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Isogamy is a form of sexual reproduction that involves gametes of the same morphology (indistinguishable in shape and size), and is found in most unicellular eukaryotes. [1] Because both gametes look alike, they generally cannot be classified as male or female . [ 2 ]
Gametes of both mating individuals can be the same size and shape, a condition known as isogamy. By contrast, in the majority of species, the gametes are of different sizes, a condition known as anisogamy or heterogamy that applies to humans and other mammals. The human ovum has approximately 100,000 times the volume of a single human sperm cell.
In isogamous species, the gametes are similar or identical in form , but may have separable properties and then may be given other different names (see isogamy). [10] Because both gametes look alike, they generally cannot be classified as male or female. For example, in the green alga, Chlamydomonas reinhardtii, there are so-called "plus" and ...
Sexual dimorphism is where the basic phenotypic traits vary between males and females of the same species. Dimorphism is found in both sex organs and in secondary sex characteristics, body size, physical strength and morphology, biological ornamentation, behavior and other bodily traits. However, sexual selection is only implied over an ...
Environmental factors and timing are key challenges to the success of external fertilization. While in the water, the male and female must both release gametes at similar times in order to fertilize the egg. [3] Gametes spawned into the water may also be washed away, eaten, or damaged by external factors.
For the advantage due to genetic variation, there are three possible reasons this might happen. First, sexual reproduction can combine the effects of two beneficial mutations in the same individual (i.e. sex aids in the spread of advantageous traits) without the mutations having to have occurred one after another in a single line of descendants.
The common fruit fly has an XY sex-determination system, as do humans and most mammals. Humans and most other mammals have an XY sex-determination system: the Y chromosome carries factors responsible for triggering male development, making XY sex determination mostly based on the presence or absence of the Y chromosome.
[19] [20] If left unrepaired, this damage would likely be lethal to gametes and inhibit production of viable progeny. Even in multicellular eukaryotes, such as humans, oxidative stress is a problem for cell survival. In this case, oxidative stress is a byproduct of oxidative cellular respiration occurring during metabolism in all cells.