Subject:
All Disciplines Arts & Humanities Biology & Life Sciences Business & Economics Chemistry & Materials Science Computer Science & Mathematics Engineering Environmental & Earth Sciences Medicine & Pharmacology Physical Sciences Public Health & Healthcare Social Sciences
Sort:
Hottest Latest Alphabetical (A-Z) Alphabetical (Z-A)
Type:
All Topic Review Biography
Topic Review
Cretaceous–Paleogene Extinction Event
The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary (K–T) extinction,[lower-alpha 2] was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the exception of some ectothermic species such as the sea turtles and crocodilians, no tetrapods weighing more than 25 kilograms (55 pounds) survived. It marked the end of the Cretaceous period, and with it the end of the entire Mesozoic Era, opening the Cenozoic Era that continues today. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows high levels of the metal iridium, which is rare in the Earth's crust, but abundant in asteroids. As originally proposed in 1980 by a team of scientists led by Luis Alvarez and his son Walter, it is now generally thought that the K–Pg extinction was caused by the impact of a massive comet or asteroid 10 to 15 km (6 to 9 mi) wide, 66 million years ago, which devastated the global environment, mainly through a lingering impact winter which halted photosynthesis in plants and plankton. The impact hypothesis, also known as the Alvarez hypothesis, was bolstered by the discovery of the 180 km (112 mi) Chicxulub crater in the Gulf of Mexico's Yucatán Peninsula in the early 1990s, which provided conclusive evidence that the K–Pg boundary clay represented debris from an asteroid impact. The fact that the extinctions occurred simultaneously provides strong evidence that they were caused by the asteroid. A 2016 drilling project into the Chicxulub peak ring confirmed that the peak ring comprised granite ejected within minutes from deep in the earth, but contained hardly any gypsum, the usual sulfate-containing sea floor rock in the region: The gypsum would have vaporized and dispersed as an aerosol into the atmosphere, causing longer-term effects on the climate and food chain. In October 2019, researchers reported that the event rapidly acidified the oceans producing ecological collapse and, in this way as well, produced long-lasting effects on the climate, and accordingly was a key reason for the end-Cretaceous mass extinction. In January 2020, scientists reported new evidence that the extinction event was mostly a result of the meteorite impact and not volcanism. Other causal or contributing factors to the extinction may have been the Deccan Traps and other volcanic eruptions, climate change, and sea level change. A wide range of species perished in the K–Pg extinction, the best-known being the non-avian dinosaurs. It also destroyed a myriad of other terrestrial organisms, including some mammals, pterosaurs, birds, lizards, insects, and plants. In the oceans, the K–Pg extinction killed off plesiosaurs and mosasaurs and devastated teleost fish, sharks, mollusks (especially ammonites, which became extinct), and many species of plankton. It is estimated that 75% or more of all species on Earth vanished. Yet the extinction also provided evolutionary opportunities: In its wake, many groups underwent remarkable adaptive radiation — sudden and prolific divergence into new forms and species within the disrupted and emptied ecological niches. Mammals in particular diversified in the Paleogene, evolving new forms such as horses, whales, bats, and primates. The surviving group of dinosaurs were avians, ground and water fowl who radiated into all modern species of bird. Teleost fish, and perhaps lizards also radiated.
  • 9.0K
  • 03 Nov 2022
Topic Review
CRISPR, Livestock, Sustainable Food Production
The growing demand for animal source foods to feed people has been pushing the livestock industry to increase productivity, a tendency that will continue throughout this century. The challenge for the coming years is to increase the food supply to ensure equity in access to high quality food, while maintaining global sustainability including combating climate change, avoiding deforestation, and conserving biodiversity, as well as ensuring animal health and welfare. The question is, how do we produce more with less? Classical methods to enhance livestock productivity based on the improvement of animal health, nutrition, genetics, reproductive technologies and management have made important contributions; however, this is not going to be enough and thus disruptive approaches are required. Genome editing with CRISPR may be a powerful contributor to global livestock transformation. 
  • 1.0K
  • 28 Jun 2021
Topic Review
Criteria Air Pollutants
Criteria air Pollutants (CAP), or criteria pollutants, are a set of air pollutants that cause smog, acid rain, and other health hazards. CAPs are typically emitted from many sources in industry, mining, transportation, electricity generation and agriculture. In many cases they are the products of the combustion of fossil fuels or industrial processes.
  • 453
  • 20 Oct 2022
Topic Review
Critical Factors in Renewable Energy Generation
The factors influencing the development of renewable energy in the electrical power sector can be grouped into four main clusters: (i) economic factors, (ii) legal and policy factors, (iii) social acceptance factors, and (iv) adverse impacts of renewable energy projects on the ecological environment.
  • 6.0K
  • 16 Dec 2021
Topic Review
Critical Mineral Raw Materials
Since 2011, the European Commission assesses a 3-year list of Critical Raw Materials (CRMs) for the EU economy within its Raw Materials Initiative. To date, 14 CRMs were identified in 2011, 20 in 2014 and 27 in 2017. These materials are mainly used in energy transition and digital technologies.
  • 510
  • 25 Oct 2022
Topic Review
Crop Plants with Silicon Application
Silicon (Si) is present in soil mainly in three different phases such as solid, liquid, and adsorbed. Solid phases can be either amorphous or crystalline. Plants take up Si from the soil which impacts their growth and nutrient accumulation. It increases plant resistance to abiotic and biotic stresses such as drought, salinity, and heavy metal, diseases, and pest infestation.
  • 989
  • 29 Apr 2022
Topic Review
Crop Residue Management in India
Crop residue management choices should be measured on the premise of productivity, gain, and environmental impact. These criteria would overlap with those employed in the approach of ecological intensification for intensive crop production systems aiming to fulfill the increasing demand for food, feed, fiber, and fuel, while meeting acceptable standards of environmental quality.
  • 466
  • 02 Dec 2021
Topic Review
Crop Sustainability and Five Domains in Mediterranean Region
Most of the Mediterranean region has experienced frequent natural disasters, expanding population, increase in temperature, and increase in the surface of the Mediterranean Sea. Furthermore, the temperature in the Mediterranean area is rising 25% faster than the rest of the globe, and in the summer, it is warming 40% faster than the global average. Climate change can alter the food supply, restrict access to food, and degrade food quality. Temperature rises, changes in precipitation patterns, changes in severe weather events, and decreased water availability, for example, might all result in lower agricultural production. The fact that most Mediterranean nations rely on imported basic foodstuffs adds to the severity of the situation. Instability and insecurity of agricultural supply in the region might lead to massive population movement, transforming most Mediterranean nations into a global source of instability.
  • 676
  • 10 Nov 2022
Topic Review Peer Reviewed
Cross-Border Territorial Development through Geographical Indications: Gargano (Italy) and Dibër (Albania)
In a globalized context, characterized by dominant trends towards the homogenization of food products and taste, local and niche productions play a vital role in creating effective strategies of territorial development. Albanian food heritage is definitely one of the most various of the Western Balkans. The Ottoman domination and the Mediterranean position just in front of Italy led to an incredible mix of cultures and traditions. As Albania is a candidate to join the European Union, it has a stronger opportunity of protecting its excellent-quality food products with PDO and PGI marks. Moreover, Albania’s territory shares fundamental features with Gargano lakes, especially with relation to the county of Dibër, where Ulez and Shkopet lakes are located. Both the areas’ traditional food products are and can be an important factor of sustainable and participatory development, and the present contribution aims at exploring possible paths of territorial development at a cross-border level, in the framework of a sort of “dialogue” between the two regions through Geographical Indications (GIs). 
  • 657
  • 01 Dec 2022
Topic Review
Cryosphere
The cryosphere (from the Greek κρύος kryos, "cold", "frost" or "ice" and σφαῖρα sphaira, "globe, ball") is an all-encompassing term for those portions of Earth's surface where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers, ice caps, ice sheets, and frozen ground (which includes permafrost). Thus, there is a wide overlap with the hydrosphere. The cryosphere is an integral part of the global climate system with important linkages and feedbacks generated through its influence on surface energy and moisture fluxes, clouds, precipitation, hydrology, atmospheric and oceanic circulation. Through these feedback processes, the cryosphere plays a significant role in the global climate and in climate model response to global changes. The term deglaciation describes the retreat of cryospheric features. Cryology is the study of cryospheres.
  • 537
  • 15 Nov 2022
  • Page
  • of
  • 271
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Encyclopedia of Fungi
Encyclopedia of Digital Society, Industry 5.0 and Smart City
Video Production Service
Feedback