Laboratory evidence indicates that life originated through chemical reactions in the primordial mixture (water, hydrogen, ammonia, and hydrogen cyanide) which blanketed the earth at its formation. These reactions were brought about by the heat, pressure, and radiation conditions then prevailing. One suggestion is that nucleosides and amino acids were formed from the primordial mixture, and the nucleosides produced nucleotides which produced the nucleic acids (DNA, the common denominator of all living things, and RNA). The amino acids became polymerized (chemically joined) into proteins, including enzymes, and lipids were formed from fatty acids and glycerol-like molecules. The final step appears to have been the gradual accumulation of DNA, RNA, proteins, lipids, and enzymes into a vital mass which began to grow, divide, and multiply.
The evolution of the various forms of life from this biochemical mass must not be considered a linear progression. Rather, the fossil record suggests an analogy between evolution and a bush whose branches go every which way. Like branches, some evolutionary lines simply end, and others branch again. Many biologists believe the pattern to have been as follows: bacteria emerged first and from them branched viruses, red algae, blue-green algae, and green flagellates. From the latter branched green algae, from which higher plants evolved, and colorless rhizoflagellates, from which diatoms, molds, sponges, and protozoa evolved. From ciliated protozoa (ciliophora) evolved multinucleate (syncytial) flatworms. These branched into five lines, one of which leads to the echinoderms and chordates. The remaining lines lead to most of the other phyla of the animal kingdom.
1. From the language of the first paragraph, it can be assumed thatI. some scientists do not accept the theories of the origin of life the passage presents.
II. the reactions that produced life required a unique combination of heat, pressure, and radiation.
III. some living forms are without DNA.
A. I only
B. I and II only
C. I and III only
D. II and III only
E. I, II, and III
2. Which of the following can we infer to be the least highly evolved?A. green algae
B. blue-green algae
C. molds
D. flatworms
E. ciliated protozoa
3. According to the passage, the evolutionary line of sponges in its proper order isA. bacteria–viruses–green algae–sponges.
B. bacteria–viruses–rhizoflagellates–sponges.
C. bacteria–red algae–blue-green algae–rhizoflagellates–sponges.
D. bacteria–blue-green algae–green flagellates–rhizoflagellates–sponges.
E. bacteria–green flagellates–rhizoflagellates–sponges.