4. Sympatric speciation commonly occurs through_______ in plants but is more likely to occur through_______ in animals.
(A)polyploidy； habitat differentiation and sexual selection
(B) habitat differentiation and sexual selection； polyploidy
(C)asexual reproduction；chromosome duplications
(D) self-pollination； polyploidy and other genetic mechanisms 

100.What is the lasting impact that Connie and Wendy have had on their team? (A) They have caused division and conflicts. (B) They have created a culture of indifference. (C) They have fostered camaraderie and inspiration. (D) They have left no impact at all.

1. The development of heart disease can result from a diet high in (A)protein. (B) unsaturated fats. (C) saturated fats. (D) sugars.

2. What is the main adaptive advantage of the C4 and CAM photosynthesis strategies over the C3 strategy? (A) They help the plant synthesize glucose efficiently under dry conditions. (B) They allow the plant to fix carbon under conditions of low CO2. (C) They allow the plant to fix carbon in cool conditions. (D) They make it possible for the plant to use the Calvin cycle at night.

3. RNA interference (RNAi) can be used by (A) researchers to induce the production of more mRNA. (B) researchers to artificially turn on gene expression. (C) viruses to stop the production of new proteins. (D) cells to prevent infections from double-stranded RNA viruses.

5. Mycorrhizal fungi are sometimes purposely introduced to new areas of land that are used for growing plants for commercial uses (e.g., landscaping, crop production, timber production). What would be the benefit of doing this? (A) The fungi absorb toxic pesticides from the ground. (B) The fungi help facilitate horticulture, agriculture, and forestry. (C) The fungi promote the evolution of new fungus species. (D) The fungi prevent competitive plant species from growing.

6. Homeostasis (A) is the maintenance of a relatively constant internal state. (B) results from hormone imbalance. (C) occurs when the external environment changes to match the internal environment. (D) is the way the internal environment influences the external environment.

7. The second vaccination is beneficial because it (A) contains mast cells that survive longer than 4-5 days. (B) stimulates production of a higher concentration of antibodies in the bloodstream. (C) requires two injections to stimulate antibody formation. (D) keeps previously produced cytotoxic T cells circulating in the bloodstream.

8. Our biological clock, which regulates the sleep-wake cycle, is housed within the (A) cerebrum. (B) hypothalamus. (C) cerebellum. (D) brainstem.

9. Which statement regarding compound eyes is TRUE? (A) They have one light-focusing lens. (B) They are poor motion detectors. (C) They can provide excellent color vision. (D) They can perceive only visible light.

10. Which of the following biomes is characterized by mild, rainy winters and hot, dry summers? (A) Tropical forest (B) Temperate grassland (C)Savanna (D) Temperate seasonal forest (E) Mediterranean woodland and shrubland