All animals with eyes or eyespots that have been studied so far share a gene in common. When mutated, the gene Pax-6 causes lack of eyes in fruit flies, tiny eyes in mice, and missing irises (and other eye parts) in humans. The sequence of Pax-6 in humans and mice is identical. There are so few sequence differences with fruit fly Pax-6 that the human/mouse version can cause eye formation in eyeless fruit flies, even though vertebrates and invertebrates last shared a common ancestor more than 500 million years ago.

The appearance of Pax-6 in all animals with eyes can be explained in multiple ways. Based on the information above, which explanation is most likely?

TLS Online TPP Program

#Question id: 13017

#Unit 10. Ecological Principles

Which of the following statements best describes the effect of climate on biome distribution?

TLS Online TPP Program

#Question id: 13018

#Unit 10. Ecological Principles

Generalized global air circulation and precipitation patterns are caused by

TLS Online TPP Program

#Question id: 13019

#Unit 10. Ecological Principles

Air masses formed over the Pacific Ocean are moved by prevailing westerlies where they encounter extensive north- south mountain ranges, such as the Sierra Nevada and the Cascades. Which statement best describes the changes that these air masses undergo?

TLS Online TPP Program

#Question id: 13020

#Unit 10. Ecological Principles

Experts in deer ecology generally agree that population sizes of deer that live in temperate climates are limited by winter snow. The deer congregate in ?yarding? areas under evergreen trees because venturing out to feed in winter is energetically too expensive when snowfall depths accumulate to above 40 cm. Deer often stay yarded until the spring thaw. Snow depth over 40 inches for more than 60 days results in high mortality due to starvation.  This observation best illustrates which of the following principles about factors that limit distribution of organisms?

TLS Online TPP Program

#Question id: 13021

#Unit 10. Ecological Principles

Which marine zone would have the lowest rates of primary productivity (photosynthesis)? 

TLS Online TPP Program

#Question id: 13022

#Unit 10. Ecological Principles

A certain species of pine tree survives only in scattered locations at elevations above 2,800 m in the western United States. To understand why this tree grows only in these specific places an ecologist should