<P> Hybridization is, however, an important means of speciation in plants, since polyploidy (having more than two copies of each chromosome) is tolerated in plants more readily than in animals . Polyploidy is important in hybrids as it allows reproduction, with the two different sets of chromosomes each being able to pair with an identical partner during meiosis . Polyploid hybrids also have more genetic diversity, which allows them to avoid inbreeding depression in small populations . </P> <P> Horizontal gene transfer is the transfer of genetic material from one organism to another organism that is not its offspring; this is most common among bacteria . In medicine, this contributes to the spread of antibiotic resistance, as when one bacteria acquires resistance genes it can rapidly transfer them to other species . Horizontal transfer of genes from bacteria to eukaryotes such as the yeast Saccharomyces cerevisiae and the adzuki bean beetle Callosobruchus chinensis may also have occurred . An example of larger - scale transfers are the eukaryotic bdelloid rotifers, which appear to have received a range of genes from bacteria, fungi, and plants . Viruses can also carry DNA between organisms, allowing transfer of genes even across biological domains . Large - scale gene transfer has also occurred between the ancestors of eukaryotic cells and prokaryotes, during the acquisition of chloroplasts and mitochondria . </P> <P> Gene flow is the transfer of alleles from one population to another . </P> <P> Migration into or out of a population may be responsible for a marked change in allele frequencies . Immigration may also result in the addition of new genetic variants to the established gene pool of a particular species or population . </P>

How microevolution and migration can affect an ecosystem