Chapter 25 Mastering Biology Review

Which of the following is a defining characteristic that all protocells had in common?

• RNA genes

• a surrounding membrane or membrane-like structure

• the ability to synthesize enzymes

• the ability to replicate RNA

Which of the following is found in eukaryotic cells but not in prokaryotic cells?

• Plasma Membrane

• DNA

• Cell wall

• Membrane-enclosed organelles

The atmosphere of early Earth probably contained no O₂ until the emergence of organisms that _____.

• used hydrogen sulfide as an energy source

• were oxygen respiring

• were chemoautotrophic

• used water as an electron source for photosynthesis

• had chloroplasts

Endosymbiosis is an evolutionary theory that explains the origin of eukaryotes and suggests a specific order in which this might have occurred. Ancestral cells engulfed and then began to use the metabolic processes of the smaller cells. Based on shared-core processes and features, which statement most accurately describes the order, the theory, and the evolutionary implications for all organisms within the domain Eukarya?

• Ancestral heterotrophic eukaryotes most likely engulfed both a heterotrophic and an autotrophic prokaryote, whereas ancestral photosynthetic eukaryotes probably provided the host cell for the first mitochondria. Over time, natural selection favored these relationships, and these cells became the ancestors of all eukaryotes.

• As carbon dioxide levels were increasing over time, natural selection would have favored organisms that acquired a photosynthetic prokaryote to convert carbon dioxide into sugars. These would have likely been the first eukaryotic cells. These ancestral cells engulfed mitochondria-like prokaryotes, which would have provided an even greater advantage for cells in this environment.

• As Earth was becoming more aerobic, mitochondria would have provided an advantage to host cells by converting "toxic" oxygen into energy for heterotrophic cells. Since mitochondria are found in all eukaryotes, these combinations likely evolved first. Photosynthetic eukaryotes probably acquired an autotrophic prokaryote, which developed an advantageous symbiotic relationship with the host cell.

• All ancestral eukaryotes would have most likely consumed a nucleus-like prokaryote that eventually became the eukaryotic nucleus. These new eukaryotic cells would have had an advantage over prokaryotic cells by acquiring a nuclear command center for regulating cellular activities.

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How was early Earth from more than three billion years ago different from today's Earth? Unlike Earth today, early Earth ________.

• had an atmosphere rich in gases released from volcanic eruptions

• had an oxidizing atmosphere

• experienced little high-energy radiation from the sun

• had an atmosphere with significant quantities of ozone

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What is the most accurate method used to measure the age of a fossil?

• use whole-life decay

• use uranium-238

• sequence fossils in rock strata

• radiometric dating

The figure shows eyes found among living molluscs, ranging from a patch of pigmented cells in a limpet to a complex, image-forming eye in a squid. Is it possible that a structure as complex as an image-forming eye evolved by natural selection?

• Yes. Because an image-forming eye is so useful, natural selection would favor less useful intermediate structures.

• Yes, if the photoreceptor cells and simple eyes that preceded it were useful to the animals in which they arose.

• No. An image-forming eye needs all of its components to function, so a partial eye would not have been useful.

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

• in particular environments, similar adaptations can be beneficial to more than one species

• a larger volume-to-surface area ratio is adaptive in many mammals

• evolution tends toward increased complexity or increased size

• evolution generally progresses toward some goal

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Insect wings may have begun to evolve as lateral extensions of the body that were used as heat dissipaters for thermoregulation. When they had become sufficiently large, these extensions became useful for gliding through the air. Additional selection refined them as flight-producing wings. If this hypothesis is correct, modern insect wings would be an example of _____.

• the loss of Hox genes in the evolution of new form

• an adaptive radiation

• mutations

• an exaptation

Which period had the greatest increase in the number of extant species?

• Cenozoic

• Mesozoic

• Permian

• Paleozoic

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