Exam 25: The History of Life on Earth

The following questions refer to the description below. 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. -Fruit fly eyes are of the compound type,which is structurally very different from the camera-type eyes of mammals.Even the camera-type eyes of molluscs,such as octopi,are structurally quite different from those of mammals.Yet,fruit flies,octopi,and mammals possess very similar versions of Pax-6.The fact that the same gene helps produce very different types of eyes is most likely due to

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

The following questions refer to the description below. You were asked to give a presentation about fossils to a group of young students.You tell the students that the fossil record shows how organisms can change over time,but unfortunately the fossil record is incomplete.After your talk a student tells you that his pet salamander has died and he wants his salamander to be fossilized.The boy plans to lay his salamander on the grass and cover the salamander's body with leaves and twigs.You had told the class that a critical step in the fossilization process is the burial of an organism. -Which of the statement(s)below lends support to your claim about the fossilization process?

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 labelled "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. -Assuming that the rate of sea-floor spreading was constant during the 1-million-year period depicted above,what should be the approximate age of marine fossils found in undisturbed sedimentary rock immediately overlying the igneous rock at the arrow labelled "II"?

The oxygen revolution changed Earth's environment dramatically.Which of the following took advantage of the presence of free oxygen in the oceans and atmosphere?

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 labelled "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. -Assuming that the rate of sea-floor spreading was constant during the 1-million-year period depicted above,Earth's magnetic field has undergone reversal at an average rate of once every

What does the circled part of the phylogenetic tree above indicate?

What is true of the amino acids that might have been delivered to Earth within carbonaceous chondrites?

Refer to the following information to answer the questions below. Fossils of Lystrosaurus,a dicynodont therapsid,are most common in parts of modern-day South America,South Africa,Madagascar,India,South Australia,and Antarctica.It apparently lived in arid regions,and was mostly herbivorous.It originated during the mid-Permian period,survived the Permian extinction,and dwindled by the late Triassic,though there is evidence of a relict population in Australia during the Cretaceous period.The dicynodonts had two large tusks,extending down from their upper jaws.The tusks were not used for food gathering,and in some species were limited to males.Food was gathered using an otherwise toothless beak.Judging from the fossil record in sedimentary rocks,these pig-sized organisms were the most common mammal-like reptiles of the Permian period. -Which of the following is the most likely explanation for the modern-day distribution of dicynodont fossils?

Which organisms would you expect to be most poorly represented in the fossil record?

What is true of the Cambrian explosion?

On the basis of their morphologies,how might Linnaeus have classified the Hawaiian silverswords?

Which of the following statements does not apply to Hox genes?

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

Several scientific laboratories across the globe are involved in research concerning the origin of life on Earth.Which graph below,if the results were produced abiotically,would have the greatest promise for revealing important information about the origin of Earth's first genetic system?

Refer to the following information to answer the questions below. Fossils of Lystrosaurus,a dicynodont therapsid,are most common in parts of modern-day South America,South Africa,Madagascar,India,South Australia,and Antarctica.It apparently lived in arid regions,and was mostly herbivorous.It originated during the mid-Permian period,survived the Permian extinction,and dwindled by the late Triassic,though there is evidence of a relict population in Australia during the Cretaceous period.The dicynodonts had two large tusks,extending down from their upper jaws.The tusks were not used for food gathering,and in some species were limited to males.Food was gathered using an otherwise toothless beak.Judging from the fossil record in sedimentary rocks,these pig-sized organisms were the most common mammal-like reptiles of the Permian period. -If an increase in dicynodont species diversity (in other words,number of species)occurred soon after the Permian extinction,and if it occurred for the same general reason usually given for the increase in mammalian diversity following the Cretaceous extinction,then it should be attributed to

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

Which of the following characteristics should have been possessed by the first animals to colonize land? 1)were probably herbivores (ate photosynthesizers) 2)had four appendages 3)had the ability to resist dehydration 4)had lobe-finned fishes as ancestors 5)were invertebrates

Bagworm moth caterpillars feed on evergreens and carry a silken case or bag around with them in which they eventually pupate.Adult female bagworm moths are larval in appearance; they lack the wings and other structures of the adult male and instead retain the appearance of a caterpillar even though they are sexually mature and can lay eggs within the bag.This is a good example of

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