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Concealed ovulation or hidden estrus is the lack of any perceptible change (e.g., a change in appearance or scent) when an adult female is fertile and near ovulation. Some examples of perceptible changes are swelling and redness of the vulva in baboons and bonobos , and pheromone release in the feline family.
Additionally, they do not show obvious physical signals of high fertility. This has led many researchers to conclude that humans lost their estrus through evolution. [11] [page needed] It has been hypothesized that this could be due to the adaptive benefits of concealed ovulation and extended sexuality. [12] [page needed] [13] [page needed]
Offspring inherit one allele for each trait from each parent. Thus, offspring have a combination of the parents' genes. It is believed that "the masking of deleterious alleles favors the evolution of a dominant diploid phase in organisms that alternate between haploid and diploid phases" where recombination occurs freely. [12] [13]
Folliculogenesis describes the progression of a number of small primordial follicles into large preovulatory follicles that occurs in part during the menstrual cycle. Contrary to male spermatogenesis , which can last indefinitely, folliculogenesis ends when the remaining follicles in the ovaries are incapable of responding to the hormonal cues ...
Mitosis is the normal process in eukaryotes for cell division; duplicating chromosomes and segregating one of the two copies into each of the two daughter cells, in contrast with meiosis. The mitosis theory states that meiosis evolved from mitosis. [9]
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
This is achieved through concealed ovulation in most animals that exhibit extended female sexuality. [19] A review of studies revealed that, in humans, females only exhibit subtle changes during estrus, making it difficult for males to assess fertility with precision. [20]
There are several key differences between these two mechanisms that may provide reasoning for the evolution of germ plasm inheritance. One difference is that typically inheritance occurs almost immediately during development (around the blastoderm stage) while induction typically does not occur until gastrulation. As germ cells are quiescent ...