What was the basis on which prokaryotes were split into two domains?
a. according to differences in cell membrane properties
b. according to differences in cell wall composition
c. according to differences in staining characteristics
d. according to differences in rRNA sequences
Ans: d. according to differences in rRNA sequences
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Ultraviolet light is a mutagen, but humans need some exposure to it to synthesize vitamin D. The amount of ultraviolet light that penetrates the skin depends on the skin's pigmentation: more melanin (skin pigment) means less penetration
Certain mutations result in decreased melanin production. Such mutations: A. are harmful only if inherited from both parents. B. are beneficial only if inherited from both parents. C. are neutral only if inherited from one parent, not the other. D. may be harmful in one environment and beneficial in another.
Which of the following statements is true regarding the pollen of gymnosperms and angiosperms? Select all correct choices
A. Pollen grains from both of these plants consist of four cells. B. A single angiosperm produces more pollen than a single gymnosperm. C. Pollen from both types of plant form pollen tubes that factor in fertilization. D. Pollen from both types of plants contain (or will form) haploid (1n) male gametes.
___________ nerves exit from between the spinal vertebrae and extend to various parts of the body.
A) Cranial B) Connecting C) Somatic D) Peripheral
Below is a list of molecules with different chemical characteristics
Knowing that all molecules will eventually diffuse across a phospholipid bilayer, select the option below that most accurately predicts the relative rates of diffusion of these molecules (fastest to slowest). alanine estrogen propanol sodium (a) alanine > propanol > sodium > estrogen (b) sodium > propanol > alanine > estrogen (c) estrogen > propanol > sodium > alanine (d) estrogen > propanol > alanine > sodium