同心华德福共学坊

 找回密码
 立即注册
搜索
热搜: 活动 交友 discuz
查看: 839|回复: 3

[转载] 转载:Where Do Organisms End?

[复制链接]

68

主题

125

帖子

467

积分

管理员

Rank: 9Rank: 9Rank: 9

积分
467
发表于 2017-5-8 19:40:18 | 显示全部楼层 |阅读模式
Where Do Organisms End? http://natureinstitute.org/pub/ic/ic3/org_and_env.htm

The Nature         Institute
        20 May Hill Road, Ghent, New York 12075  Tel: (518) 672 0116
      
This short essay was stimulated by a question Eliot Schneiderman --         a biologist and neighbor -- raised after reading the description of bloodroot         in In Context #2. Eliot mentioned that ants are known to disperse         the seeds of bloodroot. He briefly described this fascinating process         and then remarked: you described bloodroot in its annual cycle, but don't         the ants belong to the wholeness of bloodroot as well?        
My immediate reaction was: of course! I had tried to show that we need         to go beyond any one momentary state of the plant and begin to grasp it         as a process in time. But I didn't go further, which Eliot pointed out.         It is a further step to view everything we call the "environmental interactions"         of an organism as part of that organism, for without these interactions         the organism wouldn't exist. Because our minds grasp spatial entities         most easily, we tend to become lazy and not make the effort to see how         every organism extends beyond itself as a physical entity, revealing itself         functionally as part of a larger whole.        
Ants and Seeds      Seeds are a favorite food of birds, rodents, and some insects. They are       often eaten soon after the fruit opens and they fall to the ground. In the       case of bloodroot -- and many other plants -- ants do not eat the seeds       but instead pick them up and carry them to their nest. Each bloodroot seed       has a small outgrowth called an elaiosome. The elaiosome grows outside the       seed coat and is not part of the germ. It is mainly fed to the larvae of       the ants. Biochemical analysis shows that eliaosomes are nutritious, being       rich in fats and sugars. The fast-growing larvae thrive on this nutrient-rich       food.         The seed itself, retaining its potential for germination, is discarded,         usually with other organic waste from the nest. As Andrew Beattie, who         studied these ant-plant interactions, put it, the seeds are placed on         "private compost heaps" (Beattie 1985, p. 2). In fact, plants do grow         out of such "seed beds" and often are more numerous and tend to take hold         better than seeds that don't originate in ant nests.        
In this manner bloodroot spreads out in lowland forests with the help         of ants. Bloodroot is found in clusters of a few to perhaps ten or twenty         flowering stalks. These "plants" are usually connected subterraneously         -- meaning they are actually branches from the same plant that, under         good conditions, continues to grow year by year. When the ants come, they         move the plant, via the seeds, beyond these narrow bounds, and provide         the conditions for a new colony of bloodroot to develop. In this sense         the ants belong to bloodroot, just as bloodroot -- as food -- belongs         to the ants.        
Giraffes and Acacias      Giraffes prefer the leaves of acacia trees to leaves of most other plants       -- although acacias have thorns. Giraffes browse in the crowns of the trees,       reaching up to a height of fifteen or more feet. Scientists in South Africa       observed that giraffes browsed acacias near water holes more intensely than       trees far away from such water sources (du Toit et al. 1990). Acacias grow       new shoots after the onset of the rainy season (one or two times a year).       The scientists found that the shoots from the more heavily browsed trees       grew back very rapidly, and grew to greater length, which compensated for       the intense browsing. In contrast, the lightly browsed acacias grew smaller       shoots, so that the net shoot extension was the same in both habitats. In       other words, giraffe browsing stimulated growth of the acacias in relation       to the degree of browsing -- a wonderful example of dynamic balance, which       then becomes disturbed when the habitat is too small for the number of giraffes       living in it. The heavily browsed acacias reacted to giraffe feeding in another, perhaps         more surprising way. The leaves that grew in the rainy season after browsing         were more nutrient-rich and contained significantly fewer condensed tannins,         which make leaves less palatable. Tannins are substances formed after         cessation of leaf growth, while nutrient-rich phosphorus and nitrogen         compounds are formed during growth. Stimulated by browsing, the acacia         leaves remained in a more juvenile state, which is exactly the type of         leaf giraffes prefer!        
In conceiving abstractly of discrete organisms, we think of giraffe         and acacia as separate entities, which of course they are physically         when the giraffe is not feeding. But the fed-on acacia is not the same         after giraffe browsing; it takes more minerals out of the soil and forms         nutrient-rich substances in its leaves, while suppressing leaf-aging as         indicated in less tannin formation. In this way the giraffe has become         part of the acacia. Then, when it feeds again, the giraffe feeds on something         that is connected to its own activity. The apparently clear boundary between         organisms dissolves and we are led to picture organisms as interpenetrating         each other rather than being next to each other.        
Bison and Prairie      Observing bison, I'm not alone in intuitively sensing that the bison and       the prairie belong together. With the reintroduction of bison herds into       prairie reserves in the Midwest, scientists have been able to observe how       bison -- along with fire -- help to create and maintain prairies (Knapp       et al. 1999).         Ungrazed long-grass prairies tend to become populated with a fairly         small number of grass species. Bison feed mainly on grasses and usually         avoid wildflowers. When bison have grazed a previously ungrazed area for         a time, the composition of species shifts and a greater diversity of plants,         especially wildflowers, arises. A rich and dynamic balance of species         is maintained as long as the bison can move from place to place and are         not forced to overgraze an area.        
Bison are often found in late spring and early summer in areas that         burned a few months before. Frequently burnt prairie that is not grazed         typically has a low species diversity. When it is grazed by bison, not         only do the bison have young, fast-growing, and nutrient-rich grasses         to feed on (think of the giraffes and the acacias), but slowly the plant         composition becomes more diverse with more species of wildflowers and         grasses taking hold.        
If we imagine a herd of bison grazing and moving through a prairie,         then we can recognize other ways in which the bison influence the prairie.         Where bison defecate, urinate or die, leaving the carcass, a zone of fertile         soil and a new microhabitat are created. In such areas grasses tend to         thrive, attracting the bison returning to the area. Their feeding in turn         stimulates the changes discussed above. The prairie becomes, as a result,         a more diverse patchwork of microhabitats.        
This tendency is increased by a particular habit of bison: in contrast         to cattle, bison wallow. They paw the ground and then roll in the exposed         soil. This activity creates, over time, circular denuded depressions about         ten to fifteen feet in diameter and up to a foot deep in the middle. "Relic         wallows still exist in many areas where bison have not occurred in the         past 125 years" (Knapp et al., 1999). Wallows collect rain water in the         spring and support the growth of ephemeral wetland species. In the summer         they dry out and become parched, supporting only drought-tolerant plants.         Wallows thus become islands with a unique plant composition and contribute         to the diverse, patchwork character of the prairie.        
Bison are integral and active members of an entire landscape, the prairie.         We could even say they landscape the prairie. From this perspective it         seems justified to speak of the bison as an essential organ of the prairie.         (Ecologists speak of a "keystone" species.)        
The Ever-Extending Organism      These brief descriptions can lead us from a traditional notion of separate       biological organisms to the conception of an ecological organism, of which       the biological organisms are a part. Each species -- bloodroot, giraffe       or bison -- appears as a unique member of a habitat or landscape, like tissues       or organs within an organism. In turn, we can study habitats and landscapes       as dynamic members of larger ecosystems and bioregions. Finally, we are       led to the concept of the whole earth as an organism.         The further we move from the distinct biological organism to its larger         dimensions, the more difficult it becomes to produce concrete and vibrant         concepts that express organismic qualities. One always runs the danger         of relying on schematic representations of interacting ecological factors.         The ant, the fungus, the tree, the wildflower, the bacteria become mere         intersections in a web of abstractions. We want to grasp what seems to         be a palpable whole, but what we're left with has little life-blood coursing         through it.        
This is one of the reasons that I, personally, often focus on individual         species. It is easier to develop organismic, relational thinking when         one chooses a particular animal or plant as focal point from which to         radiate out. Through such work one can develop the necessary mobility         of thought to begin approaching, say, a forest habitat or a wetland in         a similar fashion. As difficult as it may be, we need more and more to          see the organism in the habitat and in the landscape; otherwise,         we wander blindly through a world of unseen relationships.        
Life-Appropriate Ecology      The science of ecology has brought, on the one hand, wonderful phenomena       into view -- without which I wouldn't have been able to write this essay.       But, on the other hand, the concepts ecologists use often stand in the way       of understanding.         Ecologists rely largely on Darwinian concepts when viewing phenomena         and framing their hypotheses, models, and explanations. On this view,         each species embodies survival strategies that allow it to survive         in the face of competition with other organisms. Every characteristic,         each process, is interpreted as a means to survival. In this context I         will ignore the inherent danger of anthropomorphizing that goes with using         such concepts. More fundamentally, they reveal an error in judgment.        
When scientists speak of survival strategies and competition, then they         have decided from the outset that organisms are single, discrete         entities. This pre-judgment then demands that organisms interact and compete         only secondarily. This is the ecological version of atomism. But         all of ecology shows -- when one looks to the phenomena and not the theories         -- that this is not the case. The organism is interaction with         other organisms within the context of a habitat.        
The single organism (or species) that is supposed to compete with others          does not exist. It is far more appropriate to view organisms as         members of a differentiable whole that has never dissolved into discrete         entities. As Kurt Goldstein points out, in biological terms competition         begins when the functioning of the whole becomes disharmonious or diseased;          then self-preservation becomes an overriding tendency in an organism         (Goldstein 1963, p. 443 ff.).        
Discussing the concept of "struggle for existence" in his seminal work,          The Origin of Species, Charles Darwin wrote that he would often         use the term in a "large and metaphorical sense....A plant on the edge         of a desert is said to struggle for life against the drought, though more         properly it should be said to be dependent on the moisture" (Darwin 1979,         p.116). Although clearly aware of his loose use of language, Darwin did         not think it was particularly relevant to understanding the phenomena.         But, in fact, it makes all the difference in the world whether one uses         the first expression, which separates the plant from the environment,         putting it into a competitive relation, or whether one uses language that         stays as close to the phenomena as possible. There is no question that         saying the plant is "dependent on moisture" is a much more accurate and         vital description than speaking of struggling or competing plants, expressions         that create distance and conjure up independent agents.        
It demands constant effort to form concepts and find expressions that         stay near to the vibrancy of the phenomena and not to drift off into much         easier atomistic, putting-things-together formulations merged with images         of competition. But if we want to gain insight into the living         interactions that characterize life, we have no choice but to overcome         the many inadequate concepts used in ecology today.        
ReferencesBeattie, Andrew (1985). The Evolutionary Ecology       of Ant-Plant Mutualisms. New York: Cambridge University Press.        
Darwin, Charles (1979). The Origin of Species.         New York: Penguin Books. (The first edition was published in 1859.)        
du Toit, Johan T. et al. (1990). Regrowth and Palatability         of Acacia Shoots Following Pruning by African Savanna Browsers. Ecology         71:149-154.        
Goldstein, Kurt (1963). The Organism. Boston:         Beacon Press. (A reprint was published in 1995 by Zone Books in New York.)        
Knapp, Alan K. et al. (1999). The Keystone Role         of Bison in North American Tallgrass Prairie. BioScience 49 (January):         39-50.        


        Original source: http://natureinstitute.org/pub/ic/ic3/org_and_env.htm
回复

使用道具 举报

68

主题

125

帖子

467

积分

管理员

Rank: 9Rank: 9Rank: 9

积分
467
 楼主| 发表于 2017-5-8 19:44:34 | 显示全部楼层
What Forms an Animal?
Craig Holdrege      
What forms an animal? A likely answer these days is "genes." Or perhaps:         "genes and environment." Such high-level abstractions reveal how little         we actually know and tend to discourage further inquiry. When I hear "genes         and environment" I yearn for something more concrete, something I can         mentally take hold of. And the only way I know to develop such saturated         concepts is to get back to the things themselves—to look carefully         at what nature presents and inch my way toward a more full-toned understanding.        

Wild and Captive Lions      A few years ago I came across a remarkable article written in 1917 by N.       Hollister, then superintendent of the National Zoo in Washington, DC. (See        end of this article.) He was studying       the lion specimen collection at the National Museum, which encompassed over       100 lion skulls and skins. Hollister noticed marked differences between       wild-killed specimens and those that had lived for a number of years at       the Washington zoo. He proceeded to make a more detailed comparative study.        
Since lions from different areas of the world and also different regions         of Africa differ substantially from one another, Hollister focused on         one subspecies—the Masai lion (Panthera leo masaica) from         East Africa. Five of the zoo-reared animals were Masai lions and had been         captured as small cubs near Nairobi, Kenya. Hollister compared these specimens         with wild-killed lions from the same area. He thus had animals from the         same subspecies and one regional population. He knew, in other words,         that he was comparing fairly close relatives and not genetically and geographically         distinct populations.        
When the five lions were brought from Kenya to the Washington zoo, they         already stood out through their very pale, grayish buff-colored fur. This         is the typical coloration of wild-living Masai lions, but contrasted starkly         with the much more darkly colored lions at the Washington zoo. Over a         period of years the fur of these imported animals darkened considerably,         becoming like that of the other lions at the zoo. Moreover, the captive         male lions grew much longer manes than wild Masai lions and they also         had longer and fuller hair tufts at their elbows.        
Immediately we ask, "Why?" But an easy answer is not forthcoming. Hollister         was cautious. He believed the higher humidity and precipitation in Washington         might have played a role in fur darkening, since humidity has been correlated         with darkening of fur, and also feathers in birds. But he also recognized         that the quality of light as well as metabolic changes due to the abnormal         life and diet in the zoo might have contributed to the differences.        
The Skulls of Wild and Captive Lions      Since an animal's fur is in direct contact with the external environment,       we can imagine that it might somehow change in relation to changing environmental       conditions. But the solid and complexly formed skull, hidden from the world       by skin and muscles, is another matter. And yet, surprisingly, the most       striking differences between the wild and zoo-reared animals were in their       skulls (see Figures 1, 2 and 3).        

         Figure 1. Top view of a zoo-reared (left) and a wild-killed           (right) lion, both adult males. Drawn to same scale. (Drawings by Christina           Holdrege. After Hollister 1917.)        


The skulls from the zoo-reared animals are much shorter and broader         than in the wild animals. They appear compact compared to the more sleek         skulls of the wild lions. When I first saw the photographs of the skulls,         I thought they had been incorrectly labeled, expecting the more stocky,         massive skull to have belonged to a wild animal. But they were correctly         labeled and I needed to consider the matter more closely. (A good exercise         in overcoming prejudice!)        
The skulls from the zoo-reared animals—whether male or female—are         not only broad but also thicker-boned. One can see this in the prominent         cheekbones (zygomatic arches, see Figure 1). The arch sweeps out further         to the sides and consists of much thicker and more rounded bone. Figure         2 shows a cross section through the bone of the zygomatic arch in a zoo-reared         and a wild animal. The difference is glaring. The zoo-reared animal's         bone is triangular in cross section with convex surfaces and rounded corners.         It consists largely of porous bone material (spongiosa). In contrast,         the wild animal's arch is narrower and has one concave and one convex         surface that meet at the top of the arch, forming a sharp ridge. The arch         has little porous bone, consisting mainly of the outer layer of strong         compact bone.        

         Figure 2. Cross section through the zygomatic arch of a wild-killed           (left) and a zoo-reared (right) lion. Adult males of same age; natural           size. (From Hollister 1917.)        


Similar differences are visible at the rear of the skull (see Figure         3). Not only is the skull of the zoo-reared animal much broader, the surfaces         and forms are more rounded with gradual transitions from convex to concave.         The skull of the wild-reared lion has much sharper, more defined edges         and angles.        

         Figure 3. View from the rear of a wild-killed (top) and a zoo-reared           (bottom) lion, both adult males. Drawn to same scale. (Drawings by Christina           Holdrege. After Hollister 1917.)        


One further interesting contrast between the skulls pertains to the         braincase (see Figure 1). Measured externally, the braincase in the skull         of a wild lion is smaller than in the zoo-reared lion. When, however,         one measures the internal cranial capacity—which is a direct indicator         of brain size—the wild lion skull is considerably larger (40 to 50         cubic centimeters greater in size). This apparent paradox is resolved         when one considers bone thickness. As in the other parts of the skull,         the bones of the braincase are substantially thicker in the skull of the         zoo-reared animal. Therefore the braincase appears externally larger but         internally leaves less room for the brain. The larger brain of wild lions         is covered by thinner, but solid, compact bone.        
Hollister writes that even an untrained observer would group the skulls         into wild and zoo-reared specimens, so apparent and uniform are the differences.         He suggests that if one were dealing with only specimens from wild animals         (or fossils), a biologist or paleontologist would think that he or she         was viewing specimens of different species (a remark that makes one wonder         about the accuracy of fossil classifications). Where does this contrast         come from?        
Activity that Sculpts      A primary activity missing from the life of a captive lion is the hunt and       kill. A hungry lion in Africa's savannah crouches in the grass, all muscles       tensed and its senses focused on the movement of a herd of antelopes or       zebras. It stalks slowly and silently toward the herd and then suddenly,       in a forceful burst of speed, sprints toward an animal, leaps, grabs onto       the neck, and pierces through blood vessels and the wind pipe with its long,       pointed canines. It pulls the prey down—using head and paws—and       holds it until it dies. If the lion is a female with young cubs, she may       drag the prey, locked into her jaws, toward the place where she's hidden       them.        
All this activity is missing from the life of a captive lion. And this         activity forms the skull. The lion uses powerful muscles to grip, bite         into and hold the prey in its jaws. The masseter muscle is especially         important for the gripping power exercised in using the incisors and canines         to pierce and hold the prey. This muscle attaches to the zygomatic arch         and to the mandible (lower jaw). A powerful muscle must be rooted in strong         bones. As the lion exercises its muscles, they not only grow but also         put tension and stress on the bones. Although we tend to think of bones         as inert structural elements of the body, they are, in fact, alive and         adaptive. With an increase in stress and tension the bones change form         and structure to meet the demands of the activity. The zygomatic arch         remolds to form a sharp ridge of compact bone as the ideal attachment         for the masseter muscle. In the same way the mandible forms thinner, more         compact bone with ridges and rougher surfaces for the strong muscles attached         to it. In contrast, the rounded, smooth zygomatic arch and mandible in         the zoo-reared lions reveals a lack of activity. The bones grow and billow         out, being hardly influenced by muscular stress and strain. Hollister         notes their juvenile appearance, which reflects the lack of change due         to inactivity.        
Likewise, the sculpting of the rear of the wild lion's skull discloses         activity. The wild lion uses its neck muscles in holding, pulling, lifting,         shaking, and dragging prey. At least seven different neck muscles attach         to the rear of the skull and every contraction sculpts the bones these         muscles are rooted in. As in the jaw, the rear of the skull forms defined         ridges and rough surfaces where the muscles attach. The little-used neck         muscles of the captive lion leave the rear of the skull largely unaltered;         the bones become more rounded and have smoother surfaces.        
The Formative World      In the life of an animal, activity is a key formative factor. The active,       hunting lion takes on a modified form compared to the inactive zoo lion.       The muscle-orchestrated movement of the lion shapes the bones. This movement,       in turn, is stimulated internally by the animal's drives (hunger) and externally       by the perception of the antelope or the zebra. In this sense the antelope       and the zebra form the lion. A remarkable thought. We all know that the       flesh of these animals nourish the lion, but now we can recognize that the       activity these animals call forth in the lion sculpts the lion's very bones.       We can go even further and say that the savannah—its soil, light, warmth       and moisture, its grasses and trees, its other animals—forms the lion.       But it becomes increasing difficult to say precisely how this larger       world influences the lion.        
The outer world that forms the lion points us to the lion. By "lion"         I mean the specific way-of-being that, for example, is open to and reacts         to antelopes and zebras in a particular way. A lion doesn't see the grass         it's crouching in as something to feed on, as does the antelope. Grass         is something to hide in and move through. In this sense the lion is a         specific world, a way to be and behave. This aspect of the lion is centered         in the bodily form it is born with. This form is given through inheritance         and then molded by activity. The hereditarily given model is something         dynamic and plastic, waiting to be filled and formed by the animal's activity.         This is what we should be picturing when we speak of a "genetic background"         or genes, not some fixed plan.        
The vast and rich ecology of the savannah stimulates the lion to activity.         In a sense it brings forth the lion and allows it to unfold its life.         This stimulation influences the whole metabolic activity of the animal,         not only the muscles and the bones. Every sense perception forms nerve         activity and influences the formation and function of the brain. The zoo         lion lives in a world that calls forth little activity. Its bones grow         large and thick, expressing the weight and inertia of its existence, while         muscles and nerves receive little stimulation. One can sense the responsibility         one takes on in having captive animals—knowing that we are cutting         them off from part of the world that enlivens and forms them. How can         we create a surrogate environment that at least to a degree is appropriate         to their needs?        
So when you hear that an animal is a product of its genes and its environment,         think of the lion. Think of the most solid part of the body—bone—being         molded by the animal's activity. In activity, the lion's specific anatomical         and behavioral readiness takes hold of a world without—the kill at         a watering hole at dusk. The antelope shapes—and so is part of—the         lion.        
* Hollister,         N. 1917. Some effects of environment and habit on captive lions. Proceedings         U.S. National Museum 53: 177-193.        


        Original source: In Context (Fall, 2001, pp. 12-14); copyright         2001 by The Nature Institute
回复 支持 反对

使用道具 举报

68

主题

125

帖子

467

积分

管理员

Rank: 9Rank: 9Rank: 9

积分
467
 楼主| 发表于 2017-5-8 20:38:28 | 显示全部楼层
The Giraffe's Short Neck  
This essay is part of a larger monograph on the holistic biology  of the giraffe.  To purchase the monograph or view it for free online, go to the Nature Institute store.       
Lamarck and Darwin Once scientists began thinking about animals in terms of evolution,         the giraffe became a welcome—and seemingly straightforward—example.         It is as if the giraffe's long neck was begging to be explained by evolutionary         theorists.
One of the first evolutionary thinkers, Jean-Baptist Lamarck, offered         a short description of how the giraffe evolved in his major work, Philosophie         Zoologique, which was published in 1809:
It is interesting to observe the result of habit in the peculiar         shape and size of the giraffe: this animal, the tallest of the mammals,         is known to live in the interior of Africa in places where the soil is         nearly always arid and barren, so that it is obliged to browse on the         leaves of trees and to make constant efforts to reach them. From this         habit long maintained in all its race, it has resulted that the animal's         forelegs have become longer than its hind-legs, and that its neck is lengthened         to such a degree that the giraffe, without standing up on its hind-legs,         attains a height of six meters. (Quoted in Gould 2002, p. 188)         
In Lamarck's view, we must imagine a situation in the past where the         best food for browsing mammals was higher up in trees, the lower vegetation         having been eaten by other animals. The ancestors of the giraffe—which         we should imagine like antelopes or deer—needed to adapt their behavior         to this changing environment. As Lamarck wrote, "variations in the environment         induce changes in the needs, habits and modes of life of living beings         ... these changes give rise to modifications or developments in their         organs and the shape of their parts" (p. 179). So Lamarck imagined that         over generations the habit of continually reaching for the higher browse         produced in the giraffe's ancestors a lengthening of the legs and neck.        
Figure 1. Giraffe in a "classic" feeding position, extending its neck,  head, and tongue to reach the leaves of an Acacia tree. (Tsavo National  Park, Kenya; drawing by C. Holdrege after a photo in Leuthold and Leuthold  1972.)


A little over sixty years later, Charles Darwin commented on giraffe         evolution in the sixth edition (1872) of his seminal book, Origin of         Species:
The giraffe, by its lofty stature, much elongated neck, fore-legs,         head and tongue, has its whole frame beautifully adapted for browsing         on the higher branches of trees. It can thus obtain food beyond the reach         of the other Ungulata or hoofed animals inhabiting the same country; and         this must be a great advantage to it during dearths.... So under nature         with the nascent giraffe the individuals which were the highest browsers,         and were able during dearth to reach even an inch or two above the others,         will often have been preserved; for they will have roamed over the whole         country in search of food.... Those individuals which had some one part         or several parts of their bodies rather more elongated than usual, would         generally have survived. These will have intercrossed and left offspring,         either inheriting the same bodily peculiarities, or with a tendency to         vary again in the same manner; whilst the individuals, less favoured in         the same respects will have been the most liable to perish.... By this         process long-continued, which exactly corresponds with what I have called         unconscious selection by man, combined no doubt in a most important manner         with the inherited effects of the increased use of parts, it seems to         me almost certain that an ordinary hoofed quadruped might be converted         into a giraffe. (Darwin 1872, pp. 177ff.)         
In many respects this is a classic formulation of how Darwin viewed         evolution: every species consists of individuals that show considerable         variations. Under certain environmental conditions particular variations         will be most advantageous. Natural selection weeds out the unadapted and         the best-adapted survive. These variations become dominant in the species         and so it evolves. In the case of giraffes, times of drought and arid         conditions give an advantage to those animals that can out-compete others         by reaching the higher, untouched leaves. They form the ancestral stock         of the animals that evolve into giraffes.
Interestingly, Darwin believed in the "inherited effects of the increased         use of parts"—a very "Larmarckian" view. Lamarck argued for the inheritance         of acquired characteristics. Darwin felt that this was key to explain         giraffe evolution; otherwise there is no guarantee that longer features         in one generation will have an effect on subsequent ones. But this view         of the inheritance of acquired characteristics is rejected by mainstream         Darwinists today.
The Long Neck as a Feeding Strategy The idea that the giraffe got its long neck due to food shortages in         the lower reaches of trees seems almost self-evident. The giraffe is taller         than all other mammals, can feed where no others can, and therefore has         a distinct advantage. It seems compelling to say that the long neck and         legs developed in relation to this advantage. Why else would the giraffe         be so tall? You find this view presented in children's books, in web descriptions         of the giraffe, and in textbooks.
But just because this explanation is widespread does not mean it is         true. In fact, this "self-evident" explanation retains its ability to         convince only as long as we do not get too involved in the actual biological         and ecological details. Various scientists have noticed that this elegant         picture of giraffe evolution dissolves under closer scrutiny. Here are         a few examples of my and their objections:
1) Since the taller, longer-necked, evolving giraffe ancestors were         also larger and heavier, they would need more food than the animals they're         competing with. Wouldn't this counterbalance their advantage in times         of dearth? Would they really have any advantage over smaller members of         the same and other species? Moreover, it is absurd to assume that only         the leaves onhigh branches were available to the giraffe during         a drought. Had this been the case, then the multitude of browsing and         grazing antelope species in Africa would all have gone extinct (or never         evolved in the first place). So, even without growing taller, the giraffe         ancestor could have competed on even terms for those lower leaves.
2) Male giraffes today are up to one meter taller than female giraffes;         newborn and young giraffes are much smaller. The moment this sexual dimorphism         manifested in the evolution of the giraffe, it would have been the males         that could have reached the higher branches. The females and young animals         would have died and the species would have gone extinct (Pincher 1949).
3) If giraffes evolved by eating high foliage during times of drought         and maximal competition for food, one would expect that giraffes today         would also feed from the high foliage during these times in order to avoid         competition. Males usually feed at greater heights than females and the         results of one study show a surprising spread (Ginnett and Demment 1997).         Male giraffes fed nearly half of the time at heights of almost five meters,         that is, in the "classical" long-necked giraffe posture. In stark contrast,         females fed around seventy percent of the time at belly height or below,         which the theory demands they should not be doing. These researchers did         not report on the seasons in which they made these observations, so their         results are of little help in discerning whether, for example, males feed         at greater heights mainly during droughts.

          Figure 2. Giraffe feeding at about shoulder height—the most prevalent         height at which giraffes feed. (South of Moremi Game Reserve, Botswana;         drawing by C. Holdrege.)        


A variety of other studies show that giraffe feeding habits vary according         to place and time (reviewed in Simmons and Scheepers 1996). Giraffes move         seasonally, and in the dry season in East Africa they tend to seek out         lower valley bottoms and riverine woodlands. There they usually feed from         bushes at or below shoulder height (about two and one half meters in females         and three meters in males). Fifty percent of the time they fed at a height         of two meters or less, which overlaps with the feeding zone of larger         herbivores such as the gerenuk and the kudu (Leuthold and Leuthold 1972;         Pellew 1984; see Figure 2). During the rainy season, when there is abundant         browse at all levels, giraffes are more likely to feed from the higher         branches, browsing fresh, protein-rich leaves. Other studies also show         that giraffes do most of their feeding at about shoulder height, with         their necks positioned nearly horizontally (Young and Isbell 1991; Woolnough         and du Toit 2001). So it looks as though giraffes are not using their         long necks the way the theory demands. And they use them even less to         reach heights in the dry season, when the theory demands they should need         them most!
4) There are other ways to reach the high foliage of trees. Goats, for         example, are known to climb into trees and eat foliage (see Figure 3).         Why didn't tree-climbing leaf-eaters (folivores) develop in the savannah?         They would have had the advantage of feeding at all levels easily and         been in that respect more adaptable than the highly specialized giraffe.         The long-necked gerenuk, an antelope, often stands on its hind limbs and         browses, reaching heights of two meters and more. The much larger and         heavier elephant even stands sometimes on its back legs and extends its         trunk to reach high limbs—but no one thinks that the elephant developed         its trunk as a result of selection pressures to reach higher food.
In sum, there is nothing in this theory that shows a compelling link         between leg and neck lengthening and feeding on high limbs. Just because         giraffes have long necks and long legs and can reach food high         in the trees does not mean that a need to reach high browse was a causative         factor in the evolution of those characteristics.

          Figure 3. A goat does not require a long neck to feed on twigs and leaves         of an oak tree. (Drawing by C. Holdrege after a photo in Butzer 2000.)        


Clearly, both Darwin's and Lamarck's conceptions of giraffe evolution         were highly speculative. The idea that giraffes developed longer legs         and necks to reach higher food seems plausible, even compelling, as long         as we do not (1) think the idea through in all its implications and (2)         take into account essential observations of giraffe behavior and ecology.         In the end, the idea is neither logically compelling nor based on fact.        
Alternative Explanatory Attempts Pincher (1949), after critiquing Darwin's explanation, suggests that         the "most extraordinary feature of the giraffe is not the length of the         neck but the length of the forelegs." By developing long legs, the giraffe         has acquired a huge stride so that it can move relatively fast for its         size. This has left the giraffe with only one predator—the lion.         Pincher therefore explains the "excessive length of its forelegs as the         effect of natural selection acting continually through the hunter-hunted         relationship, as in the case of hoofed mammals generally." The neck, in         turn, followed the lengthening legs so that the giraffe could still reach         the ground and drink.
It is strange that Pincher is able to critique Darwin's view so clearly         and yet doesn't recognize that he is proposing the same type of inadequate         explanation. The giraffe ancestor could just as well have developed greater         bulk or more running muscles, both of which would have aided in avoiding         predators. The fact is that despite its size and long stride, the giraffe         is still preyed upon by lions. And as one study of one hundred giraffes         killed by lions in South Africa showed, almost twice as many bulls were         killed as cows (Pienaar 1969; cited in Simmons and Scheepers 1996). The         longer stride of bulls evidently doesn't help them avoid lions better         than the shorter legged females. Who knows whether their long stride may         in some way make them more vulnerable? Another speculative idea into the         wastebasket.
Brownlee (1963) speculates that the lengthening of the limbs and neck         in the giraffe give the giraffe a relatively large surface area, which         should allow it to dissipate heat. This would be of advantage in the hot         tropical climate, so that the tendency toward lengthening would have been         encouraged by natural selection, since the largest animals would have         been best able to survive heat waves.
As in the other suggested "explanations," the central question is, Is         Brownlee's idea rooted in reality? Because of its long legs and neck,         the giraffe appears to have a large surface area. But surface area alone         is not important; it is the relation of the heat producing volume to surface         area that is crucial. A small animal has a small volume in relation to         a very large surface area, while a large animal very large volume in relation         to its relatively small surface area.1 Now the giraffe is a very large animal with a barrel-shaped         torso. Although its neck is long, it is also voluminous; only the lower         parts of the legs, which carry relatively few blood vessels, would act         to enlarge the surface-to-volume ratio substantially. Krumbiegel (1971)         estimates that the ratio of volume to surface in the giraffe is 11:1,         compared, say, to a smaller, long-necked antelope, the gerenuk, which         has a ratio of 4.7:1 (similar to the human). In other words, despite appearances,         the giraffe still has a very large volume in relation to its surface area         and its unique form provides no grounds to think that it evolved in relation         to dissipating heat.
More recently, Simmons and Scheepers (1996) proposed that sexual selection         has caused the lengthening and enlarging of the neck in males. These scientists         place their ideas in relation to known facts and point out shortcomings         in relation to larger contexts—a happy contrast to the other hypotheses         we've discussed. They describe how male giraffes fight by clubbing opponents         with their large, massive heads; the neck plays the role of a muscular         handle. The largest (longest-necked) males are dominant among other male         giraffes and mate more frequently. Since long-necked males mate more frequently,         selection works in favor of long necks. This would also help explain why         males have not only absolutely longer, but proportionately heavier heads         than females.
This hypothesis seems consistent with the difference between male and         female giraffes. At least it gives a picture of how the longer neck of         males can be maintained in evolution. But it doesn't tell us anything         about the origin of neck lengthening in giraffes per se—the neck         has to reach a length of one or two meters to be used as a weapon for         clubbing. How did it get that long in the first place? Moreover, the female         giraffe is left out of the explanation, and Simmons and Scheepers can         only speculate that female neck lengthening somehow followed that of males.         In the end, the authors admit that neck lengthening could have had other         causes and that head clubbing is a consequence of a long neck and not         a cause.
Does the Giraffe Really Have a Long Neck? All the above explanations of the evolution of the giraffe's long legs         and long neck are unsatisfying. Each of the authors sees problems in other         explanations, but remains within the same explanatory framework when putting         forward his own hypothesis. No one sees the necessity for stepping outside         the framework and looking at the difficulties of the overall approach.         The scientists abstract individual features (long neck, long legs, large         surface area) and consider them in isolation from the rest of the organism.         The individual feature is then placed into relation to one purported         causal factor in the environment (drought, heat, predator avoidance, male         competition). The link of individual feature to environmental factor is         supposed to explain the evolution of that feature.
But this is a highly problematic procedure. The giraffe's neck carries         out a variety of functions—it allows feeding from high branches,         serves as a weapon in males, brings the head to elevated heights that         give the giraffe a large field of view, is used as a pendulum while galloping,         and so on. Virtually all structures and organs in the animal body are         multifunctional and interact dynamically with other multifunctional structures         and organs. When scientists pick out a single function and focus solely         on it to explain a multifunctional organ, their explanation can only be         inadequate. This is comparable to believing you can paint a richly-nuanced,         colorful rendition of a landscape with one color. It just does not work.        

          Figure 4. "Short-necked" giraffes grazing. Giraffes can only reach the         ground with their mouths to drink or graze by splaying their front legs         (left) or splaying and bending their forelegs (right). (Drawing by C.         Holdrege after a photo in Dagg and Foster 1982.)        


I sometimes wonder why no one has maintained that the giraffe has, in         reality, a short neck. If you observe a giraffe drinking or, as         they occasionally do, grazing close to the ground, then you know what         I mean (see Figure 4). Giraffes do not drink often, but when they do,         they have to either splay their forelegs to the side or bend their forelegs         strongly at the wrist joint. Both procedures take time and are awkward         for the giraffe. But only in this way can it get the tip of its mouth         down to the surface of the water. So, looked at from the perspective of         drinking, the giraffe has a very short neck. Antelopes and zebras reach         the ground without bending their legs, and the long-legged elephant has         its trunk to compensate for its short neck. Only the giraffe (and its         rain forest relative, the Okapi) have necks that are so short relative         to their legs and chest that they must splay or bend their legs.
So why hasn't the giraffe become famous for its manifestly short neck?         Why don't we have evolutionary hypotheses explaining how the giraffe got         its short neck? It is because the giraffe's neck, in other respects or         from other perspectives, is long. No other mammal has such a long         neck in absolute terms or in relation to the length of its torso. We all         have seen (in life or in pictures) and been amazed by the standing giraffe,         its long neck sailing skyward, in comparison to which the ungainly, short-necked         drinking giraffe appears as exceptional, almost unfortunate behavior.        
Whether the neck is long or short depends on our perspective and on         the behavioral or anatomical context we are focusing on. We only understand         the giraffe when we view it from various perspectives and let the giraffe         show different aspects of its being. The moment we focus solely on the         "long neck"—and on it solely in terms of a food-gathering or some         other strategy—we've lost the reality of the giraffe.
Reality is richer than such explanations. The explanation may be coherent         and logical, but what it explains is not the thing itself but a specter         of it—the isolated aspect that has been abstracted from the whole         organism. In reality, the organism as a whole evolves; all its parts are         multifunctional, facilitating its interactions with its complex, changing         environment. It we don't consider all partial aspects within this larger         context, we can only have inadequate explanations void of life.
Another consequence of the usual way of explaining is that the organism         itself is atomized into individual characteristics, each having its own         explanation. Each part takes on a quasi-reality of its own, while the         whole organism—which brings forth and gives coherence to the parts—degenerates         into a kind of epiphenomenon, a mere composite of the surviving parts         that "really" count.
In sum: the whole project of explaining the evolution of an animal by         abstracting from the whole leads to unsatisfying, speculative ideas on         the one hand, and to conceptual dissolution of the unity of the organism         on the other. A more adequate understanding requires that we first investigate         the organism as a whole and how its members interrelate and interact within         the context of the whole organism and its environment. This holistic understanding         can then form the starting point for thinking about the evolution         of the animal. The evolutionary biologist Dobzhansky's famous statement         that "nothing in biology can be understood except in light of evolution"         is a grand claim, which I believe is, in the end, true. But we have a         lot of work to do before we get there, and we should not be satisfied         with short-cut evolutionary "explanations."
If evolutionary thought is to have a solid foundation, we must establish         this firm grounding in holistic understanding. As it is, stories of the         evolution of traits seem compelling until you look for their context and         foundation in the world and discover a pool of quicksand. As Simmons and         Scheepers remark about Darwin's idea of giraffe evolution, "it may be         no more than a tall story."
Note1. Assuming for the sake of explanation a spherical       body, the two-dimensional surface grows as a function of the square of the       radius, while the volume—being three-dimensional—grows as a function       of the cube of the radius. A sphere with a radius of 2.5 cm (1 inch) has       a volume-to-surface ratio of 0.8:1. A much larger sphere with a radius of       50 cm (about 20 inches) has a volume-to-surface ration of 16.7:1.        ReferencesBrownlee, A. (1963). "Evolution of the Giraffe,"          Nature vol. 200, p. 1022.
Butzer, Karl (2000). "The Human Role in Environmental         History," Nature vol. 287, pp. 2427-2428.
Dagg, Ann Innis, and J. Bristol Foster (1982). The         Giraffe: Its Biology, Behavior and Ecology. Malabar FL: Krieger Publishing         Company.
Darwin, Charles (1872). Origin of Species. Sixth         Edition. (Available online at http://pages.britishlibrary.net/ ... h/origin6th_07.html)
Ginnett, Tim, and Montague Demment (1997). "Sex         Differences in Giraffe Foraging Behavior at Two Spatial Scales," Oecologia         vol. 110, pp. 291-300.
Gould, Stephan Jay (2002). The Structure of Evolutionary         Theory. Cambridge, MA: Belknap Press.
Krumbiegel, Ingo (1971). Die Giraffe. Wittenberg         (Germany): A. Ziemsen Verlag.
Leuthold, Barbara, and Walter Leuthold (1972). "Food         Habits of Giraffe in Tsavo National Park, Kenya," E. Afr. Wildl. J.         vol. 10, pp. 129-141.
Pellew, Robin (1984). "The Feeding Ecology of a         Selective Browser, the Giraffe (Giraffa camelopardalis tippelskirchi),"          J. Zool., London vol. 202, pp. 57-81.
Pincher, Chapman (1949). "Evolution of the Giraffe,"          Nature vol. 164, pp. 29-30.
Simmons, Robert, and Lue Scheepers (1996). "Winning         by a Neck: Sexual Selection in the Evolution of the Giraffe," The American         Naturalist vol. 148, pp. 771-786.
Woolnough, A. P., and J.T. du Toit (2001). "Vertical         Zonation of Browse Quality in Tree Canopies Exposed to a Size-Structured         Guild of African Browsing Ungulates," Oecologia vol. 129, pp. 585-590.
Young, Truman, and Lynne Isbell (1991). "Sex Differences         in Giraffe Feeding Ecology: Energetic and Social Constraints," Ethology         vol. 87, pp. 79-89.


        Original source: In Context #10 (Fall, 2003, pp. 14-19); copyright         2003 by The Nature Institute         

回复 支持 反对

使用道具 举报

68

主题

125

帖子

467

积分

管理员

Rank: 9Rank: 9Rank: 9

积分
467
 楼主| 发表于 2017-5-8 21:35:07 | 显示全部楼层
Learning to See Life—Developing the Goethean Approach to Science
Craig Holdrege
I have often thought that if a teacher wanted to have one succinct motto to hang above his or her bed, she’d have a hard time finding a better one than: “characterize, don’t define.” In order to characterize, say, an animal, we have to carry within ourselves a vivid picture of its shape, how it moves, the sounds it makes, its habitat and the ways it relates to its environment. We bring alive through our imagination and speech something of the animal’s nature. We learn, for example, how the sloth spends its life hanging in and slowly moving through the boughs of rain forest trees. It recedes into its environment to the degree that it lets algae grow in its fur, which soaks up rain like a sponge, and the resulting greenish tinge makes the sloth nearly invisible in the tree crowns. It is so adapted to hanging that it is virtually helpless on the ground.  Everything about the sloth is slow—it moves slowly, it digests slowly (only climbing down to the ground once a week to, as the students would say, pee and poop), it grows slowly, reacts slowly and seems largely impervious to pain (1). When we paint a picture of the animal in this way—a process in which the students are involved—the animal can begin to live in the soul of the child or adolescent.
Characterization imbues a subject with life. To define may make something clear, but it is the kind of clarity that is all too often void of life. When Rudolf Steiner, the founder of Waldorf education, urged teachers to characterize and not define, he did so because he knew that through characterization we form living concepts that can grow and transform (2). A definition, by contrast, is fixed. Unfortunately, it is often within biology classes, with all the rote learning and memorization of definitions for multiple choice exams, where traditional outcome-based education reaches its unhappy epitome. And biology is supposed to be the science of life.  Charles Dickens gives a lovely caricature of this way of teaching in his novel Hard Times:
“In this life, we want nothing but Facts, sir; nothing but Facts!”….
“Bitzer,” said Thomas Gradgrind, “your definition of a horse.”
“Quadruped. Graminivorous. Forty teeth, namely twenty-four grinders, four eye-teeth, and twelve incisive. Sheds coat in the spring; in marshy countries, sheds hoofs too. Hoofs hard, but requiring to be shod with iron. Age known by marks in mouth.” Thus (and much more) Bitzer.
“Now girl number twenty,” said Mr. Gradgrind, “you know what a horse is.”
Of course we all need to learn facts, but isolated facts are soon forgotten and are like stones instead of nourishment for the human soul. What the students need is to see how the facts relate to each other, how the parts of an organism interact in service to the life of the whole creature. You could say that all real knowing is ecological knowing—knowing how something is part of a larger, dynamic context. If we can bring students into this way of knowing, we are preparing them for a life in a world that will not offer them pat solutions, but demand from them the ability to grow and form new ideas in relation to new and unforeseen demands.
The problem is that modern habits of thought and academic training, which encourage, above all, analysis and abstract theorizing, do not give teachers the tools they need to bring this kind of understanding to students. In fact, they tend to deaden both the propensity toward quiet and open-ended observation and the concrete, imaginative capacities a teacher needs most in order to build up exact, yet living pictures of the world.
Already over 80 years ago, Steiner saw that teachers came out of the “system” with rigid, one-sided habits of thought. He saw the Goethean approach to nature and science as a key enabling teachers to transform their own thinking and bring a more vital reality to their students:
Our way of thinking is inclined to place things side by side. This shows us how little our concepts are geared to outer reality. In outer reality things flow together…. We need to think things together, and not as separate from each other. A person who wishes only to think things separated resembles a man who wishes only to inhale, never to exhale…. Here you have something that teachers in the future will have to do; they must above all acquire for themselves this inwardly mobile thinking, this unschematic thinking.
Science will have to wake up in a Goethean sense and move from the dead to the living. This is what I mean when I say again and again that we need to learn to get beyond our dead abstract concepts and move into living, concrete concepts. (3)
In our work at The Nature Institute we are committed to helping teachers and people who want to become teachers work on this transformation. One of the challenges of this task is that learning an approach that aims to reveal life in nature entails both ridding ourselves of ingrained habits of thought and mobilizing new forces within ourselves. This process takes effort and time—it does not happen overnight. In our mentoring work we see that this transformation can occur through the focused work over a longer period of time on a concrete research project.
For example, what better way is there to learn a living approach to nature than learning from the master of life on earth, namely, the plant world? We can carefully observe how a specific plant develops—unfolds, transforms, and ages. We sketch the plant and recreate precisely in our imagination its development. In this way we take the plant as a living process into our own minds and mold our thoughts around it. When we observe other plants and make comparisons, we begin to see the specific style of growth and form in a given species. We then go further and relate the plant to its habitat—under what kinds of conditions does it thrive? How does it vary under different conditions? This kind of immersion schools our observation (we become awake to the world around us) and because the plant lives through change and variation, our thinking becomes more mobile and flexible. You could say we’re beginning to think like a plant grows. And since we have taken something of the richness of the plant world into us, we can build up pictures that are rooted in reality and out of this, living characterizations can flow.
An important element in this work involves attending to our own inner activity. We need to become keenly aware of how our thought processes interweave with our observations. Goethe spoke of “delicate empiricism,” a felicitous expression that captures the two fundamental features of scientific study (4). We orient our attention closely to the phenomena we are observing, but we also learn to become more aware of our own thought processes so that we apply our concepts in a more careful, circumspect way. Living, vital concepts are ones born out of the interaction with the phenomena themselves.
Traditional training in science often puts roadblocks in the way of this approach. Anyone studying biology today learns that the question to ask in reference to any phenomenon is: what is the underlying mechanism? This way of asking becomes habitual and in essence the only kind of question one is allowed to ask (as a scientist). This puts a straight jacket on scientific inquiry and inasmuch as the focus is on mechanisms, it is already a foregone conclusion that life is nothing other than a mechanism. However, the moment you begin—in a more open-ended way—attending to the fuller phenomenal reality, say, of a developing spring wildflower, you soon realize how inadequate mechanistic explanations are. They pale in the face of plant itself.
When we really take hold of the Goethean approach—through immersion in the phenomena themselves and self-aware thinking—it teaches us to be more critical than we are when we teach theory- or model-driven science. This is important to note, since there is the misconception that the Goethean approach is somehow “just” about observation and therefore “soft” (or even worse: warm and fuzzy) in comparison to “real” (whatever that is) science. Nothing could be further from the truth. The Goethean approach is not about opposition to traditional science; it is concerned with evolving the discipline of science further so that we can begin to understand life in a way that is modeled after life. For this to occur we have to work to transform ourselves as human beings and begin forming, as Goethe put it, new organs of perception.  Through this practice we begin to experience science as a truly human endeavor that leads us to an understanding and recognition of the deeper qualities of life on earth. We gain the capacities we need as teachers to bring the living world close to the hearts and minds of our students. 
 
Sources
1.  Holdrege, Craig. “What Does It Mean to Be a Sloth? NetFuture, #97, Nov. 3, 1999 (www.netfuture.org/1999/Nov0399_97.html.)
2.  Steiner, Rudolf. Foundations of Human Experience, lecture 9 (August 30, 1919). Great Barrington, MA: Anthroposophic Press, 1996.
3.  Steiner, Rudolf. Education as a Social Problem, lectures 4 and 6 (August 14 and 16, 1919). Great Barrington, MA: Anthroposophic Press, 1984.
4.  Goethe, Johann Wolfgang. In Goethe: Scientific Studies, Edited by D. Miller, p. 307. Princeton: Princeton U. Press, 1995.

This article originally appeared in Renewal: A Journal for Waldorf Education, Fall 2005
回复 支持 反对

使用道具 举报

您需要登录后才可以回帖 登录 | 立即注册

本版积分规则

Archiver|手机版|小黑屋|同心华德福共学坊  

GMT+8, 2019-1-22 15:20 , Processed in 0.089691 second(s), 22 queries .

Powered by Discuz! X3.2

© 2001-2013 Comsenz Inc.

快速回复 返回顶部 返回列表