The process of speciation, which has been studied by biologist for centuries, is difficult to explain. Speciation is the process of forming a new species. Charles Darwin is one of the most famous persons to study different species and how natural selection had an effect on evolution; however he never discussed how one species gives rise to another. It is known that there are theories of how speciation takes place. The four models for speciation are allopatric, sympatric, peripatric, and parapatric speciation. In speciation, there are two factors that need to occur. One is that populations diverge. The second is that populations were kept isolated. The roles of mutation and natural selection are important in speciation.
So first, to describe the role of natural selection in speciation process, a simple definition of what natural selection is must be given. Natural selection is the process where organisms better adapted to their environment tend to survive and are able to reproduce. Natural selection is one of the basic mechanisms of evolution. If you have variation, differential reproduction, and heredity, you will have evolution by natural selection as an outcome. In Darwin’s theory of natural selection, an example is given of giraffes. In this example of the giraffes, Darwin suggests that variation was a result of preexisting genetic differences among the giraffes. While this other biologist Jean-Baptiste Lamarck, believed that evolution occurred by the inheritance of acquired characteristics. He believed that the giraffe ancestor lengthened its neck by stretching to reach tree leaves, and then passed the change to the offspring. However, Darwin believed that some giraffes were just born with longer necks due to genetic diff...
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...s from the two ends mated with each other they could not produce fertile offspring. In parapatric speciation there is no specific extrinsic barrier to gene flow. The population is continuous, but nonetheless, the population does not mate randomly. Individuals are more likely to mate with their geographic neighbors than with individuals in a different part of the population’s range
Peripatric speciation is similar to allopatric speciation in exception to size. In peripatric speciation a small population is isolated at the edge of a larger population. Notice that in peripatric speciation, small population size would make full-blown speciation a more likely result of the geographic isolation because genetic drift acts more quickly in small populations. Genetic drift would cause rapid genetic change in the small population. This genetic change could lead to speciation.
As time progress on the phylogeny, Australopithecus africanus and Australopithecus afarensis were considered to be direct descendants of Proconsul heseloni. However it was decided that A. afarensis branched off and became extinct with no other descendants. Reasons for branching A. africanus and A. afarensis include the data taken from the brain vs....
...re key factors in the high rate of speciation. These conclusions are derived from the lack of correlation of phenotypic evolution with distance and differences in habitat. Instead, random individual dispersal creates frequent genetic bottlenecks. The observation that phenotypic variability decreases with increasing cave age challenges the traditional founder-effect concept, which claims that genetic variability increases with a growing population. The observation is more consistent with the founder-flush concept. However, the data has led to new questions regarding the factors that play into evolution, specifically the reaction between population density and stochastic events. Further investigation of the role that frequently replicating small founder populations plays in the generation of new species will increase knowledge of the complicated process of speciation.
In Mivart’s Genesis of Species, the author highlights the inconsistencies of Darwin’s natural selection theory. He supports his assertion by emphasizing how species placed in similar environments acquire different traits, questioning the long-term advantages of these evolved traits, and noting the logical inconsistencies of how traits can span in all directions.
The third part of the evolution theory is speciation. Speciation means that different groups of creatures that cannot exchange genes with one another cannot interbreed with one another.
What is evolution and how does it work? Evolution is the theory of how one form of life changes into another form. Evolution also is the change of a population’s inherited traits from generation to generation. Evolution helps to explain why an animal, human, and plant looks the way it does and acts the way it does; it gives an explanation of the history of life. Genes come in many varieties and the evolution helps to make it happen. Mutation, natural selection, genetic drift, and gene flow: the four forces that make the evolution work.
The process of speciation occurred through six steps. The first step was the founding of a new population, during which species A somehow ended up on one of the Galapagos islands - whether by flying or being blown by the wind is unknown. This species found a way to adapt to this new habitat, survive and reproduce and create a new population. The second step is geographic isolation, in which part of species A ended up on another of the islands in the Galapagos, most likely the same way that the original population did for the first island. These few individuals typically did not fly over open water, so they were now geographically isolated from the rest of the population. This led to the third step, changes in the gene pool, as the individuals
With the studies that Charles Darwin obtained he published his first work, “The Origin of Species.” In this book he explained how for millions of years animals, and plants have evolved to better help their existence. Darwin reasoned that these living things had gradually changed over time to help themselves. The changes that he found seemed to have been during the process of reproduction. The traits which would help them survive became a dominant trait, while the weaker traits became recessive. A good example of what Darwin was trying to explain is shown in giraffes. Long-necked giraffes could reach the food on the trees, while the short-necked giraffes couldn’t. Since long necks helped the giraffes eat, short-necked giraffes died off from hunger. Because of this long-necks became a dominant trait in giraffes. This is what Charles Darwin would later call natural selection.
Convergent evolution and evolutionary reversal can be reasons for similar traits to arise independently in species that are distantly related. With convergent evolution distantly or unrelated species generate traits that are similar for reasons other than inheritance through a common ancestor. This happens as a result of having to adapt to similar environments or ecological niches ( the role that a species plays in an ecosystem). One example of this would-be dolphins and bats. They have very little in common, however, the ability of echolocation, which they use to hunt for food, arose independently in each group.
Many scientists in the past, such as Aristotle and Plato, believed that there were no changes in populations; however, other scientists, such as Darwin and Wallace, arose and argued that species inherit heritable traits from common ancestors and environmental forces drives out certain heritable traits that makes the species better suited to survive or be more “fit” for that environment. Therefore, species do change over a period of time and they were able to support their theory by showing that evolution does occur. There were four basic mechanisms of evolution in their theory: mutation, migration, genetic drift, and natural selection. Natural selection is the gradual process by which heritable traits that makes it more likely for an organism to survive and successfully reproduce increases, whereas there is a decline in those who do have those beneficial heritable traits (Natural Selection). For example, there is a decrease in rain which causes a drought in the finches’ environment. The seeds in the finches’ environment would not be soft enough for the smaller and weaker beak finches to break; therefore, they cannot compete with the larger and stronger beak finches for food. The larger and stronger beak finches has a heritable trait that helps them survive and reproduce better than others for that particular environment which makes them categorized under natural selection (Freeman, 2002).
4)Mutation. Mutation is a completely random occurrence where new alleles are created resulting in completely new dna constructs. While this is not quite the same as a new species, it is a new DNA pattern at least.
Natural selection is the process by which random modifications (mutations), related to a distinct individual’s chance of survival by adapting to its environment (food, predators, environmental features), are selected by nature in a total logical way (lecture). Basically, natural selection functions like this: the individuals among a community with the most advantageous characteristics regard to the survival and reproduction rate will spread on these inherent genetic traits to their offspring (Futuyma, 2004). Over time, these traits will become more frequent in the genetic basis of future generations and eventually all the living species within a population will gain those features (lecture). There are three preconditions for natural selection to exist (lecture). The first one is variation. It simply means that there will be changes in the DNA and those modifications are the reason why we vary in a population. The second one is differential reproductive success. This condition suggests that some individuals have more offspring than others and it generally has to do with competition between species. The third one is heredity which supports that we inherited the genetic basis of our creators, half of each parent. In brief, natural selection is broadly associated with the capacity of species to adapt in their environment and occurs only through three primordial preconditions: variation, differential reproduction and
Migration is the movement of organisms from one location to another, migration when used in a population genetics context often refers to the movement of individuals into or out of a defined population. A sudden influx of alleles is provided when the migrating individuals stay and mate with the destination individuals. After mating is established between the migrating individuals and destination individuals, different types of gametes carrying alleles that can alter the existing proportion of alleles in the destination population is contributed by the migrating individuals.
In most cases the only thing that is known is about the chromosomal rearrangements that happen, that can then be used to find which chromosomes are the ones responsible for speciation. We know too well that one chromosome is not the only one responsible, there are other factors that also affect speciation and in most cases, it is usually more than one chromosome and different chromosomes are identified in different species. There has been a study about how the chromosome X in humans is the one that controls speciation and
Alternatively, hybridization can decrease diversity through the breakdown of reproductive barriers, the merger of previously distinctive evolutionary lineages, and the extinction of populations or species" (Todesco et al. 2016).
14. Clobert, J., Baguette, M., Benton, T. G., & Bullock, J. M. (Eds.). (2012). Dispersal ecology and evolution. Oxford University Press.