3 types of sex

Example Domain This domain is established to be used 3 types of sex illustrative examples in documents. You may use this domain in examples without prior coordination or asking for permission. Here we list the types again with their assigned code fields. MUST NOT be shipped as defaults in implementations.

Jump to navigation Jump to search This article is about sex in sexually reproducing organisms. For the act, see Sexual intercourse. Organisms of many species are specialized into male and female varieties, each known as a sex. For instance, mate choice and sexual selection can accelerate the evolution of physical differences between the sexes. Among humans and other mammals, males typically carry XY chromosomes, whereas females typically carry XX chromosomes, which are a part of the XY sex-determination system.

One of the basic properties of life is reproduction, the capacity to generate new individuals, and sex is an aspect of this process. Life has evolved from simple stages to more complex ones, and so have the reproduction mechanisms. Initially the reproduction was a replicating process that consists in producing new individuals that contain the same genetic information as the original or parent individual. Disregarding intermediates, the basic distinction between asexual and sexual reproduction is the way in which the genetic material is processed. Typically, prior to an asexual division, a cell duplicates its genetic information content, and then divides. This process of cell division is called mitosis. In complex organisms, the sex organs are the parts that are involved in the production and exchange of gametes in sexual reproduction.

Many species, both plants and animals, have sexual specialization, and their populations are divided into male and female individuals. Sexual reproduction first probably evolved about a billion years ago within ancestral single-celled eukaryotes. Sexual reproduction is a process specific to eukaryotes, organisms whose cells contain a nucleus and mitochondria. The defining characteristic of sexual reproduction in eukaryotes is the difference between the gametes and the binary nature of fertilization. Multiplicity of gamete types within a species would still be considered a form of sexual reproduction. However, no third gamete type is known in multicellular plants or animals. Sexual reproduction in eukaryotes is a process whereby organisms form offspring that combine genetic traits from both parents.

Chromosomes are passed on from one generation to the next in this process. Each cell in the offspring has half the chromosomes of the mother and half of the father. Most sexually reproducing animals spend their lives as diploid, with the haploid stage reduced to single-cell gametes. The gametes of animals have male and female forms—spermatozoa and egg cells.

These gametes combine to form embryos which develop into a new organism. Egg cells are often associated with other cells which support the development of the embryo, forming an egg. Animals are usually mobile and seek out a partner of the opposite sex for mating. Animals which live in the water can mate using external fertilization, where the eggs and sperm are released into and combine within the surrounding water. In most birds, both excretion and reproduction is done through a single posterior opening, called the cloaca—male and female birds touch cloaca to transfer sperm, a process called “cloacal kissing”. Because of their motility, animal sexual behavior can involve coercive sex. Traumatic insemination, for example, is used by some insect species to inseminate females through a wound in the abdominal cavity—a process detrimental to the female’s health.

Flowers are the sexual organs of flowering plants, usually containing both male and female parts. Like animals, plants have developed specialized male and female gametes. Within seed plants, male gametes are contained within hard coats, forming pollen. Many plants have flowers and these are the sexual organs of those plants. Flowers are usually hermaphroditic, producing both male and female gametes. In pines and other conifers the sex organs are conifer cones and have male and female forms. The more familiar female cones are typically more durable, containing ovules within them.

Male cones are smaller and produce pollen which is transported by wind to land in female cones. Because plants are immobile, they depend upon passive methods for transporting pollen grains to other plants. Many plants, including conifers and grasses, produce lightweight pollen which is carried by wind to neighboring plants. Other plants have heavier, sticky pollen that is specialized for transportation by insects. Most fungi reproduce sexually, having both a haploid and diploid stage in their life cycles. These fungi are typically isogamous, lacking male and female specialization: haploid fungi grow into contact with each other and then fuse their cells. Some fungi, including baker’s yeast, have mating types that create a duality similar to male and female roles.

Yeast with the same mating type will not fuse with each other to form diploid cells, only with yeast carrying the other mating type. Many species of higher fungi produce mushrooms as part of their sexual reproduction. Within the mushroom diploid cells are formed, later dividing into haploid spores. Sex helps the spread of advantageous traits through recombination. The vertical axis shows frequency and the horizontal axis shows time. The advantageous alleles A and B, arising independently, can be rapidly combined by sexual reproduction into the most advantageous combination AB. Exceptions are common—for example, the roundworm C.

Sometimes an organism’s development is intermediate between male and female, a condition called intersex. Like humans and other mammals, the common fruit fly has an XY sex-determination system. In genetic sex-determination systems, an organism’s sex is determined by the genome it inherits. Humans and other mammals have an XY sex-determination system: the Y chromosome carries factors responsible for triggering male development.

The “default sex,” in the absence of a Y chromosome, is female-like. Thus, XX mammals are female and XY are male. XY sex determination is found in other organisms, including the common fruit fly and some plants. In birds, which have a ZW sex-determination system, the opposite is true: the W chromosome carries factors responsible for female development, and default development is male.