Exam 25: The History of Life on Earth

Pax-6 usually causes the production of a type of light-receptor pigment. In vertebrate eyes, though, a different gene (the rh gene family)is responsible for the light-receptor pigments of the retina. The rh gene, like Pax-6, is ancient. In the marine ragworm, for example, the rh gene causes production of c-opsin, which helps regulate the worm's biological clock. Which of these most likely accounts for vertebrate vision?

The existence of evolutionary trends, such as increasing body sizes among horse species, is evidence that

The following questions refer to the description and figure below. The figure represents a cross section of the sea floor through a mid-ocean rift valley, with alternating patches of black and white indicating sea floor with reversed magnetic polarities. At the arrow labeled "I" (the rift valley), the igneous rock of the sea floor is so young that it can be accurately dated using carbon-14 dating. At the arrow labeled "III," however, the igneous rock is about 1 million years old, and potassium-40 dating is typically used to date such rocks. Note: The horizontal arrows indicate the direction of sea-floor spreading, away from the rift valley. Figure 25.1 -How many other bands of sea-floor crust in Figure 25.1 have the same magnetic polarity as the crust that directly straddles the rift valley?

Figure 25.3 -Soon after the island of Hawaii rose above the sea surface (somewhat less than 1 million years ago), the evolution of life on this new island should have been most strongly influenced by

The snowball Earth hypothesis provides a possible explanation for the

Approximately how far back in time does the fossil record extend?

The following questions refer to this hypothetical situation. A female fly, full of fertilized eggs, is swept by high winds to an island far out to sea. She is the first fly to arrive on this island, and the only fly to arrive in this way. Thousands of years later, her numerous offspring occupy the island, but none of them resembles her. There are, instead, several species, each of which eats only a certain type of food. None of the species can fly, for their flight wings are absent, and their balancing organs (in other words, halteres) are now used in courtship displays. The male members of each species bear modified halteres that are unique in appearance to their species. Females bear vestigial halteres. The ranges of all of the daughter species overlap. -In each fly species, the entire body segment that gave rise to the original flight wings is missing. The mutation(s)that led to the flightless condition could have

Recent evidence indicates that the first major diversification of multicellular eukaryotes may have coincided in time with the

The following questions refer to the paragraph below. A sediment core is removed from the floor of an inland sea. The sea has been in existence, off and on, throughout the entire time that terrestrial life has existed. Researchers wish to locate and study the terrestrial organisms fossilized in this core. The core is illustrated as a vertical column, with the top of the column representing the most recent strata and the bottom representing the time when land was first colonized by life. Figure 25.2 -Assuming the existence of fossilized markers for each of the following chemicals, what is the sequence in which they should be found in this sediment core, working from ancient sediments to recent sediments? 1)chitin coupled with protein 2)chlorophyll 3)bone 4)cellulose

The existence of the phenomenon of exaptation is most closely associated with which of the following observations that natural selection cannot fashion perfect organisms?

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?

The following questions refer to the paragraph below. A sediment core is removed from the floor of an inland sea. The sea has been in existence, off and on, throughout the entire time that terrestrial life has existed. Researchers wish to locate and study the terrestrial organisms fossilized in this core. The core is illustrated as a vertical column, with the top of the column representing the most recent strata and the bottom representing the time when land was first colonized by life. Figure 25.2 -In order to properly interpret sediment cores, it is necessary to apply the principle of

Which measurement(s)would help determine absolute dates by radiometric means?

Which of the following is the most likely explanation for the modern-day distribution of dicynodont fossils?

If two continents converge and are united, then the collision should cause

Which event is nearest in time to the end of the period known as snowball Earth?

A genetic change that caused a certain Hox gene to be expressed along the tip of a vertebrate limb bud instead of farther back helped make possible the evolution of the tetrapod limb. This type of change is illustrative of

What is thought to be the correct sequence of these events, from earliest to most recent, in the evolution of life on Earth? 1)origin of mitochondria 2)origin of multicellular eukaryotes 3)origin of chloroplasts 4)origin of cyanobacteria 5)origin of fungal-plant symbioses

What is true of the Cambrian explosion?

Which factor most likely caused animals and plants in India to differ greatly from species in nearby southeast Asia?