Results 301 to 310 of about 294,374 (349)
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Population Ecology, 1981
SummaryTheories on the evolution of litter size among organisms were reexamined. The competition theories, including that based on the r−K‐selection hypothesis, could not explain well why low‐fecundity strategies have often evolved in stressful environments such as mountain streams, deep sea and the antarctic, where interspecies competition is ...
Yosiaki Itô, Yoh Iwasa
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SummaryTheories on the evolution of litter size among organisms were reexamined. The competition theories, including that based on the r−K‐selection hypothesis, could not explain well why low‐fecundity strategies have often evolved in stressful environments such as mountain streams, deep sea and the antarctic, where interspecies competition is ...
Yosiaki Itô, Yoh Iwasa
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THE INFLUENCE OF AGE ON LITTER-SIZE
Journal of Endocrinology, 1958SUMMARY In three related strains of rats the numbers of fertile females have been found to fall with age and with the birth of successive litters. In thirty-five rats belonging to these three strains, each of which had a minimum of eight litters, the second litter was generally bigger than the first. From then on, however, litter-size gradually
D L, INGRAM, A M, MANDL, S, ZUCKERMAN
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Factors influencing litter size in pigs.
CABI Reviews, 2015Abstract Improvement of litter size in pigs through selection was considered a difficult task in the past. Low heritability, negative correlation between direct additive genetic and maternal effect, limited size of the nucleus population, expression only in females, and relatively late age of measurements, were the main reasons for slow ...
Z. Luković, D. Škorput
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Optimal offspring sizes in small litters
Evolutionary Ecology, 1995Numerous evolutionary models explore the trade-off between offspring size and offspring number. However, such models often fail when the number of offspring is small because optimal litter size (or litter size at optimal offspring size) may fall between the necessarily integer values for real litters.
Eric L. Charnov +2 more
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Litter Size, Emotionality, and Avoidance Learning
Psychological Reports, 1963In a recent experiment concerned with the interaction of genetic and ontogenetic determinants of adult behavior (Levine & Broadhurst, in press), rats from the Maudsley Reactive and Nonreactive strains which have been selected for emotional defecation, were subjected to controlled infantile stimulation (Levine, 1960) and compared with 40 nontreated ...
P. L. Broadhurst, Seymour Levine
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Selection for Litter Size in Mice
Acta Agriculturae Scandinavica, 1977(1977). Selection for Litter Size in Mice. Acta Agriculturae Scandinavica: Vol. 27, No. 4, pp. 301-318.
Øystein Joakimsen, R. L. Baker
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1969
The breeding season at high latitudes is shorter than at low, so that the possible number of parturitions is reduced. In many field studies it has been noted that samples taken from higher latitudes inside a species range had larger litter sizes.
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The breeding season at high latitudes is shorter than at low, so that the possible number of parturitions is reduced. In many field studies it has been noted that samples taken from higher latitudes inside a species range had larger litter sizes.
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Relationship between litter birthweight and litter size in five goat genotypes
Animal Production Science, 2011The aim of the present study was to use a non-linear regression approach to investigate the relationship between litter birthweight and litter size of five breeds of goat under intensive conditions in a hot arid environment. Litter-size and litter-weight data on 20 117 kids from 13 685 litters representing five breeds, namely Saanen, Toggenburg, French
Miguel Mellado +6 more
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Evolution of Litter Size in Primates
The American Naturalist, 1979Despite strong selection for low reproductive turnover in primates in general, there is a considerable number of species in which multiple births regularly occur. Since multiple births are limited to the smallest species in both suborders, Strepsirhini and Haplorhini, it appears that restrictions of scaling set a threshold for maternal size below which
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State-Dependent Optimization of Litter Size
Oikos, 1998Four inter-related theories demonstrate that the quality or state of the parent influences its optimum litter size. A review of each model highlights their similar predictions, sets the stage for an expanded theory and demonstrates that three are really special cases of state-dependent optimization.
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