AGING
Some animals have a programmed life of growth, reproduction, and death; mayflies and salmon provide commonly known examples. Others seem to continue indefinite slow growth after reaching reproductive maturity, crocodiles, some fish, and lobsters are examples. Warm blooded vertebrates generally cease growth when sexually mature because the growth zones of bones have turned into bone, so growth is limited to adding bulk - something not needed to get through the seasons of reduced food supply now that modern food production and distribution has arrived.
How I Got Interested In The Physiology Of Aging
Along with the natural interest we have about our own life expectancy, I got a boost in my interest during my doctoral research comparing two species of isopods with greatly different life cycles. The ecological factors and adaptive strategies were understandable in explaining the differences.
Less than ten years later I was involved in incorporating new information about the pogonophora in a textbook revision. As mentioned in the previous post about Ocean Circulation, the abyssal ones had life cycles several orders of magnitude longer than terrestrial and shallow water organisms. The most likely cause was an extreme deep-sea pressure affect not likely to be a factor for air-breathing organisms.
WHAT HAS HAPPENED
A lot has happened to about double the global average life expectancy of new-born babies in the last century. Probably the greatest factors have been modern medicine, disease control, care of newborns, care of mothers. Popular papers, magazines, and other sources of health information have been filled with information, much of it worth your time. There does not appear to be a secret food, exercise, or supplement that will answer all your health needs A balanced diet with portion control, reasonable activity, and physician recommended additions may be best in conjunction with.
No smoking
avoids many cancers, emphysema, intolerant non-smokers, and stress on the heart
No, or very moderate alcoholic beverage drinking
may help us avoid cirrhosis of the liver, deposition of excess abdominal fat, falls, accidents, and DUI citations, need to take vitamins and minerals to replace ones missed by less intake of fruits and vegetables
Moderation
in activities and intake of sugars, protein, saturated fat, and total calories - all are better than too much or not enough
Social life, sleep, and mental activity
yes, and you will probably be happier with your extra years
Pick your parents
too late, it doesn't matter as much as our environment. Superb genes will not help if we engage in unnecessary dangerous activity or ignore safety precautions. But don't lament your poor genes, passing on good behavior can be a factor more important in survival of offspring.
STROKES AND HEART ATTACKS
and the mental deterioration we often think comes with old age may be minimized by healthy living and a love for one another. We can be in great health with only minor accumulations of cholesterol induced deposits in blood vessels, but a sudden episode of extreme exertion could cause a few clumps in blood vessels to break free and plug blood flow to areas of the brain or heart, If it hits an unused part of the brain it may be no problem. If it is small enough it may be only a short term minor problem. But don't take the chance if you have been long retired from vigorous activity. Take a smaller shovel full of snow, or don't try to keep up with speedsters; pause and enjoy the beauty of the day, and thank God that there was a time when you could do that.
OTHER POSSIBLE AGING FACTORS
Amino acids are predominately bent in the "l" form and may over time be gradually converted to the "d" form giving rise to no, reduced, or different functionality. The process is probably gradual but may speed up due to radiation or other factors.
Telomeres that terminate the chromosomes may be reduced each cell division and reduce cell replacement in aging organisms.
Accumulation of waste, or other, products in the cells may reduce or eliminate cell function. Some organisms such as some bryozoans may dedicate scattered polyps of the colony as storage sites of waste. We can't do that. But our kidneys do their best to maintain chemical balance in the blood and eliminate many wastes. However some pollutants and toxic substances accumulate over time and are poorly eliminated.
Fat soluble contaminants accumulate in body fat as well as the insulating layer of some nerve cell processes of nerves and the brain. Metallic elements may be retained by combining with body proteins. The cumulative effect of such things may be intensified by weight loss from disease or dieting. Impairment of function of organisms can result from injury and scar tissue.
Evolution and grandparents
Multi-generational families are almost a thing of the past. But they were important in our evolutionary history by
providing child care for young during our long childhood
transferring information prior to written and electronic storage and transfer
source of knowledge and wisdom aiding survival
being the weak prey picked off by predators so others escape
monitoring and alerting
Considering genetic values that might not seem to have selective value until well after reproduction has ceased, such as factors that contribute to post-reproductive longevity, natural selection would still be effective. The genes that may not become active until late in life would be expected to be favored by natural selection as they are almost certain to be more abundant in the reproducing offspring of the ones having genes favorable to aging. It involves the same principle of group selection enabling sterile worker castes of insect to evolve features beneficial to the colony but only expressed in the sterile caste.
The rapid evolution of increased brain size in humans can probably be accounted for by the benefits of greater memory capacity. Large brains of whales and elephants, although not disproportionately large as compared to humans, have a value for retention of migration histories and social behaviors beneficial to the groups survival.
Joseph Engemann Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan May 10, 2018
Thursday, May 10, 2018
Thursday, May 3, 2018
EVOLUTION: OCEAN CIRCULATION
CURRENTS AND DENSITY
Currents of major impact on the ocean are profoundly influenced by density differences due to salinity and temperature differences. The heavier water sinks and the lighter water rises. Surface currents can be wind driven. Gravity and inertia impact currents. At the interface of moving currents, or a current and still water, turbulence and mixing can be induced.
Pure water is most dense at about four degrees centigrade. So progressively warmer water is usual found from near the bottom to near the surface. Salt concentration of the water may make the temperature stratification vary in other ways. For example, Mediterranean Sea water entering the Atlantic Ocean near the Straights of Gibraltar sometimes goes to an intermediate depth based on density level of the ocean of the same density, but with different temperature and salinity.
Most of us are familiar with the affect of the Gulf Stream on climate in Europe, by its movement north along the western Atlantic that veers east and provides milder climates to northern Europe. A similar current affects climates in the north Pacific. While such currents catch our attention, one of greater consequence has had a profound affect on evolution as it has no doubt persisted and survived assaults by asteroids, volcanic disruptions, continental drift, and variations in solar radiation. It involves a cycle of circulation that takes ten thousand or more years to complete - from icy polar water settling to abyssal depths of temperate, sub-tropical, and tropical parts of the ocean where it slowly warms and rises until it ultimately mixes with warmer surface waters and completes the cycle by returning to polar regions via currents and evaporation and precipitation. A pause in polar ice caps can exceed the ten thousand plus year trip from abyss to sea surface.
A PERSISTENT CIRCULATION PATTERN
polar region temperate - sub-tropical regions
The visual above is not to scale but indicates the North Atlantic pattern of circulation from polar regions on the left to tropical regions on the right. Similar but variable profiles would be found in the North Pacific and Southern Ocean region of Atlantic, Pacific, and Indian Oceans. The flows would diminish and seem to disappear as they meet under tropical waters.
S represents the ocean floor or sediment with a sill regulating flow from (the sometimes ice covered) Arctic Ocean water. A rise in sea level, or a subsidence of the sill can allow a greater volume of flow to the abyss of the Atlantic.
C represents the cold salt water of high density that sinks to the depths of the ocean of such great volume that the warming water rises slowly, taking ten thousand or more years to mix with the warmer and less dense overlying water.
M represents the oxygen minimum zone separated from W, the warm surface water, by a thinner mixing zone, the thermocline. The thermocline is identified by rapid change in temperature. A shallow thermocline may result in more light for photosynthesis penetrating beyond the mixing zone so the oxygen minimum will be somewhat deeper. Also, storms may produce sufficient turbulence at depths to make the oxygen minimum zone deeper. The extent of the oxygen minimum zone also responds to organisms living there and bacteria utilizing organic debris settling from the photosynthetic zone near the surface.
W, the warm water is where oxygen is replaced by photosynthesis as well as by diffusion from the atmosphere.
Hurricanes
The thickness of the thermocline is greatly affected by wave action. Calm seas may have a thermocline within a hundred meters of the surface. Hurricanes and storms can produce turbulence to make the thermocline much deeper and provide a thicker zone of warm water and heat storage that may prolong or increase subsequent storms.
The H.M.S. CHALLENGER EXPEDITION
The first major oceanographic expedition occurred from late 1873 to early 1876. One of its many accomplishments was measuring depths, temperatures, and salinity of the oceans. I had examined part of one of the fifty some volumes of its researches published later that century while I was teaching a marine biology class about a hundred years after the voyage. I don't know how many years it took me to realize that the temperature profile that I have crudely illustrated above meant that the presence of oxygen and long residence time of the deep water beneath the thermocline meant either extremely low biological activity or very few organisms.
Subsequent oceanographic work has provided more complete coverage of the oceans and greater precision in measurements without changing the basic importance of the early expedition.
The time factor
Sediment cores show the vast percentage of abyssal sediments accumulate very slowly. That helped me understand the extreme age of some bottom dwelling animals as indicated by their tubes position in sediments. The embedding in sediments was inferred from the rarity of finding their posterior ends in dredge samples, absence of tube rings on a posterior branch of the fork of branched tubes, and funnel-like rings on some species with rims oriented toward the anterior end (the exposed tentacle bearing ends giving rise to the common name, beard worms, of the Pogonophora).
My paper describing the evidence for the beard worms extreme age - Engemann, Joseph G. 1968. Pogonophora: the oldest living animals? Pap.Mich. New York
Currents of major impact on the ocean are profoundly influenced by density differences due to salinity and temperature differences. The heavier water sinks and the lighter water rises. Surface currents can be wind driven. Gravity and inertia impact currents. At the interface of moving currents, or a current and still water, turbulence and mixing can be induced.
Pure water is most dense at about four degrees centigrade. So progressively warmer water is usual found from near the bottom to near the surface. Salt concentration of the water may make the temperature stratification vary in other ways. For example, Mediterranean Sea water entering the Atlantic Ocean near the Straights of Gibraltar sometimes goes to an intermediate depth based on density level of the ocean of the same density, but with different temperature and salinity.
Most of us are familiar with the affect of the Gulf Stream on climate in Europe, by its movement north along the western Atlantic that veers east and provides milder climates to northern Europe. A similar current affects climates in the north Pacific. While such currents catch our attention, one of greater consequence has had a profound affect on evolution as it has no doubt persisted and survived assaults by asteroids, volcanic disruptions, continental drift, and variations in solar radiation. It involves a cycle of circulation that takes ten thousand or more years to complete - from icy polar water settling to abyssal depths of temperate, sub-tropical, and tropical parts of the ocean where it slowly warms and rises until it ultimately mixes with warmer surface waters and completes the cycle by returning to polar regions via currents and evaporation and precipitation. A pause in polar ice caps can exceed the ten thousand plus year trip from abyss to sea surface.
A PERSISTENT CIRCULATION PATTERN
polar region temperate - sub-tropical regions
The visual above is not to scale but indicates the North Atlantic pattern of circulation from polar regions on the left to tropical regions on the right. Similar but variable profiles would be found in the North Pacific and Southern Ocean region of Atlantic, Pacific, and Indian Oceans. The flows would diminish and seem to disappear as they meet under tropical waters.
S represents the ocean floor or sediment with a sill regulating flow from (the sometimes ice covered) Arctic Ocean water. A rise in sea level, or a subsidence of the sill can allow a greater volume of flow to the abyss of the Atlantic.
C represents the cold salt water of high density that sinks to the depths of the ocean of such great volume that the warming water rises slowly, taking ten thousand or more years to mix with the warmer and less dense overlying water.
M represents the oxygen minimum zone separated from W, the warm surface water, by a thinner mixing zone, the thermocline. The thermocline is identified by rapid change in temperature. A shallow thermocline may result in more light for photosynthesis penetrating beyond the mixing zone so the oxygen minimum will be somewhat deeper. Also, storms may produce sufficient turbulence at depths to make the oxygen minimum zone deeper. The extent of the oxygen minimum zone also responds to organisms living there and bacteria utilizing organic debris settling from the photosynthetic zone near the surface.
W, the warm water is where oxygen is replaced by photosynthesis as well as by diffusion from the atmosphere.
Hurricanes
The thickness of the thermocline is greatly affected by wave action. Calm seas may have a thermocline within a hundred meters of the surface. Hurricanes and storms can produce turbulence to make the thermocline much deeper and provide a thicker zone of warm water and heat storage that may prolong or increase subsequent storms.
The H.M.S. CHALLENGER EXPEDITION
The first major oceanographic expedition occurred from late 1873 to early 1876. One of its many accomplishments was measuring depths, temperatures, and salinity of the oceans. I had examined part of one of the fifty some volumes of its researches published later that century while I was teaching a marine biology class about a hundred years after the voyage. I don't know how many years it took me to realize that the temperature profile that I have crudely illustrated above meant that the presence of oxygen and long residence time of the deep water beneath the thermocline meant either extremely low biological activity or very few organisms.
Subsequent oceanographic work has provided more complete coverage of the oceans and greater precision in measurements without changing the basic importance of the early expedition.
The time factor
Sediment cores show the vast percentage of abyssal sediments accumulate very slowly. That helped me understand the extreme age of some bottom dwelling animals as indicated by their tubes position in sediments. The embedding in sediments was inferred from the rarity of finding their posterior ends in dredge samples, absence of tube rings on a posterior branch of the fork of branched tubes, and funnel-like rings on some species with rims oriented toward the anterior end (the exposed tentacle bearing ends giving rise to the common name, beard worms, of the Pogonophora).
My paper describing the evidence for the beard worms extreme age - Engemann, Joseph G. 1968. Pogonophora: the oldest living animals? Pap.
The extreme longevity of deep sea animals is part of a circular argument that suggests the slow replacement of the cold deep water of the ocean, which in return, suggests the extreme age of the organisms there. Fortunately, other evidence is available to augment the invalid circular reasoning. The most dramatic bit was discovery of unspoiled fruit and sandwich on a lunch recovered from the Alvin submersible research vessel many months after it sank to great depth. Several studies involving respiratory rates of deep sea organisms show greatly slowed rates compared to comparable organisms of shallow seas.
Evolutionary implications
Some major implications are discussed in numerous past posts. Two major ones are-
- the error compounded in molecular phylogeny studies (especially establishment of the Ecdysozoa concept), and the unique missing link role that the pogonophorans fulfill.
The permanence of the ocean stratification in tropical through temperate zones has provided stable environments where the extremely slow metabolism resulting from low temperature and immense pressure allowed those that slowly adapted to the abyssal region to survive. The pogonophorans are one of the most significant, but little known, groups. Neopilina is an important indicator of molluscan relationships and their annelid ancestry. Brittle stars are abundant on many areas of the ocean bottom and help us understand the selective pressures giving rise to shallow water relatives. The coelocanth fish was found at intermediate depths but is a living relative of what is otherwise known from fossils.
Will the enormous area and depth protect marine life there from the assault of a constant flow of debris and chemicals we dump from ships, atmospheric contamination and polluted streams?
The permanence of the ocean stratification in tropical through temperate zones has provided stable environments where the extremely slow metabolism resulting from low temperature and immense pressure allowed those that slowly adapted to the abyssal region to survive. The pogonophorans are one of the most significant, but little known, groups. Neopilina is an important indicator of molluscan relationships and their annelid ancestry. Brittle stars are abundant on many areas of the ocean bottom and help us understand the selective pressures giving rise to shallow water relatives. The coelocanth fish was found at intermediate depths but is a living relative of what is otherwise known from fossils.
Will the enormous area and depth protect marine life there from the assault of a constant flow of debris and chemicals we dump from ships, atmospheric contamination and polluted streams?
Joseph G. Engemann Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan May 3, 2018
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