TEKS B.7(B) - Gradualism vs Punctuated Equilibrium

The diagram shows data on the evolution of horses.

The date 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 hovved animals

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 un5il 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

The graph shows the number of taxa of reptiles whose fossilized tracks have been found.

Which statement is best supported by this 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.l

This diagram of the fossil record represents changes in mollusks over millions of years.

How can the pattern of changes 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 changes, the mollusk with the bigger shells was better adapted to 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 mollusk's shells changed gradually over time. The mollusks in the original population that has 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.

The cladogram shows the evolution of land plants as indicated by fossil records.

Which discovery would challenge the validity of this cladogram?

• A large aquatic vascular plant about 200 million years old

• A species of algae that has existed for less than one million years

• A moss species that has existed for less than 380 million years

• A fossil of a fern more than 425 million years old.