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

26. An example of a postzygotic isolating mechanism between closely related species would be which of the following? (A) One species flowers in April, the other in August. (B) The two species are pollinated by different species of bees. (C) A zygote produced by syngamy of sperm and egg of the two species contains an uneven number of chromosomes. (D) The pollen from one species will not germinate on the stigma of the other. (E) One species is terrestrial, the other totally aquatic.

27. Eudicots are recognized by: (A) straplike leaves. (B) flower parts generally in threes. (C) parallel leaf venation. (D) vascular bundles in the stem arranged in one ring. (E) no members having secondary growth.

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

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

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

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.