The cell wall<span> and the </span>central vacuole<span> help to support the plant cell and help it maintain its shape.</span>
This statement means that evolution has happened by getting the genes of the right trait expressed at the right time to help adaptability.
Explanation:
Evolution is a result of natural selection which emphasize on the survival of the fittest. But the occurrence of this trait has been possible with genetic variation. It means that if the genes for the particular feature is not present in the genome how would it occur and adapt to the environment. Thus, evolution promotes the most available option for the adaptation and hence for natural selection.
We can conclude that all features are not adaptable some are the results of genetic drift or mutations.
In case of cheetah, the faster running genes would have been there they got expressed over the period of time for better adaptability.
Answer :Erwin Chargaff a Biochemist
Explanation:
He formulated the base paring of double helix of DNA. He reasoned that since the percentage of four DNA bases are of this proportions in human;
Adenine=30.9% and Thymine =29.4%;
Guanine=19.9% and Cytosine =19.8%
Then, the amount of adenine will always be equal to thymine,
And the amount of Guanine equals to cytosine based on this percentages of distribution.
(Adenine and Guanine are large, molecule of Purines, while thymine and Cytosine are Pyrimidine)
He concluded (although scientist believed, he did not explicitly stated this) that this should be the base paring patterns in DNA molecule. This is the first Chargaff Rule.
His second rule is that the DNA composition, in the relative amount of the four bases Adenine, Thymine, Cytosine and Guanine varies in proportion from one organisms to another. And this is the basis of molecular diversity.
