In contrast, workers are wingless females with smaller body size and degenerated reproductive tracts, usually without a sperm storage organ. FromScience Daily “The data on historic claims are a much more reliable guide to the number of affected estates than surveys of farm sizes,” he said. ...
However, the hypothesis that species with single-male breeding systems (single-male polygyny and monogamy) have relatively smaller testes than species with mating systems characterized by a high potential for sperm competition (promiscuity) was supported only for polygynous species. 展开 ...
In addition, in species where sperm competition is important, relatively large investments in testis growth and ejaculate size will also be selected. The use of copulatory plugs by males of some taxa, however, can prevent sperm competition. We hypothesized that, across related species in which ...
Male reproductive success increased with size due to the polygamous system and stacking behavior of the species, but females nonetheless had greater reproductive success than males of the same size, in agreement with the size-advantage theory. Sperm storage appeared to be a critical determinant of...
There was a positive correlation between male/female sexual size dimorphism and female polygamy in both families. Although size is affected by many factors, we contend that this result is best explained by sperm competition; in butterflies, the mass of the ejaculate delivered by a male is ...
Head length of spermatozoa was measured using semen of White Leghorn, Creeper, Connecticut Random Bred, Jungle Fowl, White Wyandotte, New Hampshire and Dark Cornish cocks. Significant differences in mean length were found between breeds, but also within the group of Dark Cornish cocks. Mean length...
”同时,又根据“The sperm whale’s brain is…six times the size of a human brain. (抹香鲸的大脑是人脑的六倍。)”这样如果抹香鲸重30吨,其大脑=30xO.02%=0.15(吨),等于人脑的六倍,所以人脑重量=0.15÷6=0.025(吨),人的身体=人脑重量÷2%=0.025÷2%=0.0125(吨)=125(公斤)。B项正确。
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What is a Sperm Whale? Sperm whales(Physeter macrocephalus) are the largest toothed whales, distinguishable by their massive and blunt heads. They are also known ascachalot(a French word for "big teeth") because of their large lower teeth. Sperm whales are mammals, breathing air through their...
The intensity of sexual selection in relation to male sexual behaviour, female choice, and sperm precedence In this paper we define sexual selection on males as the variance in numbers of mates per male and show how the intensity of this selection is affected by ... MJ Wade,SJ Arnold - 《...