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In humans, barring intersex conditions causing aneuploidy and other unusual states, it is the male that is heterogametic, with XY sex chromosomes.. Haldane's rule is an observation about the early stage of speciation, formulated in 1922 by the British evolutionary biologist J. B. S. Haldane, that states that if — in a species hybrid — only one sex is inviable or sterile, that sex is more ...
The Grandmother Hypothesis states that menopause comes about into older women in order to restrict the time of reproduction as a protective mechanism. This would allow women to live longer and increase the amount of care they could provide to their grandchildren , increasing their evolutionary fitness. [ 43 ]
The Lyon hypothesis states that in cells with multiple X chromosomes, all but one are inactivated early in embryonic development in mammals. [ 3 ] [ 4 ] The X chromosomes that become inactivated are chosen randomly, except in marsupials and in some extra-embryonic tissues of some placental mammals, in which the X chromosome from the sperm is ...
All known living things are made up of one or more cells [13] All living cells arise from pre-existing cells by division. The cell is the fundamental unit of structure and function in all living organisms. [14] The activity of an organism depends on the total activity of independent cells. [15] Energy flow (metabolism and biochemistry) occurs ...
The Organizational-Activational Hypothesis states that steroid hormones permanently organize the nervous system during early development, which is reflected in adult male or female typical behaviors. [1] In adulthood, the same steroid hormones activate, modulate, and inhibit these behaviors.
The ability of a target cell to respond to a hormone depends on the presence of receptors, within the cell or on its plasma membrane, to which the hormone can bind. Hormone receptors are dynamic structures. Changes in the number and sensitivity of hormone receptors may occur in response to high or low levels of stimulating hormones.
But I believe with Thomas Jefferson that one of the chief duties of a citizen is to be a nuisance to the government of his state. As there is no world state, I cannot do this. On the other hand, I can be, and am, a nuisance to the government of India, which has the merit of permitting a good deal of criticism, though it reacts to it rather slowly.
However, the dual-hormone hypothesis also has its own flaws, and current evidence appears to only partially support the hypothesis, according to a meta-analytical evaluation in 2019 by Dekkers et al. [36] A proposed reasoning for the occasional weak evidence is that cortisol and testosterone, further interact with social context and individual ...