【正文】 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。 but once Earth was fully formed, it was large enough for its gravitational field to hold most of the remaining gases, and these formed Earth39。s surface to the present day. The lightest materials of all, including gases such as hydrogen and helium, bubbled through Earth39。 thus, even continental crust reaches only about 1/200th of the way to Earth39。s surface, where they cooled more rapidly than the better insulated materials in Earth39。s mantle, a region almost 3,000 kilometers thick between the core and the crust. With the help of bombardment by ets, whose many impacts scarred and heated Earth39。 they seem much too large and (potentially) well developed to be brand new inventions. The best we can do is put the origin of eyes somewhere between the beginning of the Cambrian explo sion, about 600 million years ago, and the death of the Burgess animals, some 530 million years ago. 12. Paragraph 6 suggests that the first eyes probably ? Came into existence 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。 those of others were on or a part of the body surface. One animal, Opabinia, had five eyes: two lateral pairs and a single medial eye。 they seem much too large and (potentially) well developed to be brand new inventions. The best we can do is put the origin of eyes somewhere between the beginning of the Cambrian explo sion, about 600 million years ago, and the death of the Burgess animals, some 530 million years ago. 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. 1. The word “aggregations” in the passage is closest in meaning to ? Parts. ? Reactions. ? Groups. ? Types. 2. Paragraph 1 supports all of the followin