Cretaceous-paleogene
Cretaceous-paleogene - Related Videos
06:48
Extinction - Student Protocol
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2019
Diversity and Extinction during the Paleogene Epoch ExpandBegin this procedure by reading the extinction reading supplement that has been printed out for you. NOTE: Alternatively, you may download the reading supplement at the link below. Click here to download the extinction reading supplement Using the information contained in the extinction reading supplements pertaining to the taxa of interest and the Chicxulub impact event, make predictions for each taxon listed in Table 1. Consider...
05:25
Extinction - Concepts
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2019
The History of Life on Earth Fossils of organisms that were different from anything alive today had been documented as early as the 17th century, but it was not until the early 19th century that scientists began to recognize that the successive layers of fossil bearing rocks were like successive pages in the history of life on earth. Although this recognition gave rise to the birth of the field of paleontology, the idea of complete global extinction of a species had yet to be fully accepted. At...
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The impact mechanism operated through several linked environmental changes. Dust, aerosols, and gases entered the atmosphere, reduced incoming sunlight, disrupted climate, and impaired photosynthesis. Lower photosynthetic activity would undermine the biological energy base that supports food webs, helping explain why the event affected organisms across ecosystems rather than only species directly exposed to the impact.
Volcanic activity may have contributed to the biological crisis, but the overview identifies the Chicxulub impact as the primary cause scientists link to the extinction. This distinction matters because it separates a strongly supported main driver from an additional environmental influence. Considering both processes allows researchers to interpret the transition as a complex crisis while preserving the central role of impact-driven atmospheric and climatic disruption.
The extinction removed many species, including non-avian dinosaurs, but it did not eliminate all life. Surviving mammals, birds, and other organisms encountered ecological opportunities as food webs were reorganized. These changes help biologists connect a severe biological crisis with longer-term evolutionary change, because altered ecosystems could influence the subsequent history of surviving groups.
Researchers can treat the boundary as a reference point for examining biological change before and after the extinction. The comparison centers on which species disappeared, which groups survived, and how food webs were reshaped. This approach links the immediate pattern of species loss with later ecosystem recovery and helps distinguish extinction effects from the longer-term consequences of ecological reorganization.
It shows that a mass extinction can operate through ecosystem-wide disruption rather than through a single, isolated loss of species. Reduced sunlight, climate disruption, and impaired photosynthesis affected conditions supporting food webs, while the disappearance of roughly three-quarters of species demonstrates the crisis's scale. The event therefore connects environmental change with widespread biodiversity loss.
Biology uses this transition to examine how extinction, survival, recovery, and evolution are connected. Its aftermath created ecological opportunities for mammals, birds, and other surviving organisms, making the boundary useful for studying how communities change after severe biodiversity loss. It also supports analysis of food-web reorganization and the long-term effects of environmental disruption on living systems.