)eiosis%uring )eiosis two crucial stages occur that cause variation within organisms these are + crossing over and independent assortment.,ndependent assortment occurs during metaphase -. When the chromosomes align in pairs at the e'uator or the cell spindle fibres attach to the centromere and depending on whether the chromosome is on the left or right of the e'uator they will be pulled to either side by the spindle fibres. The way they line up in pairs is entirely random and conse'uently impacts which side of the cell they end up on before division. This is entirely random and causes genetic variation within gametes.When paternal and maternal homologous chromosomes are oined in a bivalent chiasma can form. This is a point in which crossing over occurs between the chromosomes + multien/ymecomplexes cut and oin %!* to different homologous chromosomes 0paternal and maternal1.Crossing over and independent assortment causes many different possible combinations of alleles from mother and father to be formed and is the main cause of variation within offspring. *s explained before when advantageous alleles caused by mutation that are inherited this process is called reproductive success. 2eproductive success will increase the allelic fre'uency of the allele within the population of a species as those will have the advantage and more li#ely to survive passing on the advantageous allele ,t is necessary because the species will become better adapted to its environment and will have a competitive advantage in increasing its chance of survival against other species. 3y a process of elimination or by natural selection only the best adapted will survive.*n example of nature reducing competition between species is with algae. %ifferent species of algae have adapted to photosynthesis using different wavelengths of light and there can survive at different depths. The competition for light is massively reduced.Speciation can occur when a species is divide e.g. by geographical isolation such as a river. Speciation is the evolution of a new species form an existing one it occurs due to conditions such as temperature food sources etc. are different in the two different places. This means different alleles will be advantageous for the species and so by reproductive success the allelic fre'uencies of the two populations will change. "ver time this results in the two populations being so different that they can no longer interbreed and can therefore no longer be classed as one species. ,n this way evolution occurs. This is an example of the effects of variation within species and how it can cause a totally new species to coexist."ne of the main examples of variation in terms of survival can be seen in bacteria and its genetic resistance. *lthough mutation that is advantageous is rare populations of bacteria are so large and reproduce so rapidly that a useful mutation occurs more often than in most other organisms. This is an example of disruptive selection because most of the species is wiped out + however some may contain the mutation of resistance to the antibiotic and so they will survive hence the allele for resistance will be of high fre'uency in the new population.This is why variation within organisms is so important in the sense that if a disease does infect a population there will be few that survive and can continue the species and save it from extinction. ,f there was no variation every organism of the species would die.
Arkansas Regional LibraryNARL is a consortium of public libraries from Clay, Greene and Randolph Counties. The regional library allows for the pooling of resources to better serve the three counties.
The Gateway ProjectThe Gateway Project is a collection-sharing program for Northeast Arkansas Libraries.
The program provides a public library service to Northeast Arkansas residents without charging a non, resident fee to patrons outside a library's service area. Click here to read more.
Thanks to a partnership with Driving-Tests.org, the Corning Public Library is proud to offer free online test prep for students preparing for their AR driving tests!
Visit our exclusive website, http://corning.driving-tests.org where you can choose from several different permit tests. No library card number or personal information is needed! This resource is also great for anyone looking to brush up on their knowledge of Arkansas traffic laws or interested in getting their motorcycle license or CDL's. A helpful FAQ section addresses questions residents might have about visiting their local DMV, how to get a driver's license or permit, what to do when you move from a different state, and many other questions are answered here.
GO TO: http://corning.driving-tests.org
Corning Public Library has a Story Time the 3rd Thursday of every month at 3:30 pm. This is open to all ages with stories, music, puppets and a lot of fun.
Click here to view full Calendar.