Reproduction asexual

For years, scientists have dreamt of making robots that can self-reproduce. Someday, such a machine could be sent to explore a distant planet, where it could clone itself. 

There are several classes of reproduction, and we start with asexual vs. sexual reproduction. Asexual reproduction is the creation of new individuals whose genes all come from one parent without the fusion of egg and sperm (Campbell et al., 1999). That means that each offspring of the process is a genetic clone of the parent. 

Bacteria normally divide and reproduce by asexual reproduction in a process called binary fission. Bacteria are prokaryotes, and, as such are relatively simple BU. They carry most of their genes on a single chromosome attached to the plasma membrane. When a single bacterial ceU divides, it first replicates its chromosome and attaches it to a different membrane site. When the bacterium has grown to about twice its normal size, the plasma membrane grows inward between the two chromosomes and divides the parent ceU into two daughter cells, each with a complete genome. 

There are interactions, such as competition and adaptation, that indirectly impinge on the reproductive process. If external resources are just adequate, cellular reproduction balances with cellular death, and net reproduction is nU. If excess external resources are present, net reproduction increases beyond that necessary to maintain a static population. 

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Clone, identical cells (with respect to genetic constitution) derived from a single cell by asexual reproduction. Receptors can be cloned into cells by inserting a gene into the cell line a colony of cells results that are identical and all have the expressed receptor. 

AQUATIC INSECTS No effect on survival, behavior, or asexual reproductive capacity after 24-h exposure 23... 

Perennial plants with shielded buds and vigorous asexual reproduction are relatively radioresistant. 

Much of the behaviour of humans and society as a whole is designed to provide an opportunity for a sperm and an ovum to meet in the uterus. However, sexual reproduction is not the only means of reproduction asexual reproduction occurs frequently in the animal kingdom and in many tissues in order to increase the number of cells during growth or to maintain the number due to cell death. The question arises, therefore, why sexual reproduction has arisen at all since it is very expensive in the use of resources for example, in the process of selecting a suitable mate, and in the requirement for males, whose only function in some species is fertilisation of the females, yet they use resources that could be used by the females and by the offspring. Perhaps because of this, a few species of vertebrates (e.g. some lizards) have retained the option for asexual reproduction. This process is known as parthenogenesis. Mammals, however, have lost this option. This... 

Asexual reproduction. Growth and cell duplication that does not involve the union of nuclei from cells of opposite mating types. 

Growth Pattern Bacteria reproduce predominantly by a process known as binary fission as illustrated in Figure 5.3. This process involves several steps cell elongation, invagination of the cell wall, distribution of nuclear material, formation of the transverse cell wall, distribution of cellular material into two cells, and separation into two new cells. This is an asexual reproductive process. 

Ziegler, J. R. and Kingsbury, J. M., Cultural studies on the marine green alga Halicystis parvula-Der-besia tenuissima. I. Normal and abnormal sexual and asexual reproduction, Phycologia, 4, 105, 1964. 

Spore A uni- or multicellular, asexual, reproductive, or resting body that is resistant to unfavorable environmental conditions, and which produces a new vegetative individual when the environment is favorable. 

It should be noted that the closely related species, M. lineatus, does not undergo asexual reproduction in either the tetrathyridium or adult stage it too, has been successfully cultured to maturity in vitro (382). The possible factors inducing asexual/sexual differentiation in both these species, and in other cestodes, is further considered in Chapter 10, where in vitro systems are reviewed. 

This species has a life cycle similar to that of M. corti but, unlike it, does not undergo asexual reproduction in either the larval or adult stage. The adult of this species has also been grown in vitro from the tetrathyridium, but, in this case, the induction of sexual development appears to be related to the presence and activity of trypsin, for differentiation was inhibited or decreased by the presence of soybean trypsin inhibitor (382). 

As a search technique, using mutation and selection alone has several limitations. Evolution via asexual reproduction tends to build up deleterious mutations, ultimately limiting the potential of the experiment, an effect known as Muller s ratchet (Muller, 1964). This effect is exacerbated by high mutagenesis rates, as slightly deleterious amino acid substitutions can hitchhike with positive mutations. Recombination can act to remove neutral and deleterious mutations while allowing the accumulation of... 

The Jerusalem artichoke can reproduce by two primary means. It can reproduce and colonize an area by the allocation of photosynthate and nutrients into both asexual (tubers and, to a lesser extent, rhizomes) and sexual (seed) reproductive organs. Flexibility in the amount of resources allocated between sexual and asexual means of reproduction confers a selective advantage in that conditions that inhibit or block sexual production (lack of pollen, herbivory of floral structures, undesirable weather) allow increased allocation to asexual reproduction. Artificially reduced allocation of resources to sexual reproduction, for example, results in a substantial increase in those allocated to asexual means. With flower bud removal, more (82 vs. 69) and larger (4.4 vs. 3.8 g) tubers were formed per plant than those with unlimited sexual reproduction (Wesdey, 1993). Total biomass was not altered, potentially indicating a relatively complete diversion of resources to asexual reproduction when sexual reproduction is blocked. From a reproductive standpoint, the risk of making it to the next season is high with sexual reproduction and relatively low with asexual reproduction. Increased investment in tubers increases the opportunity for sexual reproduction in the future. 

Pavlovophyceae), i.e., a life cycle involving alternation of morphologically different haploid and diploid generations, each capable of independent asexual reproduction (Billard 1994 Edvardsen 2002 Billard and Inouye 2004 Houdan et al. 2004). Houdan et al. (2004) suggest from the phylogenetic distribution that this is the primitive state across the Prymnesiophyceae. 

Further, since the reproduction test with Daphnia only comprises asexual reproduction, this also means that investigations focusing on sexual reproduction will be lacking for substances produced up to 1,0001 per producer and year. For substances produced above this production volume, the reproduction tests using earthworms and chironomids may however be used to generate adequate population data (see Table 6.1 for OECD test guidelines concerned with reproduction available for risk... 

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