Which best describes fetal development? The heart beats and is heard during the first trimester.
The heart beats and is heard during the second trimester.
The heart beats during the first trimester, but is heard in the second trimester.
The heart beats during the second trimester, and is heard in the third trimester.

Several bird species feed in a certain species of tree. each bird species feeds in a different part of the tree. which statement is true of these bird species? a. they have adapted to different niches due to competition b. they have a carnivorous relationship with the tree species. c. they have adapted to different niches due to predation d. they have a symbiotic relationship with the tree species.

Did the vinegar diffuse all the way to the center of any of the cubes? if so, which ones? what does this tell you about surface area-to-volume ratio and the diffusion rate?

Why does controlling transcription affect prokaryotic gene expression?