Pace of Evolution

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 / an —

• single phenotype throughout multiple layers of rock

• wide range of phenotypes in each layer of rock

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

• 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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What is the best explanation of the pattern of evolution displayed in this diagram?

• B. solidus was well-adapted to its environment. A change in the environment caused the sudden appearance of B. dotus and B. stripus. After the change, all three species of butterfly were well-adapted to the new environment

• B. solidus was not well-adapted to its environment. Over time, B. solidus gradually developed into B. dotus and B. stripus. The B. solidus butterflies slowly died out.

• B. dotus and B. stripus butterflies hybridized, resulting in a new species of butterflies, the B. solidus. All three species of butterfly are well-adapted to their environment.

• B. solidus was well-adapted to its environment. Humans introduced two non-native species of butterflies to the area, B. dotus and B. stripus. The nonnative butterflies were welladapted and survived better than B. solidus.

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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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Scientists discovered fossils of a species of trilobite. By digging through the layers of sediment, they determined that a simple form of this species of trilobite appeared to be well suited for its environment. Then, a large, sudden change occurred in the environment, after which a trilobite with more segments and longer spines was better adapted to its new environment. How would a sketch of the fossil record for this species of trilobite look?

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The allele frequency does not change over the time. Which term does match this process?

• coenolution

• genetic equilibrium

• microevolution

• convergent evolution

Two contrasting theories of evolution explain changes in species found in fossil records. Gradualism was proposed by Charles Darwin, and punctuated equilibrium was more recently proposed by Niles Eldridge and Steven J. Gould. Which statement 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.

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 trilobiteWhich statement best describes the cause of the arrangement of smooth and spikey trilobite fossils observed in the fossil record?

• 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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Geologists discovered a large trilobite fossil collection near the Pecos River. The first group of fossils were found in the mountains west of the river and contained several complete fossils that the geologists labeled “Species A”. The second group of fossils were found along the eastern banks of the river and contained several complete fossils that the geologists labeled “Species B”. What hypothesis is best supported by the fossils found near the Pecos River? 8

• 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 does not accurately describe natural selection?

• Individual organisms' fur turns white during the winter to camouflage them in the snow

• The genetic composition of a population changes from one generation to the next.

• More advantageous traits become more common in populations.

• Beneficial and useful traits are inherited generation after generation.

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Which diagram represent gradualism?

• Diagram A

• Diagram B

• Diagram A and B

• None