In humans, the yolk sac in humans, the yolk sac is the site of origin for blood cells and primordial germ cells is no longer a useful structure forms the human urinary bladder passes nutrients to the embryo after digesting the yolk mass

In which of the following relationships is one organism always benefited while the other organism is always harmed

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.

Which of the following forest management practices is best for reestablishing areas of forest?