Please Help Mass extinctions have occurred repeatedly during the course of Earth's history. One of these events occurred at the end of the Cretaceous Period, during which the dinosaurs became extinct. Mammals flourished after the dinosaurs were gone. This led to a variety of genetically diverse species. Why did the mammals suddenly start diverging into different species after the dinosaurs were gone? a. Most of the predators were gone and suddenly niches were available so almost all the offspring were likely to survive and reproduce. b. Once the dinosaurs were gone, the mammals started having larger numbers of offspring in each litter to fill the empty niches. c. The mammals chose to move into the vacant niches the dinosaurs had occupied and change their body shapes to suit these new environments. d. Mammals began mutating rapidly once the dinosaurs died out and were able to create new species based on the mutations.

1. which of the following levels of protein organization shows the complete 3-d arrangement of the polypeptide chain? a) primary b) secondary c) tertiary d) quaternary 2. the carboxyl groups on a protein molecule are composed of which of the following elements? a) nitrogen and hydrogen b) carbon, hydrogen, and oxygen c) carbon and hydrogen d) nitrogen, oxygen, and carbon 3. what part of the protein molecule makes it unique from other proteins? a) the carboxyl group b) the amino group c) the peptide group d) the r group 4. which of the following is an example of a protein that plays a direct role in immune function? a) collagen b) antibodies c) enzymes d) hormones 5. which of the following statements correctly describes the composition of proteins? a) most are composed of 20 common amino acids. b) most are composed of 10 common amino acids. c) most are composed of 20 common fatty acids. d) most are composed of 10 common fatty acids.