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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 ... [...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''. Paleontology is the study of fossils: their age, method of formation, and evolutionary significance. Specimens are usually considered to be fossils if they are over 10,000 years old. The oldest fossils are around 3.48 billion years old to 4.1 billion years old. Early edition, published online before print. The observation in the 19th century that certain fossils were associated with certain rock strata led to the recognition of a geological timescale and the relative ages of different fossils. The development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the absolu ... [...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. This single extant species, has effected 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. A genus ''Pelargopappus ''Pelargopappus'' is an extinct genus of raptor related to the secretarybird that lived in early Miocene France. Only one species, the type species ''P. magnus'' is officially recognized. A second species, ''P. schlosseri'' from the mid-and lat ...'' is known from Miocene deposits in Fran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Red King Hypothesis
The Red King hypothesis contrasts with the Red Queen hypothesis, where mutualistic and cooperative interactions favor the fitness of a set of individuals through slow evolution, as opposed to having competitive interactions or having an " arms race". The hypothesis posits that individuals from different communities can establish 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 The Black Queen hypothesis (BQH) is reductive evolution theory which seeks to explain how natural selection (as opposed to genetic drift) can drive gene loss. In a microbial community, different members may have genes which produce certain chemic ...), which avoid spending energy in competing and increasing their resilience over environmental stress. The types of interaction between species determine how fast they coev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Red Queen Hypothesis
The Red Queen 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 exti ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macroevolution
Macroevolution usually means the evolution of large-scale structures and traits that go significantly beyond the intraspecific variation found in microevolution (including speciation). In other words, macroevolution is the evolution of taxa above the species level (genera, families, orders, etc.). Macroevolution is often thought to require the evolution of completely new structures such as entirely new organs. However, fundamentally novel structures are not necessary for dramatic evolutionary change. For instance, the evolution of mammal diversity in the past 100 million years has not required any major innovation. All of this diversity can be explained by modification of existing organs. In most cases, macroevolution cannot be observed directly because numerous mutations are required for large-scale changes. Hence specific methods are required to study and prove it. However, in rare cases single mutations can cause dramatic change and thus serve as models for macro-evolutionary ... [...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 pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eunectes
''Eunectes'' is a genus of boas found in tropical South America commonly called anacondas. They are a semiaquatic group of snakes and include one of the largest snakes in the world, '' E. murinus'', the green anaconda. Four species are currently recognized. Origin The recent fossil record of ''Eunectes'' is relatives sparse compared to other vertebrates and other genera of snakes. The fossil record of the 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 grc, εὐνήκτης, eunēktēs, good swimmer. Distribution and habitat Found in tropical South America from Ecuador, Brazil, Colombia and Venezuela south to Argentina. Feeding All four species are aquatic snakes that prey on other aquatic animals, including fish, river fowl, and caiman. Videos exist of anacondas preying on domesti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elasmobranch
Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including sharks (superorder Selachii), rays, skates, and sawfish (superorder Batoidea). Members of this subclass are characterised by having five to seven pairs of gill clefts 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. It has been used by different authors as equivalent to Neoselachii (the clade including modern sharks and rays and their last common ancestor) or for al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') level. Biodiversity is not distributed evenly on Earth; it is usually 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 10% of earth's surface and contain about 90% of the world's species. Marine biodiversity is usually higher along coasts in the Western Pacific, where sea surface temperature is highest, and in the mid-latitudinal band in all oceans. There are latitudinal gradients in species diversity. Biodiversity generally tends to cluster in hotspots, and has been increasing through time, but will be likely to slow in the future as a primary result of deforestation. It encompasses the evolutionary, ecological, and cultural ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58See the 2014 version of the ICS geologic time scale million years ago. It is the second and most recent epoch of the Neogene Period in the . The Pliocene follows the Epoch and is followed by the Epoch. Prior to the 2009 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bivalvia
Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estim ... that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bivalves have no head and they lack some usual molluscan organs, like the radula and the odontophore. They include the 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. The majority are filter feeders. The gills have evolved into Ctenidium (mollusc), ctenidia, specialised organs for feeding and breathing. Most bivalves bury themselves in sediment, where they a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
