CREATIVITY: Last First

The Two Way Street

Was the name of my 1974 manuscript on creativity which was never published.  Since it dealt with creativity and the value of reverse viewing, I am starting at the end with a series of cartoons it contained.

The caption "Don't say anything, he thinks he's creative." was a jab at myself.  Perhaps it was a reminder to not take myself or my ideas too seriously.  The cartoon followed the final chapter, number 13, which did not particularly talk about how to be creative, but reviewed some ideas I had entertained that did not appear in earlier chapters.

An idea for improving certification processes for teachers and my realization that administrators can be an effective source for good preceded ideas I thought important to work for as a congressman.  I did not run for congress in 1969 after thinking about it and discarding the idea.  An example of one idea entertained was the following in a section on "Social Needs."

"There were programs I was interested in pushing that were dubious campaign issues because of complexity or the potential for misunderstanding or arousing effective opposition.  As a university teacher I enjoyed a retirement program (TIAA-CREF) where my rights were immediately vested and could be taken from job to job.  Why should not all workers have that advantage?  It is especially irritating to see corporations rob older workers of their pensions by either mismanagement or corporate restructuring.  So a federally licensed pension system similar to TIAA-CREF should be a right of all."

Permission to use the above cartoon in non-profit publication or personal use is granted with the hope you will credit evolutioninsights.blogspot.com

Joseph G. Engemann    August 18, 2014

EVOLUTION: CIRCULATION

THE CIRCULATORY SYSTEM

Circulatory systems have evolved and transport things throughout the body.  So transportation is the primary function, but the things transported can be oxygen, nutrients, waste products, and molecules serving a variety of functions.  The transport of many of the substances could be accomplished by a fluid filled body cavity, or just cell to cell in very small organisms.

The need for oxygen in active large animals is greater than can be transported by oxygen dissolved in body fluid of large animals.  So respiratory pigments such a hemoglobin allow a much greater supply of oxygen to be transported rapidly. When oxygen is abundant in the just inhaled air in the lungs it will combine with hemoglobin, but when it reaches tissues where it is depleted it is released.   Typically, the depletion is due to metabolism resulting in production of carbon dioxide which is then carried on the return trip to the lungs for release and elimination with exhaled air.

Circulation of blood in animals with heart, arteries, capillaries, and veins is like a bus route.  Some things go round and round on the route.  Others, such a hormones may go round and round until they are bound up by the target organ.  Those control substances included things that stimulated or inhibited processes in the target organs.  Over time delivery of control substances for specific targets selected processes that became the nervous system enabling precision in control.  But longer acting processes where instantaneous response is not important are adequately served by the circulatory systems of organisms.

EVOLUTION OF THE CIRCULATORY SYSTEM

No circulatory system
Many students have had the opportunity to see circulation within cells while observing Amoeba, Paramecium, or plants such as Elodea with  microscopes.  Similar cytoplasmic movement can occur in animals with circulatory systems.  Movement of the organism can provide some functions of a circulatory system by leaving waste behind as areas with more oxygen and food are reached.

Gastrovascular type circulatory function
Animals in the phylum Cnidaria (jellyfish, corals, and related forms) and Platyhelminthes (flatworms) are the major groups with gastrovascular type systems.  The name comes from it being the central digestive cavity which may be branched reaching all the parts of the body and having the capacity to carry on digestion as well as circulation enhanced by body movements and sometimes cilia.

Body cavities as circulatory systems
In the previous types the space between the epidermis covering the body and the organs such as gonads and guts are filled with either mesoglea (jellylike material and few cells) or parenchyma (large water-laden cells) through which materials can diffuse, but where little metabolic work is done.  The simplest body cavity to contain organs is called a pseudocoel because it lacks a lining of epithelial cells as in those with a coelom (as found in all eucoelomate higher phyla).

The importance of the coelom for provision of circulatory function is indicated by small organisms such as the bryozoans.  In the photo below of several polyps (or zooids) of a colonial species, Pectinatella magnifica, the particles in the space between gut and body wall are circulated with the body fluid propelled by patches of ciliated cells on the lining.

Body fluids of many organisms such as the above also serve a skeletal function of support for the body when fluid is confined within the body and compressed to keep the organism inflated.  The exact evolutionary relationship of the bryozoans is not certain.  They are a very old group that may have no close ancestry to advanced phyla, or they may be derived from more advanced forms due to reduction much as occurred in the pogonophorans.

Blood vascular systems as circulatory systems
The origin of the blood vascular system is speculative.  It seems consistent with the gradation seen in animal complexity that the lateral branches (or a dorsal branch) of the digestive system seen in flatworms took on another function as the animals grew longer and developed an anal opening for the central branch.  Over time
muscles providing peristaltic movement of contents were gradually converted into hearts as needed.  The annelid worms and the fishes provide examples of some of the steps along the way to the system seen in mammals.

Blood of vertebrates
Blood cells of vertebrates are often categorized as white blood cells and red blood cells.  Most vertebrates, including fish, amphibians, reptiles, and birds, have large, nucleated, football-shaped red blood cells. Mammals have small red blood cells that are flattened disks (usually characterized as biconcave disks) that lack a nucleus when mature.  Vertebrates have hemoglobin in their red blood cells and thus help keep the viscosity of the blood lower.  The cells, in addition to lowering blood viscosity, may help improve the transfer of materials in the capillaries of organs by making the whole fluid column in the capillary move at the same speed.  The wiping action, in effect, reduces the diffusion distance for materials being exchanged.

[Note  added June 3, 2015: An important part of circulation in vertebrates is thought to be escape of water and smaller solutes, including oxygen, from the arterial end of the capillaries into the interstitial fluid; uptake at the venous end of the capillaries returns much of the fluid, and carbon dioxide; and solutes and fluid that cannot be taken back by the venous end may return to the circulatory system via the lymphatic vessels.  This circulation pattern is driven by higher hydrostatic pressure in the arterial end versus lower pressure in the venous end as well as the higher remaining concentration of larger solute molecules in the venous end.]

Blood particles, called platelets, are important in clot formation that seals off breaks in the blood vessel walls.  White blood cells are of several types important in function of the immune system.  These constituents of blood are formed in marrow found inside bones of the body.

Joseph G. Engemann         August 6, 2014

EVOLUTION: SPATIAL DIMENSIONS AND NATURAL SELECTION

NATURAL SELECTION

Survival is affected by many different things.  This post will discuss the impact of length, surface, and volume on natural selection.  Such simple physical components of an organism can have great affect on the organisms relationship to its environment as well as to physiological and mechanical functions.  The fourth dimension, time, is certainly an important component of natural selection but it is not discussed in this post.

THE LINEAR DIMENSION AND SURFACES

If an animal only grows in one dimension, length, its mass is directly proportional to its length.  Some subterranean animals find this a way to get bigger without required larger dimensions of tunnels they occupy.  For attached, or sessile, animals increased length gives them access to food items farther away from an area proportional to the square of the distance.  Surface area of the organism, ignoring the factor of tapering ends usually involved, increases in proportion to the product of length and width or circumference.  For a flat, encrusting type organism, that doubles in length and width of surface dimensions, the larger form has four times the surface area.

VOLUME OR MASS

Of course, organisms all have a third dimension, depth or the dimension at right angles to both length and width.  The product of length, width, and depth gives the volume or mass of the organism.  Organisms with complex shapes can have their volume calculated from the sum of volumes of all their parts.  A simpler measure can be equivalent to the volume of water displaced when it is immersed; its weight is also a good approximation, if it lacks mineralized parts each gram equals approximately one cubic centimeter.  The animal that doubles each dimension has volume or mass increased from one unit volume to eight units of volume as illustrated below.

THE PRACTICAL CONSEQUENCES OF INCREASED SIZE

The inequality of the ratio of linear, surface, and volume measures has great impact on design of animal bodies produced by natural selection of genetic variations.  If shapes are identical, linear measures are directly proportional to length, surface areas are proportional to the square of the linear dimension, and volume or mass is proportional to the cube of the linear dimension.

Rates of delivery of materials to and within organisms varies greatly due to variations in permeability of membranes, circulation of protoplasm within cells, binding with other molecules, circulatory systems, surface area modifications, and additional chemical and physical factors.

Mass or weight

Dinosaurs were thought to be near the maximum size for a terrestrial organism because the mass increased with the cube of the linear dimensional increase whereas the strength of the skeletal support in leg bones only increased with the square of the diameters of the bone.  If they grew bigger they would need bones too big to be contained within the organism.  Likewise muscles to move the mass increased in strength proportional to their cross-sectional area and reached the limit of practical size; muscle and bone would be unable to keep up in needed strength for greater size.

Birds, and presumably some dinosaurs, have hollow leg bones that have greater strength with less increase in weight.

The increased size of most advanced animals made the ratio of length to surface area of organs exchanging nutrients, oxygen/carbon-dioxide, and heat from body surfaces, lungs, and gut have survival improved when gills, pouches, folds, and other mechanisms increased the surface without increasing overall size.  An example is the longitudinal fold called the typhlosole in the gut of the earth worm.  The Tasmanian isopod also had a typhlosole.  However, the worm has it in a dorsal position and it has more internal structure.  The isopod has it in ventral position and it is simple in structure.  In the first picture below, the typhlosole is projects up from the bottom of the tubular gut- which has some food included.

Such modifications enabled animals descending from flatworms achieve thickness and complexity.  Flatworms are limited in thickness in part by the inability of sufficient oxygen to diffuse to active tissue more than a few cells away from the surface.

To enable many of the advances to take place, a circulatory system was necessary to effectively take out most of the need for diffusion over the distance from surface of uptake to surface of release of transported nutrients, wastes, and oxygen.  Hemoglobin and other respiratory pigments enabled greater quantities of oxygen to be transported because the combined form of oxyhemoglobin did not contribute to oxygen saturation of blood fluid.

The dorsal blood vessel and heart are shown above the gut in the two pictures below.  In the first picture arteries, labeled A are going off to each side; in the second picture the heart shows an ostium (O), the valve through which blood enters the heart from the hemocoel (the blood filled body cavity that serves the role of capillaries and veins in arthropods).

The arteries carry blood to the thin-walled pleopods, abdominal leaf-like appendages with thin walls where oxygen and carbon dioxide are exchanged with the surrounding water.  The blood then carries oxygen to the various tissues of the body on the way back to the heart.  Along the way it picks up nutrients absorbed by the gut, eventually entering the heart through the ostium.  The blood bathing the internal spaces does the job of capillary networks in higher organisms.

The gut of the Tasmanian isopod has very large cells lining it.  The photo below is an enlargement of the gut or intestinal lining (I) where it meets the rectum (R) lined with small cells.

Larger organism have greater complexity and require proportionally larger muscles and capillary networks as a result to insure adequate circulation.  Such things allow them to overcome the decreasing rate of provision of needed substances and removal of wastes found with diffusion based circulation that is adequate for microorganisms. 

[Photos are from Engemann, J. G.  1963.  A Comparison of the Anatomy and Natural History of Colubotelson thomsoni Nicholls, a South Temperate, Fresh-Water Isopod and Asellus communis Say, a North Temperate, Fresh-Water Isopod.  Ph.D. thesis, Michigan State Univ., East Lansing.  146 pp.]

Joseph G. Engemann           August 4, 2014