biologists. An international research team is now confident that the definitive answer is at hand: Sponges appeared before comb jellies.

Which came first - the sponges or the comb jellies? The consensus view among taxonomists has long been that the sponges (Porifera) represent the oldest surviving animal phylum. However, recent studies of their genomes have suggested that this title rightly belongs to the comb jellies (Ctenophora).

The issue has become one of the most hotly debated problems in evolutionary biology, because the answer has profound implications for our understanding of the entire history of animal evolution. Several studies of the question in recent years have come to discordant conclusions: Some have supported the conventional model, which favors the sponges, while others pointed to the comb jellies as being at the root of the animal kingdom.

Researchers led by Professor Gert Worheide (Chair of Palaeontology and Geobiology, Ludwig-Maximilians-Universitaet (LMU) in Munich) and Professor Davide Pisani (Bristol University, UK) have now used a refined method to re-examine the datasets employed in these investigations, and their results are unequivocal: The sponges form the earliest branch on the animals' family tree. The new study supports the idea that the results which suggested otherwise were based on the use of inadequate - and hence misleading - analytical methods.

All biologists accept that sponges and comb jellies are very ancient groups, which emerged more than 600 million years ago. Sponges are comparatively simple multicellular organisms, which lack clearly defined tissues, such as muscles, and organs like the brain. Comb jellies are structurally much more complex. They use so-called cilia to propel themselves through the oceans, and they possess nerve cells and muscle cells.

"If Ctenophora were indeed the oldest animal phylum, one would have to assume either that precursors of these organ systems were already present in the common ancestor of all animals but were lost prior to the emergence of the sponges, or that nerves and muscles evolved independently at least twice," Worheide points out.

"That would necessitate a complete revision of our picture of the evolution of the organs and the nervous system. That is the reason why it is so important to correctly define the sequence of animal emergence early in evolution."

In order to elucidate the genetic relationships between animal phyla, biologists compare the amino acid sequences of modern species with one another, and construct family trees based on the degree of difference between them. The most likely phylogenomic tree should then faithfully reflect the order in which the different phyla diverged from their common ancestor and from each other.

"Two of the important datasets used in the modelling studies which identified the comb jellies as the oldest extant animal group were made up of very heterogeneous data. We have now shown that none of the conventionally used statistical methods is capable of adequately analyzing such datasets," Worheide explains.

To minimize the compositional heterogeneity of the data, the authors of the new study employed a procedure in which the amino acid sequence data were first divided into groups based on the biochemical functions of the proteins they form, and then subjected to the modelling process. The analysis of these datasets - including those derived from the data that had previously ranked the comb jellies as the older phylum - demonstrated with high statistical confidence that the sponges are in fact the oldest of the animal groups.

"Our results confirm the classical assumptions concerning early animal evolution, and should help to put an end to the recent controversy over the origin of multicellular animals," Worheide concludes.

Research paper

EARLY EARTH
Feathered dinosaurs were extra fluffy, new research shows
Washington (UPI) Nov 30, 2017
New analysis of the remains of a bird-like dinosaur called Anchiornis suggests feathered dinosaurs were fluffier than researchers thought. Modern birds are the evolutionary offspring of a group of feathered theropod dinosaurs. Together they comprise the group known as paravians - a group that included the famed Velociraptor. The fossilized remains of an Anchiornis specimen offer ... read more

Related Links
Ludwig-Maximilians-Universitat Munchen
Explore The Early Earth at TerraDaily.com


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

Comment using your Disqus, Facebook, Google or Twitter login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

EARLY EARTH
Beijing bans fireworks, evil spirits rejoice

Southern Chile iceberg splits from glacier, threatens navigation

China, Myanmar hail close ties amid Rohingya outcry

Despite Greek shelter, Yazidis struggle to integrate

EARLY EARTH
Device could reduce the carbon footprint of ethylene production

Researchers inadvertently boost surface area of nickel nanoparticles for catalysis

UCLA engineers use deep learning to reconstruct holograms and improve optical microscopy

Study shows how to get sprayed metal coatings to stick

EARLY EARTH
Why are there no sea snakes in the Atlantic?

The world needs to rethink the value of water

Scientists discover resilient 'heart' of Great Barrier Reef

Sea turtles' sad fate: from restaurant menus to plastic 'soup'

EARLY EARTH
Arctic, major fishing nations agree no fishing in Arctic, for now

Antarctic Selfie's Journey to Space via Disruption Tolerant Networking

Antarctic landscape insights keep ice loss forecasts on the radar

Operation IceBridge 2017: The Beauty of Ice

EARLY EARTH
Tokyo 2020 to feed IOC food from disaster-hit regions

Gene discovery may halt worldwide wheat epidemic

Genome of wheat ancestor sequenced

Getting a better handle on methane emissions from livestock

EARLY EARTH
Indonesia reopening Bali airport shut by volcanic ash fears

Albania sends in military rescue as heavy rains trigger huge floods

Bali volcano burns wedding dreams, threatens economy

16 dead, 100 missing as cyclone hits India, Sri Lanka

EARLY EARTH
Regional force deploys to Lesotho over security concerns

Mali justice minister resigns after activist's acquittal

Cash and history keep Europe as Africa's prime partner

China hails new Zimbabwe leader, denies role in transition

EARLY EARTH
Chimp females who leave home postpone parenthood

Long-term logging study demonstrates impacts on chimpanzees and gorillas

What grosses out a chimpanzee?

Human evolution was uneven and punctuated, suggests new research




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement