Prokaryotic cells do not have membrane bound organelles. Eukaryotic cells do have membrane bound organelles. The membrane controls movement in and out of the cell. ... The cytoplasm fills the space between the nucleus and the cell membrane.
I'm not 100% sure, but I'd say the availability of vaccines and medicine.
Animals that use echolocation. Bats, whales, dolphins, a few birds like the nocturnal oilbird and some swiftlets, some shrews and the similar tenrec from Madagascar are all known to echolocate.