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One question I have: does this paradox apply only to fish or all aquatic species? I would imagine a coral reefs has much more diversity of invertebrates than any lake. If so could invertebrates be taking ecological niches filled by fish in freshwater environments?
This is a good point! Plus, if we look at the size of the body of water instead of just salinity, how does that skew things? I mean, just because Lake Tanganyika and Lake Baikal are fresh water, doesn't mean they aren't more ecologically akin to oceans than most rivers or shallower lakes.
I think water hardness and acidity seem like important factors for that, since the ocean has a lot of stuff dissolved in it that freshwater being fed mainly by rain is going to be deficient in (to explain acidity, I've heard some streams are really acidic, but I only know of people saying it's a problem for crustaceans in reference to ocean acidification). Intermittent availability of minerals in fresh or brackish water makes bones useful batteries for calcium and phosphate as modern bony fish partially use them, we even metabolize our bones when we have calcium deficiencies, though bone-tooth skin coverings seem to have started in the oceans. Bony fish just seem better tuned for freshwater from the perspective of adaptation since crustaceans have weaker armor if they don't use a lot of minerals, and using a lot means the animal is vulnerable to periods of low nutrients from downpours while it gets the material for the new skin. They're really effective at being plankton sized in freshwater and everywhere else more than fish have been though.
@@thetobyntr9540 are you saying that the innovator of bones was a freshwater fish? i would've assumed oceanic but i don't know. freshwater habitats are a hell of a lot older than bones so quite possible.
Is it also possible that we have just discovered a comparatively smaller percent of ocean species? It's a lot easier to find freshwater species. One you can wade to, the other requires fishing lines, nets, or scuba gear.
That's probably part of it, but a big factor is just how much easier it is to move around the ocean. Even with a hard to penetrate barrier at each of the oceans, you're still dealing with a number that's small enough to be easily counted. With lakes and rivers you're talking about thousands and possibly millions of areas that species need to work their way to and some of them are only connected by seasonal streams, even though the lake itself does exist all year round.
The common factor with every option you proposed is the fact that the ocean is 1 habitat but every river or lake is it's own. A single Tuna can range a third of the world. Not so with a lake trout.
Not necessarily, the ocean has its own barriers that form smaller habitats, it is true that there are species that live basically anywhere, but there are others that adapt to very specific places, such as reefs or the seafloor.
@@manjensen1710 The ocean still has barriers, but I think it's safe to say that it has much less barriers and individual cut off areas than freshwater environments.
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I agree, even though species appear at the same rate, the different river conditions and barriers lead to many different optimum paths in evolution. Whereas the sea is overall more uniform, the possibly roles in the environment are reduced. One highly efficient fish can overtake many others in a whole ocean, not so much in a river.
There are plenty of animals with ridiculous ranges, including "fresh", "semi freshwater?" Transiently freshwater? Fish/ aquatic creatures. Eels for the uk travel across the atlantic to do the do. Salmon in the pacific swim inland and up into the rockies to inherited spawning streams.
Alternative theory: it’s actually scaled. (Pun intended) there really is a lot more fish in the ocean than the rivers. We just haven’t discovered most of them. Reasons being, it’s much much easier to explore rivers and lakes than oceans. In a River the individual fish is more unique and noticeable so it’s easier to track them. In an ocean one fish is easier to mistake for another, even in different species, making the illusion of less fish. Its also probable that it’s a combination of all these theories that cause this
My idea is not to say fresh vs salt but to compare Inland bodies of water vs open bodies of water. Also where do brackish species fall? Since they can technically inhabit both? Seas, gulfs, and oceans are open bodies. And obviously rivers, lakes, streams are open bodies. To me there are more "fresh" or inland species due to more inland species can interact with the fish. In the ocean fish swim (run away from) fish. In the streams, EVERYTHING is out to get you. I mean yeah there are exceptions like aquatic mammals and diving birds. But in-land bodies of water means that any bird can swoop down, any mammal can dive in, any reptile can tolerate the non-frigid waters of and in-land body of water. As such the need to adapt is even higher. There are a few ways to adapt in the ocean but the in-land waters have so much more variables. You cant deep dive like you could in the ocean, you can evolve to adapt to frigid temps to avoid the reptiles, you cant grow super large like you could in the ocean. The rules for adapting are more constrained. Yes there is PLANT LIFE due to less salinity as such thats a key stone species. Then river naturally have BEAVERS, another keystone species, so theres so much more competition from every frontier. The ocean had its protections that in land bodies of water cant provide.
I think you're ignoring the vast scale of where freshwater fish can be. There are cave systems, filled with fresh water, that we have been unable to explore due to limitations. Exploration devices need to be small and flexible enough to manouvre through a lot of odd gaps, while the device needs a cable attached due to wireless transmission being blocked/interfered with the sheer amount of rocks and minerals between places. Thats not considering small ponds or marshlands where there can be any fish hiding between mosses, under sand, between twigs, looking extremely similar to another already identified species, or simply being transparent. I mean, just look at how many different new species of bugs are discovered on a yearly basis. And how many of these new species look extremely similar to already known species or how difficult they are to find. Thats humans actively being able to get up close to either catch a specimen or to take a sample for DNA testing. Thats not even considering that while freshwater and saltwater fish are very seperate habitats right now, they werent always that seperated. Its not unlikely for a lot of rivers and lakes to have been salt water, and since coast lines are to this day a huge source of biodiversity, its not unlikely that a majority of these fish followed salt water and went into the lands, and then were slowly forced to adapt to water containing less and less minerals. Since this could mean that a lot of aquatic biodiversity went land inwards, millions of years ago and that the biodiversity we see out there today is artificially lowered due to that migration too. There are a LOT of reasons why we cant narrow it down, and it is probably multiple of those reasons combined. Lakes, rivers and ponds have a lot more diverse environments overall, but the ocean would have more room for artificial diversity through more fish sharing the same environment. A mudskipper doesnt have to fear the interference of a goldfish for example, but a seabass does have to fear the interference of the eel.
I don't find this counter intuitive at all. I wouldn't expect more water to automatically give rise to more species. Each species has to fill it's own ecological niche and I don't expect there to be more niches if you just have more of the same environment. What I would expect is that the species in oceans are "more evolved"/better adapted since there is more space for benificial mutations to happen
I would say they are less evolved, because they are adapted to a static habitat where no variation exists. There would be no reason to evolve into something, when all abiotic factors remain the same both spatially and temporally.
@@silversurfer8818 Good point, "more evolved" wasn't the right way to put it. I meant something like "their fitness is closer to a local maximum because they had more opportunities to take a convergence step".
Couldn't agree more. The equation starts looking a whole lot simpler when you look at how many rivers and lakes there are versus the number of oceans. There are just so many more variations in the environment when you compare rivers and lakes rather than oceans.
As a fishkeeper, it's amazing to see how overlooked actually is by laymen the huge biodiversity of lakes and rivers - When setting up a freshwater aquarium, the variety of fish of any size, colour, shape and biological niche is absolutely stunning.
Having kept both I would say that it's the variable conditions in freshwater (seasonal run-off, evaporative chemistry etc) and oceanic conditions are much more stable (hence coral die-off from minute calcium changes) leaving freshwater fish more resilient, and better able to weather environmental changes thus leading over time to more freshwater diversity.
I would also suggest, that’s because of the fact that in a smaller habitat, there is more competition which always is the motor of evolution. To be successful the individuals have to come up with different strategies to sustain them self. Also, in the Oceans there is a bigger variety of size, there are big mammals like Whales, Dolphins and also bigger fish like Sharks. We know that bigger animals have a bigger need of territory which leads to less animals per space unit. Also, they have a slower reproduction time, I think. Both effects add up to lower reproduction rate and therefore fewer times a mutation could appear. I think a big factor is also that in fresh water there’s a bigger variety than in salt water in terms of the habitat. On the one hand we have swamps, lakes, rivers etc. and on the other hand we have the ocean (and some lakes of cause but they often end up so salty no fish can survive at all in it). This makes more different challenges for fresh water fishes which have to adapt to it in different ways. So yeah, there are a lot of different things that add up to this effect. Correct me if my logic fails at some points
Not to mention the climate affects rivers and lakes far more than the ocean! A lake in Northern Europe would be a totally different environment from a river in the Amazons.
Again, YOUR OPINION THERE ALREADY COVERED IN THIS VIDEO. This video also talk about ISOLATIONISM. But... Man.. Just watch the video again. I dont need to explain it again
@@DBT1007 you clearly dont get my points, they named some of the Ideas I was talking about in the Video but didn't explain them really andalso not everything I mentioned. So this comment has its right to exist as it's providing new information
Fun fact: Nearly 97% of the world’s water is salty or otherwise undrinkable. Another 2% is locked in ice caps and glaciers. That leaves just 1% for all of humanity’s needs - all its agricultural, residential, manufacturing, community, and personal needs.
2 main solutions are desalination (basically a filter process good enough to remove salt) And reuse, sewage is mostly water and treatment makes it safe enough to release into rivers, it is possible to treat it enough to supplement drinking water needs. (Its just most people will still be squeamish about it, myself included) And don't forget about good old fashioned use less. Also some of this 1% needs to be left alone so that lakes and rivers can continue to exist and benefit the environment and therefore us.
DISTILLED WATER=RAIN is the only water we supposed to drink. It's pure water free of nasty stuff which removes the toxins from the body/nature etc. We get minerals and vitamins from food. Now we are simply poisoining our body and the water we drink DOES NOT cleanse us at all because it's full of nasty stuff. We are living a really wrong life. This lifestyle they have indoctrinate in our generations make us sick and THEY are happy about that. RETHINK YOUR LIFE. RESEARCH. DO NOT TRUST ''SCIENCE''.
@@pinakkoladaa uhh rain isn't distilled water, rain forms around condensation nuclei which means dust and it picks up air pollution. Coal plants spew out lots of soot, Sulphur Dioxide, Nitrogen Dioxide, and Uranium. All of this gets picked up by rain and falls back down to earth. It results in the pH balance of NY lakes shifting and leaves dirt on your car after a storm in urban areas. (Cities tend have more fossil fuel power plants near them) Besides: 1. our primal ancestors drank from lakes and streams like every other animal. (And probably got a lot of water borne diseases from it) 2. Drinking nothing but true distilled water is unhealthy as you are expected to get some minerals from your filtered ground water. 3. I was raised on a well and my dog drank from our chlorinated pool and never had any side effects. (Pool water, village water, liquid pool chlorine, and laundry bleach all are the same thing, hypochlorous acid in water at different concentrations)
Thank you for having the courage to say that, as of now, we don't know! It seems that many people are really uncomfortable with "we don't know"! We need more of this as "we don't know" is the driving force of MORE science!!!
Rivers would have the most oxygenated water, among other things. But even if that somehow doesn't matter, it sounds like the problem was the initial premise.
Maybe it's just easier to monitor rivers than oceans, due to far less area? Meaning there could very well be far more ocean species we have no idea about?
I can’t remember the specifics, but when counting fish or species of fish it’s often more statistics than anything. Instead of counting every species we can find we instead create as accurate a model as possible and we guess to fill in the gaps. Assuming we actually have a good understanding of ocean ecology these kinds of models give us a general idea of both how much we do and how much we don’t know. Your point still stands, but it is something that people are aware of and try to work around.
Most land animals drink fresh water to survive, so I'd assume the transition from sea to land happened in a fresh water environment. Which could help explain the diversity paradox! Living in fresh water is more energy efficient. Consequently, this can allow for faster rates of speciation when competing for new ecological niches that appear after each extinction. Also can explain why lakes have less species, as it being a closed environment, it'll have a smaller amount of ecosystems to emerge after any given extinction. Smaller amount of niches to compete for.
Freshwater, particularly rivers have way more niches for life to find, as they span different biomes, temperatures, minerals, etc. The ever changing rivers allow for very different compositions and environments, there's a much more diverse amount of predators (bird, mammals, lizards, insects, etc) and plants because all the land-based animal and plant species interact with it. More niches allow more species to co-exist at the same time. Coasts on the other hand are mostly the same in most places. Lakes are too small and too static to give serious competition between the species that would require tight niches; they'd cause species to be stuck on local optima for quite a while.
I wouldn't say lakes are too small to have many niches, even small lakes can be over 100ft deep which creates more of a vertical separation than a horizontal one. Granted a lake with a long diameter of 2 miles is not going to have as diverse of environments as a river starting life as a mountain pond/marsh and running over 200 miles to the ocean through mountains, hills, forrests, plains and even cities.
This is exactly my thought. Freshwater habitats - and especially non-lacustrine habitats - are incredibly heterogeneous and diverse! So many unique niches to fill. Add in that they are also often very isolated and not only do you have a lot of niches to fill, you often have a different species filling each niche in different systems. Coming from Australia where basically everything is highly diverse for exactly these reasons the fish paradox just doesn't seem that odd to me I guess? I'm only a 2nd year undergrad so if this is the state of the science I'll have to defer to those better equipped but even if the numbers are odd the cause just seems pretty obvious from my perspective.
I love the sea but it terrifies me - and I suspect that creatures feel the bad vibes, too. All that emptiness carries a resonance of fear that stops exploration.
I watched a video by _Real Science_ called _Why Hybrid Animals May Take Over the North._ At around the 11:00 mark they were discussing how the hybridization of fish dramatically increases the rate of speciation.
If you compare one habitable zone of the ocean to one individual lake you will learn that the ratios are equal. The number of species in a lake and the number of fish associated with each species will be near equivalent to the number of species in that section of Ocean and the number of fish associated with each species. It's not a paradox it's just spacial geometry.
That seems very reasonable, and I believe you’re stating it as fact, not speculation, but I would ask how you plan on dividing up the oceans into habitable zones? Itwould be to easy to say that you divide it into the same n number of zones as there are lakes/rivers, but that’s not accomplishing anything toward understanding the underlying systems, it just shifts the answer to an impractical solution.
as game developer I'm 100% sure it's because "optimization" why spend more 3D model, AI, and weird gameplay in ocean where player will mostly spend it's playtime in land
This is like a super short RadioLab episode. "Let's ask a really interesting question, examine all sorts of evidence suggesting possible answers, then throw our hands up and conclude that nobody really knows for sure."
Its so refreshing to see your videos where you roughly show the scientific dialog and also were things are unexplained. its just so much more interesting and authentic than these overly polished stories about how science just knows it all
Divergent evolution relies upon two or more populations of a species being for one reason or another unable to mate with eachother, and eventually over millions of years becoming their own unique species. One major driving force behind divergent evolution is physical separation, which is nonexistent in the ocean.
I would argue that because oceans have more mobility and fewer isolated environments than freshwater, it encourages species homogenisation more than freshwater. The unusual thing isn't why freshwater environments have more fish species, but why oceans have fewer species.
Yeah, perhaps because of the vastness of the ocean, it becomes more difficult for a niche species to find a mate, so a greater diversity in fish species is selected against in the ocean, whereas in rivers it's less of a problem
Well what about non-fish species that inhabit both salt and freshwater? Are patterns similar to those shown by fish also seen among molluscs, crustaceans, worms, sponges, etc.?
I think it's way simpler than all of that. The ocean is harder to look in than rivers and lakes are. It's so hard to look in that it's actually easier to look at the bottoms of fossil oceans which happen to now be situated neatly on dry land, simultaneously explaining the wealth of speciation in marine fossils.
We do find our ocean fossils on land though. Also, the question is about modern species not past ones. Btw, any sandstone deposits were probably laid down by a shallow sea. I have some in my area and if you look at the banding of sand grain sizes you can see when the ocean levels rose and fell (large=shallow small=deep). Since only near the shore do ocean currents have the power needed to move bigger sand grains so they never make it that far out. The peak of Mount Everest is actually ancient seabed as well. Random science person away!
Could it not just be that humans have discovered more freshwater species? Vast swaths of the ocean are unexplored, while freshwater habitats are much easier to access and we spend way more time in and near them, while most of our interaction with the ocean is just at the coast.
I'd imagine that the vastness of the ocean can lead to similar levels of isolation, comparable maybe to disjointed rivers and lakes, if a fish were to drift out of its usual roaming range for example
Thank you for presenting the competing ideas on science. I find it so perplexing that people on internet sometimes just concoct an explanation through evolutionary analysis that "sound good enough" and then just regard it as truth. These evidences and rebuttals are more valid science.
1:12 Even if the ocean and freshwater areas develop new species at a similar rate, isolationism still plays a part. Just because you may have the same amount of new-speciation in both environments, the oceans being interconnected rather than divided means that it's harder for new species to compete against long established species that can migrate between areas. Conversely, lakes and rivers being isolated from other lakes and rivers means that new species are likely to have less competition from species that have developed in other freshwater areas, meaning that they can have a higher chance to stick around and develop further into distinct species in their ecological niches. Even if those niches are the same as other lakes and rivers that species can't easily travel between. That's not to say that all the oceans are all interconnected easily enough for species to migrate between oceans, there are still some ocean species that have a hard time getting from say the Atlantic to the Pacific, but oceans all sharing the same body of water can definitely help.
The fluent occupation of niches by big fish over the course of their lifetime might be part of it, no? The bigger a predatory species grows, the more often it needs to adjust it's food source to supplement its continous survival. And fish especially go through an exponential amount of niches as their growth cycle starts on the microscopic level of zooplankton for most of them. Bluefins start as 3mm larva bevore gaining literally 3million times their weight until they are fully grown, the amount of different niches they compete in over their life cycle is insane. And since ocean fish naturally grow many times larger than the average freshwater-fish while still starting from literal larva rock bottom, they can compete with and outclass every fish of the same or smaller size in every state of their growth. And since the amount and pressure of tuna for instance is over an infinitely larger area than one or two relatively big pike reproducing in a single pond of a river system, fewer species are "needed" to reach that equilibrium of new species/extinction. Also resulting, bigger predatory fish excert pressure onto the entire food pyramid permanently while a mammalian, terrestrial predator will stay on the same prey items of a single weight class all their life, with the early life being covered by milk until learning to hunt what the adults hunt. In that a lion will never exert direct pressure onto bugs for instance as the entire predatory bottom food pyramid from plant over rodents to jackals up until the big predators/prey items will never stand in direct competition with a lion. Not that's the only factor of course, if studying biology tought me anything then that a single cause is literally never the full answer.
A single cause is definitely rarely the answer. And the point about pressure exerteb by different species is a good one. I know i was surprised when i was reading through the list of prey for largemouth bass (I'm from NY) and i saw alligators on it. (Source was Wikipedia) Fish, generally will eat anything that fits in their mouths, and this includes baby alligators or ducklings. In contrast mammalian predators with hunt specific sized animals, and lynx will steal bearcubs from the den in winter to eat, they aren't defended and are the right size so they are food. (This is also one of those things you do a double take of when first hearing about)
Really cool to see an authentic representation of the scientific process - formulating an answer, then realizing it doesn't explain the facts sufficiently, formulating a new answer, etc. What's especially awesome is that the comments are full of hypotheses and debate, that's science youtube at its best!
My barely-educated guess/hypothesis would be that seas and oceans have a significantly larger diverse variety of creatures so maybe species of all the other classes or kingdoms create more competition for fish. I'm not sure how that would mean there are many more fish yet fewer fishes than fresh water habitats, I just think it might be part of the reason or an important factor.
One thing not mentioned: River speciers come easier in contact with land-animals , fungi and plants, than ocean species. I have no idea about the numbers, but it seems to me like there are more interactions with very different species, leading to more niches in generel. In addition, one comment suggested, that many of the niches which exist in both, ocean and river, are occupied by invertebrstes in oceans, which do not seem that abundaned in rivers
It's just water temperature that changes faster in rivers, this affect the quantity of oxygen in the water, so the selection is stronger, same for pollution with flooding. The ocean is more stable. Fish with beneficial genetic traits are selected faster in riviers, while in ocean they have less opportunity to shine. Even the pressure of the water changes fast in rivers, like everyday, the speed of the stream too, while in ocean it's more soft, fish can adjust their height while in rivers they are limited.
Likely a combination of these effects. In my region of the great lakes the region has changed dramatically over a several thousand year period. Lots to happen to the fish.
I think this has more to do with covering all the ecological niches in an environment, even though a pond is super tiny it still naturally ends up with bottom feeders, top predators, lower level predators, fish that eat mostly vegetation, etc. And it should be pointed out that bodies of freshwater can be extremely different, you have rivers, lakes, canals, and they can all have massively different conditions, the species that is suited for a tiny, shallow runoff pond stuffed with vegetation isn’t necessarily suited for a massive lake with a rocky bottom and a lot of open water. Even though there is less physical space for individual fish, there is still a large difference in the conditions of the different freshwater environment, and there’s still a similar set of roles to be filled by these animals. Therefor, less fish, same amount of species.
I can cite a real life example of a new species being formed in quite a short amount of time due to the construction of a dam: The Ouananiche, or known in english as a ''Salmon Trout'', is a fresh-water species of Atlantic Salmons from NA which following the construction of the dam that now contain Lac-Saint-Jean and due to the time it was built, they didn't take consideration of migratory fishes in its engineering and thus a reasonable population of salmon got stuck in the lake. Following this event, they adapted themselves to living solely in fresh water and they were quite effective at it, to the point that the species survival is pretty much insured. If you look into the tributaries and sources of certain lakes, you can figure out what happened and how the species came to get here, for most often than not fishes over the generations tend to go downhill lakes and bodies of water, and can show you which situation might be the result of artificial insemination by humans or simply natural happenstance, by comparing which species is present at which step and how it relate to their natural relationship in the wild. Per example, if you find a series of 5 lakes, find out that while the lower lakes have trout, catfishes and small fry, yet one of the higher lakes has bass in it, it can be safely assumed that it is the result of artificial seeding because Bass heavily predate upon Trout earlier stages and thus you'll hardly find them cohabiting within the same areas, so to find them in a lake at a higher altitude than the lower ones would imply they somehow found their way up there without heavily affected their prey species population and distribution within lower lakes, which is simply impossible unless they were transported there. This can be a huge problem if it caused maliciously or without care, because ie if you put bass in one of the high lakes because you wanted to fish bass in the nearby lake, every single other lake downhill will eventually suffer from an influx of bass that will inevitably destabilize the local ecosystem, and its especially evident in lakes known for trout fishing, you can find it utterly ''ruined'' in less than a decade with hardly any trout left (bass aggressive overhunt destroy the trout demographic, as they can't predate on the adult ones BUT will eagerly eat their eggs and larvea by the mouthfull)
I like how the last hairstyle was Misty the water pokemon gym leader to go with the theme. Not to sound less intellectual than everyone else's comments 😜 Great questions and theories everyone!
The thing that came to my mind at the very start was maybe this question stems from a sampling bias. I’ve heard upwards of 90% of ocean species are as yet undiscovered
Nothing evolves from one kind of animal to another. Don't believe the lie which disrespects our ancestors. (And which makes mockery of the truth which is had in Christ)
@@johnsteinat5213 the sons in law of Lot in the story in genesis 19 also didn't take serious the words of Lot when he told them God would destroy Sodom. Bible says he seemed as one that mocked to his sons in law. All that said your not family and the only destruction I can foretell is that of the unbelievers when Christ returns.
@@jumpingfan5423 I still can't tell if you're being serious, coming to an education channel and preaching a religion. It seems like you are trolling. You don't even know my religious beliefs.
You have covered quite a few of the mechanisms that could explain fresh vs marine fish species. I'd like to raise a few others. One of the reasons that we know of fewer marine fossils than freshwater fossils is that we haven't really explored the ocean floor sufficiently to say for sure that there are fewer. We rely mainly on sub-sea rock formations that have been pushed up onto the land - so something of a sub-set of the ocean fossils. Also, I think I'm right in saying that, although the number of fish in the marine environment is larger than the number of fish in freshwater, again there are several factors. There is more marine water than fresh water, and I would suggest that there are far fewer fish per cubic metre in the oceans than in fresh water. This is because the primary food production is done by algae, which exist only in the upper layers of the water and in the shallow(ish) coastal waters, so the oceans cannot support as many fish per cubic metre as freshwater does. Plus there are large parts of the ocean that are anoxic. I know that the following is certainly not a new idea, but for years (going back to the mid to late 1960s) I have wondered whether a great deal of fish evolution started in freshwater, and that it is from freshwater environments that terrestrial vertebrate life evolved. Consider the fact that all (with one or two minor exceptions) freshwater fish are teleosts (bony fish), and all (with the same exceptions) elasmobranchs (non-bony fish) are marine. And consider also that only teleosts have a swim bladder. This suggests to me that teleost fish evolved in freshwater, along with the swim bladder. Most evolutionary changes do not occur in order to take advantage of a new environment. Fish did not, I suggest, move out of the water in order to exploit the terrestrial environment. Most evolutionary advances of this sort evolve as a way to remain in their environment. I know, that sounds counter-intuitive, but bear with me. Fish growing in lakes and ponds can be subject to stagnation and low oxygen. Gulping air from the surface can help to replenish their oxygen. Those that did this would survive these conditions better, and so produce more offspring. Those that kept that bubble of air in an area of their gut that was better at gas exchange would do better, and if that area were enlarged, they would do better still. The bigger the better. And eventually you have something that could be considered to be a swim bladder - and also could eventually evolve to be a lung. But why crawl out of the water? Well, if the water gets really stagnant, and its volume shrinks, then those fish that managed to flop about on land and - by luck - maybe get to some other water would beget more young. Think African lungfish. Also catfish. So you can see a good pathway for fish to evolve swim bladders, lungs and eventually limbs. I don't really see a good pathway for marine fish to get onto land. Most seas are tidal, and the intertidal zone is fairly difficult to live in - though there are lots of species that do. Mainly seaweeds, and those animals that can hide in the moisture trapped by them. Few of those animals are fish. Above the tidal zone, there is a barren area before any terrestrial plants grow - with only lichens growing their. So a fish emerging from the sea would have to cross all this in order to get to anything worthwhile getting to. Mudskippers are the only 'intertidal' fish that I can think of - and they don't really feature as terrestrial animals. They live - as the name suggests - on the mud when they are not in the water, and do not venture onto land proper - certainly not onto dry land. So - I think - marine fish moved gradually from the sea, upriver to fresh water, where they evolved into teleosts, with bony skeleton and a swim bladder, and eventually lungs of some sort. Some managed to survive on dry land until either they managed to get to more freshwater, or they survived until the fresh water returned (African lungfish do that). Some teleosts returned to the ocean, where they continued to evolve as fish.
Logical Paradox: This is a statement or a set of statements that contradict themselves or lead to a contradiction directly through logical inference. Logical paradoxes often arise in formal logic or mathematics and challenge the underlying principles of logical reasoning. Examples include the Liar Paradox, where a statement that declares itself to be false leads to a contradiction if it's either true or false, and Russell's Paradox, which questions the nature of sets in mathematics. Scientific Paradox: A scientific paradox occurs when observations or empirical evidence contradict current scientific theory or widely accepted explanations. These paradoxes are not necessarily contradictions in logic but highlight limitations or gaps in our understanding of the natural world. They often drive scientific progress by prompting revisions of theories or the development of new theories. An example is the Twin Paradox in special relativity, which involves differing time elapsed for two twins, one traveling at high speed in space and the other remaining on Earth. (copied from another comment)
The explanation is simple: Tropical area has more species variety then temperate area, which also has more variety then polar area. In harder environments less species thrive.
Glaciers can't explain the difference between the polar and the temperate diversity. A lot of temperate places didn't have glaciers and still show the same diversity as areas affected by glaciation.
That would imply tropical reefs would be far more diverse and would have more fish species. There are more tropical reefs than there are tropical riverlakes
The most important lesson to learn in evolutionary biology - which, I think it's fair to say, most evolutionary biologists have utterly failed to learn - is that there is no _one_ explanation for anything. It is always, without exception, a combination of factors. No matter what it is you're questioning.
I'm going to make a rough guess before watching the video. Quantity of fish species doesn't equal to fish population. So while the population of fish in the oceans is uncomparable to that of fresh water, the fresh water is sparcely divided between millions of rivers, lakes and swamps, each one of which has the potential to act as its own ecological niche, its own "Galapago island". Which means that fishes sepparated between those will evolve in their own sepparate ways, creating more species in the process. Knowing how people have found entire ecosystems of unique species completely closed within a subterranean lake within a single cave, that seems perfectly logical.
I would say the varied environments of the rivers allow for more niches. It could also be that oceans, which have more species overall, have more niches filled by other animals.
Cover and shelter for escaping predators plays a big role in species diversification and numbers. Rocks, crevices and other means of shelter create a safe heaven for survival and in return the fish can safely reproduce and even diversity into other species. A lot of the ocean is just empty space, Coral reefs account for 1% of the ocean, yet are home to nearly one-quarter of all ocean species. Freshwater habitats like the Rift Lakes and Rainforest rivers have logs, leaves, stones. The Lake Malawi in Africa holds over 600 different species, most of which reside closer to the edge of the shores where it's full of big stone boulders, rocks etc. A few hundred meters in and it gets more barren just like on the ocean floor. Guess what, less cichlid species to be found there.
Question: If we take the biblical story of Noah and the flood as fact what would be the effect of fish species? and would it correlate with this paradox? (I'm not set on the Noah story being literal, just playing with the idea of what the impact could be and would it correlate)
A large factor that wasn't mentioned is that it's easier to discover all freshwater species due to smaller overall area when compared to the vast ocean. The vast ocean is very likely we only have discovered a fraction of the total amount of species.
1. The environment for fish in fresh water is constantly changing from flooding, rainy seasons and dry seasons for example. 2. There are a lot more predators to escape from when you're in rivers or ponds that are easily accessible from shorelines. I think it's clear that fresh water fish have to be more adaptable to survive. A fish in the ocean that is being stalked by a predator at the shore line needs only to swim to deeper water.
Environmental diversity is my first instinct. I'm not a biologist, I'm an engineering student, but to me the number of different environments in rivers and lakes must be much higher than the number of unique ocean environments simply due to how disconnected they are. And this also explains why species aren't constantly evolving at an incredible rate in rivers, it's simply an already-high number staying high because a decrease in diversity would be unlikely without a mass extinction event; a river fish species going extinct could ravage its ecosystem and since we don't see this constant collapse in rivers all over the world it suggests that river species are very good at adapting to environmental changes, which is an ability that makes sense given the video's earlier point about the frequency with which populations are divided by changes in the river's path.
Also consider oceans contain more viruses. And salinity may play a role. It's undoubtedly multivariable with varying amounts of constructive/destructive impacts. Fascinating stuff.
I'd hypothesize that within any essentially cohesive ecosystem, there are a finite number of niche roles for species to fill. This would imply that in a very simple model of one large lake vs. one small pond, a roughly similar number of species would evolve to fill all relevant niches, kind of like how two countries, one large and one small, would essentially have all the same industries just at different scales or proportions. Then if you were to somehow merge the two environments, many species would become invasive and many others would become extinct, until all niches are again filled by the fittest species. The water itself prevents most species jumping that barrier. Another commenter (Rugved Kulkarni) proposed the excellent idea that if the paradox is particular to fish species then it could also be accounted for by non-fish species in the oceans filling ecological roles that fish species ended up filling in freshwater.
It's almost biology, especially genetics, is far more nuanced and complicated than people think - and even consisting of far more than we even know or think we know. It's funny how often people seem to think if science says something, it's written in stone. We change our minds constantly - science is just the best model of things we have at the moment.
Given we're counting species, I wonder if we're more likely to differentiate what we fish regularly out of freshwater sources compared to the oceans (where we let subspecies be subspecies). Just, are we sure this isn't a taxonomical quirk we're projecting onto fish?
One big factor that applies to the rapid spread of freshwater species is how some fish eggs can be transported through bird feces, and be deposited across vast distances to branch off from their original populations.
Does the salinity of their environment have any effect? I know for example that freshwater fish have more parasite, higher/lower level of different minerals, etc. Maybe one of these factors make diversification more advantageous.
i believe the fact ocean species over time can migrate through rivers also help this balance of species They are not completely separated, heck salmon is a great example how rivers and the ocean are always in the process of exchange
It's easier to live in fresh water. They don't have as many predators, in northern climates where the ice freezes over they only have to worry about each other, changes to the water makeup(chemicals, salt levels, other variables) aren't usually as extreme, and they have much more specific niches they can take advantage of. Think of catfish who have access to so much random stuff that's 'edible' they will eat anything. This is also part of why they have a much harder time with invasive species and habitat changes, and why many species come in from the ocean to lay their young. Salt water also has plankton, which takes up a lot of space despite being microorganisms. Others in the comments have also posed a lot of good points, and it's probably a mix of everything. No one specific reason, life just found a way
Freshwater habitats exist inside large areas of land that themselves comprise larger and more diverse ecosystems when compared to any general stretch of ocean water. That is to say that these freshwater habitats aren't isolated from their surroundings. The ocean is mostly a singular, massive body of saltwater, with little topological diversity across its volume compared to what can be found situated on land. This leads me to think that the freshwater paradox is far more complex when we consider how the density of diverse land ecosystems around any given bodies of water will drastically influence said bodies of water, contrasting with the relatively homogeneous "geography" of the oceans, which are vastly non distinct throughout the majority of their volume.
Interesting one thing which could potentially be related to this is the evidence that the ancestor of all extant cyanobacteria particularly including the lineage which gave rise to chloroplasts were or still are freshwater specialists with the oldest extant pelagic cyanobacteria dating to the Neoproterozoic suggesting the first colonized the open ocean around the same time as the first Eukaryotic algae. That said as the evidence for cyanobacteria goes back much further than the last common ancestor of extant cyanobacteria it is likely a bit more complicated (especially since the timing for the last common ancestor of Cyanobacteria matches up fairy closely with the Sudbury impact Additionally the closest archaeal relatives to Eukaryotes are also being found from metagenomic sampling of shallow estuaries freshwater environments or soil building up the case that complex life as we know it likely originated on or around the continents back in the paleoproterozoic. If this is the case it is possible that there is just been more time for freshwater speciation relative to marine speciation. Of course fish are pretty recent in evolutionary terms compare to all this but the fossil record does support the first fish being relatively limited to shallow lagoons and estuaries potentially only colonizing the open waters during the Devonian so maybe a continent first model could work there too?
I think I’m addition to the things listed, there is far more variety with fresh water. Huge ranges of PH, completely different aquascapes, River speeds, it goes on and on. Where as ocean just kinda has maybe a couple different types of biomes. More biomes means more species.
Stable ecosystem don’t always result in more species, there becomes a point where stability can result in lower diversity. I was just learning this in my college evolution class. The most fit species come to dominate and outcompete extremely stable environments. Diversity is lowest in very unstable and very stable environments. Lakes likely provide that nice middle ground.
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first to comment
All of the ocean fish drowned in the great flood from the bible, but the freshwater ones didn`t.
@@samueltrusik3251 Pah, the bible! Never will I believe that a man as old as Moses can hold the water that long.
@@j-core2895 /;. ẞẞ।
@MinuteEarth I add 1!
One question I have: does this paradox apply only to fish or all aquatic species? I would imagine a coral reefs has much more diversity of invertebrates than any lake. If so could invertebrates be taking ecological niches filled by fish in freshwater environments?
This is a good point! Plus, if we look at the size of the body of water instead of just salinity, how does that skew things? I mean, just because Lake Tanganyika and Lake Baikal are fresh water, doesn't mean they aren't more ecologically akin to oceans than most rivers or shallower lakes.
This is an amazing point and I would like to know if the numbers do change.
Very good question.
I think water hardness and acidity seem like important factors for that, since the ocean has a lot of stuff dissolved in it that freshwater being fed mainly by rain is going to be deficient in (to explain acidity, I've heard some streams are really acidic, but I only know of people saying it's a problem for crustaceans in reference to ocean acidification). Intermittent availability of minerals in fresh or brackish water makes bones useful batteries for calcium and phosphate as modern bony fish partially use them, we even metabolize our bones when we have calcium deficiencies, though bone-tooth skin coverings seem to have started in the oceans.
Bony fish just seem better tuned for freshwater from the perspective of adaptation since crustaceans have weaker armor if they don't use a lot of minerals, and using a lot means the animal is vulnerable to periods of low nutrients from downpours while it gets the material for the new skin. They're really effective at being plankton sized in freshwater and everywhere else more than fish have been though.
@@thetobyntr9540 are you saying that the innovator of bones was a freshwater fish? i would've assumed oceanic but i don't know. freshwater habitats are a hell of a lot older than bones so quite possible.
Is it also possible that we have just discovered a comparatively smaller percent of ocean species? It's a lot easier to find freshwater species. One you can wade to, the other requires fishing lines, nets, or scuba gear.
Yup
That's probably part of it, but a big factor is just how much easier it is to move around the ocean. Even with a hard to penetrate barrier at each of the oceans, you're still dealing with a number that's small enough to be easily counted. With lakes and rivers you're talking about thousands and possibly millions of areas that species need to work their way to and some of them are only connected by seasonal streams, even though the lake itself does exist all year round.
The common factor with every option you proposed is the fact that the ocean is 1 habitat but every river or lake is it's own. A single Tuna can range a third of the world. Not so with a lake trout.
Not necessarily, the ocean has its own barriers that form smaller habitats, it is true that there are species that live basically anywhere, but there are others that adapt to very specific places, such as reefs or the seafloor.
@@manjensen1710 The ocean still has barriers, but I think it's safe to say that it has much less barriers and individual cut off areas than freshwater environments.
I agree, even though species appear at the same rate, the different river conditions and barriers lead to many different optimum paths in evolution. Whereas the sea is overall more uniform, the possibly roles in the environment are reduced. One highly efficient fish can overtake many others in a whole ocean, not so much in a river.
There are plenty of animals with ridiculous ranges, including "fresh", "semi freshwater?" Transiently freshwater? Fish/ aquatic creatures. Eels for the uk travel across the atlantic to do the do. Salmon in the pacific swim inland and up into the rockies to inherited spawning streams.
@@left4twenty exceptions.
Alternative theory: it’s actually scaled. (Pun intended) there really is a lot more fish in the ocean than the rivers. We just haven’t discovered most of them. Reasons being, it’s much much easier to explore rivers and lakes than oceans. In a River the individual fish is more unique and noticeable so it’s easier to track them. In an ocean one fish is easier to mistake for another, even in different species, making the illusion of less fish. Its also probable that it’s a combination of all these theories that cause this
Freshwater Fish are not more unique and noticeable though. Have you ever tried to identify a minnow species?
@@thesqrtofwhy758 the point i think the fellow is trying to make is space differances.
My idea is not to say fresh vs salt but to compare Inland bodies of water vs open bodies of water.
Also where do brackish species fall?
Since they can technically inhabit both?
Seas, gulfs, and oceans are open bodies.
And obviously rivers, lakes, streams are open bodies.
To me there are more "fresh" or inland species due to more inland species can interact with the fish.
In the ocean fish swim (run away from) fish.
In the streams, EVERYTHING is out to get you.
I mean yeah there are exceptions like aquatic mammals and diving birds.
But in-land bodies of water means that any bird can swoop down, any mammal can dive in, any reptile can tolerate the non-frigid waters of and in-land body of water.
As such the need to adapt is even higher.
There are a few ways to adapt in the ocean but the in-land waters have so much more variables.
You cant deep dive like you could in the ocean, you can evolve to adapt to frigid temps to avoid the reptiles, you cant grow super large like you could in the ocean. The rules for adapting are more constrained.
Yes there is PLANT LIFE due to less salinity as such thats a key stone species. Then river naturally have BEAVERS, another keystone species, so theres so much more competition from every frontier. The ocean had its protections that in land bodies of water cant provide.
I think you're ignoring the vast scale of where freshwater fish can be. There are cave systems, filled with fresh water, that we have been unable to explore due to limitations. Exploration devices need to be small and flexible enough to manouvre through a lot of odd gaps, while the device needs a cable attached due to wireless transmission being blocked/interfered with the sheer amount of rocks and minerals between places.
Thats not considering small ponds or marshlands where there can be any fish hiding between mosses, under sand, between twigs, looking extremely similar to another already identified species, or simply being transparent.
I mean, just look at how many different new species of bugs are discovered on a yearly basis. And how many of these new species look extremely similar to already known species or how difficult they are to find. Thats humans actively being able to get up close to either catch a specimen or to take a sample for DNA testing.
Thats not even considering that while freshwater and saltwater fish are very seperate habitats right now, they werent always that seperated. Its not unlikely for a lot of rivers and lakes to have been salt water, and since coast lines are to this day a huge source of biodiversity, its not unlikely that a majority of these fish followed salt water and went into the lands, and then were slowly forced to adapt to water containing less and less minerals. Since this could mean that a lot of aquatic biodiversity went land inwards, millions of years ago and that the biodiversity we see out there today is artificially lowered due to that migration too.
There are a LOT of reasons why we cant narrow it down, and it is probably multiple of those reasons combined. Lakes, rivers and ponds have a lot more diverse environments overall, but the ocean would have more room for artificial diversity through more fish sharing the same environment. A mudskipper doesnt have to fear the interference of a goldfish for example, but a seabass does have to fear the interference of the eel.
I don't find this counter intuitive at all. I wouldn't expect more water to automatically give rise to more species. Each species has to fill it's own ecological niche and I don't expect there to be more niches if you just have more of the same environment. What I would expect is that the species in oceans are "more evolved"/better adapted since there is more space for benificial mutations to happen
I would say they are less evolved, because they are adapted to a static habitat where no variation exists. There would be no reason to evolve into something, when all abiotic factors remain the same both spatially and temporally.
@@silversurfer8818 Good point, "more evolved" wasn't the right way to put it. I meant something like "their fitness is closer to a local maximum because they had more opportunities to take a convergence step".
Also, the deep water is less habitable than the shallow areas near the coast, so measuring habitable area versus water volume may make more sense.
Couldn't agree more. The equation starts looking a whole lot simpler when you look at how many rivers and lakes there are versus the number of oceans. There are just so many more variations in the environment when you compare rivers and lakes rather than oceans.
skundaihoy 👊
As a fishkeeper, it's amazing to see how overlooked actually is by laymen the huge biodiversity of lakes and rivers - When setting up a freshwater aquarium, the variety of fish of any size, colour, shape and biological niche is absolutely stunning.
I'm pretty sure biologists don't know the definition of paradox
To me it seems as if someone made up a rule to which there are more exceptions than conforming instances.
I mean this is a Falsidical paradox, which is known as the least paradoxical paradox.
Neither do archers or philosophers named Zeno.
Or maybe you don't?
@@c.jishnu378 But it is a veridical paradox...
Having kept both I would say that it's the variable conditions in freshwater (seasonal run-off, evaporative chemistry etc) and oceanic conditions are much more stable (hence coral die-off from minute calcium changes) leaving freshwater fish more resilient, and better able to weather environmental changes thus leading over time to more freshwater diversity.
I would also suggest, that’s because of the fact that in a smaller habitat, there is more competition which always is the motor of evolution. To be successful the individuals have to come up with different strategies to sustain them self. Also, in the Oceans there is a bigger variety of size, there are big mammals like Whales, Dolphins and also bigger fish like Sharks. We know that bigger animals have a bigger need of territory which leads to less animals per space unit. Also, they have a slower reproduction time, I think. Both effects add up to lower reproduction rate and therefore fewer times a mutation could appear.
I think a big factor is also that in fresh water there’s a bigger variety than in salt water in terms of the habitat. On the one hand we have swamps, lakes, rivers etc. and on the other hand we have the ocean (and some lakes of cause but they often end up so salty no fish can survive at all in it). This makes more different challenges for fresh water fishes which have to adapt to it in different ways.
So yeah, there are a lot of different things that add up to this effect. Correct me if my logic fails at some points
Not to mention the climate affects rivers and lakes far more than the ocean! A lake in Northern Europe would be a totally different environment from a river in the Amazons.
@@dundee6402 Yes you are right! the ocean woud never freeze shut!
he literally brought up that fact and debunked it
Again, YOUR OPINION THERE ALREADY COVERED IN THIS VIDEO.
This video also talk about ISOLATIONISM. But...
Man.. Just watch the video again. I dont need to explain it again
@@DBT1007 you clearly dont get my points, they named some of the Ideas I was talking about in the Video but didn't explain them really andalso not everything I mentioned. So this comment has its right to exist as it's providing new information
I appreciate all of the small Pokémon references in your videos!
Fun fact: Nearly 97% of the world’s water is salty or otherwise undrinkable. Another 2% is locked in ice caps and glaciers. That leaves just 1% for all of humanity’s needs - all its agricultural, residential, manufacturing, community, and personal needs.
Have we tried building a giant fan in the middle of the ocean that blows clouds away so fresh rainwater only falls onto land?
@@Champs-ek7lh no, you might want to patent that idea
2 main solutions are desalination (basically a filter process good enough to remove salt)
And reuse, sewage is mostly water and treatment makes it safe enough to release into rivers, it is possible to treat it enough to supplement drinking water needs. (Its just most people will still be squeamish about it, myself included)
And don't forget about good old fashioned use less.
Also some of this 1% needs to be left alone so that lakes and rivers can continue to exist and benefit the environment and therefore us.
DISTILLED WATER=RAIN is the only water we supposed to drink. It's pure water free of nasty stuff which removes the toxins from the body/nature etc. We get minerals and vitamins from food. Now we are simply poisoining our body and the water we drink DOES NOT cleanse us at all because it's full of nasty stuff. We are living a really wrong life. This lifestyle they have indoctrinate in our generations make us sick and THEY are happy about that. RETHINK YOUR LIFE. RESEARCH. DO NOT TRUST ''SCIENCE''.
@@pinakkoladaa uhh rain isn't distilled water, rain forms around condensation nuclei which means dust and it picks up air pollution. Coal plants spew out lots of soot, Sulphur Dioxide, Nitrogen Dioxide, and Uranium. All of this gets picked up by rain and falls back down to earth. It results in the pH balance of NY lakes shifting and leaves dirt on your car after a storm in urban areas. (Cities tend have more fossil fuel power plants near them)
Besides:
1. our primal ancestors drank from lakes and streams like every other animal. (And probably got a lot of water borne diseases from it)
2. Drinking nothing but true distilled water is unhealthy as you are expected to get some minerals from your filtered ground water.
3. I was raised on a well and my dog drank from our chlorinated pool and never had any side effects. (Pool water, village water, liquid pool chlorine, and laundry bleach all are the same thing, hypochlorous acid in water at different concentrations)
Thank you for having the courage to say that, as of now, we don't know! It seems that many people are really uncomfortable with "we don't know"! We need more of this as "we don't know" is the driving force of MORE science!!!
Easily one of my favorite video topics to have researched! Especially learning the wildly rapid speciation of African rift lake cichlids. 🤯
Are you the narrator?
@@anchiit Pretty sure it's him. Why else is this comment made before the vid went public?
@@anchiit yep narrator and writer!
@@julianaquascaped cool cool cool
@@anchiitabed?
Rivers would have the most oxygenated water, among other things. But even if that somehow doesn't matter, it sounds like the problem was the initial premise.
Maybe it's just easier to monitor rivers than oceans, due to far less area?
Meaning there could very well be far more ocean species we have no idea about?
I can’t remember the specifics, but when counting fish or species of fish it’s often more statistics than anything. Instead of counting every species we can find we instead create as accurate a model as possible and we guess to fill in the gaps. Assuming we actually have a good understanding of ocean ecology these kinds of models give us a general idea of both how much we do and how much we don’t know. Your point still stands, but it is something that people are aware of and try to work around.
Most land animals drink fresh water to survive, so I'd assume the transition from sea to land happened in a fresh water environment. Which could help explain the diversity paradox! Living in fresh water is more energy efficient. Consequently, this can allow for faster rates of speciation when competing for new ecological niches that appear after each extinction. Also can explain why lakes have less species, as it being a closed environment, it'll have a smaller amount of ecosystems to emerge after any given extinction. Smaller amount of niches to compete for.
Excellent, that's how science works, perfect example of how science left to different options and discuss itself watching for a better explanations.
Freshwater, particularly rivers have way more niches for life to find, as they span different biomes, temperatures, minerals, etc. The ever changing rivers allow for very different compositions and environments, there's a much more diverse amount of predators (bird, mammals, lizards, insects, etc) and plants because all the land-based animal and plant species interact with it. More niches allow more species to co-exist at the same time. Coasts on the other hand are mostly the same in most places. Lakes are too small and too static to give serious competition between the species that would require tight niches; they'd cause species to be stuck on local optima for quite a while.
I wouldn't say lakes are too small to have many niches, even small lakes can be over 100ft deep which creates more of a vertical separation than a horizontal one.
Granted a lake with a long diameter of 2 miles is not going to have as diverse of environments as a river starting life as a mountain pond/marsh and running over 200 miles to the ocean through mountains, hills, forrests, plains and even cities.
This is exactly my thought. Freshwater habitats - and especially non-lacustrine habitats - are incredibly heterogeneous and diverse! So many unique niches to fill. Add in that they are also often very isolated and not only do you have a lot of niches to fill, you often have a different species filling each niche in different systems. Coming from Australia where basically everything is highly diverse for exactly these reasons the fish paradox just doesn't seem that odd to me I guess? I'm only a 2nd year undergrad so if this is the state of the science I'll have to defer to those better equipped but even if the numbers are odd the cause just seems pretty obvious from my perspective.
Pretty smart of you. My brian isn't so good.
I love the sea but it terrifies me - and I suspect that creatures feel the bad vibes, too. All that emptiness carries a resonance of fear that stops exploration.
Its a strange thing coz the emptiness of space doesnt give us the same vibe.
@@michaelh7741 At least you can see in space, and you know there isnt something lurking right under you.
I watched a video by _Real Science_ called _Why Hybrid Animals May Take Over the North._ At around the 11:00 mark they were discussing how the hybridization of fish dramatically increases the rate of speciation.
If you compare one habitable zone of the ocean to one individual lake you will learn that the ratios are equal. The number of species in a lake and the number of fish associated with each species will be near equivalent to the number of species in that section of Ocean and the number of fish associated with each species. It's not a paradox it's just spacial geometry.
so this paradox is more than likely a logical fallacy?
@@FireBolt-xq5dt I guess it's both ...
That seems very reasonable, and I believe you’re stating it as fact, not speculation, but I would ask how you plan on dividing up the oceans into habitable zones? Itwould be to easy to say that you divide it into the same n number of zones as there are lakes/rivers, but that’s not accomplishing anything toward understanding the underlying systems, it just shifts the answer to an impractical solution.
as game developer I'm 100% sure it's because "optimization"
why spend more 3D model, AI, and weird gameplay in ocean where player will mostly spend it's playtime in land
That's why deep fish are so weird, they were procedurally generated
ok TierZoo
This is like a super short RadioLab episode. "Let's ask a really interesting question, examine all sorts of evidence suggesting possible answers, then throw our hands up and conclude that nobody really knows for sure."
Its so refreshing to see your videos where you roughly show the scientific dialog and also were things are unexplained. its just so much more interesting and authentic than these overly polished stories about how science just knows it all
Divergent evolution relies upon two or more populations of a species being for one reason or another unable to mate with eachother, and eventually over millions of years becoming their own unique species.
One major driving force behind divergent evolution is physical separation, which is nonexistent in the ocean.
I would argue that because oceans have more mobility and fewer isolated environments than freshwater, it encourages species homogenisation more than freshwater.
The unusual thing isn't why freshwater environments have more fish species, but why oceans have fewer species.
Yeah, perhaps because of the vastness of the ocean, it becomes more difficult for a niche species to find a mate, so a greater diversity in fish species is selected against in the ocean, whereas in rivers it's less of a problem
Most of the ocean is aquatic desert.
Well what about non-fish species that inhabit both salt and freshwater? Are patterns similar to those shown by fish also seen among molluscs, crustaceans, worms, sponges, etc.?
I think it's way simpler than all of that. The ocean is harder to look in than rivers and lakes are. It's so hard to look in that it's actually easier to look at the bottoms of fossil oceans which happen to now be situated neatly on dry land, simultaneously explaining the wealth of speciation in marine fossils.
We do find our ocean fossils on land though. Also, the question is about modern species not past ones.
Btw, any sandstone deposits were probably laid down by a shallow sea. I have some in my area and if you look at the banding of sand grain sizes you can see when the ocean levels rose and fell (large=shallow small=deep). Since only near the shore do ocean currents have the power needed to move bigger sand grains so they never make it that far out.
The peak of Mount Everest is actually ancient seabed as well.
Random science person away!
This answers questions I'd never thought to ask, and left me with new questions!🤔
Bravo! Well done!👏👏👏
Could it not just be that humans have discovered more freshwater species? Vast swaths of the ocean are unexplored, while freshwater habitats are much easier to access and we spend way more time in and near them, while most of our interaction with the ocean is just at the coast.
I'd imagine that the vastness of the ocean can lead to similar levels of isolation, comparable maybe to disjointed rivers and lakes, if a fish were to drift out of its usual roaming range for example
Thank you for presenting the competing ideas on science. I find it so perplexing that people on internet sometimes just concoct an explanation through evolutionary analysis that "sound good enough" and then just regard it as truth. These evidences and rebuttals are more valid science.
1:12
Even if the ocean and freshwater areas develop new species at a similar rate, isolationism still plays a part.
Just because you may have the same amount of new-speciation in both environments, the oceans being interconnected rather than divided means that it's harder for new species to compete against long established species that can migrate between areas. Conversely, lakes and rivers being isolated from other lakes and rivers means that new species are likely to have less competition from species that have developed in other freshwater areas, meaning that they can have a higher chance to stick around and develop further into distinct species in their ecological niches. Even if those niches are the same as other lakes and rivers that species can't easily travel between.
That's not to say that all the oceans are all interconnected easily enough for species to migrate between oceans, there are still some ocean species that have a hard time getting from say the Atlantic to the Pacific, but oceans all sharing the same body of water can definitely help.
this man sounds like he's constantly about to drop into a kermit impression
The fluent occupation of niches by big fish over the course of their lifetime might be part of it, no?
The bigger a predatory species grows, the more often it needs to adjust it's food source to supplement its continous survival.
And fish especially go through an exponential amount of niches as their growth cycle starts on the microscopic level of zooplankton for most of them.
Bluefins start as 3mm larva bevore gaining literally 3million times their weight until they are fully grown, the amount of different niches they compete in over their life cycle is insane. And since ocean fish naturally grow many times larger than the average freshwater-fish while still starting from literal larva rock bottom, they can compete with and outclass every fish of the same or smaller size in every state of their growth.
And since the amount and pressure of tuna for instance is over an infinitely larger area than one or two relatively big pike reproducing in a single pond of a river system, fewer species are "needed" to reach that equilibrium of new species/extinction.
Also resulting, bigger predatory fish excert pressure onto the entire food pyramid permanently while a mammalian, terrestrial predator will stay on the same prey items of a single weight class all their life, with the early life being covered by milk until learning to hunt what the adults hunt.
In that a lion will never exert direct pressure onto bugs for instance as the entire predatory bottom food pyramid from plant over rodents to jackals up until the big predators/prey items will never stand in direct competition with a lion.
Not that's the only factor of course, if studying biology tought me anything then that a single cause is literally never the full answer.
A single cause is definitely rarely the answer.
And the point about pressure exerteb by different species is a good one. I know i was surprised when i was reading through the list of prey for largemouth bass (I'm from NY) and i saw alligators on it. (Source was Wikipedia)
Fish, generally will eat anything that fits in their mouths, and this includes baby alligators or ducklings. In contrast mammalian predators with hunt specific sized animals, and lynx will steal bearcubs from the den in winter to eat, they aren't defended and are the right size so they are food. (This is also one of those things you do a double take of when first hearing about)
Really cool to see an authentic representation of the scientific process - formulating an answer, then realizing it doesn't explain the facts sufficiently, formulating a new answer, etc.
What's especially awesome is that the comments are full of hypotheses and debate, that's science youtube at its best!
This makes me remember the episode on how there is more species in nutrient poor areas.
My barely-educated guess/hypothesis would be that seas and oceans have a significantly larger diverse variety of creatures so maybe species of all the other classes or kingdoms create more competition for fish. I'm not sure how that would mean there are many more fish yet fewer fishes than fresh water habitats, I just think it might be part of the reason or an important factor.
One thing not mentioned: River speciers come easier in contact with land-animals , fungi and plants, than ocean species. I have no idea about the numbers, but it seems to me like there are more interactions with very different species, leading to more niches in generel.
In addition, one comment suggested, that many of the niches which exist in both, ocean and river, are occupied by invertebrstes in oceans, which do not seem that abundaned in rivers
Niches.
@@CountingStars333 thanks! (english is not my first language)
It's just water temperature that changes faster in rivers, this affect the quantity of oxygen in the water, so the selection is stronger, same for pollution with flooding. The ocean is more stable. Fish with beneficial genetic traits are selected faster in riviers, while in ocean they have less opportunity to shine. Even the pressure of the water changes fast in rivers, like everyday, the speed of the stream too, while in ocean it's more soft, fish can adjust their height while in rivers they are limited.
Likely a combination of these effects. In my region of the great lakes the region has changed dramatically over a several thousand year period. Lots to happen to the fish.
I think this has more to do with covering all the ecological niches in an environment, even though a pond is super tiny it still naturally ends up with bottom feeders, top predators, lower level predators, fish that eat mostly vegetation, etc. And it should be pointed out that bodies of freshwater can be extremely different, you have rivers, lakes, canals, and they can all have massively different conditions, the species that is suited for a tiny, shallow runoff pond stuffed with vegetation isn’t necessarily suited for a massive lake with a rocky bottom and a lot of open water. Even though there is less physical space for individual fish, there is still a large difference in the conditions of the different freshwater environment, and there’s still a similar set of roles to be filled by these animals. Therefor, less fish, same amount of species.
...first? wow I feel like it's 2008
You're the first! So old school... - Ever
I love learning science from Squidward. Now u can't unhear it
0:10 what about the 0.3% of the water?
Ice
Ice
Ice
Ice
Groundwater
I can cite a real life example of a new species being formed in quite a short amount of time due to the construction of a dam: The Ouananiche, or known in english as a ''Salmon Trout'', is a fresh-water species of Atlantic Salmons from NA which following the construction of the dam that now contain Lac-Saint-Jean and due to the time it was built, they didn't take consideration of migratory fishes in its engineering and thus a reasonable population of salmon got stuck in the lake. Following this event, they adapted themselves to living solely in fresh water and they were quite effective at it, to the point that the species survival is pretty much insured.
If you look into the tributaries and sources of certain lakes, you can figure out what happened and how the species came to get here, for most often than not fishes over the generations tend to go downhill lakes and bodies of water, and can show you which situation might be the result of artificial insemination by humans or simply natural happenstance, by comparing which species is present at which step and how it relate to their natural relationship in the wild. Per example, if you find a series of 5 lakes, find out that while the lower lakes have trout, catfishes and small fry, yet one of the higher lakes has bass in it, it can be safely assumed that it is the result of artificial seeding because Bass heavily predate upon Trout earlier stages and thus you'll hardly find them cohabiting within the same areas, so to find them in a lake at a higher altitude than the lower ones would imply they somehow found their way up there without heavily affected their prey species population and distribution within lower lakes, which is simply impossible unless they were transported there. This can be a huge problem if it caused maliciously or without care, because ie if you put bass in one of the high lakes because you wanted to fish bass in the nearby lake, every single other lake downhill will eventually suffer from an influx of bass that will inevitably destabilize the local ecosystem, and its especially evident in lakes known for trout fishing, you can find it utterly ''ruined'' in less than a decade with hardly any trout left (bass aggressive overhunt destroy the trout demographic, as they can't predate on the adult ones BUT will eagerly eat their eggs and larvea by the mouthfull)
At 1:34 you can clearly see Luke SkyWater vs Darth Laker
I’ll see myself out
It's the isolation, that's the main factor. You said it yourself, the recent study you mentioned also confirms this
I’m one of the ocean going fish that went extinct long ago.
Okay, the fish with light sabers just about killed me.
It just has to be aliens...
I like how the last hairstyle was Misty the water pokemon gym leader to go with the theme. Not to sound less intellectual than everyone else's comments 😜 Great questions and theories everyone!
I thought the answer was going to be isolation.
Great video...it almost felt like a CGP Grey topic, and I'm here for it!
I think that since we haven’t explored the ocean as much as rivers and lakes that we simply haven’t discovered a lot of the ocean’s species
0:17 what's the remaining bit?
Ice
@@Owen_loves_Butters Isn't that freshwater?
@@cycrothelargeplanet No because it isn't water
@@Owen_loves_Butters frozen water isn't water?
@@cycrothelargeplanetyou can't swim or drink it
The thing that came to my mind at the very start was maybe this question stems from a sampling bias. I’ve heard upwards of 90% of ocean species are as yet undiscovered
Today's fish is trout à la carte. Enjoy your meal.
Fish *taste good*
Used to watch your channel 6-7 years ago
Subbed
As long as the fish stay delicious they can evolve were they please (where someone can get them to me)
Nothing evolves from one kind of animal to another. Don't believe the lie which disrespects our ancestors. (And which makes mockery of the truth which is had in Christ)
Good Fish
@@jumpingfan5423 I can't tell if you are serious or not
@@johnsteinat5213 the sons in law of Lot in the story in genesis 19 also didn't take serious the words of Lot when he told them God would destroy Sodom. Bible says he seemed as one that mocked to his sons in law. All that said your not family and the only destruction I can foretell is that of the unbelievers when Christ returns.
@@jumpingfan5423 I still can't tell if you're being serious, coming to an education channel and preaching a religion. It seems like you are trolling. You don't even know my religious beliefs.
You have covered quite a few of the mechanisms that could explain fresh vs marine fish species. I'd like to raise a few others.
One of the reasons that we know of fewer marine fossils than freshwater fossils is that we haven't really explored the ocean floor sufficiently to say for sure that there are fewer. We rely mainly on sub-sea rock formations that have been pushed up onto the land - so something of a sub-set of the ocean fossils.
Also, I think I'm right in saying that, although the number of fish in the marine environment is larger than the number of fish in freshwater, again there are several factors. There is more marine water than fresh water, and I would suggest that there are far fewer fish per cubic metre in the oceans than in fresh water. This is because the primary food production is done by algae, which exist only in the upper layers of the water and in the shallow(ish) coastal waters, so the oceans cannot support as many fish per cubic metre as freshwater does. Plus there are large parts of the ocean that are anoxic.
I know that the following is certainly not a new idea, but for years (going back to the mid to late 1960s) I have wondered whether a great deal of fish evolution started in freshwater, and that it is from freshwater environments that terrestrial vertebrate life evolved. Consider the fact that all (with one or two minor exceptions) freshwater fish are teleosts (bony fish), and all (with the same exceptions) elasmobranchs (non-bony fish) are marine. And consider also that only teleosts have a swim bladder. This suggests to me that teleost fish evolved in freshwater, along with the swim bladder. Most evolutionary changes do not occur in order to take advantage of a new environment. Fish did not, I suggest, move out of the water in order to exploit the terrestrial environment. Most evolutionary advances of this sort evolve as a way to remain in their environment. I know, that sounds counter-intuitive, but bear with me. Fish growing in lakes and ponds can be subject to stagnation and low oxygen. Gulping air from the surface can help to replenish their oxygen. Those that did this would survive these conditions better, and so produce more offspring. Those that kept that bubble of air in an area of their gut that was better at gas exchange would do better, and if that area were enlarged, they would do better still. The bigger the better. And eventually you have something that could be considered to be a swim bladder - and also could eventually evolve to be a lung.
But why crawl out of the water? Well, if the water gets really stagnant, and its volume shrinks, then those fish that managed to flop about on land and - by luck - maybe get to some other water would beget more young. Think African lungfish. Also catfish.
So you can see a good pathway for fish to evolve swim bladders, lungs and eventually limbs.
I don't really see a good pathway for marine fish to get onto land. Most seas are tidal, and the intertidal zone is fairly difficult to live in - though there are lots of species that do. Mainly seaweeds, and those animals that can hide in the moisture trapped by them. Few of those animals are fish. Above the tidal zone, there is a barren area before any terrestrial plants grow - with only lichens growing their. So a fish emerging from the sea would have to cross all this in order to get to anything worthwhile getting to.
Mudskippers are the only 'intertidal' fish that I can think of - and they don't really feature as terrestrial animals. They live - as the name suggests - on the mud when they are not in the water, and do not venture onto land proper - certainly not onto dry land.
So - I think - marine fish moved gradually from the sea, upriver to fresh water, where they evolved into teleosts, with bony skeleton and a swim bladder, and eventually lungs of some sort. Some managed to survive on dry land until either they managed to get to more freshwater, or they survived until the fresh water returned (African lungfish do that).
Some teleosts returned to the ocean, where they continued to evolve as fish.
Well, nature and science are all weird and… fishy
There's more energy available in the rivers. More light hits the bottom, more minerals in the water, plant life means more variability
This is evidently not a paradox...
Logical Paradox: This is a statement or a set of statements that contradict themselves or lead to a contradiction directly through logical inference. Logical paradoxes often arise in formal logic or mathematics and challenge the underlying principles of logical reasoning. Examples include the Liar Paradox, where a statement that declares itself to be false leads to a contradiction if it's either true or false, and Russell's Paradox, which questions the nature of sets in mathematics.
Scientific Paradox: A scientific paradox occurs when observations or empirical evidence contradict current scientific theory or widely accepted explanations. These paradoxes are not necessarily contradictions in logic but highlight limitations or gaps in our understanding of the natural world. They often drive scientific progress by prompting revisions of theories or the development of new theories. An example is the Twin Paradox in special relativity, which involves differing time elapsed for two twins, one traveling at high speed in space and the other remaining on Earth.
(copied from another comment)
Why would anyone assume that the 50% of fish species we’ve seen in the ocean is anywhere close to the total amount of species in the ocean?
The explanation is simple: Tropical area has more species variety then temperate area, which also has more variety then polar area. In harder environments less species thrive.
Not always that simple. Have you watched this?: th-cam.com/video/mWVATekt4ZA/w-d-xo.html - Ever
actually it's the opposite : th-cam.com/video/mWVATekt4ZA/w-d-xo.html
Glaciers can't explain the difference between the polar and the temperate diversity. A lot of temperate places didn't have glaciers and still show the same diversity as areas affected by glaciation.
Equatorial areas have very rich soil and very greedy vegetation, yet they show much greater diversity then everything else.
That would imply tropical reefs would be far more diverse and would have more fish species. There are more tropical reefs than there are tropical riverlakes
0:27 that lanternfish looks awfully familiar…
The most important lesson to learn in evolutionary biology - which, I think it's fair to say, most evolutionary biologists have utterly failed to learn - is that there is no _one_ explanation for anything.
It is always, without exception, a combination of factors. No matter what it is you're questioning.
Global flood?
maybe fish are more likely to mutate in shallow rivers than deep under countless layers of water which act to dilute radiation
Well that was a waste of my time.
I'm going to make a rough guess before watching the video.
Quantity of fish species doesn't equal to fish population. So while the population of fish in the oceans is uncomparable to that of fresh water, the fresh water is sparcely divided between millions of rivers, lakes and swamps, each one of which has the potential to act as its own ecological niche, its own "Galapago island". Which means that fishes sepparated between those will evolve in their own sepparate ways, creating more species in the process.
Knowing how people have found entire ecosystems of unique species completely closed within a subterranean lake within a single cave, that seems perfectly logical.
"Less than a tenth of 1% [...]" is probably the most convoluted way to say 0.1% or one hundredth.
I would say the varied environments of the rivers allow for more niches. It could also be that oceans, which have more species overall, have more niches filled by other animals.
Cover and shelter for escaping predators plays a big role in species diversification and numbers. Rocks, crevices and other means of shelter create a safe heaven for survival and in return the fish can safely reproduce and even diversity into other species.
A lot of the ocean is just empty space, Coral reefs account for 1% of the ocean, yet are home to nearly one-quarter of all ocean species. Freshwater habitats like the Rift Lakes and Rainforest rivers have logs, leaves, stones. The Lake Malawi in Africa holds over 600 different species, most of which reside closer to the edge of the shores where it's full of big stone boulders, rocks etc. A few hundred meters in and it gets more barren just like on the ocean floor. Guess what, less cichlid species to be found there.
Question: If we take the biblical story of Noah and the flood as fact what would be the effect of fish species? and would it correlate with this paradox?
(I'm not set on the Noah story being literal, just playing with the idea of what the impact could be and would it correlate)
A large factor that wasn't mentioned is that it's easier to discover all freshwater species due to smaller overall area when compared to the vast ocean. The vast ocean is very likely we only have discovered a fraction of the total amount of species.
1. The environment for fish in fresh water is constantly changing from flooding, rainy seasons and dry seasons for example.
2. There are a lot more predators to escape from when you're in rivers or ponds that are easily accessible from shorelines.
I think it's clear that fresh water fish have to be more adaptable to survive. A fish in the ocean that is being stalked by a predator at the shore line needs only to swim to deeper water.
I like how you use Misty as the mascot
Environmental diversity is my first instinct. I'm not a biologist, I'm an engineering student, but to me the number of different environments in rivers and lakes must be much higher than the number of unique ocean environments simply due to how disconnected they are. And this also explains why species aren't constantly evolving at an incredible rate in rivers, it's simply an already-high number staying high because a decrease in diversity would be unlikely without a mass extinction event; a river fish species going extinct could ravage its ecosystem and since we don't see this constant collapse in rivers all over the world it suggests that river species are very good at adapting to environmental changes, which is an ability that makes sense given the video's earlier point about the frequency with which populations are divided by changes in the river's path.
3:06 "I'm not saying it's aliens ... but it's aliens." XD
Also consider oceans contain more viruses. And salinity may play a role. It's undoubtedly multivariable with varying amounts of constructive/destructive impacts. Fascinating stuff.
I'd hypothesize that within any essentially cohesive ecosystem, there are a finite number of niche roles for species to fill. This would imply that in a very simple model of one large lake vs. one small pond, a roughly similar number of species would evolve to fill all relevant niches, kind of like how two countries, one large and one small, would essentially have all the same industries just at different scales or proportions. Then if you were to somehow merge the two environments, many species would become invasive and many others would become extinct, until all niches are again filled by the fittest species. The water itself prevents most species jumping that barrier.
Another commenter (Rugved Kulkarni) proposed the excellent idea that if the paradox is particular to fish species then it could also be accounted for by non-fish species in the oceans filling ecological roles that fish species ended up filling in freshwater.
It's almost biology, especially genetics, is far more nuanced and complicated than people think - and even consisting of far more than we even know or think we know. It's funny how often people seem to think if science says something, it's written in stone. We change our minds constantly - science is just the best model of things we have at the moment.
This is a great example that you have to look at all the details, not look at one statistic and make a conclusion
Given we're counting species, I wonder if we're more likely to differentiate what we fish regularly out of freshwater sources compared to the oceans (where we let subspecies be subspecies). Just, are we sure this isn't a taxonomical quirk we're projecting onto fish?
One big factor that applies to the rapid spread of freshwater species is how some fish eggs can be transported through bird feces, and be deposited across vast distances to branch off from their original populations.
I like to think the things I didn't know to think.
The drawing of different kinds of fish, liked.
how many fish puns did u use
minute earth: yes
Does the salinity of their environment have any effect? I know for example that freshwater fish have more parasite, higher/lower level of different minerals, etc. Maybe one of these factors make diversification more advantageous.
i believe the fact ocean species over time can migrate through rivers also help this balance of species
They are not completely separated, heck salmon is a great example how rivers and the ocean are always in the process of exchange
It's easier to live in fresh water. They don't have as many predators, in northern climates where the ice freezes over they only have to worry about each other, changes to the water makeup(chemicals, salt levels, other variables) aren't usually as extreme, and they have much more specific niches they can take advantage of. Think of catfish who have access to so much random stuff that's 'edible' they will eat anything. This is also part of why they have a much harder time with invasive species and habitat changes, and why many species come in from the ocean to lay their young. Salt water also has plankton, which takes up a lot of space despite being microorganisms. Others in the comments have also posed a lot of good points, and it's probably a mix of everything. No one specific reason, life just found a way
Freshwater habitats exist inside large areas of land that themselves comprise larger and more diverse ecosystems when compared to any general stretch of ocean water. That is to say that these freshwater habitats aren't isolated from their surroundings. The ocean is mostly a singular, massive body of saltwater, with little topological diversity across its volume compared to what can be found situated on land. This leads me to think that the freshwater paradox is far more complex when we consider how the density of diverse land ecosystems around any given bodies of water will drastically influence said bodies of water, contrasting with the relatively homogeneous "geography" of the oceans, which are vastly non distinct throughout the majority of their volume.
I guess you could say this mystery has left biologists pretty lost at sea
"...weird mating rituals,"
Hey, stop kink shaming me man! I like what I like ok?!
Welcome to science. Where if you solve a puzzle, there is a high chance that it will get more complicated and all of your work will be half incorrect.
Interesting one thing which could potentially be related to this is the evidence that the ancestor of all extant cyanobacteria particularly including the lineage which gave rise to chloroplasts were or still are freshwater specialists with the oldest extant pelagic cyanobacteria dating to the Neoproterozoic suggesting the first colonized the open ocean around the same time as the first Eukaryotic algae. That said as the evidence for cyanobacteria goes back much further than the last common ancestor of extant cyanobacteria it is likely a bit more complicated (especially since the timing for the last common ancestor of Cyanobacteria matches up fairy closely with the Sudbury impact
Additionally the closest archaeal relatives to Eukaryotes are also being found from metagenomic sampling of shallow estuaries freshwater environments or soil building up the case that complex life as we know it likely originated on or around the continents back in the paleoproterozoic. If this is the case it is possible that there is just been more time for freshwater speciation relative to marine speciation. Of course fish are pretty recent in evolutionary terms compare to all this but the fossil record does support the first fish being relatively limited to shallow lagoons and estuaries potentially only colonizing the open waters during the Devonian so maybe a continent first model could work there too?
I think I’m addition to the things listed, there is far more variety with fresh water. Huge ranges of PH, completely different aquascapes, River speeds, it goes on and on. Where as ocean just kinda has maybe a couple different types of biomes. More biomes means more species.
Stable ecosystem don’t always result in more species, there becomes a point where stability can result in lower diversity. I was just learning this in my college evolution class. The most fit species come to dominate and outcompete extremely stable environments. Diversity is lowest in very unstable and very stable environments. Lakes likely provide that nice middle ground.