|
Atavism
In biology, an atavism is a modification of a biological structure whereby an ancestral genetic trait reappears after having been lost through evolutionary change in previous generations. Atavisms can occur in several ways; one of which is when genes for previously existing phenotypic features are preserved in DNA, and these become expressed through a mutation that either knocks out the dominant genes for the new traits or makes the old traits dominate the new one. A number of traits can vary as a result of shortening of the fetal development of a trait (neoteny) or by prolongation of the same. In such a case, a shift in the time a trait is allowed to develop before it is fixed can bring forth an ancestral phenotype. Atavisms are often seen as evidence of evolution. In social sciences, atavism is the tendency of reversion. For example, people in the modern era reverting to the ways of thinking and acting of a former time. The word ''atavism'' is derived from the Latin ''ata ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evidence Of Common Descent
Evidence of common descent of living organisms has been discovered by scientists researching in a variety of disciplines over many decades, demonstrating that all life on Earth comes from a single ancestor. This forms an important part of the evidence on which evolutionary theory rests, demonstrates that evolution does occur, and illustrates the processes that created Earth's biodiversity. It supports the modern evolutionary synthesis—the current scientific theory that explains how and why life changes over time. Evolutionary biologists document evidence of common descent, all the way back to the last universal common ancestor, by developing testable predictions, testing hypotheses, and constructing theories that illustrate and describe its causes. Comparison of the DNA genetic sequences of organisms has revealed that organisms that are phylogenetically close have a higher degree of DNA sequence similarity than organisms that are phylogenetically distant. Genetic fragments ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prothorax
The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on each side. The prothorax never bears wings in extant insects (except in some cases of atavism), though some fossil groups possessed wing-like projections. All adult insects possess legs on the prothorax, though in a few groups (e.g., the butterfly family Nymphalidae) the forelegs are greatly reduced. In many groups of insects, the pronotum is reduced in size, but in a few it is hypertrophied, such as in all beetles (Coleoptera). In most treehoppers (family Membracidae, order Hemiptera), the pronotum is expanded into often fantastic shapes that enhance their camouflage or mimicry. Similarly, in the Tetrigidae, the pronotum is extended backward to cover the flight wings, supplanting the function of the tegmina. See also *Glossary of en ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation tends to exist within any given population as a result of genetic mutation and recombination. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or more rare within a population. The evolutionary pressures that determine whether a characteristic is common or rare within a population constantly change, resulting in a change in heritable characteristics arising over successive generations. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms, and molecules. The theory of evol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vestigial Tail
The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds. While tails are primarily a feature of vertebrates, some invertebrates including scorpions and springtails, as well as snails and slugs, have tail-like appendages that are sometimes referred to as tails. Tailed objects are sometimes referred to as "caudate" and the part of the body associated with or proximal to the tail are given the adjective "caudal". Function Animal tails are used in a variety of ways. They provide a source of locomotion for fish and some other forms of marine life. Many land animals use their tails to brush away flies and other biting insects. Most canines use their tails to comunicate mood and intention . Some species, including cats and kangaroos, use their tails for balance; and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tubal Pregnancy With Embryo
Tubal ( he, תֻבָל, ''Ṯuḇāl'', ), in Genesis 10 (the "Table of Nations"), was the name of a son of Japheth, son of Noah. He is known to be the father of the Caucasian Iberians (ancestors of the Georgians) according to primary sources. Later, Saint Jerome refashioned the Caucasian Iberia (Georgia) into the Iberian Peninsula (Western Europe) and Isidore of Seville consolidated this mistake. Modern scholarship Modern scholarship has identified the biblical Tubal with Tabal, an Anatolian state and region mentioned in Assyrian sources. Tabal was a post-Hittite Luwian state in Asia Minor in the 1st millennium BC. Its neighbours, the Mushki, are traditionally associated with Meshech. Some historians further connect Tabal and Tubal with the tribe on the Black Sea coast later known to the Greeks as Tibareni, although this connection is uncertain. The Tibareni and nearby tribes, the ''Chalybes'' (Khalib/Khaldi) and the Mossynoeci (''Mossynoikoi'' in Greek), were sometimes consider ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Limbless Vertebrate
Many vertebrates have evolved limbless, limb-reduced, or apodous forms. Reptiles have on a number of occasions evolved into limbless forms – snakes, amphisbaenia, and legless lizards (limb loss in lizards has evolved independently several times, examples include the families Pygopodidae and Dibamidae and species of '' Isopachys'', '' Anguis'', and '' Ophisaurus)''. The same is true of amphibians – caecilians, Sirenidae (a clade of salamanders that are limbless except for atrophied front limbs), Amphiumidae (a clade of salamander with extremely atrophied limbs that appear non-functional) and at least three extinct groups ( Aïstopoda, Lysorophia, and Adelospondyli). Larval amphibians, tadpoles, are also often limbless. Legless forms of reptiles and amphibians probably evolved so as to be able to move underground or in water more easily. Some analyses suggest that elongation and undulatory locomotion (slithering) evolved first, before limb loss. The debate about the or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parthenogenesis
Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development of embryos occur in a gamete (egg or sperm) without combining with another gamete (e.g., egg and sperm fusing). In animals, parthenogenesis means development of an embryo from an unfertilized egg cell. In plants, parthenogenesis is a component process of apomixis. In algae, parthenogenesis can mean the development of an embryo from either an individual sperm or an individual egg. Parthenogenesis occurs naturally in some plants, algae, invertebrate animal species (including nematodes, some tardigrades, water fleas, some scorpions, aphids, some mites, some bees, some Phasmatodea and parasitic wasps) and a few vertebrates (such as some fish, amphibians, reptiles and birds). This type of reproduction has been induced artificiall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oribatida
Oribatida (formerly Cryptostigmata), also known as oribatid mites, moss mites or beetle mites, are an order of mites, in the "chewing Acariformes" clade Sarcoptiformes. They range in size from . There are currently 12,000 species that have been identified, but researchers estimate that there may be anywhere from 60,000 to 120,000 total species. Oribatid mites are by far the most prevalent of all arthropods in forest soils, and are essential for breaking down organic detritus and distributing fungi. Oribatid mites generally have low metabolic rates, slow development and low fecundity. Species are iteroparous with adults living a relatively long time; for example, estimates of development time from egg to adult vary from several months to two years in temperate forest soils. Oribatid mites have six active instars: prelarva, larva, three nymphal instars and the adult. All these stages after the prelarva feed on a wide variety of material including living and dead plant and fungal m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dewclaw
A dewclaw is a digit – vestigial in some animals – on the foot of many mammals, birds, and reptiles (including some extinct orders, like certain theropods). It commonly grows higher on the leg than the rest of the foot, such that in digitigrade or unguligrade species it does not make contact with the ground when the animal is standing. The name refers to the dewclaw's alleged tendency to brush dew away from the grass.Danziger, D., & McCrum, M. (2008). ''The Thingummy: A book about those everyday objects you just can't name''. London: Doubleday. On dogs and cats the dewclaws are on the inside of the front legs, similarly to a human's thumb, which shares evolutionary homology. Although many animals have dewclaws, other similar species do not, such as horses, giraffes and the African wild dog. Dogs Dogs almost always have dewclaws on the inside of the front legs and occasionally also on the hind legs. Unlike front dewclaws, rear dewclaws tend to have little bone or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae. Their blood is not totally contained in vessels; some circulates in an open cavity known as the haemocoel. Insects are the most diverse group of animals; they include more than a million described species and represent more than half of all known living organisms. The total number of extant species is estimated at between six and ten million; In: potentially over 90% of the animal life forms on Earth are insects. Insects may be found in nearly all environments, although only a small number of species reside in the oceans, which are dominated by another arthropod group, crustaceans, which recent research has indicated insects are nested within. Nearly all insects hatch from eggs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cetacean
Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel themselves through the water with powerful up-and-down movement of their tail which ends in a paddle-like fluke, using their flipper-shaped forelimbs to maneuver. While the majority of cetaceans live in marine environments, a small number exclusively reside in brackish water or fresh water. Having a cosmopolitan distribution, they can be found in some rivers and all of Earth's oceans, and many species inhabit vast ranges where they migrate with the changing of the seasons. Cetaceans are famous for their high intelligence and complex social behaviour as well as for the enormous size of some of the group's members, such as the blue whale which reaches a maximum confirmed length of 29.9 meters (98 feet) and a weight of 173 tonnes (190 short tons ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phasmatodea
The Phasmatodea (also known as Phasmida, Phasmatoptera or Spectra) are an order of insects whose members are variously known as stick insects, stick-bugs, walking sticks, stick animals, or bug sticks. They are also occasionally referred to as Devil's darning needles, although this name is shared by both dragonflies and crane flies. They can be generally referred to as phasmatodeans, phasmids, or ghost insects, with phasmids in the family Phylliidae called leaf insects, leaf-bugs, walking leaves, or bug leaves. The group's name is derived from the Ancient Greek ', meaning an apparition or phantom, referring to their resemblance to vegetation while in fact being animals. Their natural camouflage makes them difficult for predators to detect; still, many species have one of several secondary lines of defense in the form of startle displays, spines or toxic secretions. Stick insects from the genera '' Phryganistria'', '' Ctenomorpha'', and '' Phobaeticus'' include the world's l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
