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Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.

Need ! will give 20 points! what are two ways that diatoms differ from slime molds? the external coverings of diatoms are made up of (silica, chitin or peptidoglycan), while slime molds have cell walls containing (silica, peptidoglycan or chitin). diatoms are (chemoheterotrophs, photoautotrophs or chemoautotrophs) because they make food through photosynthesis, while slime molds are (heterotrophs, phototrophs or autotrophs) because they eat decaying plant matter.

Accuracy in the translation of mrna into the sequence of amino acids in a polypeptide depends on specificity in which of the following? 1) binding of ribosomes to mrna 2) shape of the a and p sites of ribosomes 3) attachment of amino acids to trnas 4) bonding of the anticodon the codon and the attachment of amino acids to trnas