24. History of Life on Earth

In arthropods, the Hox genes Ubx and abd-A are largely expressed in the same tissues. The illustrations below show in red which tissues both Ubx and abd-A are expressed in three species of arthropods. Based on this illustration, which statement is consistent with the data?

_{Images adapted from: Jennifer K. Grenier, Theodore L. Garber, Robert Warren, Paul M. Whitington, Sean Carroll}

_{Evolution of the entire arthropod Hox gene set predated the origin and radiation of the onychophoran/arthropod clade,}

_{Current Biology, Volume 7, Issue 8, 1997, Pages 547-553,}

_{ISSN 0960-9822,}

_{https://doi.org/10.1016/S0960-9822(06)00253-3.}

Which of the following statements about the Cambrian Explosion are true?

I) Before the Cambrian Explosion, most organisms had soft bodies.

II) The Permian extinction created new ecological niches that were exploited during the Cambrian Explosion.

III) After the Cambrian Explosion, new morphological features like limbs and jaws are observed.

Which of the following statements are true?

I) Adaptive radiations often follow mass extinction events as organisms adapt to fill previously occupied niches.

II) Adaptive radiations are common on new volcanic islands where organisms can occupy many new environments.

III) The evolution of a new trait can trigger adaptive radiation as organisms are able to outcompete resident organisms in many different environments.