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"ペラジックサメの初期ミオセンの絶滅"に関するコメント

  • 0Geological-Palaeontological Department, Natural History Museum Vienna, 1010 Vienna, Austria.
Clinical Neuroscience (new York, N.y.) +

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まとめ

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The Fossil Record 02:56

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The fossil record documents only a small fraction of all organisms that have ever inhabited Earth. Fossilization is a rare process, and most organisms never become fossils. Moreover, the fossil record only exhibits fossils that have been discovered. Nevertheless, sedimentary rock fossils of long-lived, abundant, hard-bodied organisms dominate the fossil record. These fossils offer valuable information, such as an organism's physical form, behavior, and age. Studying the fossil record helps...

Speciation Rates 01:07

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Overview

Speciation usually occurs over a long evolutionary time scale, during which the species may be isolated or continue to interact. If two emerging species start to interbreed, reproductive barriers may be weak, and gene flow can occur again. At this point, the selection of hybrids across the two populations may either stabilize the newly mixed group into a single population or reinforce the distinction between them as new species. Speciation may occur gradually or rapidly, and in some...

Conservation of Declining Populations 02:07

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Conservation of declining population focuses on ways of detecting, diagnosing, and halting a population decline. The approach uses methods to prevent populations from going extinct.

Conservation efforts often utilize scientific approaches to identify the reasons, or the agents, causing the population to decline. This approach then devises steps to remove, oppose, or neutralize the agents.

Conservation efforts may also introduce a test group to determine the probable cause of the decline. The...

What is Evolutionary History? 02:35

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Scientists record evolutionary history by analyzing fossil, morphological, and genetic data. The fossil record documents the history of life on Earth and provides evidence for evolution. However, both fossil and living organisms offer evidence that outlines Earth’s evolutionary history.

Phylogenetic trees illustrate the evolutionary relationships among these organisms. Scientists infer organisms’ common ancestry by evaluating shared morphological and genetic characteristics....

Habitat Fragmentation 02:31

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Habitat fragmentation describes the division of a more extensive, continuous habitat into smaller, discontinuous areas. Human activities such as land conversion, as well as slower geological processes leading to changes in the physical environment, are the two leading causes of habitat fragmentation. The fragmentation process typically follows the same steps: perforation, dissection, fragmentation, shrinkage, and attrition.

Perforation and dissection often occur during the initial stages of...

Threats to Biodiversity 01:50

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There have been five major extinction events throughout geological history, resulting in the elimination of biodiversity, followed by a rebound of species that adapted to the new conditions. In the current geological epoch, the Holocene, there is a sixth extinction event in progress. This mass extinction has been attributed to human activities and is thus provisionally called the Anthropocene. In 2019 the human population reached 7.7 billion people and is projected to comprise 10 billion by...