2. In the fractionation of homogenized cells using differential centrifugation, which of the following will require the greatest speed to form pellets at the bottom of the tube?
(A) nuclei
(B) mitochondria
(C) chloroplasts
(D) ribosomes

28. Throughout its range, a species of fern is locally adapted to wetter conditions in some areas. In other areas, it is locally adapted to drier conditions. Other populations are adapted to higher light intensities； some populations are adapted to lower light intensities. These locally adapted populations are referred to as: (A) ecotypes. (B) ecotones. (C) populons. (D) edaphonomes. (E) competitors.

29. Which of the following characteristic and biome does NOT match? (A) Transitional biome often between grasslands and forests: Woodlands (B) Richest soil in essential elements: Tropical savanna (C) Majority of plant biomass may be underground: Arctic tundra (D) May be dominated by 1 to 2 species: Taiga (E) Soil thin and rocky, in some cases reduced to pebbles: Desert

30. Radiolabelled isotope dating is an important method to determine the age of a fossil. A 14C content analysis of a plant fossil showed that its content is 0.03125 fold as much 14C as the atmosphere. The half-life of 14C is 5730 years. The age of the fossil is close to which of the following? (A) 1000 years (B) 5730 years (C) 28000 years (D) 35000 years (E) 70000 years

1. Which of the following is the smallest structure that would most likely be visible with a standard research-grade light microscope? (A) mitochondrion (B) double membrane of nucleus (C) ribosome (D) virus

3. Why a modern transmission electron microscope (TEM) can achieve a resolution of about 0.2 nanometers, whereas a standard light microscope has a maximum resolution of about 200 nanometers? (A) Glass lenses in light microscopes refract light, which reduces resolution. (B) Contrast is enhanced by staining with atoms of heavy metal. (C) Electron beams have much shorter wavelengths than visible light. (D) The electron microscope has a much greater ratio of image size to real size.

4. Which of the following is a major difference between prokaryotic cells and eukaryotic cells? (A) Prokaryotic cells have cell walls, while eukaryotic cells do not. (B) Eukaryotic cells have flagella, while prokaryotic cells do not. (C) Eukaryotic cells have membrane-bound organelles, while prokaryotic cells do not. (D) Prokaryotic cells are generally larger than eukaryotic cells.

5. Which of the following are found in plant, animal, and bacterial cells? (A) mitochondria (B) ribosomes (C) chloroplasts (D) endoplasmic reticulum

6. What is the function of the nuclear pore complex found in eukaryotes? (A) It regulates the movement of proteins and RNAs into and out of the nucleus. (B) It synthesizes the proteins required to copy DNA and make mRNA. (C) It synthesizes secreted proteins. (D) It assembles ribosomes from raw materials that are synthesized in the nucleus.

7. The nuclear lamina is an array of intermediate filaments that line the inner side of the nuclear membrane. If a chemical treatment caused the lamina to disassemble, what would you expect to be the most likely immediate consequence? (A) closing of nuclear pores (B) the inability of the nucleus to divide during cell division (C) a loss of genetic information from chromosomes (D) a change in the shape of the nucleus

8. A cell with a predominance of rough endoplasmic reticulum is most likely. (A) producing large quantities of proteins for secretion (B) producing large quantities of proteins in the cytosol (C) producing large quantities of carbohydrates to assemble an extensive cell wall matrix (D) producing large quantities of carbohydrates for storage in the vacuole