Sex Appearance Research Articles

Were eukaryotes made by sex?: Sex might have been vital for merging endosymbiont and host genomes giving rise to eukaryotes.

I hypothesize that the appearance of sex facilitated the merging of the endosymbiont and host genomes during early eukaryote evolution. Eukaryotes were formed by symbiosis between a bacterium that entered an archaeon, eventually giving rise to mitochondria. This entry was followed by the gradual transfer of most bacterial endosymbiont genes into the archaeal host genome. I argue that the merging of the mitochondrial genes into the host genome was vital for the evolution of genuine eukaryotes. At the time this process commenced it was unprecedented and required a novel mechanism. I suggest that this mechanism was meiotic sex, and that its appearance might have been THE crucial step that enabled the evolution of proper eukaryotes from early endosymbiont containing proto-eukaryotes. Sex might continue to be essential today for keeping genome insertions in check. Also see the video abstract here: https://youtu.be/aVMvWMpomac.

Studies on the manifestation of characters relating to sex appearance in the silkworm, Bombyx mori

Studies on the manifestation of characters relating to sex appearance in the silkworm, Bombyx mori

Understanding key issues in gender-variant children and young people

Children, parents and other family members are often concerned if the behaviour of the child is more like that of children of the opposite gender, or when they show signs that they are uncomfortable with their physical sex appearance. Gender identity disorders in children and young people (those up to the age of 17 years) are rare. According to the Department of Health, they are best understood as a natural, although unusual, variation in human development. Gender variance is complex and involves psychological, biological, family and social issues. A multidisciplinary approach to care and treatment is advocated. This article provides nurses with some understanding of gender variance in children and young people in order for them to begin to help children, young people and their families.

Bangiomorpha pubescensn. gen., n. sp.: implications for the evolution of sex, multicellularity, and the Mesoproterozoic/Neoproterozoic radiation of eukaryotes

Multicellular filaments from the ca. 1200-Ma Hunting Formation (Somerset Island, arctic Canada) are identified as bangiacean red algae on the basis of diagnostic cell-division patterns. As the oldest taxonomically resolved eukaryote on recordBangiomorpha pubescensn. gen. n. sp. provides a key datum point for constraining protistan phylogeny. Combined with an increasingly resolved record of other Proterozoic eukaryotes, these fossils mark the onset of a major protistan radiation near the Mesoproterozoic/Neoproterozoic boundary.Differential spore/gamete formation showsBangiomorpha pubescensto have been sexually reproducing, the oldest reported occurrence in the fossil record. Sex was critical for the subsequent success of eukaryotes, not so much for the advantages of genetic recombination, but because it allowed for complex multicellularity. The selective advantages of complex multicellularity are considered sufficient for it to have arisen immediately following the appearance of sexual reproduction. As such, the most reliable proxy for the first appearance of sex will be the first stratigraphic occurrence of complex multicellularity.Bangiomorpha pubescensis the first occurrence of complex multicellularity in the fossil record. A differentiated basal holdfast structure allowed for positive substrate attachment and thus the selective advantages of vertical orientation; i.e., an early example of ecological tiering. More generally, eukaryotic multicellularity is the innovation that established organismal morphology as a significant factor in the evolutionary process. As complex eukaryotes modified, and created entirely novel, environments, their inherent capacity for reciprocalmorphologicaladaptation, gave rise to the “biological environment” of directional evolution and “progress.” The evolution of sex, as a proximal cause of complex multicellularity, may thus account for the Mesoproterozoic/Neoproterozoic radiation of eukaryotes.

Studies on the manifestation of characters relating to sex appearance in the silkworm, Bombyx mori

Studies on the manifestation of characters relating to sex appearance in the silkworm, <i>Bombyx mori</i>

Differentiation in Protozoa*

SYNOPSIS. Two main kinds of morphogenetic events occur among protozoa: (1) reproduction; (2) processes of reorganization, including encystment, excystment, sexual processes, structural and physiological adaptations exhibited in the course of complex life cycles, and restorative events elicited by environmental stimuli. Examples of such events are discussed with reference both to their own intrinsic interest and to their value in the study of cellular differentiation in general. Stomatogenesis in ciliates provides a remarkable instance of extensive and rapid differentiation. The phenomenon may be studied to advantage not only in reproduction but also in the macrostome‐microstome transformation. Other simple transformations in protozoa providing unparalleled material for experiments on cytodifferentiation under controlled conditions are excystment and encystment, the amebo‐flagellate transformation, and the leishmania‐leptomonad change. The more complex transformations occurring in the life cycles of trypanosomes and in the appearance of sex under the influence of an insect hormone provide additional material of basic significance to an understanding of differentiation.