Chapter 13 The images on this CD have been lifted directly, without change or modification, from textbooks and image libraries owned by the publisher, especially from publications intended for college majors in the discipline. Consequently, they are often more richly labeled than required for our purposes. Further, dates for geological intervals may vary between images, and between images and the textbook. Such dates are regularly revised as better corroborated times are established. Your best source for current geological times is a current edition of the textbook, whose dates should be used when differences arise.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Survivors—Lingula  A marine organism (brachiopod) occupying vertical burrows in sand and mud has survived morphologically unchanged since the Silurian.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Survivors—Horseshoe crabs  The horseshoe crab, an inhabitant of marine shores, has lived morphologically unchanged since the Ordovician. A horseshoe crab in ventral (underside) view is shown.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Koala  The koala lives in Australia and feeds exclusively on the leaves of eucalyptus trees whose toxic oils are harmful to other herbivores.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Extinction episodes—marine animals  The standing diversity of marine invertebrate and vertebrate animals is shown. Five abrupt drops in diversity can be identified.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Adapting to changes  As environment changes, the population at “A” experiences a decline (bell-shaped curve) through time and becomes extinct. At “B,” the original population declines to extinction, but before then a lineage diverges via speciation to survive.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Applied island biogeography  Principles of island biogeography applied to the management of nature reserves helps make decisions about survival of organisms living in the reserve. In each comparison, design A is superior to B.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Origin and extinction  The rise and fall of various groups of animals are shown relative to the geologic time scale. The Permo-Triassic and Cretaceous extinctions are evident.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Extinction of dinosaurs  After their demise at the end of the Cretaceous, dinosaurs were replaced as dominant land vertebrates by birds and mammals. [The geologic dates given here are now revised, but provide a relative picture of groups.]

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Plate tectonics  The crustal surface of the Earth is broken up into plates that abut against each other and move about carrying their continents to every changing positions. Present day plates are shown.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Collision zones  Movement of the Earth’s crustal plates results in their slow collision with each other. Usually one plate over rides another, as shown here. Note how the ocean basin between them changes in size and depth, thereby changing sea level against the side of the continents.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Continents and extinctions  At the end of the Permian (Late Paleozoic), the major continents of the world were joined together into a super continent, Pangaea. At the end of the Cretaceous (end of the Mesozoic), the great land mass of Pangaea had begun to break apart into the basic continents we recognize today.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Cosmic collision  At the end of the Cretaceous, an asteroid or comet struck the Earth in the location of present day Yucatan Peninsula in Mexico. Although such a collision certainly occurred, it is debated whether or not this collision was directly responsible for the dinosaur extinctions.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display After the dinosaurs  Extinction of the dinosaurs left may ecological niches empty. In part, the subsequent flourishing of mammals and birds represents an adaptive radiation into many of these vacated life styles.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Asteroid collision with the Earth  This figure depicts events on the young planet Earth when, still hot from its cosmic birth, it endured a pummeling by rocky debris 4 billion years ago. This bombardment waned but did not cease entirely. A similar strike by cosmic debris (asteroid or comet) is thought by some scientists to have caused the extinction of dinosaurs 65 million years ago.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE 13.2 Species—Area Curve  If the size of an island is plotted against the number of species present on it, a direct relationship usually holds—the more area, the more species. Reptile and amphibian species in the West Indies are plotted here. (Data from MacArthur and Wilson 1967.)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE 13.3 Immigration and Extinction on Islands  (a) Immigration curve. As colonists fill the island, the rate of arrival of new species drops. (b) Extinction curve. As colonists fill up the island, the rate at which species disappear increases. (After MacArthur and Wilson 1967.)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE 13.4 Species Equilibrium  Where immigration and extinction curves cross, an equilibrium number of species is reached. In this example, there are 10 species on the nearby mainland, making it possible for up to 10 species to be on the island. However, in this example the equilibrium sustainable by the island is 6.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE 13.5 Distance and Area Effects on Species Equilibrium  (a) Distance effect. If our island (from figure 13.4) were moved farther from the mainland, the equilibrium would shift to the left, settling at 2, and some species would become extinct on the island. (b) Area effect. A large island reaches a higher equilibrium than a small island.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE 13.6 Phylogeny of a Group  Given is a family of fossil organisms. To follow declines in numbers over time, we pick a starting point and then follow these species forward in time (thick lines). Starting with 10 species (A–J) in this family, some become extinct, leaving 7, 5, 4, 2, and 1 remaining species on successive time intervals. Below the phylogeny, these numbers are plotted (semilog plot) showing the constant decline through time.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE 13.7 Evolutionary Survivorship Curves  (a) Protists: foraminifera. (b) Mammals: artiodactyla—deer, elk, and related species. (c) Pteridophyta: ferns and related species. (d) Mammals: perissodactyla—horses and related species. M.Y.: millions of years passed. (After Van Valen 1973.)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE 13.8 Extinction Episodes—Random Sample  Of more than 19,000 genera, 10 samples of 1,000 genera were chosen at random and the percentage becoming extinct was plotted. Major peaks of mass extinction are indicated.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE 13.9 Extinction Episodes—Tetrapods  The number of tetrapod families, the standing diversity, is plotted beginning with the first tetrapods in the Devonian. Six mass extinctions are indicated where diversity abruptly drops. Notice that the curve starts sharply upward during the Tertiary—this is a reflection of some increase in diversity, especially among birds and mammals, but also an artifact of the better preservation of fossils as we approach the present. (After Benton 1989.)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE Extinction Episodes—Marine Animals  Plotted a slightly different way from figure 13.8, the standing diversity of marine invertebrate and vertebrate animals is shown. Five abrupt drops in diversity are numbered (1-5). The relative magnitudes of these drops were determined by measuring from the stage before to the stage after the extinction event. These relative magnitudes are given in parenthesis. (After Raup and Sepkoski 1982.)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE Extinction Episodes—Families of Marine Animals  The number of marine animals going extinct per million years is plotted. The solid line (regression line) expresses the average—fewer than 8 species extinctions per million years. The parallel dashed lines are the statistical confidence limits that bound the “background” extinction rate. Elevated levels of extinction above background are “mass extinctions,” indicated with the five points (1–5) corresponding to geological time intervals. (After Raup and Sepkoski 1982.)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE Mesozoic Tetrapods-Ancestors and Survivors  Together, the Ornithischia* plus the Saurischia* constitute the “dinosaurs.” Notice that birds and mammals are early contemporaries of the dinosaurs.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE Nasal Turbinates  Frontal view of a human skull. The paired orbits bound the single teardrop-shaped nasal opening between. Seen deep in the nasal opening are the vertical, thin turbinate bones.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE The Great Exchange — North and South America  Separate faunas and floras evolved on these continents when they were separate during the Cenozoic. About 2 to 3 million years ago, the Isthmus of Panama formed, providing a land bridge between the continents that became a route of migration and exchange between the continents. Among the placental mammals, many arising in North America dispersed south, and many originating in South America dispersed north.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE Continental Drift  (a) Pangaea formed at the end of the Permian as the result of previously separate continental landmasses fusing together into this single supercontinent. (b) Continents broke up again at the end of the Cretaceous.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE Perimeter Area  When a landmass (a) is broken in two (b), this adds area along the perimeter where they split. This adds to the intertidal area. When two landmasses (b) are brought together (a), this results in loss of available intertidal area.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE Continental Shelves  Because of the sloped geometry of the continents, a drop in sea level along a continental shelf eliminates large areas of intertidal habitat (dark shaded) compared to a similar drop in sea level against a steeply sloped drop-off area (light shaded).

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE Sea Level Drop, Permo-Triassic  Note that as the sea level dropped (a) at the end of the Permian, there was a corresponding loss of marine animals (b). Sea level is expressed as a percentage of possible coverage, which began falling about 30 to 35 million years ago (solid arrow) before the end of the Permian. Estimates of absolute drop in level range from 300 to 600 feet (100Ð200 m). Tick marks along horizontal axes represent geologic stages of varying duration. (After Schopf, 1974.)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE Phanerozoic Extinctions and Ice Ages  Ice ages are indicated along this geologic time line for comparison to five mass extinction episodes. Note that there is no tight correlation between ice ages and mass extinctions.