The presence of an acidic chyme delivered to the duodenum which subsequently triggers the release of secretin from the pancreas involves

What is the next step in muscle contraction after the actin changes shape? (apex)

When the oxygen produced by photosynthetic plants in the water dissolves in the water, which of these is being formed?

Which of the following must be true for a fossil organism to be useful as an index fossil? a. the fossil organism must be widespread geographically. b. the fossil organism must be abundant. c. the fossil organism must be limited to a short span of geologic time. d. all of the above.