what happens to a flatworm when it is immersed in barium
ChatGPT said:
When a flatworm is immersed in barium, the outcome depends on the form of barium used. Barium in general is toxic to living organisms, but here's a breakdown:
1. Barium Ions (e.g., Barium Chloride - BaCl₂)
Toxicity: Highly toxic to flatworms and other invertebrates.
Effect: Disrupts normal nerve and muscle function by blocking potassium channels, which are crucial for nerve impulse transmission.
Result: The flatworm may experience:
Loss of movement or erratic movement
Muscle spasms or paralysis
Death, depending on concentration and exposure time
2. Barium Sulfate (BaSO₄)
Insoluble & Inert: Commonly used in medical imaging (e.g., X-rays) because it doesn't dissolve in water.
Effect on Flatworms: Minimal, unless impurities are present—generally non-toxic due to poor solubility.
Summary
Soluble barium salts (like barium chloride): Harmful or lethal to flatworms.
Insoluble barium compounds (like barium sulfate): Generally harmless.
Do you know which form of barium you're referring to? I can give you more detailed effects if you do!
You said:
there is a report of the death of the head leaving the tail which revgererates a new head immune to barium poining in Seymour Garte, Perry Marshall, and Stuart Kauffman have published an article in the journal Entropy titled “The Reasonable Ineffectiveness of Mathematics in the Biological Sciences.”
ChatGPT said:
Yes, the phenomenon you've described has been documented in scientific research. When planarian flatworms are exposed to barium chloride (BaCl₂), a potent potassium channel blocker, their head tissues degenerate within approximately 72 hours. Remarkably, if these worms remain in the BaCl₂ environment, they can regenerate new heads that are resistant to the toxic effects of barium. PubMed+3PMC+3ResearchGate+3
This adaptation suggests that planarians possess a form of physiological plasticity, allowing them to modify their regenerative processes in response to environmental stressors. The regenerated heads not only restore normal morphology but also exhibit insensitivity to BaCl₂, indicating a successful adaptation to the previously harmful conditions.PMC
This case exemplifies how biological systems can sometimes defy straightforward mathematical modeling, as discussed in the article "The Reasonable Ineffectiveness of Mathematics in the Biological Sciences" by Seymour Garte, Perry Marshall, and Stuart Kauffman. The authors argue that the complexity and adaptability of living organisms often challenge the predictive power of mathematical frameworks traditionally used in the physical sciences.
ChatGPT said:
The phenomenon of planarian flatworms regenerating barium-insensitive heads after exposure to barium chloride (BaCl₂) has been documented in scientific literature. A key study titled "Regenerative Adaptation to Electrochemical Perturbation in Planaria: A Molecular Analysis of Physiological Plasticity" reports that exposure to BaCl₂ causes degeneration of the planarian head, but continued exposure leads to the regeneration of a new head that is insensitive to BaCl₂. ResearchGate+2PubMed+2PMC+2
This study provides a detailed analysis of the molecular and physiological mechanisms underlying this adaptation, including changes in ion channel expression and the role of specific molecular pathways. The findings suggest that planarians can adapt to electrochemical stress by altering their physiology during regeneration.
While this study is a primary source documenting this specific phenomenon, other research has explored related aspects of planarian regeneration and physiological adaptation. For example, studies have investigated the role of ion transport and membrane voltage in planarian head regeneration, highlighting the importance of bioelectric signals in regenerative processes. PMC+2Cell+2PubMed+2
These studies collectively contribute to our understanding of the remarkable regenerative capabilities of planarians and their ability to adapt to environmental stressors.
[[Although the remarks concerning evolution in this article are important I am more interested in the fact that we do not know how a brain with 302 neurons functions. But of course we fully understand our own brains with 86b neurons I first posted about this worm in 2018 and not much progress has been made.....]]
Recently, we published a piece by Eric Cassell on the fact that even the tiniest known brain, that of the wormC. elegans, is not simple. These facts he sets out raise some very interesting questions.
The worm’s apparent simplicity makes it a favorite lab animal — for example, it was the first animal whose brain was mapped. Researchers have learned that, with fewer than 400 neurons, it can handle both associative and non-associative learning.
Cassell, author of Animal Algorithms (2021), offered a number of remarkable facts about the worm and I thought I’d summarize a few of them again here, along with some questions:
The worm, 1 millimetre in length, consists of only 900 cells. Thus neurons comprise a large proportion of its total cell count.
The worm actually comes in two forms: males which have 385 neurons and hermaphrodites (both sexes) which have 302 neurons. In both cases, it seems that over one-third of all its cells are neurons. But if we compare the worm to the human, we see a considerable difference: The human body has roughly 30 trillion cells and the human brain only 86 billion. Of course, there are neurons distributed throughout the human body. Even so, the proportion of human neurons to other human cells seems much lower.
Perhaps the worm’s brain has roughly the minimum number of neurons any brain must have for simple bodily functions and learning — irrespective of the size of the rest of the body.
Equipped with those 400 neurons, the worm can feed, fast, mate, lay eggs, swim in liquids and crawl on solids. In fact, the worms’ “social lives” can become, well, quite complex:
Cassell writes,
In addition to basic behaviors, C. elegans is also capable of learning, including associative and non-associative learning. A paper published in the Journal of Neurochemistry documented the learning behaviors, including attraction and aversion to salt, temperature, and other substances. What might be surprising to many is that this learning involves both short-term and long-term memory mechanisms, which include regulation of neurotransmitters.
When even simple life forms are complex, the origin of life question arises: Were there ever life forms that were so simple that they could merely self-assemble, as our official doctrine of the origin of life proposes?
Cassell offers several observations that touch on this question:
… even though the brain is tiny, it does not have a simple structure. One might expect the smallest known brain to have a structure that is either relatively uniform or random. An example of a uniform structure is that found in crystals, which form a symmetrical lattice. A random structure would be expected if the positions of the neurons were not specified, but rather develop through a random process. Contrary to being either uniform or random, the brain does have a complex structure that is specified and repeatable.
Yes, that’s the problem of specified complexity: In a world where nature, left to itself, produces either uniform order or chaos, we find a level of information-rich order that requires an underlying intelligence. And in this case, that information-rich order is alive.
And just when we think we might have finally got down to the truly simple, basic part:
A second observation is that the brain contains a large number (approximately 100) of different types of neurons, both in terms of design and function. They are not all identical. That also would not be expected for the smallest brain. A third observation is that small neural networks within the brain control various behaviors, such as the touch response network. It is possible that some of these neural networks are irreducibly complex.
Irreducibly complex means that the current structure cannot have arisen via a gradual buildup from simpler to more complex steps. It’s not that simpler versions could not do the job as efficiently; rather, none of them could do it at all.
Cassell quotes a research paper that attempts to account for C. elegans’s unexpectedly busy little brain:
The mere existence of such structures may actually further underscore the directed evolution to form such clusters, which presumably carry fine functional roles along the neurites. Taken together, local compartmentalized activities, facilitated by the clustered synaptic organizations revealed herein, can enhance computational and memory capacities of a neural network. Such enhancement may be particularly relevant for animals with a compact neural network and with limited computational powers, thereby explaining the evolutionary forces for the emergence of these synaptic organizations.
But wait. Did the researchers say “directed evolution”? As Cassell notes, the term has never been generally accepted in the research literature. That’s probably because it implies underlying purpose or design. Here we have no quarrel with that idea. But it appears to abandon the idea of gradual, random assembly of even the C. elegans brain via natural selection acting on random mutation.
So Here We Are…
Looking at the very simplest brain known, we find both specified and irreducible complexity. It is all very far removed from the organic elements that are the building blocks of life. And yet we aren’t yet anywhere near the types of brains that think, in the sense that a dog thinks.
However evolution happens, it is beginning to sound far more complex than the sort of theory that made Richard Dawkins feel intellectually fulfilled as an atheist.
Did Evolution Give Us Free Will? Daniel Witt March 4, 2025, 8:21 AM
Did Evolution Give Us Free Will? Daniel Witt March 4, 2025, 8:21 AM
If you pick up a book up about free will by a materialist neuroscientist, you are generally safe to assume that the point of it will be to explain that free will is merely an illusion — that we are actually at the whim of the blind forces of Nature, and are therefore not responsible for our actions. So it’s surprising and somewhat refreshing to see a self-proclaimed naturalist defend free will. That’s what Trinity College Dublin neurobiologist Kevin Mitchell sets out to do in Free Agents: How Evolution Gave Us Free Will.
As Denyse O’Leary has noted about the book, the scientific debate over free will seems to be reviving a bit, with another book by another prominent scientist arguing the opposite position released the same year (Determined by Robert Sapolsky). So after reading Mitchell’s book, I thought it would be worth digging into the details of his argument a bit for Evolutions News readers.
Does the book succeed? By my assessment, no and yes and no. There are really several different questions at play here: Do we have a will? Is it free? Did evolution give it to us? And if so, how? Each of these subjects has its own set of scientific and philosophical difficulties, and the book is not equally persuasive on every point. To keep the various strands of the argument straight, let’s go in order, following the subtitle. We’ll start with “how evolution gave us”…
“How Evolution Gave Us…”
Anyone expecting a defense of the claim that Darwinian processes can or did create complex neurological systems will be disappointed. That’s not the point of the book. With a very few exceptions1, Dr. Mitchell works from the tacit assumption that (a) there is no real limit to what Darwinian processes can achieve, and (b) that anything that exists in biology must have arisen through Darwinian processes. That means the book is largely concerned with describing what exists in nature, with “evolved” acting as a synonym for “is.”
Thus, phrases like “mechanisms evolved” prevail throughout the book. Complex systems are simply “built” or “invented” or even “designed,” without much concern given to the concrete details or the relevant engineering problems. The following passage is typical:
More complex creatures emerged, colonizing and creating new niches, with expanded repertoires of possible actions. A system was then required to coordinate the movement of all the organism’s constituent parts and select among actions. Muscles evolved, along with neurons to coordinate them, initially distributed in simple nerve nets. As evolution proceeded, the nervous system became more complex, linking sensory structures to muscles via intervening layers of interneurons. The meaning of signals became disconnected from immediate action, giving rise to internal representations…
In all fairness, Mitchell presumably did not set out to defend Darwinian evolution against other possible explanations. The heart of Free Agents is not really in explaining how we evolved to be what we are, but rather in simply describingwhat we are, according to the cutting edge of neurobiology. That’s where the book shines.
“Free”
One view of free will, called “compatibilism,” maintains that materialistic determinism and free will are really compatible. This position is apparently quite popular in philosophy of mind circles, and has been argued by Daniel Dennett and other famous philosophers. The argument says, first, that it doesn’t matter if an organism “could have done otherwise” — what matters is that the organism is the source of the action. That is, we can reasonably be said to have free will if we are able to do what we want, even if we are not able to want what we want. Second, compatibilists point out that organisms and their environments are so complex that there is no way, even theoretically, to predict what an organism will do in a future situation. So for all practical purposes, we are free.
Mitchell finds these arguments unconvincing. They seem to be saying that if we just change our perspective, or our definitions, the problem will go away. “But I cannot escape feeling that some sleight of hand is part of this line of argument,” he writes. “It feels as if some (presumably unwitting) misdirection is going on — as if the primary problem has been circumvented or even denied, rather than confronted.” Instead, there ought to be some genuine indeterminacy in the system, or else “no matter how complex, the agent will be pushed around deterministically by its own components.”
I think the “sleight of hand” Mitchell senses is the confusing of epistemology with ontology: confusing what can be known with what is. Regardless — Mitchell argues that the fuss is unnecessary. There is really no reason that free will needs to be compatible with strict determinism, he says, because physics, as it turns out, is not strictly deterministic. That requirement is a relic from a bygone era, when everything seemed to move inexorably according to simple Newtonian laws. Most modern quantum physicists, in contrast, agree that particles seem to actually have a degree of freedom or true randomness to their movement. So, Mitchell says, “there is nothing in the laws physics that rules out the possibility of agency or free will, a priori.”
In fact, various studies seem to show organisms acting in a non-deterministic way. In one fascinating experiment, an electrical probe was attached directly to a leech’s central nervous system, allowing the experimenters to bypass the complexities of environment altogether and administer the exact same stimulus, repeatedly. Even under such perfectly controlled conditions, there seemed to be no way to predict how a leech (like the one pictured above) would respond to the stimulus each time.
This apparent indeterminacy scales all the way up to more complex behaviors and situations, resulting in what is known as the Harvard Law of Animal Behavior: “Under carefully controlled experimental circumstances, an animal will behave as it damn well pleases.”
So Far, So Good
But what about the experiments that seem to show the opposite, that free will is a mere illusion?
There are quite a few famous experiments of this kind, but in Mitchell’s professional opinion, they show nothing of the sort.
For example, Benjamin Libet’s now-famous 1983 experiment showed a signal called a “readiness potential” in the brain a fraction of a second before the subject was conscious of choosing to move his hand. Many have taken this to be definitive proof that free will is only an illusion: at the moment we think we are freely choosing, the brain has actually decided beforehand.
Mitchell writes that this interpretation is “to put it mildly, a drastic overinterpretation”:
That is because the design of the experiment makes it effectively irrelevant for the question of free will. The participants made an active and deliberate decision when they agreed to take part in the study and to follow the instructions of the researchers. Those instructions explicitly told them to act on a whim: “to let the urge to act appear on its own at any time without any preplanning or concentration on when to act.” They had no reason to want to move their hand more at one point than another because nothing was at stake. And so, it seems they did indeed act on a whim: they (decided to) let subconscious processes in their brains decide, by drawing on inherent random fluctuations in neural activity.
This is what a different group of neuroscientists, led by Aaron Schurger, concluded from analyzing the data from the original experiment — that the test subjects had (instinctively, of course) set a certain potential level of neuronal activity, deciding that when random fluctuations in the brain reach that level, they would take the proscribed action.
So now you have two plausible interpretations of the data.
But Which One Is True?
Another experiment, led by Uri Maoz and Liad Mudrik, sought to distinguish between the two possibilities. The researchers gave half the test subjects a decision with no serious consequences, and half a decision with consequences that they cared about. Sure enough, when the subjects were given inconsequential decision, a readiness potential preceded the decision, as in Libet’s experiments. But when the decision mattered, no readiness potential was detected.
“Overall then,” Mitchell writes, “Libet’s experiments have very little relevance for the question of free will. They do not relate to deliberative decisions at all, where readiness potential is not observed. Instead, they confirm, first, that neural activity in the brain is not completely deterministic and, second, that organisms can choose to harness the inherent randomness to make arbitrary decisions in a timely fashion.”
So much for “free.” We’ll examine what Mitchell has to say about “will” tomorrow.
Notes
E.g., Mitchell mentions that the now-classic view that symbiosis might have been necessary to make the switch from prokaryotic to eukaryotic life.
Rabbi Dr. Dovid Gottlieb is a senior faculty member at Ohr Somayach in Jerusalem. An author and lecturer, Rabbi Gottlieb received his Ph.D. in mathematical logic at Brandeis University and later become Professor of Philosophy at Johns Hopkins University. His book Ontological Economy: Substitutional Quantification and Mathematics was published by Oxford in 1980; The Informed Soul was published by Artscroll in 1990, and has recently been reprinted. He is a regular lecturer at kiruv conferences and known for his stimulating and energetic presentations on philosophical issues of Jewish interest.
1. Barium Ions (e.g., Barium Chloride - BaCl₂)
2. Barium Sulfate (BaSO₄)
Summary
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