Paramecium are single cell eukaryotes that live in fresh (pure) water. They have a vacuole that contracts to expel excess water that enters the cytoplasm. Eukaryotes that live in salt water do not need these vacuoles because * 1. there is more solute inside their cytoplasm than outside it
2. there is the same amount of solute outside their cytoplasm as in it
3. salt will not enter their cytoplasm
4. water can't cross their cell membrane

Based on the observation that only male crickets produce a song, you hypothesize that a male's song is a form of communication to potential mates. you set up a simple experiment to test this hypothesis. in the laboratory, you place a male snowy tree cricket in enclosure a, which is adjacent to enclosureb. in enclosure b, you place other insects, one at a time, and observe their responses to the male's song. the enclosures are designed so that the two insects being tested cannot see or smell each other, but sound is transmitted from enclosure a to enclosureb.