Some biologists believe that life on Earth is in the midst of a sixth major mass-extinction event caused by
A) human activity.
B) a gradual decrease in global temperature.
C) loss of genetic diversity due to inbreeding.
D) coevolution of predator and prey species.
E) sustainable agriculture efforts.
A
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Several scientists, including Charles and Francis Darwin, Frits Went and others, demonstrated that auxins caused stems to bend toward light in a series of elaborate experiments. Went was the researcher who finally determined that bending of the stem toward light was a result of which mechanism?
A. Light caused a reduction in auxin concentration and a reduction in stem elongation on the lighted side of the plant stem, and thus a bending in the direction of the light. B. The transport of auxin to the shaded side of the plant stem stimulated stem elongation and a bending in the direction of the light. C. Auxin concentration was equal on both sides (lighted and shaded) of the stem; however, the apical meristem responded to the presence of light. D. A combination of positive phototropism and a negative gravitropism. E. The stems actually were responding to the agar blocks that had been used in the experiments.
Which of the following is not a characteristic of Saccharomyces cultures?
a. The cells are haploid. b. The cells have a relatively short generation time. c. Cells reproduce asexually by budding. d. The cells can be induced to reproduce sexually. e. All answers are true of Saccharomyces cultures.
Two boys are on a camping trip and need birch bark to start their cooking fire. They cleanly remove a six-inch strip of bark from around the entire circumference of the trunk. Explain what eventually will happen to this tree
What will be an ideal response?
The accompanying figure is a micrograph of what kind of tissue?
a. cardiac muscle b. skeletal muscle c. smooth muscle d. cartilage e. dense connective