You can already see how important these principles are to evolution. Traits can be inherited from parent to offspring, and the natural occurrence of different alleles creates variation within a population.
A Punnett Square is a model used by scientists to demonstrate this kind of inheritance. The genotypes — the genetic codes — of the parents are on the sides of the square.
They each have two alleles — one from each of their own parents. One allele is selected from each parent and the resulting genotypes are then combined like a multiplication table. These show the possible genotypes of a single offspring. Since genes independently assort each time parents procreate, each offspring has a possibility of being one of the four genotypes produced. A dominant allele is always written in capital letters, and a recessive allele is always written in lowercase.
To determine the phenotype, or physical trait, of the possible offspring, just look at the genotype. If there is a capital letter, even just one, the offspring will have a dominant phenotype. If it has two recessive alleles, it will bear the recessive phenotype. This was the earliest form of genetics, which is still called Mendelian or Classical genetics. In reality, scientists have discovered that genes are much more complicated.
Some traits require the combined action of multiple genes, like hair color. Others have more than two alleles, like blood type, which has three alleles — A, B, and O. To make matters more complicated, the A and B alleles of blood are codominant. An individual who inherits an A from one parent and a B from another has AB blood type.
Some genes are regulated by other genes, and some genes will not function if a mutation is present. The short answer is, yes, our genes determine our bodies. They provide the biological information that makes us who we are.
Although future developments in science and medicine may allow us to change parts of ourselves, right now we cannot change our genetic code. For example, we cannot change the genes that give us our natural hair color. Instead, if we want to change our hair color, we would have to dye it. The same is true for many disorders and diseases that have a genetic origin; we cannot change them once we inherit them from our parents.
This is misleading at best. This article summarizes multiple independent lines of evidence that evolution is the best scientific description of the process by which life has diversified.
God is the creator and sustainer of all things, and evolution is the best scientific explanation for the relatedness of life on Earth. Evolutionary creationists believe that God created humans in his image, and that God created humans using natural processes that scientists describe as evolution. How can these beliefs work together? Properly understood, evolution is a scientific theory about the development of life and is consistent with Christian theology.
Does human genetic variation today provide evidence that we can trace our ancestry exclusively from a single couple? Biology, philosophy and religion work together to help us to understand the world we live in and to better know God. Part Three in the Uniquely unique mini-series. We look to morality, language, and culture, and start to see that our species is quite an outlier.
Author of "Thriving with Stone Age Minds," Justin Barrett responds to the reaction some people have to the idea of evolutionary psychology. Part Two in the Uniquely unique mini-series. When we look for what makes humans unique on this planet, looking at our biology is an obvious first step.
Structures that are absent in some groups often appear in their embryonic forms and disappear by the time the adult or juvenile form is reached. For example, all vertebrate embryos, including humans, exhibit gill slits at some point in their early development. These disappear in the adults of terrestrial groups, but are maintained in adult forms of aquatic groups such as fish and some amphibians.
Great ape embryos, including humans, have a tail structure during their development that is lost by the time of birth. The reason embryos of unrelated species are often similar is that mutational changes that affect the organism during embryonic development can cause amplified differences in the adult, even while the embryonic similarities are preserved.
The geographic distribution of organisms on the planet follows patterns that are best explained by evolution in conjunction with the movement of tectonic plates over geological time. Broad groups that evolved before the breakup of the supercontinent Pangaea about million years ago are distributed worldwide. Groups that evolved since the breakup appear uniquely in regions of the planet, for example the unique flora and fauna of northern continents that formed from the supercontinent Laurasia and of the southern continents that formed from the supercontinent Gondwana.
Australia has an abundance of endemic species—species found nowhere else—which is typical of islands whose isolation by expanses of water prevents migration of species to other regions. Over time, these species diverge evolutionarily into new species that look very different from their ancestors that may exist on the mainland.
Like anatomical structures, the structures of the molecules of life reflect descent with modification. Evidence of a common ancestor for all of life is reflected in the universality of DNA as the genetic material and of the near universality of the genetic code and the machinery of DNA replication and expression.
Fundamental divisions in life between the three domains are reflected in major structural differences in otherwise conservative structures such as the components of ribosomes and the structures of membranes. In general, the relatedness of groups of organisms is reflected in the similarity of their DNA sequences—exactly the pattern that would be expected from descent and diversification from a common ancestor.
DNA sequences have also shed light on some of the mechanisms of evolution. Groups that evolved since the breakup appear uniquely in regions of the planet, such as the unique flora and fauna of northern continents that formed from the supercontinent Laurasia and of the southern continents that formed from the supercontinent Gondwana. The presence of members of the plant family Proteaceae in Australia, southern Africa, and South America is best due to their appearance prior to the southern supercontinent Gondwana breaking up.
Australia has an abundance of endemic species—species found nowhere else—which is typical of islands whose isolation by expanses of water prevents species migration.
Over time, these species diverge evolutionarily into new species that look very different from their ancestors that may exist on the mainland. Like anatomical structures, the structures of the molecules of life reflect descent with modification.
Evidence of a common ancestor for all of life is reflected in the universality of DNA as the genetic material and in the near universality of the genetic code and the machinery of DNA replication and expression. Fundamental divisions in life between the three domains are reflected in major structural differences in otherwise conservative structures such as the components of ribosomes and the structures of membranes.
In general, the relatedness of groups of organisms is reflected in the similarity of their DNA sequences—exactly the pattern that would be expected from descent and diversification from a common ancestor. DNA sequences have also shed light on some of the mechanisms of evolution. This video defines evolution and discusses several varieties of evidence that support the Theory of Evolution:.
Although the theory of evolution generated some controversy when it was first proposed, it was almost universally accepted by biologists, particularly younger biologists, within 20 years after publication of On the Origin of Species. Nevertheless, the theory of evolution is a difficult concept and misconceptions about how it works abound. Scientists have a theory of the atom, a theory of gravity, and the theory of relativity, each of which describes understood facts about the world.
In the same way, the theory of evolution describes facts about the living world. As such, a theory in science has survived significant efforts to discredit it by scientists.
This is a mischaracterization. Evolution is the change in genetic composition of a population over time, specifically over generations, resulting from differential reproduction of individuals with certain alleles.
When thinking about the evolution of a characteristic, it is probably best to think about the change of the average value of the characteristic in the population over time. If one measures the average bill size among all individuals in the population at one time and then measures the average bill size in the population several years later, this average value will be different as a result of evolution. Although some individuals may survive from the first time to the second, they will still have the same bill size; however, there will be many new individuals that contribute to the shift in average bill size.
First, the statement must not be understood to mean that individual organisms evolve. A changed environment results in some individuals in the population, those with particular phenotypes, benefiting and therefore producing proportionately more offspring than other phenotypes. This results in change in the population if the characteristics are genetically determined.
It is also important to understand that the variation that natural selection works on is already in a population and does not arise in response to an environmental change.
For example, applying antibiotics to a population of bacteria will, over time, select a population of bacteria that are resistant to antibiotics. The resistance, which is caused by a gene, did not arise by mutation because of the application of the antibiotic.
The gene for resistance was already present in the gene pool of the bacteria, likely at a low frequency.
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