Early Evolution and the GOE

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Questions and Answers

Given the conditions of early Earth, which metabolic process would LEAST likely have been utilized by the earliest chemoautotrophs in hydrothermal vent environments?

Reduction of ferric iron ($Fe^{3+}$) to ferrous iron ($Fe^{2+}$) coupled with ATP synthesis.
Anaerobic oxidation of methane ($CH_4$) coupled with sulfate ($SO_4^{2-}$) reduction.
Photoexcitation of retinal pigments to establish a proton-motive force in the absence of chlorophyll. (correct)
Oxidation of hydrogen sulfide ($H_2S$) to elemental sulfur ($S^0$) to generate a proton gradient for chemiosmosis.

Concerning the Great Oxidation Event (GOE), which statement MOST accurately describes its impact on the biogeochemical cycling of iron and subsequent eukaryotic evolution?

The GOE resulted in the precipitation of banded iron formations, effectively removing bioavailable iron from the oceans and creating a selective pressure for the evolution of novel iron acquisition mechanisms in early eukaryotes. (correct)
The GOE led to an increased concentration of dissolved iron in the oceans, facilitating the proliferation of iron-reducing bacteria and delaying the evolution of aerobic respiration in eukaryotes.
The GOE had negligible effects on iron biogeochemical cycling, as iron oxidation was primarily driven by abiotic processes, and eukaryotic evolution was predominantly influenced by endosymbiotic events.
The GOE caused a shift in the dominant oxidation state of iron in terrestrial environments, leading to a decrease in the rate of chemical weathering and a subsequent decline in eukaryotic diversification.

Given current scientific models of endosymbiosis, which observation would MOST strongly challenge the prevailing theory regarding the origins of mitochondria and chloroplasts?

Discovery of a modern prokaryote lacking ribosomes with high sequence similarity to eukaryotic ribosomal RNA.
Identification of a eukaryotic gene essential for mitochondrial function encoded within the nuclear genome but exhibiting clear phylogenetic affinity to a bacterial lineage distinct from alpha-proteobacteria. (correct)
Characterization of a novel archaeal species capable of phagocytosing bacteria without subsequent digestion.
Isolation of a virus capable of transferring genetic material between distantly related prokaryotic species.

Assuming that the Ediacaran biota represent a stem group of early animals, which characteristic would be LEAST expected based on current phylogenetic understanding of animal evolution?

Fossil evidence of a complex nervous system with centralized ganglia and specialized sensory organs. (A) Signup and view all the answers

Concerning the Cambrian Explosion, what poses the GREATEST challenge to interpreting this event solely as a result of increased oxygen availability?

Geochemical evidence indicates that oxygen levels were already elevated well before the Cambrian boundary. (A) Signup and view all the answers

Which scenario would present the MOST significant challenge to the prevailing hypothesis that the development of mineralized exoskeletons during the Cambrian was primarily driven by selective pressure from increased predation?

Geochemical evidence indicating a sharp decline in seawater calcium concentrations during the Cambrian Period. (C) Signup and view all the answers

Which statement provides the MOST compelling argument against the hypothesis that the initial colonization of land by plants was primarily driven by the avoidance of marine predation?

Early land plants lacked the complex structural defenses (e.g., spines, toxins) found in many contemporary marine algae. (A) Signup and view all the answers

How did the evolution of specialized appendages in arthropods influence their transition to terrestrial environments, and how did this morphological adaptation subsequently affect the evolutionary trajectories of other terrestrial animal groups?

Morphological flexibility enabled arthropods to adapt to terrestrial environments, leading to an increase in predation pressure on early tetrapods and driving the evolution of defensive mechanisms. (C) Signup and view all the answers

Which developmental adaptation in early tetrapods MOST directly facilitated the exploitation of terrestrial environments and influenced the subsequent diversification of amniotes?

Development of an amniotic egg to enable reproduction away from water. (D) Signup and view all the answers

Considering the evolutionary history of tetrapods, what is the MOST likely explanation for the persistence of amphibian life cycles that require both aquatic and terrestrial environments?

Amphibian life cycles provide a selective advantage by allowing exploitation of different food resources and habitats during development. (D) Signup and view all the answers

Which factor MOST likely explains the rapid diversification and global distribution of angiosperms during the Cretaceous period compared to gymnosperms?

Angiosperms developed symbiotic relationships with animal pollinators and seed dispersers, facilitating their spread to novel habitats. (B) Signup and view all the answers

How would the sudden extinction of insect pollinators affect the evolutionary trajectory of angiosperms, and what alternative strategies might plants employ to ensure reproductive success?

Angiosperms might evolve self-pollination mechanisms or develop mutualistic relationships with other animal groups, such as birds or mammals. (A) Signup and view all the answers

What evolutionary pressures might explain the development of increased reliance on eyesight in vertebrates during the transition to land, and how might these pressures have differed between early terrestrial predators and herbivores?

Improved eyesight was essential for navigating heterogeneous landscapes and detecting potential threats, with predators developing binocular vision and herbivores maintaining wider fields of view. (A) Signup and view all the answers

Which of the following represents an insurmountable obstacle to the widespread applicability of uniformitarianism when interpreting early Archean geological and biological processes?

The significantly higher geothermal gradient in the Archean, leading to fundamentally different tectonic regimes and hydrothermal activity. (B) Signup and view all the answers

Which aspect of the evolution of lignin in vascular plants MOST profoundly altered terrestrial biogeochemical cycles and influenced the subsequent evolution of terrestrial ecosystems?

Lignin's recalcitrance to microbial degradation led to the accumulation of organic carbon in soils, driving changes in nutrient availability and soil structure. (A) Signup and view all the answers

Flashcards

Evolution

A process where life has developed innovations, allowing organisms to make use of the planets resources.

Late Heavy Bombardment

A period of intense meteorite impacts on early Earth.

Stromatolites

Structures created when mats of cyanobacteria are smothered by fine calcite mud in shallow marine environments; bacteria grow through the mud, creating layered structures.

Cyanobacteria

Organisms that require sunlight to create their own food via photosynthesis, using carbon dioxide and producing oxygen.