Chat with AIExam 18: Evolution and the Fossil Record
The ________ [two words] is a well-known set of soft-bodied organisms living just before the Cambrian period,which probably includes at least simple animals and early bilaterians.
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VerifiedEdiacara biota
Molecular analyses suggest that the major lineages of animals diverged hundreds of millions of years before their first known appearances in the fossil record.Some scientists propose that the reason for this discrepancy is that the earliest animals were small and larval-like,leaving no trace in the fossil record.Generate an alternative hypothesis that explains this discrepancy,and suggest how the two hypotheses could plausibly be tested.
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Answered by Examlex AI CopilotAn alternative hypothesis to explain the discrepancy between molecular analyses and the fossil record could be that the early animals were soft-bodied and lacked the hard parts necessary for fossilization. This hypothesis suggests that the lack of fossil evidence is not due to the size or larval-like nature of the early animals, but rather their lack of preservation potential.
To test the first hypothesis, scientists could conduct further molecular analyses on a wider range of animal species to refine the divergence dates and compare them to the fossil record. They could also look for potential larval forms in the fossil record that may have been previously overlooked.
To test the alternative hypothesis, researchers could focus on areas with exceptional preservation conditions, such as Lagerstätten deposits, to search for soft-bodied early animal fossils. They could also use advanced imaging techniques, such as CT scanning, to examine fossil specimens for evidence of soft tissues that may not be visible to the naked eye.
By testing both hypotheses, scientists can work towards a better understanding of the early divergence and evolution of animals, and potentially reconcile the discrepancies between molecular and fossil evidence.
David Raup and Jack Sepkoski showed that rates of background extinction have been slowly declining in the animal kingdom throughout the Phanerozoic era.Compare and contrast two possible explanations as to why these rates are declining.
(37) Answered by Examlex AI CopilotOne possible explanation for the declining rates of background extinction throughout the Phanerozoic era is the concept of ecological stability. As ecosystems become more established and diverse over time, they may become more resilient to environmental changes and disruptions. This increased stability could lead to a decrease in the overall rate of extinction, as species are better able to adapt and survive in their respective niches.
Another possible explanation is the idea of evolutionary adaptation. As species evolve and diversify over time, they may develop traits and characteristics that make them better suited to their environments and less susceptible to extinction. This process of natural selection could lead to a gradual decrease in the overall rate of extinction as species become better adapted to their surroundings.
These two explanations are not mutually exclusive and likely work in tandem to contribute to the declining rates of background extinction observed throughout the Phanerozoic era. Both ecological stability and evolutionary adaptation play important roles in shaping the long-term patterns of extinction in the animal kingdom.
The accompanying figure shows the results of Jackson and Cheetham's studies on fossil and living cheilostome bryozoans.What can you infer from these diagrams? 
(45) Imagine that you find a fossil skeleton of a Late Devonian vertebrate.Which feature would enable you to conclude that it was fully a tetrapod?
(32) Which of the following was NOT a likely consequence of the Chicxulub meteorite impact 65.5 million years ago?
(30) Trace fossils record the behavior of ancient organisms,but not necessarily their form; it is often difficult or impossible to link a given trace fossil with the precise species that made it.Nonetheless,trace fossils provide valuable data for reconstructing the history of life.Your textbook mentions that dinosaur trackways can be used to estimate living dinosaurs' speed.Generate another way in which trace fossils could contribute to paleontological studies even if the identities of their makers are unclear.
(30) An example of a plesiomorphy in the earliest fossil birds would include ________.
(30) Which well-known paleontologist created a global database of marine animal families to study changes in diversity through time?
(28) The expression "pull of the recent" refers to the fact that ________.
(28) The study of the fossilization process itself is called ________.
(35) We may be living in the middle of the sixth great mass extinction,as human activity directly and indirectly drives species to extinction.How might the study of past mass extinctions show us how the current extinction might play out? Can paleontology give us any information that might help us mitigate the effects of the current extinction?
(43) Rock layers right at the K-Pg boundary have enriched concentrations of the element iridium.This is significant for understanding the mass extinction that happened at the time,because ________.
(37) The relatively rapid appearance of animal phyla in the Cambrian period is correlated with a rise in ________ at the same time.
(34) Why is it inaccurate to refer to early synapsids as "mammal-like reptiles"?
(33) The range of shapes found among members of a taxon may be thought of as a multidimensional space called a(n)________.
(27) Hawaiian fruit flies descend from a single common ancestor that reached the islands and rapidly diversified into a wide range of ecological niches.This is a good example of ________.[two words]
(35) David Jablonski and colleagues found that species of bivalves with which of the following trait(s)persisted longer,and were less likely to die out,during times of background extinction?
(31) The accompanying figure shows the results of comparative analyses of two clades: the horseshoe crabs,and the king crabs and hermit crabs.What can you conclude from these diagram? 
(40) Which of the following is NOT one of the "Big Five" mass extinctions?
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