Genetic variation<span> is essential for </span>natural selection<span> because </span>natural selection can only increase or decrease frequency of alleles that already exist in the population.Genetic variation<span> is caused by: mutation
i pulled this off of the site i got the information from i hope this helps you out if not sorry
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Answer:
e. PhoU keeps PhoR bound to the phosphate transporter protein Pst
Explanation:
PhoU is a membrane protein known to regulate the transport of phosphate (Pi) between cellular compartments. It has been discovered that mutations in this protein cause lethality because the cell becomes incapable of controlling the intracellular levels of Pi, this being toxic for the cell. PhoR is a histidine kinase/phosphatase. When the Pi level is considered to be a limiting factor, PhoR autophosphorylates at a histidine residue and then donates its phosphoryl group to PhoB. On the other hand, when the Pi level is high, this protein removes the phosphoryl group from phospho-PhoB. Finally, the Pst is a signal transduction protein that acts as a transporter capable of switching its conformation during the transport of PI.
Answer: second
Explanation:Early humans most likely experienced changes in climate forcing migration to find animals for food, changes in climate alternating rivers with droughts and floods and changes in environment causing animal habits changes.
Explanation:
All the changes that early humans could have experienced, I think, are related to the changes that animals and the lands could have suffered. They lived much more closer to them than we do now; now we sometimes don't realize how global warming is affecting our planet because we are not that close to the lands and the crops and we don't usually raise animals for our consumption, we just buy at the shop. But, early humans could sense every change related with that because this was the way they lived. So, migration to find animals, changes in climate alternating rivers with droughts and floods and changes in animal habits are the ones I believe they could have suffered.