EVOLUTION: THE BODY CAVITY

BODY CAVITY, THE COELOM

The coelom has some very important functions that are seldom discussed in biology books and classes.

The coelom, the body cavity containing some organs, would seem like it is almost nothing.  But it is a nothing that is quite important in the evolution of animals.  When the space around the internal organs is filled with large cells having little to do other than filling up the space, the organism is said to be acoelomate, or lacking a body cavity.  When the same area is filled with fluid, the organism is said to be pseudocoelomate, or having a false body cavity.  Those animals that are coelomate, a designation meaning they have a true body cavity, may not have much fluid in the cavity.

The illustration of Nereis, above, shows the dorsal side opened above six of the parapodia (leg) bearing segments to show the coelom.  Nereis is an advanced polychete annelid, presumably more complicated than the ancestral one giving rise to the Pogonophora, but closer to the one giving rise to arthropods.

The evolutionary sequence was from acoelomate to pseudocoelomate to coelomate.  The difference between a pseudocoelomate and a coelomate animal is the absence or presence of a epithelial lining or peritoneum which is present in a coelomate animal and absent in a peudocoelomate animal.  The embryological origin of a true coelom varies.  If it develops from a split in cells of the mesoderm (the middle layer of cells in an embryo, it is said to be schizocoelous.  If it develops from outpocketing from the embryonic gut it is said to be enterocoelous.

IMPORTANT FUNCTIONS OF A COELOM

Isolation of organs for

physiological independence

          spatial independence when moving

                   minimal lubrication needed

          prevention of adhesions and

                   mouth formation and/or anastomoses

                   (a fundamental property of the underlying tissues

                 Of gut and blood vessels?)

Physiological independence is provided by the epithelium (peritoneum) covering the organs.  The covering provides a barrier to losing large molecules designed for function of the organ as well as preventing entry from those of other organs.  Thus the proper mix of chemicals needed for the specific role of the organ is not disrupted and/or is easier to maintain.  The barrier effect works because all coelomates have a circulatory system.  When a circulatory system is not present as in most pseudocoelomates the body cavity can provide many of its functions in supplying needed materials and removing wastes from the area for disposal by excretory and respiratory organs.

Spatial independence means the organs can reposition themselves without great distortion during movements.  For example, they don't get bent or squeezed so a gland is less likly to lose contol of providing its secretions appropriately.  The gentle activity they get from movements of the body is enough to help maintain normal function.  Activity is good for one's health if it is not too extreme.

The peritoneum covering the organs and lining the cavity are flattened cells making a smooth cover so that only a little moisture is needed for lubrication of movements.  Because the peritoneum is continuous from body wall to organ covering it forms a double layer or mesentary which provides two functions; it keeps the organs from getting twisted around or out of position and it can contain the blood vessels servicing the organ.  If an organ, such as kidney, is behind the peritoneum of the body wall, it  is said to be retroperitoneal in position; it then keeps its position better than if it were more flexibly located in a position just limited by its mesentaries. 

Prevention of adhesions is an important function because many tissues have the ability to fuse with other tissue if the peritoneum is not intact.  That is a property important in embryological development.  

The tissue of the primitive gut (the endoderm) of an embryo can fuse to the other layer (the ectoderm) and be the location of a mouth or an anus.  This property was important for the new location of the mouth to develop in pogonophoran ancestors as they moved into food-rich shallow seas and reform the digestive system as now seen in deuterostomes.

When the fusion and opening occurs as noted for the embryo it is fine.  But when surgical or other disruption of the peritoneum of adjacent organs occurs it can result in a new connection that is usually not wanted.  Such a structure connecting two parts of the digestive system is called a fistula. It may not be wanted, but is usually better than having an opening from the gut allowing contamination of the coelomic cavity, a typically fatal situation without rapid treatment.

Evolutionary considerations

The coelom was an effective way of solving some of the problems of increased body size.  Small organisms did not need special organs for overcoming the distance involved in moving all sorts of things used and produced by specialized organs.  Diffusion through fluids and tissues could take care of the problem.  But as size increased, direct diffusion was inadequate for moving things more than a few cells distance.  So to get adequate oxygen to tissues, some became flatter as they grew.  

Others (acoelomates) filled underlying spaces with jelly-like material that was nearly inert metabolically.  Others (pseudocoelomates) could get larger and have organs in the pseudocoel with enough fluid filling it to give them some escape from distortions with movement.  Also the fluid could move around and serve some of the transport role of a circulatory system.

Still other acoelomates had branches of the digestive system reaching to all regions of the body so movements of fluid in the gut could perform some of the vascular functions.  Hence, that type of development of the digestive system was called a gastro-vascular type of body cavity.

So coelom development was important when accompanying blood vascular system, respiratory, excretory, and endoskeletons needed for greatly increased size.  Of course there were other developments of importance.  One was the skin was no longer a single layer of cells or other simple covering; in the skin of vertebrates the epidermal layer is now serviced and supported by a dermal layer supplied with blood vessels and nerves.

When we talk about systems of the body, we seldom think of, or include, the coelom.  Too bad.

Four paragraphs back, I said "Others filled . . ."  -  is just a short way of saying "by the process of natural selection, survivors gradually, with the variants of the condition we are discussing, replaced the ancestral traits."

The views about the biology of the coelom expressed above are not based on experimental science in a direct way, but are more a view based on understanding of biological functions.  A quick survey of a small variety of texts (evolution, animal physiology, vertebrate biology, and an invertebrate reference on smaller coelomate phyla) provided no functional discussion.  The list under "important functions of a coelom" was in my journal notes for 10/03/06 that I read a few days ago and remembered talking to my classes about, in part, many years ago.  I don't remember the lectures or articles or books that may have inspired it.

Joseph G. Engemann     Emeritus Professor of Biological Science, Western Michigan University
Kalamazoo, Michigan    February 27, 2015 

MOLECULAR AND HUMAN EVOLUTION

Why today's comments?

I happened across an old personal journal entry from October 13, 2006 with the follow (slightly edited).

Kimura and Ohto 1961 on Molecular evolution is good for general principles, but the final page in particular need rebuttal about- 

assumption that verbal arguments based on evolutionary principles will become useless as computer approaches improve; and- 

presumption that neutral mutations are increasing at the same rate in “living fossils” as they are in others changing more rapidly. 

Aspects of human evolution thought about this morning (may be in the literature but) included: bipedal human ancestors were favored in surviving drying conditions at forest edge by ability to reach fruit on small branches better than others living in trees or as quadrupeds on ground.  Ancestors were also favored by being able to see other tree clumps across neighboring grasslands, and ability to see over grass to avoid predators or even frighten them by their erect posture providing an imposing frontal profile. Of course, views of Hamilton (Life’s Color Code) need to be included in discussion of human evolution.

The two rebuttal needing assumptions of the 1961 article cited were in error because (1) verbal arguments may be able to bridge a linear impasse a computer approach is incapable of evaluating.  And (2) neutral mutation rates would seldom increase at the same rate in "living fossils" as they are in other organisms.  (1) is shown by the failure of molecular phylogeny programs to compensate for generation time.  (2) is dramatically shown by the appearance of pogonophorans via "long-branch attraction" within computer generated trees of other groups.

Hamilton's book provides good evidence of how observation and reason can provide insightful understanding of human evolution. 

Numerous other posts of this blog provide support for the above rebuttals.  Although evolution may be used in labels with topics other than evolution, it is almost always used in labels for relevant evolution posts.  

Joseph G. Engemann      Kalamazoo, Michigan     February 20, 2015

SNOW STORM STIMULUS

"The weather outside is frightful"

Is the way an old song in a movie starts.  Then it moves on to positive things about a relationship.  Well, I just was doing somewhat the same after looking out the window.  Snow was coming down in bursts to add to the already significant accumulation.  But it was no where near the amount Boston had been experiencing.  As long as power doesn't go out the gas furnace will run and keep us reasonably warm.  As I lingered over coffee and my last piece of toast, I started musing about the value of a snow storm.

GLACIERS

They were an important part of the way God made the world where we live.  The Great Lakes wouldn't exist if enormous glaciers of the not so distant ice ages had not carved them deeper by successive advances from what is now Canada.  Where bed rock is visible the scratches of embedded rocks the glaciers picked up show how they did the job of gouging out the lakes efficiently.

The melting glaciers left a large quantity of the load of rocks and sand they were carrying to form a deep layer of glacial till deeply covering places such as southern Michigan.  That till was layered in many places by the flow of melting water. So layers of rock, sand, and clay are able to provide an abundant source of ground water that is relatively pure until we pollute it by some of our activities.

Mountain glaciers still exist.  Many are getting smaller or even disappearing.  The annual snow fall can still replace much of the supply for summer melt to maintain streams and water resources of western states.  But it is not as reliable.  I understand "Grasshopper Glacier" in Glacier National Park has disappeared.  It used to release locusts of no longer existing species, captured in its accumulation in the distant past, from the melting front of the glacier.

      A woman working in an Austrian field while snow is still in the Alps

    A small glacier on top of the Zugspitze, the tallest mountain in Germany

Although global warming is currently having a considerable affect on the Northern Hemisphere glaciers, those of Antarctica may still be growing or maintaining themselves.  Once the continental glaciers of North America melted sufficiently, their elevation was not enough to keep snowfall and temperatures at levels to compensate for summer melting.

GROUND WATER

In Michigan, enough rain falls to replenish the ground water.  The soil does a pretty good job of purifying the water of contaminants from simple agricultural and domestic activities.  Deep well injection of wastes, fracking, and waste dumps improperly sited and sealed can drain into deep aquifers used for well water supplies without soil being able to effectively oxidize, filter, or somehow remove toxic wastes.

Aquifers can be enormous.  One in the United States runs from some distance west of northern Illinois for hundreds of miles to the southwest.  But heavy use of well water for irrigation has depleted its store of water at a rate exceeding replacement.  A somewhat similar phenomenon is affecting oases in the northern Sahara.  There, the lowered water table of the enormous store largely left during the ice ages has caused browning and death of some vegetation around the periphery of oases.  And some wells show progressively deeper excavation to reach water.

SEASONS AND EVOLUTION

With or without global warming, the seasons will continue.  Short term effects on an annual basis will favor selection for either or both, a north-south oriented seasonal migration, or adaptions for either cooler or warmer conditions.  Long term effects are similar, but continuation of the same alternation can result in greater change in a species.

Lighter coloration and chunkier bodies are selected for in colder regions.  Greater development of melanin pigment in the skin reduces U-V light penetration, thus the production of vitamin D in the skin is less likely to reach toxic levels in tropical climates.  Distribution, types, and amounts of hair, fur, or feathers are simple evolutionary solutions for adapting to light and temperature of local conditions.  Migration provides a substitution of behavioral change for physical change needed to adapt to climate.

Speed of climate change may be too great for annual migration or adaptation to prevent extinction.  Will polar bears survive if summer ice is eliminated in the Arctic Ocean?  I don't know.  Did rapid warming reduce appropriate habitat for mastodons and mammoths, or did early human hunters eliminate them? I don't know.  Perhaps it was both acting together.

Species can often adapt by migration over longer periods of time to new favorable locations unless too much desert, ocean, or mountain range, or intervening populations of predators, or other unfavorable habitat intervenes.  It would have been hard for a mammoth to find a log to float on across the Gulf of Mexico.  East-West migrations were successful in making Europe, Asia, and North America share very similar groups of species of plants and animals.  A land bridge formed between Russia and Alaska was a major factor.  Fresh water along the glacial front in that area probably enabled many genera of fresh-water fish that are now shared reach the opposite continent.

SUMMER THUNDER STORMS

Will I have to wait for confinement by another snow storm now or next year, or will a summer thunder storm that keeps me off the golf course provide an inspirational interlude?

Joe Engemann    Kalamazoo, Michigan     February 14, 2015

Creativity, Bee Language and Dyslexia

CREATIVITY

There are so many factors that determine creativity it is doubtful that we could ever make a routine that would consistently develop geniuses.  Creativity is not a single attribute signifying greatness in a field of interest.  Is it determined by number of successes?  Is it determined by skill or novelty?  Is it determined by I.Q. or genius?  I think creativity is a subjective attribute of a person and cannot be measured with scientific accuracy nor other objective measure.  Perhaps it is one thing that might be measured better than most things can be- with a popularity poll.

IQ and GENIUS

High intelligence quotients and genius are typically viewed in popular usage as synonyms or very similar, if not identical, superior mentalities.  This may be evident in a current TV program, Child Genius, in which astounding feats of memory seem to be a major measure of genius in the competition.  I do not think genius nor creativity are measured by speed of recall ability nor size of a set of facts.  Perhaps it is my own bias that thinks so because I am a mental plodder compared to many bright people, and, with age, the certainty of remembering something during a conversation is increasingly remote.

I.Q. has memory efficiency as a major component.  Breadth of knowledge is another major component.  Both can be measured with a suitable test that typically combines both components.  Ability to apply those mental skills is less easily measured accurately.  The general public, with some justification tends to label those in academia as being disconnected with the practical world and in an "ivory tower".  They also frequently apply the label "lacking common sense" to those in and outside of academia that proclaim themselves geniuses.

LANGUAGE OF BEES

Bees have the ability to communicate with other bees, but it is more of a monologue than a dialogue such as we think is important in conversation.  The bee language was largely determined in its major aspects by Karl von Frisch many years ago.  Refinements have been found more recently.  The basic facts discovered by von Frisch were transfer of food substances for tasting to identify the foods to be sought, and dances that help the other bees find the sources of those foods.

Distance was communicated by a circular dance indicating it was near the hive so "go and find it".  Direction was communicated by a waggle dance on the face of the honeycomb with the direction angle relative to the sun being the straight up direction.  Distance in the waggle dance was proportional to the length of the waggle dance.

The first information, the food, was the first thing conveyed by the sample.  The last information was the direction and distance with the dance.  The amount of honey the workers consumed before departing on the foraging trip was determined by the distance.  Perhaps the amount was also determined automatically by feeding proportional to the flight distance communicated by the length of the dance.  The order of the information flow may be seen in the following section.

DYSLEXIA

Last in, first out, may indicate a basic mental process as old as the bee language.  When letters come out in reverse order when we are dyslexic, it results in written language difficulties for a dyslexic.  But their brains are commonly thought to function at a higher than average level in other respects - perhaps even at the level of genius.  I don't know how many numerals of a large number could be recited backwards by a dyslexic, but I bet it would be many more than a non-dyslexic could do.

I've always wondered if I, as a child, was borderline dyslexic with the difficulty I had in distinguishing right from left.  The distinction could be in directions communicated or printing a capital N, Z and some other letters in reverse orientation.

The elements of switching order of things can come out as a "spoonerism" when switching initial letters of words in a two word phrase gives new words with a different meaning.  I'm surprised I didn't name the post of a week or so ago Ting Kut, instead of King Tut.

PIG LATIN

Pig Latin is a slightly more complicated transposition of word elements than in a spoonerism.  My brother was very proficient at it but I was quite slow in my processing of it.  Talking it was widespread fun for kids eighty years ago.  It had some use in World War II for communicating, perhaps with captive GI's, to keep their captors from knowing what they were saying.

Before "Pig Latin" dies as a language the basis for it as I remember it was- merely switching order of the first and the last part of each word, then adding something like -a, ay, or -eh.  It really garbles it up for those not having high proficiency with the English Language.

MEMORY

If the ancient process of storing and retrieving information in the nervous system began with a simple process, probably well before bees evolved (our closest common ancestor with bees was an annelid worm), then it is not surprising that there are elements of memory principles that are basic to our mental functions.  I sat down a little after noon to write this post less than an hour after thinking of it, mostly as I was showering.  I left the Sunday paper, that is one of my favorite weekly reading chores, to write this- now about two hours post shower.  I did it so quickly because remembering connections of thoughts diminishes rapidly with time and I soon have a difficult time seeing why what I thought was important really was.  The measure is better determined at a later time.  It would be best to wait a year or so, but I will probably settle for an hour or two (or after I've read the paper, especially the comics).

Joseph G. Engemann    Kalamazoo, Michigan     February 8, 2015, 2:29 PM EST

Final proof-reading question:  What is "igpay atinlay"?

ROCK GROWTH IN ALKALINE LAKE

SEDIMENT DATING

Carbon isotope comparisons are a useful tool for dating fossils and age of sediments.  The increase in carbon fourteen in the atmosphere due to the activities in the nuclear age has necessitated correction factors for more recently produced materials.  But there is another factor affecting ratios of carbon isotopes that needs to be considered in some cases.

Marine sediments
I became aware of one factor while considering the isotope aging of carbon in pogonophoran tubes as a method of aging pogonophorans.  The likelihood that the tubes were made from fossil food in the sediments would make them look older than the ratio would indicate made me abandon that approach.

Fresh-water sediments
Date of continental glacier recession may be more recent than some studies indicate for a somewhat similar reason.  Carbon used for photosynthesis, by plants in fresh-water lakes, may have the ratio distorted, to values indicating older dates of formation by intrusion of carbon, in compounds depleted of radioactive carbon, carried in groundwater passing through ancient limestone to springs in lakes.

The broad leaved species of pond weeds (Potamogeton spp.) are often encrusted with lime in moderately alkaline lakes.  They could be analyzed to provide a partial correction factor of the ratio of fossil carbon to atmospheric carbon in such locations if they contributed to formation of surrounding bogs.

The rocks of lake shores in such locations may also provide a clue.  They can be recently formed by algae such as the ones below from Fish Lake in Allegan County, Michigan.

      Marl concretions from Fish Lake

     Cross-section of one of the marl concretions from Fish Lake

Two rocks are shown in the upper picture.  The left one is shown split open in the lower picture and the green of the algae is evident in the outer layers, but less evident in the inner layers.  Most of the marl concretions making up the shallow sediment surface along the shore were much smaller in size.  These photos were taken in the summer of 1954 on a limnology class field trip from the Michigan State University Kellogg Biological Station on Gull Lake.

LAWRENCE LAKE

Lawrence Lake is a lake in the same glaciated region.  Robert G. Wetzel (1975, Limnology, Saunders, Philadelphia) notes on page 40 that "groundwater largely from springs contributed nearly 40 per cent of the annual water income to calcareous Lawrence Lake Michigan" and about ten percent was from precipitation and the remainder was from streams.  If the source of water in streams is from springs the streams could also contribute to distortion of ratios of carbon as compared to the atmospheric source, where the radioactive isotope is naturally produced.  The half-life for the decay of radioactive carbon is about 5730 years.  So plants from Lawrence Lake might start with a ratio indicating they were formed almost 4000 years before they really were formed.

From his own research, Wetzel, page 367, says "carbonate deposits encrusting the submersed parts of macrophytes in calcareous hard water often exceed the weight of the plant material".  On the same page he noted some of the carbon dioxide, bicarbonate, and calcium process producing the encrustation.  It is presumably similar to the same process of photosynthesis involvement in the algae producing the "rocks" illustrated above.

Dr. Wetzel took over as resident limnologist a few years after I took limnology.  He produced much research, especially based on examples at Lawrence Lake.  His work at that time contained one of the few available studies of relative contributions of different components of lake ecosystems.  It was noted for that reason in an environmental conference I attended in Miami, Florida, over forty years ago.  But large lakes would have a higher proportion of their productivity coming from their plankton communities if they have a greater proportion of deeper areas.

ICE AGE ANIMALS

I am not familiar with studies dating the demise of the mastodons and mammoths of North America.  If the dates were determined by radiocarbon dating of their tissues, it could be erroneously older if their food was primarily or largely aquatic vegetation.  The dating of the retreat of the glaciers opening up land for them might also be dated erroneously older if the dating used aquatic vegetation or bog material.


Joseph G. Engemann    Emeritus Professor of Biological Science, Western Michigan University   February 5, 2015

EVOLUTION AND THE SECRET OF THE TREE OF LIFE

THE TREE OF LIFE

The tree of life, as currently accepted by main-stream science, has an unaccounted for error.  It is no secret to you if you have read all my posts, but the molecular phylogeny of major phyla has major errors for lack of understanding long-branch attraction.  Or as I have shown from numerous citations elsewhere, abundant evidence that direct measurement of DNA differences of species is almost certain to produce an erroneous tree-of-life for phyla if it is calculated from those differences.

LONG BRANCH ATTRACTION

Molecular phylogenies are sometimes plagued with the pogonophorans or some other group appearing in some central position in a phylogeny when the researcher is quite certain it should not be there.  They may note that it doesn't seem to belong there, or, I suspect, sometimes they leave it out because they think it is a long-branch attraction appropriate to ignore.  Maybe they just remember not to use the group for an out-group [a group inserted that is reasonably presumed to be outside the cluster being investigated].  The correct solution is to figure out why it happened - something they cannot do without introducing a major variable of molecular clocks all ignore.  I have discussed elsewhere how the nematodes may also have a slower rate of change in their genome and thus produce an example of long branch attraction.

THE POGONOPHORA

The Pogonophora are specialized descendants of polychaete annelids of which the ancient ones are ancestral to all vertebrates via hemichordates and cephalochordates as indicated in Our Evolutionary Lineage (Post  79).    [ http://evolutioninsights.blogspot.com/2014/12/our-evolutionary-lineage.html ]

That post also lists approximate times of origins of groups in that lineage.  From that we can see that the pogonophorans evolved about a billion years ago.  Some are little changed to this day, if they stayed in the abyss, from perhaps 600 million years ago when the hemichordate line branched off from some of the pogonophorans moving into shallower waters.  From hemichordates the cephalochordates branched off, perhaps 500 million years ago.

THE CAMBRIAN

About 500 million years ago the Cambrian began.  Most major phyla had representatives in the Cambrian.  Trilobites were arthropods whose fossils are only found in rocks through the Cambrian to the end of the Palaeozoic.  Arthropods are obvious annelids descendants that have an origin from polychaetes, as do pogonophorans.  Mollusks had a comparable origin from polychaetes.

The stability of conditions in the Cambrian enabled pogonophorans ancestors to migrate to shallower seas and survive following the end of major asteroid bombardment episodes.  As they established themselves in shallow seas, the reduced pressure enabled physiological processes involving diffusion to speed up to a 1,000 times greater speed.  A better food supply also contributed to the process.  The recovery of gut development by the hemichordate descendants accompanied other developments as the worms moved out of their tubes and took on a more active life getting particulate food, mostly by filtration instead of the diffusion on which the pogonophorans had become dependent.

Parallel lines from the polychaete-pogonophora line gave rise to echinoderms and probably some of the lophophorate phyla that also made their appearance in the Cambrian.

CALCULATING THE LONG BRANCH ATTRACTION

We can ignore the fact that pogonophoran tube analysis (in earlier blogs) indicates the individuals can live from 10,000 to a million or more years.  Just taking the pressure differential effect on physiology indicates evolutionary selection is likely to be 1,000 times more rapid in shallow seas than in abyssal ones.

The ancestor that remained and reproduced in the abyss over the past billion years would be expected to have one million nucleotide substitutions in their DNA while a descendant that had been near the surface has 500 million nucleotide substitutions in the past half-billion years.  Another descendant branching off at the same time would also have 500 million nucleotide substitutions in the past half-billion years.

Others branching from the new lines, say one from each line 400 million years ago, each would have 400 million nucleotide substitutions in each of their lines as differences.

THE SURPRISE

Now, the four groups would all have more in common with the pogonophoran that now has half a million changes from the point of common ancestry with the other four groups that each has 500 million changes.

The branching of the new groups would be correctly interpreted from the differences as *800.0 million changes from their nearest relative and *1,000.0 million from each of their more distant pair of relatives, but only *500.5 million changes from the pogonophoran.  The pogonophoran now looks closest to all by the long branch attraction, an artifact of different rates of evolution whether by physiological speed or long generation time, or by both as I think it is.

The closer the groups studied, in a phylogenetic study of relationships, the more likely it is that pogonophorans will not show up as a close relative within a group.  Thus species, genus, and families in an order are unlikely to appear related to pogonophorans unless the study is of pogonophorans.

If you look at the estimated times of origins you can see that terrestrial vertebrate classes had their origins over three hundred million years ago. but most modern orders were likely beginning almost two hundred million years ago.  Nearly the same thing could be said about the insects.  Whereas echinoderms are a more ancient group with classes going back to the Cambrian; they even have several extinct classes.

Until the molecular phylogeneticists calculate a major tree of life taking the above into consideration they will continue to be wrong about their view of relationships of phyla.  They have a lot to contribute if they stop making that error. 

*The numbers used in the examples above are not precise and are only used for a simplified example of the principles involved and are calculated by summing the changes of both ancestral lines from their point of branching.

Joseph G. Engemann     Kalamazoo, Michigan   February 2, 2015