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Mutations occur when there is a change in the DNA of an organism. These changes happen at random, and can either harm, benefit, or not affect the organism at all. These changes in DNA are significant because DNA is reponsible for the phenotypes and behaviours of different organisms. If the DNA is changed, then their way of being (whether it is appearance or not will) will change. If these change/mutations, are in anyway useful, they will most likely be preserved through natural selection and contribute to evolution

The transfer of genes between populations, caused by dispersion of reproductive cells, and migration to different geographic locations is gene flow. Gene flow is a source of genetic variation, because by either method it pertains to the introduction of unfamiliar traits into another population. This introduction allows for the apparition of previously non-existent traits within the population.

During sexual reproduction a random combination of parental genes are inherited by the offspring. This random selection of genes allows for variations within the offspring. This variability allows for the process of evolution by natural selection, in which the advantageous genes are passed on to the descendants. However, since the combination of DNA acts randomly disadvantageous genes, such as genes for genetic disorders can also be carried throughout generations as well

The Five Evolutionary Mechanism of

Natural Selection

biotechnology

Naturel Selection

Biotechnology

Natural Selection

sexual selection

genetic variation

Artificial Selection

Biotechnology has many applications in today's society, including applications in the medical, industrial, and agricultural areas. Some medical applications include the creation of diagnosis and treatment technologies such as vaccines, drugs, and diagnostic testing equipment. We also use biotechnology to help scientist manipulate crops and plants in order to produce disease pesticide and drought resistant crops.

The environment certainly favors certain individuals over others. In fact, the environment selects individuals that adapt better in their environment. There are three different types of selection process the environments go through. These selective pressures may be abiotic (natural factors ie. climate) or biotic (predators)

Stabilization Selection

Disruptive Selection

Directional Selection

Stabilization selection is when the environment favours that average variation of a trait. So in a environment with medium length flowers, average length bills for hummingbirds will be favoured. In the case of humans, average birth weights are favoured over very low or very high birth weights

Directional selection is when the environment favours the variations of a certain trait (phenotype) of a species. For example, an environment that has longer and shorter flowers might favour longer and shorter billed humingbirds over medium size (average) lengths.

Disruptive Selection is when the environment favours the most extreme version of a trait. This will be shown as either a shift from an average condition, or even a previous extreme trait. So in an environment that has long flowers, when before it had short flowers, longer billed hummingbirds will be favoured. This type of selection is also expressed among many plants, where the larger and tastier fruit will usually be preferred.

For example, Australian eucalyptus trees (GM tree's) have been altered to withstand freezing temperatures. It has been modified in order for scientists to see how north they can bring in trees. However, plantation of these gm trees require massive amounts of pesticides and it emits greenhouse gases to ou environment.

A good example is of genetically modified trees. These trees have been successfully manipulated in order to grow wider, straighter trunks that can be better used in the wood industry. These trees can then pollinate other natural trees, and the modified genes can be distributed. These man-made modifications are also contributing to genetic variation.

Sexual Selection

Sexual selection is the favoring in certain traits in animals that give that animal an advantage in terms of finding a mate.

These selections are usually based on the male phenotypes. For example, physical traits such as bright coloration to attract female counterparts or extenuated features, such as a large build or big antlers attract the females by impressing them or compete with other males. Although variation such as vibrant coloring and antlers result in an improvement in reproduction, they are often at the expense of being vulnerable to predators, hindering their survival. In the case of male tundra frogs, they have a mating call; fringe-lipped bats (who eat these frogs) use this mating call to find them. So in short, the more the frog calls, the more likely he is to be eaten, and is more likely to find a mate, and the less the frogs calls, the safer he will be, but the less likely he is to find a mate

Genetic Variation

The three main causes of genetic variation include mutations, gene flow, and sex.

Artificial Selection

Mutations

Gene Flow

In this case, people (instead of nature), are the selectors of which animal will reproduce. Typically, there will be farmers trying to get animals with the best traits to mate so they can produce the most desirable offspring.

figure 1

Figure 1 shows us that production of different everyday vegetables used at home are products of artificial selection by selecting the desired traits from wild mustard to produce many other vegetables.

Sexual Reproduction

Genetic Drift

According to the Hardy-Weinburg principle, in a population where only random chance is at work, the allele frequencies are expected to stay constant throughout many different generations This means that if something is to change the allele frequency, there has been an evolutionary change as well

The Founder Effect

Genetic Drift

The founder effect occurs when a small number of individuals from a species create a new population in a new region (usually an isolated region such as an island). The genetic variation that is found within this group of establishing individuals is random, and its this random arrangement that will determine the genetic make-up of the future generations on the island. A good example is of Darwin's Finches. A small population of them were isolated to the Galapagos Islands. This initial group, by chance, had a different mix of alleles that were found on the mainland. By chance there could have been a lot of birds carrying a rare allele. In this case, on the isolated islands, this rare allele would be passed down more frequently, making it more commonly found on the island then it was on the main lands.

Genetic drift is essentially a shift of genetic makeup of the next generations. Particularly, in small population genetic drift can result in the presence of a certain allele of being either very prominent or very scarce. When we refer to "genetic drift", we are usually focusing on smaller populations, whereas natural selection focuses on a much larger and broader population. In these smaller populations, can cause a more apparent changes in allele frequency, where as in larger populations, it is almost insignificant.

Bottleneck Effect

Genetic bottlenecks result in an extreme reduction of the population, which also results in a loss of the genetic diversity in that region. Bottleneck events are caused by a dramatic reduction in a population size and this usually results in a genetic drift. Generally, rare alleles are more likely to be completely eliminated in the bottle effect.

The only problem is that if we look at just one species, if the population is suddenly reduced to a very small number, then all the future offspring that orginate after that will all be very genetically similar. If that happens, the whole population is in danger of being wiped out from something like a disease because their immune systems will most likely all react in a similar fashion. For example, cheetahs, who have very little genetic variation because they have been subjected to a genetic bottleneck have a low fertility rate and a high mortality rate.

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