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Showing papers in "Biological Reviews in 1979"


Journal ArticleDOI
TL;DR: Factors that influence the evolution of growth rate and determine its variation among species of birds are discussed in this paper.
Abstract: Summary 1. This paper discusses factors that influence the evolution of growth rate and determine its variation among species of birds. Growth rate is related to evolutionary fitness through the use of time, energy, and nutrients. In addition, balances between factors favouring rapid growth and those favouring slow growth may be investigated directly by experiment and by comparative observation. 2. David Lack (1968) proposed that the growth rate of the young is the optimum balance between selection for rapid growth to reduce the vulnerable period of development and selection for slow growth to reduce the energy requirements of the young. 3. To test Lack's hypothesis, the growth rates of birds, estimated by fitting sigmoid equations to curves relating weight to age, were surveyed widely from the literature. Among all species examined, growth rate was inversely related to adult weight. Among birds of similar size, most variation in growth rate was related to the degree of maturity of the neonate. Altricial chicks, which depend upon their parents for food and warmth, grow more rapidly than precocial chicks, which are self-sufficient shortly after hatching. Lack's hypothesis, which predicts a direct relationship between growth rate and mortality rate, was not supported. 4. I propose that the key to understanding variation in growth rate among birds lies in the balance between rate of cell proliferation or cell growth, on one hand, and acquisition of mature function, on the other. This idea is consistent with principles of cellular and developmental biology. It is supported by comparisons of (a) the neonates of different species, (b) the individual over the course of the developmental period, and (c) tissues whose use is acquired at different stages of development, wherein more mature individuals or tissues grow more slowly than those with less developed function. 5. Species of birds that are classified as semi-precocial develop precocially but grow rapidly. Although these seemingly violate the general rule relating growth rate to precocity, a closer inspection of their development reveals that they too support the rule. In the Common Tern, the legs, which are the key organ in precocial development, grow at the expected slow rate. The body as a whole grows rapidly because the growth increment of the legs is small and their growth is completed quickly. 6. Growth rates of precocial birds do not decrease abruptly at hatching. This points more to gradual tissue differentiation than to the pattern of procurement and allocation of energy as the primary control for growth rate. 7. Precocious development is favoured when the chicks are capable of self-feeding or when food supplies are distant from the next site and travelling time between one and the other is long. Precocity of the neonates frees both parents to feed at a distant food source. 8. Some species having diets with low levels of protein or other nutrients may grow slowly in order to match nutrient requirements to their availability in the diet. This pattern is indicated especially among the Procellariiformes, which feed an oily diet to their young, and also among tropical fruit-eating birds. 9. Some tropical, pelagically-feeding sea-birds that rear only one offspring at a time may not be able to procure food sufficient to support rapid chick growth. Alternative explanations for slow growth among these species include difficulty in obtaining essential nutrients and more precocious development of activity than in related species having more rapid growth.

343 citations


Journal ArticleDOI
TL;DR: In this paper, the regenerative power of axons in the C.N.S. was investigated in the peripheral nervous system, including wound of the brain and spinal cord.
Abstract: 11 . Pertinent experimental data . . . . . . . . . . . . 157 (I) Regeneration in the peripheral nervous system . . . . . . . . 158 (2) Axonal regeneration in the C.N.S. . . . . . . . . . . 158 (a) Wounds of the brain and spinal cord . . . . . . . . . 158 . I59 (3) Neurosecretory axons . . . . . . . . . . . . 160 (4) Monoaminergic fibres . . . . . . . . . . . . 161 ( 5 ) Regeneration through spinal roots . . . . . . . . . . 161 (6) Primary olfactory neurones . . . . . . . . . . . 161 (7) Regeneration of axons into non-neural tissues transplanted into the brain . . . 162 (a) Skin . . . . . . . . . . . . . . . 162 (b) Striated muscle . . . . . . . . . . . . . 162 (c) Smoothmuscle . . . . . . . . . . . . . 162 (d) Other tissues . . . . . . . . . . . . . 163

278 citations


Journal ArticleDOI
D. J. Cove1
TL;DR: In Aspergillus nidulans, at least 16 genes can mutate to affect the reduction of nitrate to ammonium, a process requiring two enzymes, nitrate reduct enzyme and nitrite reductase.
Abstract: Summary (1) In Aspergillus nidulans, at least 16 genes can mutate to affect the reduction of nitrate to ammonium, a process requiring two enzymes, nitrate reductase and nitrite reductase. (2) niaD is the only gene whose effects on enzyme structure are confined to nitrate reductase alone. It specifies a core polypeptide, one or more of which form the basic subunit of nitrate reductase, molecular weight 50000. (3) At least five cnx genes together specify a molybdenum co-factor, necessary for the activity of nitrate reductase, and of xanthine dehydrogenases I and II. The cnxH gene specifies a polypeptide component of this co-factor, and the cnxE and F gene products are involved in co-factor elaboration, The role of the remaining cnx genes is at present unknown. (4) Functional nitrate reductase has a molecular weight of 200000 and is likely to consist of four subunits, together with one or more molecules of the cnx-specified co-factor. (5) The co-factor plays a catalytic role in the aggregation of nitrate-reductase subunits. (6) The niiA gene is the structural gene for nitrite reductase. (7) Other genes affecting nitrate assimilation are either regulatory or bring about their effects indirectly. (8) Of the genes affecting nitrate assimilation, close linkage is found only between the niiA and niaD genes. (9) Nitrate and nitrite reductases are subject to control by nitrate induction and ammonium repression. (10) Nitrate induction is mediated by the nirA gene whose product must be active for the niiA and niaD genes to be expressed. Since most niaD mutants produce nitrite reductase constitutively, it is likely that the nirA gene product is normally inactivated by nitrate reductase, but only when the latter is not complexed with nitrate, (11) Ammonium repression is mediated by the areA gene, whose product must be active for the expression of the niiA and niaD genes, and which is inactive in the presence of ammonium. (12) The tamA gene may function similarly to the areA gene, both gene products being necessary for the expression of the niiA and niaD genes. (13) Although the niiA and niiD genes are probably contiguous, they are not likely to be organized into a structure equivalent to a bacterial operon. (14) Whereas the areA and nirA genes regulate the synthesis of nitrate and nitrite reductases, it is probable that at least nitrate reductase is also subject to post-translational control, the presence of active enzyme being correlated with high levels of NADPH. (15) The regulation of the pentose-phosphate pathway, of mannitol-I-phosphate dehydrogenase and of certain activities required for the catabolism of some nitrogen-containing compounds appears to be connected with that of nitrate assimilation. In all cases, it is probable that the nirA gene and nitrate reductase itself are involved.

255 citations


Journal ArticleDOI
TL;DR: For example, acquired digestive enzymes: a windfall of mycophagy as mentioned in this paper have been used to exploit the properties of fungal mycelium for the purpose of obtaining acquired enzymes.
Abstract: CONTENTS I. Intmduction . . . . . . . . . 11. Arthropod-fungal associations . . . . . . . (I) Arthropods associated with sporophores . . . . (2) Arthropods in habitats which include fungal mycelium . (3) Insects involved symbiotically with fungi . . . . 111. Nutritive characteristics of fungal tissue . . . . . (I) Caloric value . . . . . . . . (2) Elemental composition . . . . . . . (3) The macronutrients of fungi . . . . . . (4) The micronutrients of fungi . . . . . . (5) summary. . . . . . . . . . IV. Digestive and metabolic requirements imposed on mycophagous species by the special characteristics of fungal tissue. . . . . . . . (I) Fungal polysaccharides . . . . . . . . . . (2) Fungal sterols . . . . . . . . . . . . (3) Urea and ammonia . . . . . . . . . . . (4) Secondary metabolites . . . . . . . . . . (5) Summary. . . . . . . . . . . . . V. Acquired digestive enzymes: a windfall of mycophagy . . . . . (I) Enzymes active against plant cell-wall polysaccharides . . . . (2) Enzymes active against fungal constituents. . . . . . . (3) Enzymes active against phenolic substances . . . . . . (4) Requirements imposed by the exploitation of acquired digestive enzymes . (5) Acquired digestive enzymes: a closing comment . . . . . VI. summary . . . . . . . . . . . . . VII. Acknowledgement . . . . . . . . . . . . VIII. References . . . . . . . . . . . . . i

184 citations


Journal ArticleDOI
TL;DR: In this article, the authors propose a method to solve the problem of the problem: this article...,.. ].. ).. ]... )...
Abstract: CONTENTS

126 citations



Journal ArticleDOI
TL;DR: In this paper, the authors propose a method to solve the problem of the problem: this paper...,.. ].. ).. ]... )...
Abstract: CONTENTS

80 citations


Journal ArticleDOI
TL;DR: Plant tissue cultures form the basis of a number of techniques which have been developed to effect genetic changes in plants and progress is being made in the application of these techniques in breeding new, disease‐resistant cultivars.
Abstract: Summary 1. Plant tissue cultures form the basis of a number of techniques which have been developed to effect genetic changes in plants. Progress is being made in the application of these techniques in breeding new, disease-resistant cultivars. 2. It is possible to induce and select for mutants among populations of cultured plant cells. Novel disease-resistant plants of a small number of species have been regenerated from cells selected in culture for their resistance to toxins produced by pathogens, both with and without prior exposure to mutagens. It is not known whether such procedures are widely applicable, and the nature of the genetic changes involved has not yet been determined. 3. The tissues of plant species which are propagated vegetatively are normally genetic mosaics with regard to many characteristics, including resistance to disease. Thus, some of the plants regenerated from cultured cells of such species are more resistant to pathogens than the parent plants. Novel plants produced in this way are already being used in some breeding programmes. 4. Many attempts have been made to modify the genomes of cultured plant cells by means of exogenous nucleic acids. The evidence for integration and replication of this genetic material is equivocal. The technique, therefore, offers no immediate prospects for the development of novel disease-resistant plants, but may be important in the long term as methods are perfected for using plasmids and other agents as carriers of useful genes. 5. Steady advances are being made in producing somatic hybrids of crop plants by fusion of isolated protoplasts. In the long term it may be possible to use protoplast fusion to transfer desirable disease-resistance traits between related species which cannot be hybridized by conventional breeding methods. 6. The culture of excised embryos may be used to grow interspecific and inter-generic hybrid plants in cases where incompatibility occurs after normal fertilization. The technique is already being used by breeders in the production of disease-resistant hybrids of crop species. 7. It is concluded that tissue culture has a limited but useful role to play in the development of novel disease-resistant crop plants.

65 citations



Journal ArticleDOI
TL;DR: For the purposes of this review the term ‘carpoid’ is used to include such animals, known generally as the cornute and mitrate carpoids, but now either referred to the echinoderm class Stylophora or the chordate subphylum Calcichordata.
Abstract: Among Palaeozoic fossils, carpoids are perhaps the most curious and enigmatic. A truly bewildering catalogue of descriptive terms, orientations, interpretations and classifications has been applied to these early echinoderm-lie creatures, known generally as the cornute and mitrate carpoids, but now either referred to the echinoderm class Stylophora (Ubaghs, 1968 b) or the chordate subphylum Calcichordata (Jefferies, 1967 et seq.). For the purposes of this review the term ‘carpoid’ is used to include such animals. Carpoids are not a large or common group of fossils; in all only some 30 cornute and mitrate genera have been described. They appear first in the early Middle Cambrian with an undescribed cornute genus from Utah (Ubaghs, 1975, p. 85) and with the slightly younger Ceratocystis and they are known last from the Lower or Middle

55 citations


Journal ArticleDOI
TL;DR: The comparative anatomy of the vertebrates (including the comparative embryology and vertebrate palaeontology) has much to offer zoologists because it is here that the authors see best the actual transformation of organs into homologous but vastly different structures which function quite differently.
Abstract: The comparative anatomy of the vertebrates (including the comparative embryology and vertebrate palaeontology) has much to offer zoologists because it is here that we see best the actual transformation of organs into homologous but vastly different structures which function quite differently. We have the possibility also of understanding how animals can so change that the evolutionary results are separated into different classes. The description in the middle of the last century by Owen of the first discovered mammal-like reptiles did not arouse great interest, perhaps because much of the material was of indifferent quality and the techniques then available for their preparation and study were primitive when compared with those available today. It was the visit paid by Seeley to South Africa later in the century, and particularly his accounts of such cynodonts as Cynognathus ceratinotus, which aroused serious interest. One result of this was that Broom migrated to South Africa and during the next half century described hundreds of specimens collected from the Permo-Triassic Karroo fauna, the majority of which were synapsid, or mammal-like, reptiles. Later Watson’s accounts (1911, 1913) of the cynodont Diademodon attempted for the first time to interpret the real nature of, and to some extent, the mode of life of these animals. His account of the lower jaws of cynodonts, drawing attention to the reduced postdentary bones, caused Palmer (1913) to compare them with the ear bones of an embryo marsupial. The resemblance was such as to establish finally Reichert’s long famous theory, based entirely on living animals, that the mammalian malleus, incus and stapes were the homologues of the reptilian articular, quadrate and columella auris. But Palmer’s comparison also showed that the mammalian tympanic bone was unquestion-

Journal ArticleDOI
TL;DR: The nucleus has a distinctive carbohydrate chemistry, the main features of which are the lack of glycosphingolipid, the high density of carbohydrate per unit area of nuclear membrane, the presence of glycosaminoglycan in the nuclear matrix and possibly the nuclear membranes, and the existence of Glycosylated non‐histone proteins.
Abstract: Summary 1. The nucleus has a distinctive carbohydrate chemistry, the main features of which are the lack of glycosphingolipid, the high density of carbohydrate per unit area of nuclear membrane, the presence of glycosaminoglycan in the nuclear matrix and possibly the nuclear membranes, and the existence of glycosylated non-histone proteins. 2. The nucleus has considerable autonomy in its metabolism of glycosaminoglycan and has a capacity for glycosyl transfers involving glycosyl dolichyl phosphates and pyrophosphates. This latter activity probably resides in the nuclear membranes. 3. The soluble fraction of the nucleoplasm contains the total cellular CMP-sialic-acid synthetase and, hence, all sialic acid metabolism passes through the nucleus, which may have a regulatory role. Uncertainty remains as to the sialic acid content of the glycoproteins of the nucleus and it is likely to vary between cell types. 4. Malignancy is associated with several alterations in the glycosylation of nuclear membranes, including increased levels of sialic acids in the glycoproteins of the inner nuclear membrane: changes in glycosylation of the matrix and chromatin are not yet well defined. In malignancy, some nuclear glycoproteins may possibly appear in other cellular membranes.

Journal ArticleDOI
TL;DR: Animals must depend upon plants for the primary synthesis of other vitally important biochromes including flavins, flavonoids, quinones, and notably the carotenoids, which must be assimilated by animals, directly or ultimately from the plant kingdom.
Abstract: Summary 1. Animals, in common with plants, are capable of elaborating their own supplies of tetrapyrrolic pigments, i.e. the porphyrins and bilichromes, as well as pterins and certain indolic biochromes, including melanins and indigoids. But they must depend upon plants for the primary synthesis of other vitally important biochromes including flavins, flavonoids, quinones, and notably the carotenoids. These must be assimilated by animals, directly or ultimately from the plant kingdom. 2. Colour is expressed in certain large organic molecules as a consequence of chemical resonance, evoked by the presence of unsaturated intra-molecular bonds. This condition, allied closely with chemical instability and metabolic reactivity, thus underlies certain biocatalytic functions, fulfilled for example by some biochromic molecules, such as oxidative enzymes, and some vitamins and hormone-like regulators. 3. Commonest examples of such biocatalysts include the several classes named above, conspicuously such porphyrinic tetrapyrroles as chlorophyll, haemoglobin, and the oxidases and peroxidases, including cytochromes and catalase. Among the open-chained members or bilichromes, we find some of these in red algae; phyto-chrome initiates numerous vital biochemical processes in green plants; and bilirubin and biliverdin are found in blood and bile of animals. 4. Among the pterins are members which simulate closely some physiological functions of vitamins B1 and B2. Some promote sexual activity in aphids, and in the royal jelly of honeybees, they determine whether a hatchling shall develop into a queen or a neuter worker. 5. Riboflavin, acquired in minute but fundamentally necessary amounts by animals' consumption of plants, whether directly or indirectly, is a unit of the vitamin B2 complex, and is stored either unmodified or conjugated with the animal's protein. 6. Flavonoids and quinones are similarly acquired from ultimate plant sources. Such compounds may or may not undergo minor chemical modifications within the bodies of consumers. Quercitin, a flavonoid, favours normality of the eye-lens, skin and blood capillaries, while, among the naphthoquinones, the K vitamins ensure blood coagulability. The benzoquinones include the Q-enzymes or ubiquinones, which serve as metabolic oxidative catalysts. 7. Integumentary melanins, derived from oxidative degeneration of tyrosine, chiefly by animals as well as by certain plants, may serve usefully in screening underlying tissues against injurious light rays or, in insects, as well as in some cold-blooded vertebrates, may be capable of effecting either concealment or advertisement. Related to these so-called indole pigments are the indigoids which are breakdown products of tryptophan, and are encountered chiefly in excretory materials, some especially under pathological conditions. Dibromindigo, an ancient dye recovered from certain marine gastropods, is something of an enigmatic exception. 8. Among the carotenoids, manufactured de novo only by plants, are found the known precursors of the A vitamins. It is these compounds that represent by far the most prominent members of the world's pigment crop. In their handling of ingested carotenoids, animals emphasize any of several metabolic alternatives, e.g. (a) non-selective assimilation of all types; (b) rejection of all classes from any storage; (c) selective uptake of the hydrocarbon or carotene kind; or (d) solely of the alcoholic or other oxygen-containing members (xanthophylls); or finally (e) oxidative conversion of carotenes or xanthophylls into innovated red or other richly coloured derivatives. Some animals are without A vitamins among any carotenoids they may store. Numbers of arthropods so characterized nevertheless exhibit photokinetic responses. Plants are without vitamin A per se, carrying only carotenoid precursors thereof; however, single-celled phototactic phytoplankton, e.g. dinoflagellates, respond to light by their diurnal vertical migrations. It seems reasonable to suppose that animals, evolving from the primitive plant world, must have inherited therefrom many similarities in their cytoplasmic constitution and basic metabolic needs, but not in all instances the means of fully supplying them. They must, accordingly, continue to rely upon the plant world for the synthesis, de novo, of materials such as carbohydrates (for fuel, inter alia) and many amino acids for their protein upkeep, as well as certain biocatalysts, notably of the bio-chromic type, such as vitamins, e.g. B2 (riboflavin), B12 (cyanocobalamin), thenaphthoquinone K vitamins, and the A provitamin pigments, including carotenes and close chemical relatives thereof, although the animals have developed the capacity to split such pigments, deriving thus for themselves the A vitamins proper.

Journal ArticleDOI
TL;DR: Competition and co-existence and changes in growth rate, stability of population numbers, and species interactions are reviewed.
Abstract: 11. Biological considerations 75 (I) Intraspecific competition and displacement . * * 75 (2) A simple ‘biological model’ . . . . 75 (3) The ‘illusion of plenty’ . . . . . 7 6 (4) Diseased and dying animals . . . . 7 6 111. Simulations . . . . 78 (I) A simple predator-prey model . . 78 ( a ) Stability of population numbers . 79 (i) Restriction on equations . . 80 (ii) Food for prey . . . . . 81 (iii) Restrictions on input parameters . . . . 81 (b) Exploitation . . . . . . . 81 (c) Yields . . . . 82 (d) Composition of the population . * 83 (e) Reproduction . 84 (a ) Stability . . . . . . . . 85 (b) Exploitation and yields . . . . . 8 5 (c) Species interactions . . . . . . 8 6 IV. Further biological considerations . . . . . . 8 6 (I) Displacement pressure . . . . . . . 8 6 (2) Mortality . . . . . . . . 88 (3) Changes in growth rate . . . . . 8 9 (4) Competition and co-existence . . . . . . 89 v.summary. . . . . . . . . 90 . . . . .

Journal ArticleDOI
TL;DR: In this article, the authors propose a method to solve the problem of the problem: this article...,.. ].. ).. ]... )...
Abstract: CONTENTS