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Pull Of The Recent
The Pull of the Recent (POR) describes a phenomenon in which a combination of factors causes palaeontologists to overestimate diversity towards the present day. Biased preservation and sampling in the fossil record results in past biodiversity estimates to be lower with modern taxa being considered more diverse because present biodiversity is the best sampled. However the overall impact of the POR does not seem to be as large as originally thought. Marine invertebrates Sepkoski showed a global increase in marine biodiversity since the Cambrian. The cause of this, according to the Pull of the Recent, is due to favourable sampling by taphonomic processes of more recent fossils (time proportional to destruction of all geological records), as well as the ease of studying extant taxa. However, the impact of the POR has may not be as strong as previously thought and that this bias may diminishes with more detailed study. The POR was believed to distort the shape of marine invertebrate p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fossil Record
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood and DNA remnants. The totality of fossils is known as the ''fossil record''. Though the fossil record is incomplete, numerous studies have demonstrated that there is enough information available to give a good understanding of the pattern of diversification of life on Earth. In addition, the record can predict and fill gaps such as the discovery of '' Tiktaalik'' in the arctic of Canada. Paleontology includes the study of fossils: their age, method of formation, and evolutionary significance. Specimens are sometimes considered to be fossils if they are over 10,000 years old. The oldest fossils are around 3.48 billion years to 4.1 billion years old. Early edition, published online before print. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sagittariidae
Sagittariidae is a family of raptor with one living species—the secretarybird (''Sagittarius serpentarius'') native to Africa—and a few fossil taxa. This single extant species has affected the fossil record of the group by ‘pulling’ the temporal range of the family to the present, an artifact called the Pull of the recent. German naturalists Otto Finsch and Gustav Hartlaub established the taxon name as a subfamily—Sagittariinae—in 1870. Although their term postdated Gypogeranidae of Vigors (1825) and Serpentariidae of Selys Longchamps (1842), the genus name ''Sagittarius'' (described in 1783) had priority over ''Gypogeranus'' Illiger, 1811 and ''Serpentarius'' Cuvier, 1798. Genera There are at least four genera: * †''Amanuensis'' Mourer-Chauviré, 2003 * †'' Amphiserpentarius'' Gaillard, 1908 * †'' Pelargopappus'' Stejneger, 1885 * '' Sagittarius'' Hermann,1783 The genus '' Pelargopappus'' is known from Miocene deposits in France. The genus ''Amanuensis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Red King Hypothesis
The Red King hypothesis contrasts with the Red Queen hypothesis, where Mutualism (biology), mutualistic and cooperative interactions favor the Fitness (biology), fitness of a set of individuals through Evolution, slow evolution, as opposed to having competitive interactions or having an "evolutionary arms race, arms race". The hypothesis posits that individuals from different communities can establish Biological interaction, positive interactions for long periods of time when there is a great benefit for both parties, also through mutual help, individuals from different species (communities) can share different tasks to build a niche (Black Queen hypothesis), which avoid spending energy in competing and increasing their resilience over environmental stress. The types of interaction between species determine how fast they Coevolution, coevolve: parasites and their hosts are thought to co-evolve more rapidly, while partners in a mutualistic relationship are thought to evolve more slow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Red Queen Hypothesis
The Red Queen's hypothesis is a hypothesis in evolutionary biology proposed in 1973, that species must constantly adapt, evolve, and proliferate in order to survive while pitted against ever-evolving opposing species. The hypothesis was intended to explain the constant (age-independent) extinction probability as observed in the paleontological record caused by co-evolution between competing species; however, it has also been suggested that the Red Queen hypothesis explains the advantage of sexual reproduction (as opposed to asexual reproduction) at the level of individuals,Bell, G. (1982). The Masterpiece Of Nature: The Evolution and Genetics of Sexuality. University of California Press, Berkeley, 378 pp. and the positive correlation between speciation and extinction rates in most higher taxa. Origin In 1973, Leigh Van Valen proposed the hypothesis as an "explanatory tangent" to explain the "law of extinction" known as "Van Valen's law", which states that the probability of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Punctuated Equilibrium
In evolutionary biology, punctuated equilibrium (also called punctuated equilibria) is a Scientific theory, theory that proposes that once a species appears in the fossil record, the population will become stable, showing little evolution, evolutionary change for most of its geological history. : ''Reprinted in'' * * This state of little or no morphological change is called ''stasis''. When significant evolutionary change occurs, the theory proposes that it is generally restricted to rare and geologic time scale, geologically rapid events of branching speciation called cladogenesis. Cladogenesis is the process by which a species splits into two distinct species, rather than one species gradually transforming into another. Punctuated equilibrium is commonly contrasted with phyletic gradualism, the idea that evolution generally occurs uniformly by the steady and gradual transformation of whole lineages (anagenesis). In 1972, paleontologists Niles Eldredge and Stephen Jay Goul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macroevolution
Macroevolution comprises the evolutionary processes and patterns which occur at and above the species level. In contrast, microevolution is evolution occurring within the population(s) of a single species. In other words, microevolution is the scale of evolution that is limited to intraspecific (within-species) variation, while macroevolution extends to interspecific (between-species) variation. The evolution of new species (speciation) is an example of macroevolution. This is the common definition for 'macroevolution' used by contemporary scientists. However, the exact usage of the term has varied throughout history. Macroevolution addresses the evolution of species and higher taxonomic groups (genera, families, orders, etc) and uses evidence from phylogenetics, the fossil record, and molecular biology to answer how different taxonomic groups exhibit different species diversity and/or morphological disparity. Origin and changing meaning of the term After Charles Darwin p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Push Of The Past
The push of the past is a type of survivorship bias associated with evolutionary diversification when extinction is possible. Groups that survive a long time are likely to have “got off to a flying start”, and this statistical bias creates an illusion of a true slow-down of diversification rate through time. Birth–Death modelling in evolutionary studies The evolutionary processes of speciation and extinction can be modelled with a stochastic “ birth–death model” (BDM), which is an important component in the study of macroevolution. A BDM assigns each species a certain probability of splitting (\lambda) or going extinct (\mu) per interval of time. This gives rise to an exponential distribution, with the number of species in a particular clade ''N'' at any time ''t'' given by N_= N_e^, although this expression only gives the expected value when N and t are large (see below). In the special case of there being no extinction, this simplifies to the so-called " Yule pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eunectes
Anacondas or water boas are a group of large boas of the genus ''Eunectes''. They are a semiaquatic group of snakes found in tropical South America. Three to five extant and one extinct species are currently recognized, including one of the largest snakes in the world, ''E. murinus'', the green anaconda. Description Although the name applies to a group of snakes, it is often used to refer only to one species, in particular, the common or green anaconda (''Eunectes murinus''), which is the largest snake in the world by weight, and the second longest after the reticulated python. Origin The recent fossil record of ''Eunectes'' is relatively sparse compared to other vertebrates and other genera of snakes. The fossil record of this group is effected by an artifact called the Pull of the Recent. Fossils of recent ancestors are not known, so the living species 'pull' the historical range of the genus to the present. Etymology The name ''Eunectes'' is derived from . The Sout ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elasmobranch
Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including modern sharks ( division Selachii), and batomorphs (division Batomorphi, including rays, skates, and sawfish). Members of this subclass are characterised by having five to seven pairs of gill slits opening individually to the exterior, rigid dorsal fins and small placoid scales on the skin. The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The details of this jaw anatomy vary between species, and help distinguish the different elasmobranch clades. The pelvic fins in males are modified to create claspers for the transfer of sperm. There is no swim bladder; instead, these fish maintain buoyancy with large livers rich in oil. The definition of the clade is unclear with respect to fossil chondrichthyans. Some authors consider it as equivalent to Neoselachii (the crown group clade including modern sharks, rays, and all o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biodiversity
Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distributed evenly on Earth. It is greater in the tropics as a result of the warm climate and high primary productivity in the region near the equator. Tropical forest ecosystems cover less than one-fifth of Earth's terrestrial area and contain about 50% of the world's species. There are latitudinal gradients in species diversity for both marine and terrestrial taxa. Since Abiogenesis, life began on Earth, six major mass extinctions and several minor events have led to large and sudden drops in biodiversity. The Phanerozoic aeon (the last 540 million years) marked a rapid growth in biodiversity via the Cambrian explosion. In this period, the majority of Multicellular organism, multicellular Phylum, phyla first appeared. The next 400 mil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58See the 2014 version of the ICS geologic time scale million years ago (Ma). It is the second and most recent epoch of the Neogene Period in the Cenozoic, Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch. Prior to the 2009 revision of the geologic time scale, which placed the four most recent major glaciations entirely within the Pleistocene, the Pliocene also included the Gelasian Stage, which lasted from 2.59 to 1.81 Ma, and is now included in the Pleistocene. As with other older geologic periods, the Stratum, geological strata that define the start and end are well-identified but the exact dates of the start a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bivalvia
Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consisting of a hinged pair of half-bivalve shell, shells known as valve (mollusc), valves. As a group, bivalves have no head and lack some typical molluscan organs such as the radula and the odontophore. Their gills have evolved into ctenidium (mollusc), ctenidia, specialised organs for feeding and breathing. Common bivalves include clams, oysters, Cockle (bivalve), cockles, mussels, scallops, and numerous other family (biology), families that live in saltwater, as well as a number of families that live in freshwater. Majority of the class are benthic filter feeders that bury themselves in sediment, where they are relatively safe from predation. Others lie on the sea floor or attach themselves to rocks or other h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
