Biota

“ Thus the energy produced by the plant travels through the food chain. When the prairie falcon dies, scavengers—including insects and other invertebrates, birds, and mammals—redistribute its wealth among themselves; the rest is decomposed by bacteria. Thus, eventually, the nutrients on which the plants depend return to the soil.
When we look at any living organism, whether it is plant, herbivore, carnivore, parasite, scavenger, or decomposer, we are soon made aware of its associations with other living things, each puzzle piece leading us to another and another. ”

“ The plants have collected stores of organic matter, and their minute germs, along with microscopic species, are floating everywhere in the sea. Nay, there may be abundant examples of those Amœba-like germs of aquatic plants, simulating for a time the life of the animal, and then returning into the circle of vegetable life. In these some might see precursors of the Protozoa, though they are probably rather prophetic analogues than blood relations. The plant has fulfilled its function as far as the waters are concerned, and now arises the opportunity for the animal. ”

“ The difficulty is very often to know where to draw the line. Probably no flowering plant is quite independent of the labour and work of its neighbours. As we have tried to show in another chapter, a long preliminary cultivation by bacteria, lichens, and mosses is required before flowering plants can develop on bare rock. That is also necessary in all cases where the soil is mineral or inorganic, without any organic dust or fragments of vegetable or animal matter. Bacteria must always begin the work by preparing nitrates and other salts. ”

“ In the case of the decomposition of the woody matter of the tree trunk, the process is begun by the agency of moulds, for this group of organisms alone appears to be capable of attacking such hard woody structure. The later part of the decay, however, is largely carried on by bacterial life. In the decomposition of the animal tissues, bacteria alone are the agents. Thus the process by which organic matter is dissipated into the air or incorporated into the soil is one which is primarily presided over by bacterial life. ”

“ All this plant and animal waste—twigs, leaves, limbs, fallen trees, feathers, hair, feces, and carcasses—is processed by the armies of decomposers that thrive on the forest floor. With the aid of larger creatures that break up the plant and animal tissue, most microscopic bacteria are able to decompose from a hundred to a thousand times their own weight every day.
Few trees die of old age in the forest. The seedling mortality rate is necessarily high, since far greater numbers of seeds germinate each year than can reach maturity. ”

“ The primitive forms of plant life gradually developed into more perfect organisms, until the mosses, ferns, cycads gave way to flowering plants, perhaps 10,000,000 years ago at a very conservative estimate. In some way bacteria learned to establish a partnership with some kinds of plants, such as clover, alfalfa, soy beans, etc. These plants, together with the bacteria, are the important factors in our agriculture as regards the maintenance of a supply of nitrogen in our soils. ”

“ Such plants, which always consist of single cells, are called one-celled; they are found among the lowest forms of the microscopic world, among the algae and the fungoids. The green coating that covers the rocks, the tree-trunks, and the shingles of the roof, is resolved by the microscope into innumerable green round cells; the brown scum that floats upon ponds and ditches exposed to the sun, the yeast-plant, the bacteria that produce putrefaction, are one-celled plants of this kind. ”

“ Organisms that form part of the organic complex of the soil range from the more conspicuous species, such as slugs and snails, insects, spiders, wood lice, millepedes, earthworms and eelworms, to such microscopic forms as protozoa, fungi, algæ and bacteria, the last three being members of the plant kingdom. ”

“ In the lake itself small, one-celled algae floated about in the waves and currents. Bacteria grew on the lake bottom and in the water and helped to contribute to the organic ooze that built up on the bottom. Fungi, wonderfully preserved in oil shales, are further indicators that Fossil Lake was a fresh-water lake and deep enough to have depths below the zone of sunlight penetration (Bradley 1964a) . Reeds, rushes, and similar lake-shore plants grew in shallow, near-shore waters.
The large amount of organic material in the rocks is evidence of the prolific microscopic plant growth in the lake. ”

“ The great cycle of changes occurring in the soil whereby organic matter is gradually transformed and again made available as plant food is entirely dependent upon micro-organisms. Until a decade ago it was thought that bacteria were by far the most important group concerned in the bringing about of these changes, but recent studies have shown that, in at all events certain arcs of this great organic cycle, the fungi have, perhaps, an equal part to play. ”

“ The production of sufficient soil by mineralogical decay as well as by the decay of organisms, plant and animal, may be regarded as having been a preliminary to larger plant-growth; and though at present the dependence is far less close than that among animals, yet the benefits yielded to metaphytes by the decomposing actions carried on by protophytes, as well as those carried on by microbes permeating the soil, imply a continued general interdependence throughout the aggregate of plant-forms, apart from more special interdependences. ”

“ Botrydium usually increases by buds which form on the green bladder, break away and grow into new plants. Should the level of the water in the pond rise, and the little plant become submerged, it splits up into a number of small bodies, each provided with a minute whip-like organ, with which they swim rapidly ashore where they develop into new plants. In dry weather the plant forms a number of little cells each one surrounded by a firm cell wall. When moisture comes again these little [93] cells give rise to structures which will grow into new plants. ”

“ The so-called Fission-Fungi or Bacteria differ from the Schizophyceae or Fission-Algae in the cell-contents being either colourless, blood-red or green, but never blue-green. We may regard the Bacteria, generally, as the lowest forms of plants; they are extremely simple organisms which have been derived from some primitive types which possessed the power of independent existence and contained chlorophyll—that important substance which enables a plant to obtain its carbon first-hand from the carbon dioxide of the atmosphere. ”

“ Bitumen is also found in a notable quantity, and a peculiar soapy substance, a species of animal matter, the cause, perhaps, of the cadaverous flavour already mentioned. The water, which when first caught is bright and clear, becomes turbid if left to cool, and throws down a pale-brown sediment. Ehrenberg, the celebrated microscopist of Berlin, who has examined specimens of this sediment under his microscope, declares it to be composed of fossil animalcules inconceivably minute; these animalcules being a portion of the material out of which Nature builds up the solid strata of the globe. ”

“ In ordinary arable soil there exist motile rod-like bacteria, Bacterium radicicola. These enter the root-hairs of leguminous plants, and passing down the hair in the form of a long, slimy (zoogloea) thread, penetrate the tissues of the root. As a result the tissues become hypertrophied, producing the well-known nodule. In the cells of the nodule the bacteria multiply and develop, drawing material from their host. Many of the bacteria exhibit curious involution forms (“bacteroids”) , which are finally broken down and their products absorbed by the plant. ”

“ The various activities of the soil bacteria have a vital importance to the growth of higher plants, which are dependent for their existence on certain of these processes. In the first place, as we have seen, bacteria decompose the tissues of higher plants and produce humus materials, which are essential to the maintenance of good physical properties in the soil. Then the nitrate supply on which most higher plants depend is produced by the decomposition of organic nitrogen compounds by bacteria in their search for energy. ”

“ The animal world, so far as true land-forms are concerned, is limited to types like the protozoa (lowest in the organic scale) , rotifera and minute insect-like mites which lurk hidden away amongst the tufts of moss or on the under side of loose stones. Bacteria, most fundamental of all, at the basis, so to speak, of animal and vegetable life, have a manifold distribution. ”

“ Just as man and all land animals depend ultimately for their food supply upon grass and other green-leaved plants which, under the influence of sunlight, are able to transform the inorganic constituents of the atmosphere and the soil into organic foodstuffs—albumen, fat, carbohydrates—so the minute unicellular marine plants of the plankton are able, under the influence of sunlight, to convert the inorganic constituents of their environment into fat, albumen and carbohydrate. Upon these minute organisms, therefore, directly or indirectly, all marine life depends. ”

“ In experimental investigation it is essential that observations be made on a pure species, or, as Johannsen (Johannsen, "Ueber Erblichkeit in Populationen und reinen Linien", Jena, 1903.) says, on a pure "line." What has long been recognised as necessary in the investigation of fungi, bacteria and algae must also be insisted on in the case of flowering plants; we must start with a single individual which is reproduced vegetatively or by strict self-fertilisation. In dioecious plants we must aim at the reproduction of brothers and sisters. ”

“ Finally, the invested or invaded cell may so adapt itself to the demands of the invader that a sort of arrangement is arrived at by which life in common—Symbiosis—is established, each organism doing something for the other and each taking something from the other. In this latter case, which is often realised—e.g. lichens, leguminous plants and the organisms in their root-nodules, mycorrhiza, etc.—we leave the domain of disease, which supervenes indeed if the other symbiont is lacking. ”

“ The way in which they work is too difficult to explain here, but to get an idea of the romance of the underground world one must try to picture to oneself these swarms and myriads of germs and bacteria all incessantly and busily engaged at their several duties. In the uppermost layers there are probably in a single cubic inch of good soil from 54,000,000 to 400,000,000 of these microbes. Many are absolutely necessary to the harvest; a few may be of little importance, but there are sure to be some of those dangerous sorts which might devastate a continent with disease in a single summer. ”

“ Stated briefly, my conclusion is that the algae of the 183French authors may be definite organic bodies, but it is unwise to attempt to determine their affinities within such narrow limits as have been referred to in the above résumé. The structure of the bituminous deposits is worthy of careful study, and it is by no means impossible that further research might lead us to accept the view of the earlier investigators, that the brightly coloured organic-like bodies may be inorganic in origin. ”

“ The fusion of the two gametes results in the production of the sexual spore, called the “o-o-spore;” it develops at once into the second generation, or second stage in the life-cycle of the moss plant, which is called the “spo-ro-phyte.” It consists of the seta and capsule; the lower end (“foot”) of the seta becomes early embedded and fixed in the tissue of the gametophyte, and from it is derived the nourishment necessary to complete the development of the sporophyte, or the plant that produces the numerous non-sexual spores. ”

“ How can the good bacteria be encouraged to grow, and the bad ones prevented from forming? The necessary conditions for the growth of good bacteria are air, water, darkness, humus matter and freedom from acid condition of the soil. If the soil is acid then these other 'chaps' set up their work; so we must see to it that our soils are well cultivated, well aired, have plenty of manure, and, if acid, have a liming, so that these bacteria missionaries can start their good work. ”

“ These green or greenish plants and animals are the producers, using the energy of the sunlight to help them in building up carbon compounds out of air, water, and salts. The animals which feed on the producers, or on other animals, are the consumers. Between the two come those open-sea bacteria that convert nitrogenous material, e.g. from dead plants or animals that other bacteria have rotted, into forms, e.g. nitrates, which plants can re-utilise. ”

“ In a factor culture, the area is divided into two or more parts which are given different amounts of water or of light, in order to determine the influence of slight variations upon the same competitors. In somewhat similar fashion, an attempt has been made to ascertain the bearing of biotic factors upon competition. Cultures are easily made in which Cuscuta or parasitic fungi are used to place certain species at a disadvantage. Permanent cultures are obtained by allowing the plants to ripen and drop their seeds for several generations, just as in nature. ”

“ Krasilnikov's great contribution to science was discovering how soil microorganisms assist the growth of higher plants. Bacteria are very fussy about the substrate they'll grow on. In the laboratory, one species grows on protein gel, another on seaweed. One thrives on beet pulp while another only grows on a certain cereal extract. Plants "understand" this and manipulate their soil environment to enhance the reproduction of certain bacteria they find desirable while suppressing others. This is accomplished by root exudates. ”