Petromyzon marinus, an invasive species in the North American Great Lakes.
It's a basic delusion of the creation cult that evolutionary biologists are turning their backs on the Theory of Evolution in favour of their childish notion of magic by a magic creator for which there is not an iota of scientific evidence. This probably tells us more about the ignorant gullibility of their target dupes and the contempt in which they are held by the cult leaders, than creationist frauds would want us to know.
The lie is designed to fool creationists into thinking that their childish superstition is ahead of science because their abysmal ignorance of the subject gives them a better understanding of biology than people who have university degrees in the subject and who use it every working day to reveal new facts and develop new medicines or more efficient agriculture, or simply to reveal the truth about the world we live in.
Creationists have also been fooled into thinking these millions of working biomedical scientists, their research assistants and staff of research institutes, together with those who publish the science journals, are all lying to mislead people because they 'hate' the imaginary, unproven creator, and none of them has ever broken ranks and blown the whistle on the 'deception'.
Meanwhile, in the grown-up world outside the creationist rabbit hole, real scientists are discovering facts that show how evolution from common ancestors involves genetic changes, just the way the Theory of Evolution predicts.
What information do you have on the common ancestor of the jawed and jawless vertebrates? The common ancestor of jawed (gnathostomes) and jawless vertebrates (agnathans) is an important subject of study in evolutionary biology, as it sheds light on the early development and diversification of vertebrates. Here is a summary of what is known about this common ancestor:One of the common ancestors - that of the jawed and jawless vertebrates - gave rise to all the jawed aquatic and terrestrial vertebrates and the two orders of extant jawless vertebrates, the hagfish and the lampreys.
Key Characteristics
Evolutionary Context
- Basic Vertebrate Features: The common ancestor likely had fundamental vertebrate features such as a notochord, a dorsal nerve cord, and segmented muscle blocks (myomeres). These are shared characteristics of all vertebrates.
- Cranial Structures: It probably had a simple cartilaginous or partially ossified skull, but no jaws. This is inferred from the anatomy of extant jawless vertebrates like lampreys and hagfish, and fossil agnathans.
- Sensory Systems: This ancestor would have had a rudimentary sensory system, including eyes and possibly simple structures for detecting vibrations in the water.
- Gill Structures: It likely had gill arches, which in later lineages evolved into the jaw structures in gnathostomes. These gill arches were primarily used for respiration.
- Body Covering: It might have had a skin covered in some sort of dermal armor or scales, providing some level of protection, as seen in some early vertebrate fossils.
Fossil Evidence
- Cambrian Explosion: The split between jawed and jawless vertebrates likely occurred during or just after the Cambrian Explosion, around 500 million years ago. This was a period of rapid evolutionary diversification.
- Conodonts and Ostracoderms: Early jawless vertebrates, such as conodonts and ostracoderms, provide clues about what the common ancestor might have been like. Conodonts are known for their tooth-like elements, while ostracoderms had bony armor plates.
- Developmental Biology: Comparative embryological studies suggest that many of the genetic and developmental pathways used to form jaws in gnathostomes were present in this common ancestor, but were initially used for different functions such as supporting gills.
Genetic Insights
- Haikouichthys and Myllokunmingia: These early Cambrian vertebrates provide some of the best fossil evidence for what early vertebrates looked like. They had some primitive vertebrate features but lacked jaws.
- Arandaspids and Heterostracans: These are examples of early jawless vertebrates that give insights into the diversity and complexity of early vertebrate life before the evolution of jaws.
Modern Analogues
- Gene Duplication: Genetic studies have shown that two rounds of whole-genome duplication occurred early in vertebrate evolution. These duplications provided the genetic material necessary for the development of new structures, such as jaws.
- Homeobox (Hox) Genes: Research on Hox genes, which play a critical role in the development of body plans, indicates that the basic blueprint for vertebrate development was already established in the common ancestor of jawed and jawless vertebrates.
Evolutionary Significance
- Lampreys and Hagfish: Modern jawless vertebrates, especially lampreys, are often studied as analogs to the common ancestor. They provide living examples of primitive vertebrate features and developmental processes.
Understanding this common ancestor helps scientists understand key evolutionary transitions, such as the development of jaws, which allowed vertebrates to exploit new ecological niches and led to the great diversity of modern vertebrate life.
Which species of marine lamprey has recently colonised the North American Great Lakes?
The species of marine lamprey that has recently colonized the North American Great Lakes is the sea lamprey (Petromyzon marinus). The sea lamprey is an invasive species in this region, having a significant impact on the ecosystem and the fish populations within the Great Lakes.
Impact on the Ecosystem
- Predatory Behavior: Sea lampreys are parasitic and attach themselves to fish, feeding on their blood and body fluids. This can lead to the decline of native fish populations, as many fish cannot survive the attacks.
- Economic Impact: The presence of sea lampreys has had a considerable economic impact on the Great Lakes fisheries, which are valued both commercially and recreationally.
Management and Control Efforts
- Lampricides: One of the primary methods for controlling sea lamprey populations is the use of chemical lampricides, which target the larval stage of the lampreys in streams and rivers.
- Barriers and Traps: Physical barriers and traps are also employed to prevent sea lampreys from reaching spawning grounds.
- Sterile Male Release: Another method involves releasing sterilized male lampreys into the population to reduce successful reproduction rates.
Historical Context
The sea lamprey was first observed in the Great Lakes in the early 20th century, and its presence has been attributed to man-made changes, such as the construction of shipping canals, which allowed the species to bypass natural barriers and enter the freshwater systems of the Great Lakes.
In a recent evolutionary change, the predatory marine lamprey, Petromyzon marinus, has recently adapted to fresh water and invaded the North American Great Lakes, where it is devastating fish stocks. However, that example of recent evolution is not the subject of this article, but the evolutionary change that occurred about 500 million years ago which resulted in the divergence between the jawed and jawless vertebrates, one of which was, in effect, ancestral to all terrestrial and most aquatic vertebrates, including humans.
The genetic (i.e., evolutionary) changes that initiated the divergence into these two branches of vertebrates very likely occurred during or shortly after the Cambrian, between 540 and 486 million years ago - in other words, several hundred million years before creationists think the Universe was magicked out of nothing by a magic spell cast by a magic man who had assembled himself out of nothing.
What those changes were is the subject of a recent research paper in Nature Ecology & Evolution by a team of scientists from the Department of Molecular Bioscience, Northwestern University, Evanston, Illinois, and Anjali Rao of the Research Department, Gilead Sciences, Foster City, CA, USA, led by Carole LeBonne of Northwestern, and an article by Win Reynolds in Northwestern Now:
Lampreys possess a ‘jaw-dropping’ evolutionary origin
Invasive, blood-sucking fish ‘may hold the key to understanding where we came from’
One of just two vertebrates without a jaw, sea lampreys that are wreaking havoc in Midwestern fisheries are simultaneously helping scientists understand the origins of two important stem cells that drove the evolution of vertebrates.
Northwestern University biologists have pinpointed when the gene network that regulates these stem cells may have evolved and gained insights into what might be responsible for lampreys’ missing mandibles.
The two cell types — pluripotent blastula cells (or embryonic stem cells) and neural crest cells — are both “pluripotent,” which means they can become all other cell types in the body.
In a new paper, researchers compared lamprey genes to those of the Xenopus, a jawed aquatic frog. Using comparative transcriptomics, the study revealed a strikingly similar pluripotency gene network across jawless and jawed vertebrates, even at the level of transcript abundance for key regulatory factors.
But the researchers also discovered a key difference. While both species’ blastula cells express the pou5 gene, a key stem cell regulator, the gene is not expressed in neural crest stem cells in lampreys. Losing this factor may have limited the ability of neural crest cells to form cell types found in jawed vertebrates (animals with spines) that make up the head and jaw skeleton.
The study was published today (July 26) in the journal Nature Ecology & Evolution.
By comparing the biology of jawless and jawed vertebrates, researchers can gain insight into the evolutionary origins of features that define vertebrate animals including humans, how differences in gene expression contribute to key differences in the body plan, and what the common ancestor of all vertebrates looked like.
Lampreys may hold the key to understanding where we came from. In evolutionary biology, if you want to understand where a feature came from, you can't look forward to more complex vertebrates that have been evolving independently for 500 million years. You need to look backwards to whatever the most primitive version of the type of animal you're studying is, which leads us back to hagfish and lampreys — the last living examples of jawless vertebrates.
Professor Carole LaBonne, led author
Department of Molecular Biosciences
Northwestern University, Evanston, IL, USA And National Institute for Theory and Mathematics in Biology
Chicago, IL, USA.
An expert in developmental biology, LaBonne is a professor of molecular biosciences in the Weinberg College of Arts and Sciences. She holds the Erastus Otis Haven Chair and is part of the leadership of the National Science Foundation’s (NSF) new Simons National Institute for Theory and Mathematics in Biology.
LaBonne and her colleagues previously demonstrated that the developmental origin of neural crest cells was linked to retaining the gene regulatory network that controls pluripotency in blastula stem cells. In the new study, they explored the evolutionary origin of the links between these two stem cell populations.
Neural crest stem cells are like an evolutionary Lego set. They become wildly different types of cells, including neurons and muscle, and what all those cell types have in common is a shared developmental origin within the neural crest.
Professor Carole LaBonne.
While blastula stage embryonic stem cells lose their pluripotency and become confined to distinct cell types fairly rapidly as an embryo develops, neural crest cells hold onto the molecular toolkit that controls pluripotency later into development.
LaBonne’s team found a completely intact pluripotency network within lamprey blastula cells, stem cells whose role within jawless vertebrates had been an open question. This implies that blastula and neural crest stem cell populations of jawed and jawless vertebrates co-evolved at the base of vertebrates.
Northwestern postdoctoral fellow and first author Joshua York observed “more similarities than differences" between the lamprey and Xenopus.
While most of the genes controlling pluripotency are expressed in the lamprey neural crest, the expression of one of these key genes — pou5 — was lost from these cells. Amazingly, even though pou5 isn’t expressed in a lamprey’s neural crest, it could promote neural crest formation when we expressed it in frogs, suggesting this gene is part of an ancient pluripotency network that was present in our earliest vertebrate ancestors.
Dr. Joshua R. York, first author
Department of Molecular Biosciences
Northwestern University, Evanston, IL, USA.
The experiment also helped them hypothesize that the gene was specifically lost in certain creatures, not something jawed vertebrates developed later on.
Another remarkable finding of the study is that even though these animals are separated by 500 million years of evolution, there are stringent constraints on expression levels of genes needed to promote pluripotency. The big unanswered question is, why?
Professor Carole LaBonne.
Abstract
The neural crest is a vertebrate-specific stem cell population that helped drive the origin and evolution of vertebrates. A distinguishing feature of these cells is their multi-germ layer potential, which has parallels to another stem cell population—pluripotent stem cells of the vertebrate blastula. Here, we investigate the evolutionary origins of neural crest potential by comparing neural crest and pluripotency gene regulatory networks of a jawed vertebrate, Xenopus, and a jawless vertebrate, lamprey. We reveal an ancient evolutionary origin of shared regulatory factors in these gene regulatory networks that dates to the last common ancestor of extant vertebrates. Focusing on the key pluripotency factor pou5, we show that a lamprey pou5 orthologue is expressed in animal pole cells but is absent from neural crest. Both lamprey and Xenopus pou5 promote neural crest formation, suggesting that pou5 activity was lost from the neural crest of jawless vertebrates or acquired along the jawed vertebrate stem. Finally, we provide evidence that pou5 acquired novel, neural crest-enhancing activity after evolving from an ancestral pou3-like clade. This work provides evidence that both the neural crest and blastula pluripotency networks arose at the base of the vertebrates and that this may be linked to functional evolution of pou5.
York, J.R., Rao, A., Huber, P.B. et al.
Shared features of blastula and neural crest stem cells evolved at the base of vertebrates. Nat Ecol Evol (2024). https://doi.org/10.1038/s41559-024-02476-8
© 2024] Springer Nature Ltd.
Reprinted under the terms of s60 of the Copyright, Designs and Patents Act 1988. In summary then, it was probably loss of genetic information that meant the jawless fish continued as jawless fish - something that creationists are told is invariably fatal, so can't play any part in evolution.
And no sign there of any loss of confidence in evolution as the foundation theory of biology and the best available tool for explaining the facts.
When the creationist cult leaders lie to their dupes, they show that their cult is for ignorant fools who'll fall for lies and won't have the intellectual integrity to check. This is something we've known about creationism ever since creationists began to display their ignorance and intellectual bankruptcy on the Internet about 25 years ago, since when, belief in creationism has been declining by about 0.5-1 percentage points per annum in the USA to its lowest point ever at 37% whilst acceptance of evolution has more than doubled to 24 percentage points. On current trends, the latter will overtake the former in about 4 years, bringing the USA more into line with other developed economies.
Advertisement
What Makes You So Special? From The Big Bang To You
How did you come to be here, now? This books takes you from the Big Bang to the evolution of modern humans and the history of human cultures, showing that science is an adventure of discovery and a source of limitless wonder, giving us richer and more rewarding appreciation of the phenomenal privilege of merely being alive and able to begin to understand it all.
Available in Hardcover, Paperback or ebook for Kindle
Advertisement
Ten Reasons To Lose Faith: And Why You Are Better Off Without It
This book explains why faith is a fallacy and serves no useful purpose other than providing an excuse for pretending to know things that are unknown. It also explains how losing faith liberates former sufferers from fear, delusion and the control of others, freeing them to see the world in a different light, to recognise the injustices that religions cause and to accept people for who they are, not which group they happened to be born in. A society based on atheist, Humanist principles would be a less divided, more inclusive, more peaceful society and one more appreciative of the one opportunity that life gives us to enjoy and wonder at the world we live in.
Available in Hardcover, Paperback or ebook for Kindle
No comments:
Post a Comment
Obscene, threatening or obnoxious messages, preaching, abuse and spam will be removed, as will anything by known Internet trolls and stalkers, by known sock-puppet accounts and anything not connected with the post,
A claim made without evidence can be dismissed without evidence. Remember: your opinion is not an established fact unless corroborated.