【正文】 long before 600 million years ago ? Came into existence at a late point in the Cambrian period ? Existed before the animals of the Burgess Shale existed ? Were larger than those of animals found in the Burgess Shale Paragraph 1: Putting a date on the first appearance of eyes depends on what one means by eye. If the term refers to a multicellular an, even if it has just a few cells, then by definition, eyes could not form before there were multicellular animals. ■But many protists (animallike, plantlike, or funguslike unicellular anisms that require a waterbased environment) can detect light by using aggregations of pigment molecules, and they use this information to modify their metabolic activity or motility (the ability to move spontaneously and independently). ■One of the familiar living examples, probably known to anyone who has taken a biology class, is the aquatic protozoan Euglena, which has an eyespot near its motile fIagellum (hairlike structure). ■Some living protists are very like their ancestral forms embedded in ancient sedimentary rocks, and this similarity suggests that the ability to detect light and modify behavior in response to light has been around for a very long time. ■Animals arose from one of such unicellular creatures, perhaps from one already specialized for a primitive kind of vision. 13. Look at the four squares [■] that indicate where the following sentence could be added to the passage. Molaria spinifera and H. Optata, both of which lived in water levels beyond the reach of light, fit into this category. 14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. Drag your choices to the spaces where they belong. To review the passage, click on View Text. Answer Choices ? The ability of some unicellular anisms to detect light and change their behavior accordingly suggests that eyes did not originate with multicellular animals. ? The earliest eyes apparently contained molecules that were capable of forming and focusing images. ? Too few fossils from the Precambrian have been found to determine which if any Precambrian anisms had eyes. ? Evidence from the Burgess Shale suggests that eyes of some early animals were similar to the eyes of living crustaceans. ? Fossil evidence suggests that anisms in the Burgess Shale with faceted eyes developed later than anisms in the Burgess Shale with n onfaceted eyes. ? The large size and possible plexity of the eyes of some anisms in the Burgess Shale suggest that their eyes were not the first eyes. TPO362 The origin of Earth’s atmosphere In order to understand the origin of Earth39。s surface, where they cooled more rapidly than the better insulated materials in Earth39。s surface to the present day. The lightest materials of all, including gases such as hydrogen and helium, bubbled through Earth39。s atmosphere, we must go back to the earliest days of the solar system, before the plas themselves were formed from a disk of rocky material spinning around the young Sun. This material gradually coalesced into lumps called plaesimals as gravity and chance smashed smaller pieces together, a chaotic and violent process that became more so as plaesimals grew in size and gravitational pull. Within each orbit, collisions between plaesimals generated immense heat and energy. How violent these processes were is suggested by the odd tilt and spin of many of the plas, which indicate that each of the plas was, like a billiard ball, struck at some stage by another large body of some kind. Visual evidence of these processes can be seen by looking at the Moon. Because the Moon has no atmosphere, its surface is not subject to erosion, so it retains the marks of its early history. Its face is deeply scarred by millions of meteoric impacts, as you can see on a clear night with a pair of binoculars. The early Earth did not have much of an atmosphere. Before it grew to full size, its gravitational pull was insufficient to prevent gases from drifting off into space, while the solar wind (the great stream of atomic particles emitted from the Sun) had already driven away much of the gaseous material from the inner orbits of the solar system. So we must imagine the early Earth as a mixture of rocky materials, metals, and trapped gases, subject to constant bombardment by smaller plaesimals and without much of an atmosphere. 1. The word coalesced in the passage is closest in meaning to ? Collided ? Joined ? Changed ? Shrank 2. The word chaotic in the passage is closest in meaning to ? Rapid ? Disanized ? Intense ? Longlasting 3. All of the following are true of the plaesimals mentioned in paragraph 1 EXCEPT: ? They were formed of rocky material spinning around the early Sun. ? They collided violently with each other. ? They gradually grew in size. ? They lost their atmospheres as they were hit by larger bodies. 4. The word retains in the passage is closest in meaning to ? Reveals ? Acquires ? Hides ? Preserves 5. The author discusses the Moon in paragraph 1 in order to ? Help explain why Earth had fewer meteoric impacts than other plas in the solar system ? Show why it is difficult to understand how the first plaary atmospheres developed ? Help explain the processes that took place in the formation of large plaary bodies in the solar system ? Illustrate why the Moon39。s core is mostly iron because, pared to most other elements on early Earth, iron ? was denser ? me