16. Which of the following is a density-independent factor in a population?
(A) Food
(B) Weather
(C) Habitat
(D) Carrying capacity

12. Lipid-soluble signaling molecules, such as aldosterone, can diffuse across the cell membranes but affect only target cells because? (A) Only target cells have responsive DNA segments (B) Intracellular receptors are present only in target cells (C) Only target cells have enzymnes that convert aldosterone to active form (D) Aldosterone-responsive genes are only present in the target cells

13. The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the corresponding bones in whales have very different shapes and proportions. However, genetic data suggest that all three kinds of organisms diverged from a common ancestor at about the same time. Which of the following is the most likely explanation for these data? (A) Forelimb evolution was adaptive in people and bats, but not in whales (B) Whales are not properly classified as mammals (C) Genes mutate faster in whales than in humans or bats (D) Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy

14. Which of the following is the correct description of the tropical rain forest? (A) Long summers and mild winters (B) Low temperature, rain uniform during the year (C) Warm temperatures and continual rains allow plant growth year-round (D) Low rainfall and dry weather

15. Chemoautotrophs? (A) Use inorganic compound (such as methane) as energy source and CO2 as a carbon source (B) Use light as energy source and organic compound as a carbon source (C) Use organic compound as energy source and organic compound as a carbon source (D) Use light as energy source and CO2 as a carbon source

17. Gymnosperms? (A) Ovary becomes the fruit after fertilization (B) Undergo double fertilization (C) Do not have vascular tissues (D) Bear seeds on exposed surfaces of spore-bearing structures

18. Which of the following tools of DNA technology is incorrectly paired with its use? (A) DNA polymerase_polymerase chain reaction to amplify specific DNA fragments (B) Electrophoresis_separation of DNA fragments by size (C) DNA ligase_ cutting DNA to create DNA segments with specific ends (D) Reverse transcriptase_use mRNA to synthesize DNA

19. The most direct ancestors of land plants were probably (A) Kelp (brown alga) that formed large beds near the shorelines (B) Green al gae (C) Photosynthesizing prokaryotes (cyanobacteria) (D) Liverworts and mosses

20. In addition to seeds, which of the following characteristics is unique to the seed- producing plants? (A) Sporopollenin (a component of spore outer walls) (B) Lignin present in cell walls (C) Megaphylls (D) Pollen

21. Much of the animal diversity is a result of the evolution of novel ways to (A) Reproduce (B) Arrange cells into tissues (C) Sense, feed, and move (D) Form an embryo and establish a basic body plan

22. Vertebrates and tunicates share? (A) A notochord and a dorsal, hollow nerve cord (B) The formation of structures from the neural crest (C) A high degree of cephalization (D) Jaws adapted for feeding