Life history characteristic ofCyrtomium falcatum around the natural northern boundary in Hokkaido, with reference to the alternation of generations

1984 ◽  
Vol 97 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Toshiyuki Sato
Keyword(s):  
Life History ◽  
Northern Boundary ◽  
Life History Characteristic ◽  
Alternation Of Generations

scholarly journals On Apogamy and the development of Sporangia upon fern prothalli

1898 ◽  
Vol 63 (389-400) ◽  
pp. 56-61
Keyword(s):  
Life History ◽  
Point Of View ◽  
The Other ◽  
Normal Life ◽  
Other Hand ◽  
General Importance ◽  
Two Generations ◽  
History Of ◽  
Alternation Of Generations

The two most important deviations from the normal life-history of ferns, apogamy and apospory, are of interest in themselves, but acquire a more general importance from the possibility that their study may throw light on the nature of alternation of generations in archegoniate plants. They have been considered from this point of view Pringsheim, and by those who, following him, regard the two generations as homologous with one another in the sense that the sporophyte arose by the gradual modification of individuals originally resemblin the sexual plant. Celakovsky and Bower, on the other hand, maintaint the view tha t the sporophyte, as an interpolated stage in the life-history arising by elaboration of the zygote, a few thallophytes.

THE BISEXUAL AND AGAMIC GENERATIONS OF BESBICUS MIRABILIS (HYMENOPTERA: CYNIPIDAE), AND THEIR ASSOCIATE INSECTS

1967 ◽  
Vol 99 (2) ◽  
pp. 187-196 ◽  
Author(s):  
David Evans
Keyword(s):  
Life History ◽  
Life Histories ◽  
First Record ◽  
Alternation Of Generations

AbstractAlternation of generations, or heterogony, wherein progeny resemble their grandparents but not their parents, is a little-known aspect of some cynipid life histories. This study represents the first record of its occurrence within the genus Besbicus, until now recognized solely from agamic females. The bisexual generation described herein has not been described previously. The literature on B. mirabilis (Kinsey) is reviewed briefly and some of the difficulties of cynipid study are assessed. The life history and ecology of both generations is presented and the immediate insect associates are discussed.

scholarly journals CHROMOSOMAL ALTERNATION OF GENERATIONS IN NEREOCYSTIS LUETKEANA (MERTENS) POSTELS AND RUPRECHT

1961 ◽  
Vol 39 (7) ◽  
pp. 1711-1724 ◽  
Author(s):  
Lindley Kemp ◽  
Kathleen Cole
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Nuclear Division ◽  
Basal Cells ◽  
Cytological Examination ◽  
Male And Female ◽  
Nereocystis Luetkeana ◽  
History Of ◽  
Alternation Of Generations

A cytological examination of the life history of Nereocystis luetkeana has shown that an alternating chromosome number corresponds to the morphological alternation of generations. The first division sequence of the zoosporangial nucleus is meiotic and is followed by three, usually synchronous, mitotic divisions. Thirty-two zoospores are liberated from each sporangium, and their germination gives rise to male and female gametophytes. Genotypic determination of the sexes is believed to take place in Nereocystis. Mitosis in the gametophytes is regular and cytokinesis follows each nuclear division, producing few cells in the female and many cells in the male gametophytes. Thirty-one chromosomes can be counted at the mitotic prophase. Oogamy exists in Nereocystis and fertilization takes place after the egg is extruded from the oogonium. Nuclear division in the sporophyte appears to be preceded by division of the nucleolus. Colorless and non-septate rhizoids develop as elongations of the basal cells of the sporophyte.Temperature is an important factor in the development of various stages of the life cycle of Nereocystis grown in culture, particularly in the gametophytic stage where sexual structures are produced only at temperatures less than 10 °C and vegetative growth is most prolific at 14–18 °C.Some of the unfertilized eggs develop parthenogenetically and give rise to stunted, deformed plants with multinucleate cells.

Inter- and Intra-Population Variation in the Fecundity of Chinook Salmon (Oncorhynchus tshawytscha) and its Relevance to Life History Theory

1984 ◽  
Vol 41 (3) ◽  
pp. 476-483 ◽  
Author(s):  
M. C. Healey ◽  
W. R. Heard
Keyword(s):  
Life History ◽  
Racial Differences ◽  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Population Variation ◽  
Reproductive Age ◽  
Life History Characteristic ◽  
Trade Off ◽  
Life History Pattern ◽  
The Mean

Chinook salmon (Oncorhynchus tshawytscha) varied significantly in fecundity both between years within populations and between populations throughout their range. Generally less than 50% of the variation in fecundity between individuals within populations could be explained by variation in length. A small additional amount of variation could be attributed to racial differences (e.g. red or white fleshed types) but age, seasonal timing of subpopulations, and stream or ocean type life history pattern did not contribute significantly to variation in fecundity beyond their correlation with length. A great deal of individual variation in fecundity remains to be explained in chinook salmon. The slopes of the regression of fecundity on length for all populations were low in comparison with other fishes, indicating that fecundity increases slowly with increasing size in chinook. The mean age of reproducing females varied among populations, and populations that reproduced at an older age were more fecund at a common length than populations that reproduced at a younger age. The increase in fecundity with increasing age of maturity was consistent with theoretical predictions of the trade-off between fecundity and mortality in fish of reproductive age. The mean age of reproduction within a population, however, was considerably older than the predicted optimum age of reproduction based on the trade-off between increasing fecundity with age and natural mortality. These observations suggest that chinook have sacrificed fecundity for increased size in the allocation of surplus energy, a life history characteristic that is consistent with the survival value of size in anadromous salmon.

scholarly journals Life history of a short-lived squid (Sepioteuthis australis): resource allocation as a function of size, growth, maturation, and hatching season

2006 ◽  
Vol 63 (6) ◽  
pp. 995-1004 ◽  
Author(s):  
Gretta T. Pecl ◽  
Natalie A. Moltschaniwskyj
Keyword(s):  
Life History ◽  
Body Shape ◽  
Adult Life ◽  
Reproductive Investment ◽  
Reproductive Condition ◽  
Trade Offs ◽  
Size Growth ◽  
History Of ◽  
Slow Growing ◽  
Alternation Of Generations

Abstract Many cephalopods continue growing while laying multiple egg batches over the adult life, with repro-somatic allocation continuing beyond attainment of reproductive maturity. Many species show extreme individual variation in reproductive investment. Factors driving this variation in adult Sepioteuthis australis were evaluated by examining allocation of energy to somatic and reproductive growth as a function of body shape, growth rate, maturation, and hatching season. Hatching season influence was sex-specific; males hatched in warmer months had greater reproductive investment, faster growth, and better somatic and reproductive condition, whereas females hatched in spring and summer had less reproductive investment. Seasonal impacts on life history resulted in an “alternation of generations”, with slow-growing squid in poor condition and with high levels of reproductive investment producing a generation with completely different life-history characteristics. This suggests that abiotic and biotic conditions that change seasonally could play a large role in determining energy allocated to reproduction. However, this was not driving trade-offs between size and number of offspring. Life-history trade-offs should be detectable as negative correlations between relevant traits. However, in Sepioteuthis australis there was little evidence of trade-offs between reproduction and growth or condition of individuals, suggesting a “live for today” lifestyle.

scholarly journals Dynamics in a simple evolutionary-epidemiological model for the evolution of an initial asymptomatic infection stage

2020 ◽  
Vol 117 (21) ◽  
pp. 11541-11550 ◽  
Author(s):  
Chadi M. Saad-Roy ◽  
Ned S. Wingreen ◽  
Simon A. Levin ◽  
Bryan T. Grenfell
Keyword(s):  
Life History ◽  
Evolutionary Dynamics ◽  
Evolutionarily Stable Strategy ◽  
Life History Strategy ◽  
Population Level ◽  
Epidemiological Model ◽  
Life History Strategies ◽  
Life History Characteristic ◽  
Substantial Impact ◽  
Trade Offs

Pathogens exhibit a rich variety of life history strategies, shaped by natural selection. An important pathogen life history characteristic is the propensity to induce an asymptomatic yet productive (transmissive) stage at the beginning of an infection. This characteristic is subject to complex trade-offs, ranging from immunological considerations to population-level social processes. We aim to classify the evolutionary dynamics of such asymptomatic behavior of pathogens (hereafter “latency”) in order to unify epidemiology and evolution for this life history strategy. We focus on a simple epidemiological model with two infectious stages, where hosts in the first stage can be partially or fully asymptomatic. Immunologically, there is a trade-off between transmission and progression in this first stage. For arbitrary trade-offs, we derive different conditions that guarantee either at least one evolutionarily stable strategy (ESS) at zero, some, or maximal latency of the first stage or, perhaps surprisingly, at least one unstable evolutionarily singular strategy. In this latter case, there is bistability between zero and nonzero (possibly maximal) latency. We then prove the uniqueness of interior evolutionarily singular strategies for power-law and exponential trade-offs: Thus, bistability is always between zero and maximal latency. Overall, previous multistage infection models can be summarized with a single model that includes evolutionary processes acting on latency. Since small changes in parameter values can lead to abrupt transitions in evolutionary dynamics, appropriate disease control strategies could have a substantial impact on the evolution of first-stage latency.

XVII.—Studies in the Ectocarpaceæ. I. The Life-History and Cytology of Pylaiella litoralis, Kjellm

1924 ◽  
Vol 53 (2) ◽  
pp. 343-360 ◽  
Author(s):  
Margery Knight
Keyword(s):  
Life History ◽  
Characteristic Feature ◽  
Life Histories ◽  
Marine Algae ◽  
Land Plants ◽  
Terrestrial Plants ◽  
Recent Suggestion ◽  
Alternation Of Generations

During the last few years attention has been focussed somewhat sharply upon the Marine Algæ, partly on account of the recently investigated life-histories of some of the larger Phæophyceæ, and partly because of a recent suggestion that the Marine Algæ may represent the stock from which all higher land-plants have originated. Interest has naturally centred on the problem of the origin of an alternation of generations among the seaweeds, comparable to that which has become a characteristic feature in the life-histories of higher terrestrial plants.

scholarly journals III. On apogamy and the development of sporangia upon fren prothalli

1898 ◽  
Vol 190 ◽  
pp. 187-238 ◽  
Keyword(s):  
Life History ◽  
Life Histories ◽  
Asexual Generation ◽  
First Case ◽  
History Of ◽  
The Subject ◽  
True Relation ◽  
The One ◽  
Vergleichende Untersuchungen ◽  
Alternation Of Generations

The two chief modifications of the normal course of the life-history of a fern, apogamy and apospory, are of interest in themselves, but have acquired a more extended importance from the possibility that their occurrence may aid in indicating the true relation between the sexual and spore-bearing generations, and so throw light on the nature of “alternation of generations” in archegoniate plants. This aspect has been recognised since the discovery of the phenomena, and will be best appreciated by tracing the progress of opinion on the nature of alternation from the time of Hofmeister to the present day. Only the more important contributions bearing on the subject can be mentioned in this place. With the publication of the ‘Vergleichende Untersuchungen’ (1851), the fact of the regular alternation of a sexual with an asexual generation in the life-history of Bryophyta, Pteridophyta, and Gymnosperms was established. Hofmeister subse­ quently extended the observation to Angiosperms. In the work mentioned, and in the ‘Higher Cryptogamia,’ published some ten years later, no views as to the nature of alternation of generations are discussed. With the extension of accurate know­ledge of the life-histories of Thallophytes, the attempt was made to compare the different individuals of the same species of Alga and Fungi with the sexual and asexual generations of archegoniate plants. Two main views of the nature of alter­nation in the latter were put forward. On the one hand, Celakovsky regarded alternation of generations in the Archegoniatse and a few Thallophyta as essentially different from that found in the majority of the latter group. He distinguished the two types as antithetic and homologous alternation respectively. Pringsheim however, held that the sexual and spore-bearing generations were homologous with one another, alike in Thallophyta and Archegoniatse. In support of this view he relied upon the instances of apospory which he had experimentally induced in Mosses, together with the occurrence of apogamy in Ferns, the first case of which had been discovered by Farlow a few years before. He also compared the life-histories of a number of Thallophytes witli one another and with that of the Moss, and showed how the reduction of the first neutral generation in some of the formerled to a condition of things not dissimilar to the relation existing between the moss sporogonium and the sexual plant. Additional cases of apogamy in Ferns were subsequently discovered by DeBary and the subject fully discussed. Subsequently Druery found the first instance of an aposporous fern, and this and other examples were investigated by Bower.

Interrelationships of factors of social development are more complex than Life History Theory predicts

2019 ◽  
Vol 42 ◽  
Author(s):  
Boris Kotchoubey
Keyword(s):  
Life History ◽  
Social Development ◽  
Life History Theory ◽  
Strong Correlations ◽  
Behavioral Features

Abstract Life History Theory (LHT) predicts a monotonous relationship between affluence and the rate of innovations and strong correlations within a cluster of behavioral features. Although both predictions can be true in specific cases, they are incorrect in general. Therefore, the author's explanations may be right, but they do not prove LHT and cannot be generalized to other apparently similar processes.

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