Whales are related back to a hairy, 4-legged land mammal that eventually led to the formation of flippers without phalanges, a blow hole that became more dorsal, and other defining features. All of this has been backed by fossil evidence, especially that found within a certain desert region (can’t remember the name) that has a vast amount of whale fossils from many different time periods
Answer: polar ice caps form
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It is the comparison of the nucleotide sequences in DNA
The “R” Horizon would be 5
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In order to be useful in treating human infections, antibiotics must selectively target bacteria for eradication and not the cells of its human host. Indeed, modern antibiotics act either on processes that are unique to bacteria--such as the synthesis of cell walls or folic acid--or on bacterium-specific targets within processes that are common to both bacterium and human cells, including protein or DNA replication. Following are some examples.
Most bacteria produce a cell wall that is composed partly of a macromolecule called peptidoglycan, itself made up of amino sugars and short peptides. Human cells do not make or need peptidoglycan. Penicillin, one of the first antibiotics to be used widely, prevents the final cross-linking step, or transpeptidation, in assembly of this macromolecule. The result is a very fragile cell wall that bursts, killing the bacterium. No harm comes to the human host because penicillin does not inhibit any biochemical process that goes on within us.
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