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Hi
It is true that on the Galapagos islands Darwin observed tortoises with a dome and saddle shaped shells, you can see both in attached image.
Darwin observed that Galapagos Tortoises had the shells with different shapes depending on the Island they live, For example: The tortoises with saddle shaped shells were able to reach up to eat leaves of plants while the tortoises with dome shaped shells would not reach up and they would eat food from on ground sources. This made him think that the differences in tortoise shell is also a strong evidence that indicates that how tortoises have adapted themselves to better get their food as per the available resources and how they have evolved from same ancestral specie into two different species. This point also helped him in proposing the theory of evolution by natural selection.
Hope it helps!
Tectonic plate movements, volcanic eruptions, earthquakes, and climate change have shifted wildlife habitats, wiped out large numbers of species, and created opportunities for the evolution of new species. Hope this helped!
Answer:
A. Yes, because the %A approximately equals the %T and the %G approximately equals the %C in both species.
Explanation:
According to Chargaff's rule, in all cellular DNAs, the number of adenosine residues (A) is equal to the number of thymidine residues (T). And the number of guanosine residues (G) is equal to the number of cytidine residues (C). Therefore, the sum of the purine residues equals the sum of the pyrimidine residues (A+ G= C+ T). It is based on the fact that a purine base always pairs with a pyrimidine base in a double helix DNA.
Chargaff’s rule is followed in all the double-helical DNA molecules irrespective of the species. In DNAs of sea urchin and salmon, the percentage of adenine is equal to that of the thymine and the percentage of guanine is equal to that of the cytosine. Therefore, Chargaff's rule is followed.
The allele would be called codominant
When a dominant and recessive allele exist in an organism, only the dominant allele will be expressed. Dominant allele always mask the recessive because the gene code a protein while recessive gene doesn't. When both gene code a protein, they will be codominant and both gene will be expressed. The result could be a mixed effect. In this case, the purple is mixed color of red and blue.
