1. plasma membrane
The plasma membrane is selectively permeable.
Yes, it does, but not the way people think. it doesn't gain it from the weight of all the people. the earth takes mass from elsewhere, as our population continues to grow.
"The first and second hominids were able to mate and produce offspring, but the first and third hominids could not." <span>Although that might be the case, it might also not. "More similar" needn't be 'similar enough' (disregarding the fact that all homonid specimens involved could happen to share the same sex). </span>
<span>"The first and second hominids shared the same geographic location, while the third was isolated." </span>
<span>That information would be revealed by the geographic location they came from. </span>
<span>"The first and second hominids most likely became extinct before the third hominid species." </span>
<span>Perhaps or perhaps not. As ancestral lineages can survive for longer than descendant lineages, it needn't apply. Still, I suppose the non-existent law of averages provides some sort of justification for the use of "Most likely". </span>
<span>"The first and second hominids have a more recent common ancestor than the first and third hominids." </span>
<span>Assuming these are all in the same neat lineage, then the most recent common ancestor of the first and second is also the most recent common ancestor of the first and the third.</span>