Which of the following statements best describes the history of life on Earth?
A) The Earth had multicellular life-forms for most of its history.
B) The Earth had single-celled life-forms for most of its history.
C) The Earth was lifeless far longer than it had living things.
D) The Earth had photosynthetic organisms about 100 million years after it formed.
Answer: B
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Which of the following are thought to have occurred because of the increase of oxygen (O2) in the atmosphere during and after the Silurian Period?
A. Conquest of land by arthropods. B. Conquest of land by arthropods and vertebrates. C. Increases in animal body sizes and conquest of land by plants. D. Conquest of land by arthropods and vertebrates, and plants. E. Conquest of land by arthropods and vertebrates and an increase in animal body sizes.
Which cell structure is most likely responsible for sensing gravity?
A. central vacuole B. Golgi appartus C. chloroplast D. amyloplast E. apical meristem
The products of the process in the accompanying figure are:a
enzymes. b. amino acids. c. monosaccharides. d. molecules of glycerol. e. representative of a glycoside linkage.
Answer the following statements true (T) or false (F)
1. The internal structure of procaryotic flagella is the same as the internal structure of eucaryotic flagella. 2. The internal structure of eucaryotic cilia is the same as the internal structure of eucaryotic flagella. 3. The production of endospores by bacteria is a reproductive mechanism. 4. Bacteria never have cilia and eucaryotic cells never have pili. 5. The 3-Domain System of classification is based on differences in the structure of transfer RNA (tRNA) molecules.