The main function of the placenta is to a) direct the blood flow to the pelvis. b) allow the mixing of maternal and fetal blood. c) surround the embryo and protect it from shock. d) allow the fetus to receive nutrients and oxygen.

Describe the response the kidneys have to dehydration and excessive water intake. what happens to the concentration of urine in each case ?

Use the phylogenetic tree to the right to determine which statement below is true. organisms a and f are not related. organism e is more closely related to organism b than organism f. organisms c and d are more closely related than organisms a and b. phylogenetic trees

What's wrong with this ecological pyramid? (multiple choice)1. secondary consumers should be at the bottom of the pyramid2. the sun has an arrow leading to decomposers 3. primary consumers should come after the sun4. energy retained should increase from the bottom to the top5. the sun should be at the bottom of the pyramid