Pollen production is an essential step in sexual reproduction of seed plants. This section will briefly focus on the ostensible disadvantages of sexual reproduction as compared to relative advantages in asexual reproduction. Given that sexual reproduction abounds in multicellular organisms, this section is followed by a lengthy overview of theories aiming to elucidate the advantages of sex and sexual sexual astrology book pdf. 50:50 male-to-female representation, and only the females of this species can bear offspring.
Contrast this outcome with an asexual species, where each member of the 100-organism population is capable of bearing young. This diagram illustrates the twofold cost of sex. This idea is sometimes referred to as the two-fold cost of sexual reproduction. It was first described mathematically by John Maynard Smith. In his manuscript Smith further speculated on the impact of an asexual mutant arising in a sexual population. Technically the problem above is not that of sexual reproduction but a problem of having a subset of organisms incapable of bearing offspring. This is a consequence of the fact that gametes from sexually reproducing species are haploid.
Again however, this is not applicable to all sexual organisms. There are numerous species which are sexual but do not have a genetic-loss problem because they do not produce males or females. Depending on the presence or absence of these phenomena, the existing ways of reproduction can be divided into asexual, hermaphrodite and dioecious forms. The sexual process and sexual differentiation are different phenomena, and, in essence, are diametrically opposed. Transition from the hermaphrodite to dioecious state leads to a loss of at least half of the diversity.
So, the main question is to explain the advantages given by sexual differentiation, i. For the advantage due to genetic variation, there are three possible reasons this might happen. Also, the necessary mutations do not have to have occurred one after another in a single line of descendants. For the advantage due to DNA repair, there is an immediate large benefit of removing DNA damage by recombinational DNA repair during meiosis, since this removal allows greater survival of progeny with undamaged DNA.