Few plants actually self-pollinate. The mechanism is seen most often in some legumes such as peanuts. In another legume, soybeans, the flowers open and remain receptive to insect cross pollination dur ...
The human sperm cell is the reproductive cell in males and will only survive in warm environments; once it leaves the male body the sperm's survival likelihood is reduced and it may die, thereby decre ...
In animals, egg cells are also known as ova (singular ovum, from the Latin word ovum meaning egg or egg cell). The term ovule is used for the young ovum of an animal. In higher animals, ova are produc ...
Main article: Double fertilisationThe pollen tube does not directly reach the ovary in a straight line. It travels near the skin of the style and curls to the bottom of the ovary, then near the recept ...
In contrast to a gamete, the diploid somatic cells of an individual contain one copy of the chromosome set from the sperm and one copy of the chromosome set from the egg cell; that is, the cells of th ...
There are two types of cells, eukaryotes, which contain a nucleus, and prokaryotes, which do not. Prokaryotic cells are usually single-celled organisms, while eukaryotic cells can be either single-cel ...
Cyril Darlington was born in Chorley, a small cotton town in Lancashire, England in 1903. His father, William was a teacher at a small school. He had one brother six years older. When he was eight, th ...
The main subset of androgens, known as adrenal androgens, is composed of 19-carbon steroids synthesized in the zona reticularis, the innermost layer of the adrenal cortex. Adrenal androgens function a ...
A number of twin studies have attempted to compare the relative importance of genetics and environment in the determination of sexual orientation. In a 1991 study, Bailey and Pillard found that 52% of ...
Further information: Signal transductionHormonal signaling involves the following steps:Biosynthesis of a particular hormone in a particular tissueStorage and secretion of the hormoneTransport of the ...
Natural sex steroids are made by the gonads (ovaries or testes), by adrenal glands, or by conversion from other sex steroids in other tissue such as liver or fat.Synthetic sex steroidsThere are also m ...
A common type of dimorphism is ornamentation. A frequent component of such dimorphic ornamentation is sexual dichromatism, meaning that the sexes of a given species differ in coloration, such as is co ...
Sex steroid-induced differentiation of adult reproductive and other behavior has been demonstrated experimentally in many animals. In some mammals, adult sex-dimorphic reproductive behavior (e.g., mou ...
Main article: XY sex-determination systemA baby’s sex is determined at the time of conception. When the baby is conceived, a chromosome from the sperm cell, either X or Y, fuses with the X chromosome ...
Main article: Sex determination systemHumans, many mammals, insects and other animals have an XY sex-determination system. Humans have forty-six chromosomes, including two sex chromosomes, XX in femal ...
