7B Fossil Records

Looking through the fossil record, there are times when numerous fossils look to just appear all at the same time, with similar characteristics. What is a good explanation for this?

• A change in the environment occurred, and animals choose to express different traits.

• New species are always occurring, and there is no reason for it.

• Ancient man killed off all the animals, and they raised new animals, which are then found in the fossil record.

• A change in the environment caused different genetic traits to allow for a greater chance of survival.

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Tiktaalik roseae, better known as the "fishapod," is a 375 million year old fossil fish which was discovered in the Canadian Arctic in 2004. The discovery of Tiktaalik roseae sheds light on a pivotal point in the history of life on Earth: when the very first fish ventured out onto land. What impact does the discovery of Tiktaalik roseae have on the fossil record?

• The existence of "fishapod" features in a fish is significant because it marks the earliest appearance of these unique features in the fossil record.

• The fossil record is unchanged because the animals before and after "fishapod" were very similar.

• "Fishapod" is a fossil between a fish and an animal, displaying characteristics of the ancestors and the new lineage.

• "Fishapod" would be considered a missing link because scientist were unaware of the gap in the fossil record.

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What hypothesis is best supported by the fossils found near the Pecos River?

• Species A and B were direct competitors for food. Species A was more successful, causing the extinction of Species B.

• Species A and B were direct competitors for food. Species B was more successful, causing the extinction of Species A.

• A change occurred in the environment. Species A was not well adapted to the new environmental conditions, while Species B was well adapted to the new environmental conditions.

• A change occurred in the environment. Species B was not well adapted to the new environmental conditions, while Species A was well adapted to the new environmental conditions.

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Which statement below supports gradualism but does not support punctuated equilibrium?

• Species show little evolutionary change over an extended period of geological time, and as a result, stasis is seen in the fossil record.

• Speciation occurs during periods of rapid geological change.

• Speciation is a slow process that happens in steady small changes.

• Fossils of species found in the lower strata of the fossil record are geologically older than the species found in strata toward the top.

This diagram of the fossil record represents changes in mollusks over millions of years. How can the pattern of change in the fossil record best be explained?

• The mollusks were well adapted to their stable environment. A large, sudden change occurred in their environment. After the change the mollusks with the bigger shells were better adapted for the new environment.

• The mollusks were well adapted to their stable environment. The mollusks hybridized with a smaller species of mollusk. A new species of mollusk with a bigger shell resulted.

• The mollusks were not well adapted to their environment. The length of the mollusks’ shells changed gradually over time. The mollusks in the original population that had small shells died over a period of many years.

• The mollusks were well adapted to their environment. Humans introduced a new species of mollusk that was not adapted to this environment. The introduced mollusk outcompeted the native mollusk species.

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The diagram shows data on the evolution of horses. The data in the diagram is evidence that —

• a new species of horse suddenly appeared

• horses slowly developed over time

• horses have similar stages of rapid embryological development

• horses have a common ancestry with other hooved animals

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The graph shows the number of taxa of reptiles whose fossilized tracks have been found. Which statement is best supported by these data?

• Competition for food and shelter among reptile species was very low during the Triassic period.

• A great extinction occurred during the Jurassic period.

• Environmental conditions for speciation were most favorable for reptiles during the Permian period.

• Reptiles adapted to a terrestrial environment during the Cretaceous period.

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Observe the fossil record above. Trilobite fossils are some of the most common fossils due to their ease of fossilization and long period of existence. Trilobite species walked along the ocean floor causing them to easily be covered by sediment. Trilobites existed for over 271 million years, longer than the dinosaurs and humans combined. These characteristics provide humans with a large amount of fossil evidence for trilobites. Which statement below best describes the cause of the arrangement of smooth and spikey trilobite fossils observed in the fossil record above?

• The smooth trilobites were able to dig deeper into the soil than the spikey trilobites because they did not have protruding spikes that would catch on rocks in the ocean floor.

• Smooth trilobites could no longer blend in with the soil and grew spikes as an adaptation to protect themselves from predators gradually over time.

• The smooth trilobites were not able to compete with the spikey trilobites for food and slowly became extinct as the spikey trilobites became more dominant in the environment.

• A change in the environment caused the smooth trilobites to no longer be well adapted for the conditions. Spikey trilobites were well adapted to the new environment and began to thrive.

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As creatures become adapted to a particular environment, a type of natural selection called stabilizing selection can cause a decrease in genetic diversity throughout the population. The fossil record for an organism that has undergone stabilizing selection for millions of years will most likely look like-

• a single phenotype throughout multiple layers of rock

• a single phenotype in each layer of rock with each layer containing a different phenotype

• a wide range of phenotypes in each layer of rock

• a single phenotype in a few layers of rock and then a change to a different phenotype in a few layers of rock

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Niles Eldredge and Stephen Jay Gould researched the lenses of the eyes of fossil trilobites of different species. In 1972 they published a paper in which they described the tendency of a species to remain the same until a sudden change in the environment causes a new related species to appear. Which hypothesis was most challenged by the work of Eldredge and Gould?

• Redi’s hypothesis that spontaneous generation does not occur

• Haeckel’s hypothesis that embryological development mimics the evolution of species

• Wallace’s hypothesis that geography affects the distribution of species

• Darwin’s hypothesis that the development of species is a slow, gradual process

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