Why does it take so long for the stomach to empty a meal into the small intestines?

What was the land like over 500 million years ago? what was under the sea?

What would be the result if crossing over did not happen during meiosis in humans? a. there would be less genetic variation in humans. b. parents would be more likely to look like their children. c. the human population could not reproduce. d. children would have more chromosomes.

Why did adult crab numbers decline in he ecosystem, even though sea stars were still available?