Portal:Mesozoic

The Archaea (/ɑːrˈkiːə/ (listen) or /ɑːrˈkeɪə/; singular archaeon) constitute a domain or kingdom of single-celled microorganisms. These microbes are prokaryotes, meaning that they have no cell nucleus or any other membrane-bound organelles within their cells.

The Archaea show many differences in their biochemistry from other forms of life, and so they are now classified as a separate domain in the three-domain system. So far, the Archaea have been further divided into four recognized phyla. Classification is still difficult, because the vast majority have never been studied in the laboratory.

Archaea and bacteria are quite similar in size and shape, but despite this visual similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes. Other aspects of archaean biochemistry are unique, such as their reliance on ether lipids in their cell membranes. Archaea use a much greater variety of sources of energy than eukaryotes: ranging from familiar organic compounds such as sugars, to ammonia, metal ions or even hydrogen gas. Salt-tolerant archaea use sunlight as an energy source, and other species of archaea fix carbon. Archaea reproduce asexually by binary fission, fragmentation, or budding.

Archaea are found in a broad range of habitats, includingsoils, oceans, marshlands and the human colon and navel. Archaea are now recognized as a major part of Earth's life and may play roles in both the carbon cycle and the nitrogen cycle. (see more...)

Paleontology or palaeontology (/ˌpeɪliɒnˈtɒlədʒi, ˌpæli-, -ən-/) is the scientific study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments (their paleoecology). As a "historical science" it attempts to explain causes rather than conduct experiments to observe effects. Paleontological observations have been documented as far back as the 5th century BC. The science became established in the 18th century as a result of Georges Cuvier's work on comparative anatomy, and developed rapidly in the 19th century. The term itself originates from Greek: παλαιός (palaios) meaning "old, ancient," ὄν, ὀντ- (on, ont-), meaning "being, creature" and λόγος (logos), meaning "speech, thought, study".

Paleontology lies on the border between biology and geology. It now uses techniques drawn from a wide range of sciences, including biochemistry, mathematics and engineering. Use of all these techniques has enabled paleontologists to discover much of the evolutionary history of life, almost all the way back to when Earth became capable of supporting life, about 3,800 million years ago. As knowledge has increased, paleontology has developed specialized sub-divisions, some of which focus on different types of fossil organisms while others study ecology and environmental history, such as ancient climates. Body fossils and trace fossils are the principal types of evidence about ancient life, and geochemical evidence has helped to decipher the evolution of life before there were organisms large enough to leave fossils. (see more...)

• ...that Polar dinosaurs could have walked to Australia, because during the early Cretaceous the continent of Australia was still linked to Antarctica?
• ... that the limestone quarries near Ein Yabrud in the Judean Mountains have produced the only fossils for the extinct snakes Pachyrhachis and Haasiophis?
• ... that the stegosaurid Miragaia had more neck vertebrae than almost all of the sauropod dinosaurs, known for their long necks?
• ... that the Jurassic crocodile relative Phyllodontosuchus had two types of teeth; one type resembled those of some herbivorous dinosaurs, indicating it may not have been a strict carnivore?
• ... that based on its skull anatomy, the small Early Jurassic crocodile relative Dibothrosuchus probably had a keen sense of hearing and was vocal like modern crocodiles?

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