HMS Beagle, from an 1841 watercolour by Owen Stanley. Charles Darwin's work during the Beagle expedition let him study at first hand geology, fossils and a multitude of living organisms as well as meeting native peoples. He methodically collected an enormous number of specimens, many new to science, which established his reputation as a naturalist and made him one of the precursors of ecology.

The range of evidence of evolution show us how evolution has taken place, and what natural selection has to explain. HMS Beagle (1841 watercolor by Owen Stanley) The two-dimensional work of art depicted in this image is in the public domain in the United States and in those countries with a copyright term of life of the author plus 100 years. ... HMS Beagle (1841 watercolor by Owen Stanley) The two-dimensional work of art depicted in this image is in the public domain in the United States and in those countries with a copyright term of life of the author plus 100 years. ... In his lifetime Charles Darwin gained international fame as an influential scientist examining controversial topics. ... HMS Beagle (centre) from an 1841 watercolour by Owen Stanley, painted during the third voyage while surveying Australia. ... A fossil Ammonite Fossils (from Latin fossus, literally having been dug up) are the mineralized or otherwise preserved remains or traces (such as footprints) of animals, plants, and other organisms. ... The word ecology is often used in common parlance as a synonym for the natural environment or environmentalism. ... A speculative phylogenetic tree of all living things, based on rRNA gene data, showing the separation of the three domains, bacteria, archaea and eukaryotes. ... Natural Selection is the phrase Charles Darwin used in 1859 in his book The Origin of Species to name the natural process he proposed to be responsible for the origin of new species and the adaptation of organisms to their environments. ...

Fossils are important for estimating when various lineages developed. As fossilization is an uncommon occurrence, usually requiring hard parts (like bone) and death near a site where sediments are being deposited, the fossil record only provides sparse and intermittent information about the evolution of life. Fossil evidence of early life is sparse before the evolution of organisms with hard body parts, such as shell, bone, and teeth, but exists in the form of ancient microfossils and the fossilization of ancient burrows and a few soft-bodied organisms. A fossil Ammonite Fossils (from Latin fossus, literally having been dug up) are the mineralized or otherwise preserved remains or traces (such as footprints) of animals, plants, and other organisms. ... Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ... Ever since recorded history began, and probably before, people have found pieces of rock and other hard material with indentations from the remains of dead organisms. ...

Comparison of the genetic sequence of organisms reveals that organisms that are phylogenetically close have a higher degree of sequence similarity than organisms that are phylogenetically distant. Further evidence for common descent comes from genetic detritus such as pseudogenes, regions of DNA which are orthologous to a gene in a related organism, but are no longer active and appear to be undergoing a steady process of degeneration. In biology, phylogenetics (Greek: phylon = tribe, race and genetikos = relative to birth, from genesis = birth) is the study of evolutionary relatedness among various groups of organisms (e. ... A pseudogene is a nucleotide sequences that is similar to a normal gene, but is not expressed as a functional protein. ... Orthologs are genes in different species which evolved from a common ancestral gene. ...

Since metabolic processes do not leave fossils, research into the evolution of the basic cellular processes is also done largely by comparison of existing organisms. Many lineages diverged at different stages of development, so it is theoretically possible to determine when certain metabolic processes appeared by comparing the traits of the descendants of a common ancestor. Santorio Santorio (1561-1636) in his steelyard balance, from Ars de statica medecina, first published 1614 Metabolism (from μεταβολισμος (metabolismos)) is the biochemical modification of chemical compounds in living organisms anggjgjhnd cell (b). ...

Evidence from palaeontology

Figure 1: Insect trapped in resin.

When organisms die, they are often decomposed rapidly or consumed by scavengers, leaving no permanent evidences of their existence. Occasionally, some organisms become preserved in some ways. The preserved remains or traces of organisms from a past geological age embedded in rocks by natural processes are called fossils. They are extremely important as they provide direct evidence of evolution and detailed information on the evolutionary history of life on Earth. Palaeontology is the study of past life on the Earth based on fossil records and their relations to different geological time and geological layers. Download high resolution version (980x1360, 144 KB) Resin This image shows resin with an insect (an ant?). Photographer André Karwath aka Aka Date 2005-04-23 License GNU FDL Camera data Camera Nikon D70 Lens Tamron SP AF 90mm/2. ... Download high resolution version (980x1360, 144 KB) Resin This image shows resin with an insect (an ant?). Photographer André Karwath aka Aka Date 2005-04-23 License GNU FDL Camera data Camera Nikon D70 Lens Tamron SP AF 90mm/2. ... Decomposition is the reduction of bodies and other formerly living organisms into simpler forms of matter; and most particularly to the fate of the body, after death. ... It has been suggested that this article or section be merged with consumption (economics). ... Harvestman eating the tail of a five-lined skink The word scavenger, in zoology, refers to animals that consume already dead organic life-forms. ... // The geological time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of the Earth. ... Sedimentary, volcanic, plutonic, metamorphic rock types of North America. ... This timeline of evolution of life outlines the major events in the development of life on the planet Earth. ... Earth is the third planet in the solar system. ... A paleontologist carefully chips rock from a column of dinosaur vertebrae. ...

For fossilization to take place, the traces and remains of organisms must be quickly buried so that weathering and decomposition did not occur. Skeletal structures or other hard parts of the organisms are the most commonly occurring form of fossilized remains. There are also some trace "fossils" showing moulds, cast or imprints of some previous organisms, Moldy cream cheese Molds (British English: moulds) are various fungi that cover surfaces as fluffy mycelium and usually produce masses of asexual, sometimes sexual spores. ...

As an animal dies, the organic materials gradually decay away, such that the bones become porous. If the animal is subsequently buried in mud, mineral salts will infiltrate into the bones and gradually fill up the pores. The bones will harden into stones and are preserved forever as fossils. This process is known as petrification. If dead animals are covered by wind-blown sand, and if the sand is subsequently turned into mud by heavy rain or floods, the same process of mineral infiltration may occur. Apart from petrification, the dead bodies of organisms may be well preserved in oil, in ice, in hardened resin of coniferous trees (amber, Fig. 1), in tar, or in anaerobic, acidic peat. Sometimes, fossilisation can be a trace, an impression of a form, for example, a leaf or a footprint, which is made in layers that then harden. Grays illustration of a human femur, a typically recognized bone. ... In computer gaming, a MUD (Multi-User Dungeon or Domain or Dimension) is a multi-player computer game that combines elements of role-playing games, hack and slash style computer games and social instant messaging chat rooms. ... Minerals are natural compounds formed through geological processes. ... In geology, petrifaction or petrification is the process by which organic material is converted into stone or a similar substance. ... Patterns in the sand Sand is an example of a class of materials called granular matter. ... Rain falling For other uses see Rain (disambiguation). ... Look up Flood in Wiktionary, the free dictionary. ... Preservation is a broad term, applying in several areas where items are preserved or conserved in some manner. ... Natural olive oil Synthetic motor oil Oil is a generic term for a chemical compound that is not miscible with water, and is in its liquid state at common ambient temperatures. ... Frozen Waterfall in the Rhön mountains A natural, 4 tonne, block of ice on a beach in Iceland Ice can refer any of the 14 known solid phases of water. ... Insect trapped in resin. ... Orders & Families Cordaitales † Pinales   Pinaceae - Pine family   Araucariaceae - Araucaria family   Podocarpaceae - Yellow-wood family   Sciadopityaceae - Umbrella-pine family   Cupressaceae - Cypress family   Cephalotaxaceae - Plum-yew family   Taxaceae - Yew family Vojnovskyales † Voltziales † The conifers, division Pinophyta, are one of 13 or 14 division level taxa within the Kingdom Plantae. ... Amber pendants. ... Look up Anaerobic in Wiktionary, the free dictionary. ... For alternative meanings see acid (disambiguation). ... Peat in Lewis, Scotland Peat is an accumulation of partially decayed vegetation matter. ... It has been suggested that this article or section be merged with Tracing. ...

Fossil records

Figure 2: Fossil trilobite. Trilobites were hard-shelled animals, related to living crabs and shrimps, and first appeared in significant numbers 500 mya and died out 250 mya. Evidence suggests that they changed very little over many millions of years.

It is possible to find out how a particular group of organisms evolved by arranging its fossil records in a geological sequence. Such a sequence can be worked out because fossils are mainly found in sedimentary rock. Sedimentary rock is formed by layers of silt or mud on top of each other. Thus the resulting rock contains a series of horizontal layers or strata. Each layer contains fossils which are typical for that time period when they were laid down. The lowest strata contain the oldest rock with the earliest fossils while the highest strata contain the youngest rock with recent fossils. Download high resolution version (878x1041, 124 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (878x1041, 124 KB) Wikipedia does not have an article with this exact name. ... Orders Agnostida Redlichiida Corynexochida Lichida Phacopida Proetida Asaphida Harpetida Ptychopariida doubtful order Nektaspida Trilobites are extinct arthropods in the class Trilobita. ... Sections Dromiacea Raninoida Heterotremata Thoracotremata The term crab is often applied to several different groups of short (nose to tail) decapod crustaceans with thick exoskeletons, but only members of the Brachyura are true crabs; other taxa, such as hermit crabs, porcelain crabs, king crabs, and horseshoe crabs are, despite superficial... Superfamilies and families Alpheoidea Alpheidae - snapping shrimps Barbouriidae Hippolytidae Ogyrididae Atyoidea Atyidae Bresilioidea Agostocarididae Alvinocarididae Bresiliidae Disciadidae Mirocarididae Campylonotoidea Bathypalaemonellidae Campylonotoidae Crangonoidea Crangonidae Glyphocrangonidea Galatheacaridoidea Galatheacarididae Nematocarcinoidea Eugonatonotidae Nematocarcinidae Rhynchocinetidae Xiphocarididae Oplophoroidea Oplophoridae Palaemonoidea Anchistioididae Desmocarididae Euryrhynchidae Gnathophyllidae Hymenoceridae Kakaducarididae Palaemonidae Typhlocarididae Pandaloidea Pandalidae Thalassocarididae Pasiphaeoidea Pasiphaeidae Procaridoidea Procarididae Processoidea... In astronomy, geology, and paleontology, mya is an acronym for million years ago and is used as a unit of time to denote length of time before the present. ... In biology and ecology, extinction is the ceasing of existence of a species or group of taxa. ... Two types of sedimentary rock: limey shale overlaid by limestone. ... Silt refers to soil or rock particles of a certain very small size range (see grain size). ... This article is about the geologic use of the term, for other uses see Stratum (disambiguation) Interstate road cut through limestone and shale strata in eastern Tennessee In geology and related fields, a stratum (plural: strata) is a layer of rock or soil with internally consistent characteristics that distinguishes it...

A succession of animals and plants can also be seen from fossil records. Fossil evidence supports a theory of progressive increase in complexity of organisms. By studying the number and complexity of different fossils at different stratigraphic levels, it shows that: Succession is the act or process of following in order or sequence. ... Stratigraphy, a branch of geology, is basically the study of rock layers and layering (stratification). ...

• Older fossil-bearing rocks contain fewer types of fossilized organisms and they all have a simpler structure.
• Younger rocks contain a greater variety of fossils with increasingly complex structures.

In the past, the ages of various strata and the fossils found were roughly estimated by geologists. They did so, for instance, by estimating the time for the formation of sedimentary rock layer by layer. Today, by measuring the proportions of radioactive elements and stable element in a given rock, the ages of fossils can be precisely dated by scientists. This technique is known as radiometric dating. Throughout the fossil record, many species which appear at an early stratigraphic level disappear at a later level. This is interpreted in evolutionary terms as indicating the times at which species originated and became extinct. Geographical regions and climatic conditions have varied throughout the Earth’s history. Since organisms are adapted to particular environments, the constantly changing conditions may have favoured a mechanism for evolutionary change. Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ... A chemical element, often called simply element, is a chemical substance that cannot be divided or changed into other chemical substances by any ordinary chemical technique. ... Radiometric dating is a technique used to date materials based on a knowledge of the decay rates of naturally occurring isotopes, and the current abundances. ... Earth is the third planet in the solar system. ...

Evolutionary development of modern horse

Figure 3: Evolution of horse showing reconstruction of the fossil species obtained from successive rock strata. The foots diagrams are all front views of the left forefoot. The third metacarpal is shaded throughout. The teeth are shown in longitudinal section.

The horse provides one of the best examples of evolutionary history (phylogeny) based on an almost complete fossil record found in North American sedimentary deposits from the early Eocene to the present (Fig. 3). Image File history File links Download high resolution version (1146x1392, 351 KB) Evolution of horse File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (1146x1392, 351 KB) Evolution of horse File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Evolution of horse showing reconstruction of the fossil species obtained from successive rock strata. ... The metacarpus is the intermediate part of the hand skeleton that is located between the fingers distally and the carpus which forms the connection to the forearm. ... Binomial name Equus caballus Linnaeus, 1758 nugget For other uses, see Horse (disambiguation). ... In biology, phylogenetics (Greek: phylon = tribe, race and genetikos = relative to birth, from genesis = birth) is the study of evolutionary relatedness among various groups of organisms (e. ... World map showing North America A satellite composite image of North America. ... The Eocene epoch (56-34 Ma) is a major division of the geologic timescale and the second epoch of the Palaeogene period in the Cenozoic era. ...

Horse starts with a little animal called Hyracotherium which lived in North America in Eocene age about 54 million years ago and then spread across to Europe and Asia. Fossil remains of Hyracotherium obtained from Eocene rocks in North America show it to have differed from modern horse in three important respects: Europe is conventionally considered one of the seven continents of Earth which, in this case, is more a cultural and political distinction than a physiographic one, leading to various perspectives about Europes borders. ... World map showing the location of Asia. ...

• It was a small animal (like the size of a fox) lightly built and adapted for running;
• The limbs were short and slender and the feet elongated so that the digits were almost vertical. There were 4 digits in the forelimbs and 3 digits in the hindlimbs;
• The incisors were small and the molars had low crowns with rounded cusps covered in enamel.

The probable course of development of horses from Hyracotheium to Equus (modern horse) involved at least 12 genera and several hundred species. The major trends seen in the development of horse to changing environmental conditions and may be summarized as follows: // A Red Fox (Vulpes vulpes) A fox is a member of any of 27 species of small omnivorous canids. ... A forelimb is an anterior limb on an animals body. ... A hind limb is a posterior limb on an animal. ... Incisors are the first kind of tooth in heterodont mammals. ... A molar is the fourth kind of tooth in mammals. ... In common parlance, a cusp is an important moment usually regarded as a decision point upon which consequent events are determined. ... The word enamel can mean more than one thing: Tooth enamel Vitreous enamel Enamel (markup language) Enameled wire This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Equus is Latin for horse; it may refer to: Equus, the genus of horses and their close relatives. ... In biology, a genus (plural genera) is a taxonomic grouping. ... In biology, a species is the basic unit of biodiversity. ...

• increase in size (from 0.4m to 1.5m);
• lengthening of limbs and feet;
• reduction of lateral digits;
• increase in length and thickness of the third digit;
• increase in width of incisors;
• replacement of premolars by molars; and
• increases in tooth length, crown height of molars.

The fossils plants found in different strata show that the marshy, wooded country in which Hyracotherium lived was gradually replaced by a drier type. Survival now depended on the head being in an elevated position for gaining a good view of the surrounding countryside, and on a high turn of speed for escape from predators. Hence the increase in size and the replacement of the played-out foot by the hoofed foot. The drier, harder ground would make the original splayed-out foot unnecessary for support. The changes in the teeth can be explained by assuming that the diet changed from soft vegetation to grass. A dominant genus from each geological period has been selected to show the progressive development of the horse. However, it is important to note that there is no evidence that the forms illustrated are direct relatives of each other. Incisors are the first kind of tooth in heterodont mammals. ... The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. ... A molar is the fourth kind of tooth in mammals. ... Freshwater marsh in Florida In geography, a marsh is a type of wetland, featuring grasses, rushes, reeds, typhas, sedges, and other herbaceous plants (possibly with low-growing woody plants) in a context of shallow water. ... A tree trunk as found at the Veluwe, The Netherlands Wood derives from woody plants, notably trees but also shrubs. ... Look up country in Wiktionary, the free dictionary. ... Rural areas are sparsely settled places away from the influence of large cities and towns. ... Speed (symbol: v) is the rate of motion, or equivalently the rate of change of position, expressed as distance d moved per unit of time t. ... This snapping turtle is trying to make a meal of a Canada goose, but the goose is too wary. ... Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants, and is, by far, the most abundant biotic element of the biosphere. ... An area of grass-like plants Grass generally describes a monocotyledonous green plant characterized by slender leaves, called blades, which usually grow arching upwards from the ground. ... Kinship is a biological and/or familial relationship between two organisms. ...

Limitations

The fossil record is an important source for scientists when tracing the evolutionary history of organisms. However, because of limitations inherent in the record (see below), there are not fine-scales of intermediate forms between related groups of species. This lack of continuous fossils in the record is a major limitation in tracing the descent of biological groups. Furthermore, there are also much larger gaps between major evolutionary lineages. These gaps are often referred to as "missing links". A transitional fossil is the fossil remains of a creature that exhibits primitive traits in comparison with the more derived life-forms it is related to. ...

There is a gap of about 100 million years between the early Cambrian period and the later Ordovician period. The early Cambrian period was the period from which numerous fossil of sponges, cnidarians (e.g. corals), echinoderms (e.g. brittle stars), molluscs (e.g. snails) and arthropods (e.g. trilobites) are found. In the later Ordovician period, the first animal that really possessed the features of a fish (a vertebrate ) appeared. In other words, no fossils of an intermediate type between invertebrates and vertebrates have been found. The Cambrian is a major division of the geologic timescale that begins about 542 Ma (million years ago) at the end of the Proterozoic eon and ended about 488. ... The Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era. ... Classes Calcarea Hexactinellida Demospongiae The sponges or poriferans (from Latin porus pore and ferre to bear) are animals of the phylum Porifera. ... Classes Anthozoa - Corals and sea anemones Cubozoa - Sea wasps or box jellyfish Hydrozoa - Hydroids, hydra-like animals Scyphozoa - Jellyfish Cnidaria is a phylum containing some 10,000 species of relatively simple animals found exclusively in aquatic environments (most species are marine). ... Subclasses Alcyonaria Zoantharia See text for orders. ... Classes Asteroidea Blastoidea (extinct) Concentricycloidea Crinoidea Echinoidea Holothuroidea Ophiuroidea The echinoderms (Echinodermata) are a phylum of marine animals found in the ocean at all depths. ... Orders Oegophiurida Ophiurida Phrynophiurida Brittle stars are echinoderms, closely related to starfish. ... Classes Caudofoveata Aplacophora Polyplacophora - Chitons Monoplacophora Bivalvia - Bivalves Scaphopoda - Tusk shells Gastropoda - Snails and Slugs Cephalopoda - Squids, Octopuses, etc. ... The name snail applies to most members of the molluscan class Gastropoda that have coiled shells. ... Subphyla and Classes Subphylum Trilobitomorpha Trilobita - trilobites (extinct) Subphylum Chelicerata Arachnida - spiders,scorpions, etc. ... Orders Agnostida Redlichiida Corynexochida Lichida Phacopida Proetida Asaphida Harpetida Ptychopariida doubtful order Nektaspida Trilobites are extinct arthropods in the class Trilobita. ... Atlantic herring, Clupea harengus: one of the most abundant species of fish in the world. ... Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Invertebrate is a term coined by Jean-Baptiste Lamarck to describe any animal without a spinal column. ...

Some of the reasons for the incompleteness of fossil records are listed below:

• in general, the probability that an organism becomes fossilized after death is very low;
• some species or groups are less likely to become fossils because they are soft-bodied;
• some species or groups are less likely to become fossils because they live (and die) in conditions that are not favourable for fossilization to occur in;
• many fossils have been destroyed by land movements and erosion;
• some fossil remains are complete, but most are fragmentary;
• some evolutionary change occurs in populations at the limits of a species' ecological range, and as these populations are likely to be small the probability of fossilization is lower (see punctuated equilibrium);
• similarly, when environmental conditions change, the population of a species is likely to be greatly reduced, such that any evolutionary change induced by these new conditions is less likely to be fossilized;
• most fossils convey information about external form, but little or nothing about how the organism functioned (see Figure 4);
• using present-day biodiversity as a guide, this suggests that the fossils unearthed represent only a fraction of the large number of species of organisms that lived in the past;

Punctuated equilibrium (or punctuated equilibria) is a theory in evolutionary biology which states that most sexually reproducing species will show little to no evolutionary change throughout their history. ...

Living fossils

Main article: Living fossil

According to fossil records, some modern species of plants and animals are found to be almost identical to the species that lived in ancient geological ages. They are existing species of ancient lineage that have remained morphologically (and probably also physiologically) somewhat unchanged for a very long time. Consequently they are called living fossils. Living fossil is not actually a scientific term. It is a laymen's term. Living fossil really refers to the fact that laymen can sometimes easily recognize an extinct relative of a living species, even though that extinct species may be millions and in some cases hundreds of millions of years old. Living fossil was originally a journalist's rather hyperbolic nickname for a coelacanth; an organism we once thought to be extinct and found out later still existed. It would perhaps be better referred to as a Lazarus taxon. Living fossil is a term for any living species (or clade) of organism which closely resembles species otherwise only known from fossils and has no close living relatives. ... Comparative anatomy is the study of similarities and differences in organisms. ... Physiology (in Greek physis = nature and logos = word) is the study of the mechanical, physical, and biochemical functions of living organisms. ... Living fossil is a term for any living species (or clade) of organism which closely resembles species otherwise only known from fossils and has no close living relatives. ... In paleontology, a Lazarus taxon (plural taxa) is a taxon that disappears from one or more periods of the fossil record, only to appear again later. ...

Examples of living fossils that currently do not have many living species include the tuatara, the nautilus, the horseshoe crab or kingcrab, the coelacanth, the ginkgo and the metasequoia. Modern coelecanths (Latimeria spp.)do not look like their extinct relatives except superficially, however, they are both obviously coelcanths but they are in different genera. Binomial name Limulus polyphemus Linnaeus, 1758 The horseshoe crab (Limulus polyphemus) is an arthropod that is more closely related to spiders than crabs. ... Species Latimeria chalumnae Latimeria menadoensis Coelacanth (meaning hollow thorn, from the Greek coelia, κοιλιά (hollow) and acanthos, άκανθος (thorn)); IPA: ) is a species of fish and represents the oldest living lineage of jawed fish known to date. ... Binomial name Ginkgo biloba L. The Ginkgo (Ginkgo biloba), frequently misspelled as Gingko, and sometimes known as the Maidenhair Tree, is a unique tree with no close living relatives. ... Binomial name Metasequoia glyptostroboides Hu & Cheng The Dawn Redwood (Metasequoia glyptostroboides) is a fast growing tree in the conifer family Cupressaceae native to the Sichuan-Hubei region of China. ...

Evidence from comparative anatomy

Comparative study of the anatomy of groups of animals or plants reveals that certain structural features are basically similar. For example, the basic structure of all flowers consists of sepals, petals, stigma, style and ovary; yet the size, colour, number of parts and specific structure are different for each individual species. Comparative anatomy is the study of similarities and differences in the anatomy of organisms. ... Clivia miniata bears bright orange flowers. ... Flower of the Primrose Willowherb (Ludwigia octovalvis) showing petals and sepals A sepal is one member or part of the calyx of a flower. ... A petal is one member or part of the corolla of a flower. ... Look up stigma on Wiktionary, the free dictionary. ... Style may refer to genre, design, format, or appearance, including: Clothing: fashion Flower part: flower Music: music genre Sundial part: Gnomon Titles or honorifics: Style (manner of address) including Chinese courtesy names Web design: Cascading Style Sheets Writing: style guide and literary genre Linguistics: Variation in language use of an... Human female internal reproductive anatomy Ovaries are egg-producing reproductive organs found in female organisms. ... You may be looking for one of the following: Dimensions: length, width, height Clothing measurements such as shoe size or dress size Geometry Measurement Gelatinous or glutinous substance made from glue, wax, clay or similar Or the following command-line Unix tool: Size (Unix) This is a disambiguation page: a... Color is an important part of the visual arts. ... A number is an abstract entity that represents a count or measurement. ...

Homologous structures and divergent (adaptive) evolution

If widely separated groups of organisms are originated from a common ancestry, they are expected to have certain basic features in common. The degree of resemblance between two organisms should indicate how closely related they are in evolution: Several equivalence relations in mathematics are called similarity. ...

• Groups with little in common are assumed to have diverged from a common ancestor much earlier in geological history than groups which have a lot in common;
• in deciding how closely related two animals are, a comparative anatomist looks for structures which, though they may serve quite different functions in the adult, are fundamentally similar, suggesting a common origin. Such structures are described as homologous; and
• in cases where the similar structures serve different functions in adults, it may be necessary to trace their origin and embryonic development, to look for more similarities derived from a common ancestor.

When a group of organism share a homologous structure which is specialized to perform a variety of functions in order to adapt different environmental conditions and modes of life are called adaptive radiation. The gradual spreading of organisms with adaptive radiation is known as divergent evolution. Missing link is a term for a transitional form from the fossil record that connects an earlier species to a later one, or which connects two different species to an earlier ancestor. ... The structure of a thing is how the parts of it relate to each other, how it is put together. This contrast with process, which is how the thing works; but process requires a viable structure. ... The term adult describes any mature organism, but normally it refers to a human: one that is no longer a child / minor and is now either a man or a woman. ... Homology is an important concept in several disciplines: Homology (anthropology) in archaeology and anthropology. ... Adaptive radiation describes the rapid speciation of a single or a few species to fill many ecological niches. ... Divergent evolution occurs when a biological characteristic (such as a structure in two or more species or two or more genes) has a common evolutionary origin, but that characteristic has diverged over evolutionary time. ...

Pentadactyl limb

Figure 5a: The principle of homology illustrated by the adaptive radiation of the forelimb of mammals. All conform to the basic pentadactyl pattern but are modified for different usages. The third metacarpal is shaded throughout; the shoulder is crossed-hatched.

The pattern of limb bones called pentadactyl limb is an example of homologous structures (Fig. 5a). It is found in all classes of tetrapods (i.e. from amphibians to mammals). It can even be traced back to the fins of certain fossil fishes from which the first amphibians are thought to have evolved. The limb has a single proximal bone (humerus), two distal bones (radius and ulna), a series of carpals (wrist bones), followed by five series of metacarpals (palm bones) and phalanges (digits). Throughout the tetrapods, the fundamental structures of pentadactyl limbs are the same, indicating that they originated from a common ancestor. But in the course of evolution, these fundamental structures have been modified. They have become superficially different and unrelated structures to serve different functions in adaption to different environments and modes of life. This phenomenon is clearly shown in the forelimbs of mammals. For example: Image File history File links Download high resolution version (2222x1578, 768 KB) Created by Jerry Crimson Mann 06:25, 2 August 2005 (UTC). ... Image File history File links Download high resolution version (2222x1578, 768 KB) Created by Jerry Crimson Mann 06:25, 2 August 2005 (UTC). ... Homology is an important concept in several disciplines: Homology (anthropology) in archaeology and anthropology. ... In biology, dactyly is the arrangement of digits (fingers and toes) on the hands, feet, or sometimes wings of an animal. ... Groups See text. ... Orders Subclass Labyrinthodontia- extinct Subclass Lepospondyli- extinct Subclass Lissamphibia   Anura   Caudata   Gymnophiona Amphibians (class Amphibia) are a taxon of animals that include all tetrapods (four-legged vertebrates) that do not have amniotic eggs. ... Orders Subclass Multituberculata (extinct) Plagiaulacida Cimolodonta Subclass Palaeoryctoides (extinct) Subclass Triconodonta (extinct) Subclass Eutheria (includes extinct ancestors)/Placentalia (excludes extinct ancestors) Afrosoricida Artiodactyla Carnivora Cetacea Chiroptera Cimolesta (extinct) Creodonta (extinct) Condylarthra (extinct) Dermoptera Desmostylia (extinct) Embrithopoda (extinct) Hyracoidea Insectivora Lagomorpha Litopterna (extinct) Macroscelidea Mesonychia (extinct) Notoungulata (extinct) Perissodactyla Pholidota Plesiadapiformes... A fin is a surface used to produce lift and thrust or to steer while traveling in water, air, or other fluid media. ... The humerus is a long bone in the arm or fore-legs (animals) that runs from the shoulder to the elbow. ... RADIUS (Remote Authentication Dial In User Service) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ... The ulna (Elbow Bone) [Figs. ... In human anatomy, the carpal bones are the bones of the human wrist. ... In human anatomy, the wrist is the flexible and narrower connection between the forearm and the hand. ... A human hand typically has four fingers and a thumb. ... The Kataeb Party, better known in English-speaking countries as the Phalange, is a Lebanese political party that was first established as a Maronite nationalist youth movement in 1936 by Pierre Gemayel. ...

• In the monkey, the forelimbs are much elongated to form a grasping hand for climbing and swinging among trees.
• In the pig, the first digit is lost, and the second and fifth digits are reduced. The remaining two digits are longer and stouter than the rest and bear a hoof for supporting the body.
• In the horse, the forelimbs are adapted for support and running by great elongation of the third digit bearing a hoof.
• The mole has a pair of short, spade-like forelimbs for burrowing.
• The anteater uses its enlarged third digit for tearing down ant hills and termite nests.
• In the whale, the forelimbs become flippers for steering and maintaining equilibrium during swimming.
• In the bat, the forelimbs have turned into wings for flying by great elongation of four digits, and the hook-like first digit remains free for hanging from trees.

Cynomolgus Monkey at Batu Caves, Malaysia Monkeys, Mori Sosen (1749-1821) A monkey is any member of two of the three groupings of simian primates. ... Species Sus barbatus Sus bucculentus Sus cebifrons Sus celebensis Sus domesticus Sus heureni Sus philippensis Sus salvanius Sus scrofa Sus timoriensis Sus verrucosus Pigs are ungulates native to Eurasia collectively grouped under the genus Sus within the Suidae family. ... Mole may mean: Mole (animal), a small burrowing mammal Mole (espionage), a spy working under deep cover Mole (sauce), a Mexican sauce made from chile peppers and other spices, including chocolate Mole (skin marking), a small spot of darkened pigment on the skin Mole (unit) is the SI unit for... A burrow is a hole or tunnel dug into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion. ... Families Cyclopedidae Myrmecophagidae Anteaters are the 4 mammal species of the suborder Vermilingua commonly known for eating ants and termites. ... Subfamilies Dorylomorph subfamilies Apomyrminae Cerapachyinae Dorylinae Ecitoninae Formicomorph subfamilies: Aneuretinae Dolichoderinae Formicinae - e. ... Families Reticulitermes spp. ... Whales are the largest species of exclusively aquatic mammals, members of the order Cetacea, which also includes dolphins and porpoises. ... The term flipper has a number of meanings: Some animals, such as sea turtles, have limbs which are formed into flippers - see: flipper (anatomy). ... Suborders Megachiroptera Microchiroptera See text for families. ... A Laughing Gull on the beach in Atlantic City. ... Look up Hook in Wiktionary, the free dictionary. ... The coniferous Coast Redwood, the tallest tree species on earth. ...

Insect mouthparts

Figure 5b: Adaptive radiation of insect mouthparts: a, antennae; c, compound eye; lb, labrium; lr, labrum; md, mandibles; mx, maxillae.

The basic structures are the same which include a labrum (upper lip), a pair of mandibles, a hypopharynx (flor of mouth), a pair of maxillae and a labium. These structures are enlarged and modified, others are reduced and lost. The modifications enable the insects to exploit a variety of food materials (Fig. 5b): Image File history File links Download high resolution version (898x857, 240 KB) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (898x857, 240 KB) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Adaptive radiation describes the rapid speciation of a single or a few species to fill many ecological niches. ... Antennae (singular antenna), are the paired appendages connecting to the first (and in crustaceans also to the second) segment of the head of the members of all subphyla of the arthropods except Chelicerata. ... Compound eye of a dragonfly Compound eye of Antarctic krill as imaged by an electron microscope A compound eye is a visual organ found in certain arthropods such as insects and crustaceans. ... A labrum (Latin for lip) is the large vessel of a warm bath in the Roman thermae. ... The mandible (inferior maxillary bone) (together with the maxilla) is the largest and strongest bone of the face. ... In human anatomy, the hypopharynx is the bottom part of the pharynx, and is the part of the throat that connects to the esophagus. ... The maxillae are the largest bones of the face, except for the mandible, and form, by their union, the whole of the upper jaw. ... A labium (plural is labia) is any of four folds of tissue of the female external genitalia. ...

(A) Primitive state — biting and chewing: e.g. grasshopper. Strong mandibles and maxillae for manipulating food. Families Superfamily: Tridactyloidea Cylindrachaetidae Ripipterygidae Tridactylidae Superfamily: Tetrigoidea Tetrigidae Superfamily: Eumastacoidea Chorotypidae Episactidae Eumastacidae Euschmidtiidae Mastacideidae Morabidae Proscopiidae Thericleidae Superfamily: Pneumoroidea Pneumoridae Superfamily: Pyrgomorphoidea Pyrgomorphidae Superfamily: Acridoidea Acrididae Charilaidae Dericorythidae Lathiceridae Lentulidae Lithidiidae Ommexechidae Pamphagidae Pyrgacrididae Romaleidae Tristiridae Superfamily: Tanaoceroidea Tanaoceridae Superfamily: Trigonopterygoidea Trigonopterygidae Xyronotidae Grasshoppers are herbivorous insects of...

(B) Ticking and biting: e.g. honey bee. Labium long to lap up nectar; mandibles chew pollen and mould wax. The honeybee is a colonial insect that is often maintained, fed, and transported by farmers. ... In Greek mythology, nectar and ambrosia are the food of the gods. ... SEM image of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomoea purpurea), hollyhock (Sildalcea malviflora), lily (Lilium auratum), primrose (Oenothera fruticosa), and castor bean (Ricinus communis). ... Wax has traditionally referred to a substance that is secreted by bees (beeswax) and used by them in constructing their honeycombs. ...

(C) Sucking: e.g. butterfly. Labrum reduced; mandibles lost; maxillae long forming sucking tube. Families Superfamily Hesperioidea: Hesperiidae Superfamily Papilionoidea: Papilionidae Pieridae Nymphalidae Lycaenidae Riodinidae A butterfly is a flying insect of the order Lepidoptera, and belongs to one of the superfamilies Hesperioidea (the skippers) or Papilionoidea (all other butterflies). ...

(D) Piercing and sucking: e.g. female mosquito. Labrum and maxillae form tube; mandibles form piercing stylets; labrum grooved to hold other parts. Genera See text. ...

Analogous structures and convergent evolution

Figure 6: Inverted retina of vertebrate (left) and non-inverted retina of octopus (right)

Under similar environmental conditions, fundamentally different structures in different groups of organisms may undergo modifications to serve similar functions. This phenomenon is called convergent evolution. Similar structures, physiological processes or mode of life in organisms apparently bearing no close phylogenetic links but showing adaptions to perform the same functions are described as analogous, for example: Image File history File links Created by Jerry Crimson Mann 07:07, 2 August 2005 (UTC). ... Image File history File links Created by Jerry Crimson Mann 07:07, 2 August 2005 (UTC). ... This article or section does not cite its references or sources. ... Analogy is either the cognitive process of transferring information from a particular subject (the analogue or source) to another particular subject (the target), or a linguistic expression corresponding to such a process. ...

• Wings of bats, birds and insects;
• the jointed legs of insects and vertebrates;
• tall fin of fish, whale and lobster;
• eyes of the vertebrates and cephalopod molluscs (squid and octopus). Fig. 6 illustrates difference between an inverted and non-inverted retina, the sensory cells lying beneath the nerve fibres. This results in the sensory cells being absent where the optic nerve is attached to the eye, thus creating a blind spot. The octopus eye has a non-inverted retina in which the sensory cells lie above the nerve fibres. There is therefore no blind spot in this kind of eye. Apart from this difference the two eyes are remarkably similar, an example of convergent evolution.

While previously believed to be an example of convergent evolution [L. Plate, Allgemeine Zoologie und Abstammungs-lehre, Fischer-Verlag, Jena, Germany, 1924], eye development of vertebrates and invertebrates can be linked to a common ancestor. The PAX6 gene is identified not only in squid and drosophila, but also in human and mouse and frog and zebrafish. This finding [Hill et al Nature 1991, Ton et al., Cell 1991] has re-written the biology textbooks. Suborders Megachiroptera Microchiroptera See text for families. ... Orders Many - see section below. ... Classes & Orders See taxonomy Insects are invertebrate animals of the Class Insecta, the largest and (on land) most widely-distributed taxon within the phylum Arthropoda. ... Classes & Orders See taxonomy Insects are invertebrate animals of the Class Insecta, the largest and (on land) most widely-distributed taxon within the phylum Arthropoda. ... Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... A fin is a surface used to produce lift and thrust or to steer while traveling in water, air, or other fluid media. ... Atlantic herring, Clupea harengus: one of the most abundant species of fish in the world. ... Whales are the largest species of exclusively aquatic mammals, members of the order Cetacea, which also includes dolphins and porpoises. ... Subfamilies and Genera Neophoberinae Acanthacaris Thymopinae Nephropsis Nephropides Thymops Thymopsis Nephropinae Homarus Nephrops Homarinus Metanephrops Eunephrops Thymopides Clawed lobsters comprise a family (Nephropidae, sometimes also Homaridae) of large marine crustaceans. ... This article or section does not cite its references or sources. ... Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Orders Subclass Coleoidea Belemnoidea (extinct) Sepiida Sepiolida Spirulida Teuthida Octopoda Vampyromorphida Subclass Ammonoidea(extinct) Subclass Nautiloidea The Cephalopods (head-foot) are the mollusk class Cephalopoda characterized by bilateral body symmetry, a prominent head, and a modification of the mollusk foot, a muscular hydrostat, into the form of arms or tentacles. ... Suborders Myopsina Oegopsina Squids are the large, diverse group of marine cephalopods popular as food in cuisines as widely separated as Korean and Italian. ... Families 14 in two suborders, see text. ... Human eye cross-sectional view. ... An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, which conducts electrical impulses away from the neurons cell body or soma. ... The optic nerve is the nerve that transmits visual information from the retina to the brain. ... The term blind spot has several meanings. ... // Introduction Paired box (Pax) genes are a family of tissue specific transcription factors containing a PAIRED domain and usually a partial or complete homeodomain. ...

Vestigial organs

A further aspect of comparative anatomy is the presence of vestigial organs. Organs that are smaller and simpler in structure than corresponding parts in the ancestral species are called vestigial organs. They are usually degenerated or underdeveloped. The existence of vestigial organs can be explained in terms of changes in the environment or modes of life of the species. Those organs are thought to be functional in the ancestral species but have now become unnecessary and non-functional. Examples are the vestigial hind limbs of whales, the balancers (vestigial hind wings) of flies and mosquitos, vestigial wings of flightless birds such as ostriches, and the vestigial leaves of some xerophytes (e.g. cactus) and parasitic plants (e.g. dodder). A Laughing Gull on the beach in Atlantic City. ... The Mediterranean fruit fly, or medfly, Ceratitis capitata Dance fly male Empis tesselata The flesh-fly, Sarcophaga carnaria As defined by entomologists, a fly (plural flies) is any species of insect of the order Diptera. ... Binomial name Struthio camelus Linnaeus, 1758 The ostrich (Struthio camelus) is a flightless bird native to Africa. ... In botany, a leaf is an above-ground plant organ specialized for photosynthesis. ... A xerophyte describes a plant that has structural (xeromorphic) and physiological adaptations which enable them to survive, or even thrive, in areas with very little free moisture. ... Genera See Taxonomy of the Cactaceae Cactus is the name given to any member of the flowering plant family Cactaceae. ... The term Dodder may refer to a number of topics: The parasitic Cuscuta plant. ...

Evidence from geographical distribution

Biologists have discovered many puzzling facts about the presence of certain species on various continents and islands (biogeography). This article or section does not cite its references or sources. ... Biogeography is the science which deals with patterns of species distribution and the processes that result in such patterns. ...

Continental distribution

All organisms are adapted to their environment to a greater or lesser extent. If the abiotic and biotic factors within a habitat are capable of supporting a particular species in one geographic area, then one might assume that the same species would be found in a similar habitat in a similar geographic area, e.g. in Africa and South America. This is not the case. Plant and animal species are discontinuously distributed throughout the world: Habitat (from the Latin for it inhabits) is the place where a particular species lives and grows. ... A satellite composite image of Africa Africa is the worlds second-largest and second-most populous continent, after Asia. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ...

• Africa has short-tailed (Old World) monkeys, elephants, lions and giraffes.
• South America has long-tailed monkeys, pumas, jaguars and llamas.

An even greater differences can be found if Australia is taken into consideration though it occupies the same latitude as South America and Africa. Marsupials like the kangaroo can be found in Australia, but are totally absent from Africa and are only represented by the opossum in South America and the Virginia Opossum in North America: The Old World consists of those parts of Earth known to Europeans before the voyages of Christopher Columbus; it includes Europe, Asia, and Africa (collectively known as Africa-Eurasia), plus surrounding islands. ... Genera and Species Loxodonta Loxodonta cyclotis Loxodonta africana Elephas Elephas maximus Elephas recki † Stegodon † Mammuthus † Elephantidae (the elephants) is a family of animals, and the only remaining family in the order Proboscidea. ... Binomial name Panthera leo (Linnaeus, 1758) The Lion (Panthera leo) is a mammal of the family Felidae. ... Binomial name Giraffa camelopardalis Linnaeus, 1758 The Giraffe (Giraffa camelopardalis) is an African even-toed ungulate mammal, the tallest of all land-living animal species. ... This article or section is in need of attention from an expert on the subject. ... Binomial name Panthera onca (Linnaeus, 1758) The jaguar (Panthera onca) is a large member of the cat family found primarily in the warm regions of the Americas. ... Binomial name Lama glama (Linnaeus, 1758) The llama (Lama glama) is a large camelid that originated in North America and then later on moved on to South America. ... Latitude, usually denoted symbolically by the Greek letter φ, gives the location of a place on Earth north or south of the Equator. ... Orders Superorder Ameridelphia Didelphimorphia Paucituberculata Superorder Australidelphia Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Marsupials are mammals in which the female typically has a pouch (called the marsupium, from which the name Marsupial derives) in which it rears its young through early infancy. ... Species Macropus rufus Macropus giganteus Macropus fuliginosus A kangaroo is any of several large macropods (the marsupial family that also includes the wallabies, tree-kangaroos, wallaroos, pademelons and the Quokka: 65 species in all). ... This article or section should be merged with Virginia_opossum The word opossum (usually pronounced without the leading O, or with only a very slight schwa) refers either to the Virginia Opossum in particular, or more generally to any of the other marsupials of magnorder Ameridelphia. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... Binomial name Didelphis virginiana (Kerr, 1792) The Virginia Opossum (Didelphis virginiana) is the only marsupial found in North America. ... World map showing North America A satellite composite image of North America. ...

• The echidna and duckbilled platypus, the only living representatives of primitive egg-laying mammals (monotremes), can be found only in Australia and are totally absent in the rest of the world.
• On the other hand Australia has very few placental mammals except those that have been introduced by human beings.

Species Genus Tachyglossus    T. aculeatus Genus Zaglossus    Z. attenboroughi    Z. bruijnii    Z. bartoni    Z. hacketti(extinct)    Z. robustus(extinct) Echidnas, also referred to by the name spiny anteaters, are the only surviving monotremes apart from the Platypus. ... Binomial name Ornithorhynchus anatinus (Shaw, 1799) The Platypus (Ornithorhynchus anatinus) is a small, half-aquatic mammal endemic to the eastern part of Australia, and one of the five extant species of monotremes, the only mammals that lay eggs instead of giving birth to live young (the other four are echidnas). ... Families Kollikodontidae(extinct) Ornithorhynchidae- Platypus Tachyglossidae- Echidnas Steropodontidae(extinct) Monotremes (monos, single + trema, hole; refers to the cloaca) are mammals that lay eggs, instead of giving birth to live young like marsupials (Metatheria) and placental mammals (Eutheria). ...

Explanation

Figure 7: Diagrams to the land bridge between continents in past geological time (A) and the barriers formed (B) due to the submergence of land bridges.

The main groups of modern mammal arose in Northern Hemisphere and subsequently migrated to three major directions: Image File history File links Download high resolution version (1082x379, 100 KB) Created by Jerry Crimson Mann 10:07, 2 August 2005 (UTC). ... Image File history File links Download high resolution version (1082x379, 100 KB) Created by Jerry Crimson Mann 10:07, 2 August 2005 (UTC). ... Land bridge is essentially a historical term; it refers to dry land exposed during periods of low sea level (see regression), connecting what are now separate continents or islands. ... Insert non-formatted text here The Northern Hemisphere is the half of a planets surface (or celestial sphere) that is north of the equator (the word hemisphere literally means half ball). On the Earth, the Northern Hemisphere contains most of the land and population. ...

• to South America via the land bridge in the Bering Strait and Isthmus of Panama; A large number of families of South American marsupials became extinct as a result of competition with these North American counterparts.
• to Africa via the Strait of Gibraltar; and
• and to Australia via South East Asia to which it was at one time connected by land

The shallowness of the Bering Strait would have made the passage of animals between two northern continents a relative easy matter, and it explains the present-day similarity of the two faunas. But once they had got right down into the southern continents, they presumably became isolated from each other by various types of barrier. Land bridge is essentially a historical term; it refers to dry land exposed during periods of low sea level (see regression), connecting what are now separate continents or islands. ... Satellite photo of the Bering Strait Nautical chart of the Bering Strait The Bering Strait is a sea strait between Cape Dezhnev, the eastmost point of the Asian continent and Cape Prince of Wales, the westernmost point of the American continent, approximately 85 km (58 mi) in width, with a... The Isthmus of Panama. ... The Strait of Gibraltar as seen from space. ... Fauna is a collective term for animal life. ...

• The submerging of the Isthmus of Panama: isolates the South American fauna
• the Mediterranean Sea and the North African desert: partially isolate the African fauna; and
• the submerging of the original connection between Australia and South East Asia: isolates the Australian fauna

Once isolated, the animal in each continent has shown adaptive radiation (Fig. 7) to evolve along their own lines. Satellite image The Mediterranean Sea is a part of the Atlantic Ocean almost completely enclosed by land, on the north by Europe, on the south by Africa, and on the east by Asia. ...

Evidence for migration and isolation

Map of the world showing distribution of present members of camel. Solid black lines indicate possible migration routes.

The fossil record for the camel indicated that evolution of camels started in North America, from which they migrated across the Bering Strait into Asia and hence to Africa, and through the Isthmus of Panama into South America. Once isolated they evolved along their own lines, giving the modern camel in Asia and Africa and llama in South America. Image File history File links Created by Jerry Crimson Mann 10:57, 2 August 2005 (UTC). ... Image File history File links Created by Jerry Crimson Mann 10:57, 2 August 2005 (UTC). ... Species Camelus bactrianus Camelus dromedarius A camel is either of the two species of large even-toed ungulate in the genus Camelus, the Dromedary (single hump) and the Bactrian Camel (double hump). ...

Continental drift

The same kinds of fossils are found from areas known to be adjacent to one another in the past but which, through the process of continental drift, are now in widely divergent geographic locations. For example, fossils of the same types of ancient amphibians, arthropods and ferns are found in South America, Africa, India, Australia and Antarctica, which can be dated to the Paleozoic Era, at which time these regions were united as a single landmass called Gondwana. [1] Sometimes the descendants of these organisms can be identified and show unmistakable similarity to each other, even though they now inhabit very different regions and climates. Portrayal of shifting continents The concept of continental drift was first proposed by Alfred Wegener. ... The Palaeozoic is a major division of the geologic timescale, one of four geologic eras. ... Pangaea was formed by the merging of two continents, Laurasia and Gondwana East African and Kuungan Orogens 550 Ma reconstruction showing final stages of assembly The southern supercontinent Gondwana (originally Gondwanaland) included most of the landmasses which make up todays continents of the southern hemisphere, including Antarctica, South America...

Oceanic island distribution

Evidence from comparative embryology

Comparative embryology shows how embryos start off looking the same. As they develop, their similarities slowly decrease until they take the form of their particular class.

For example, adult vertebrates are diverse, yet their embryos are quite similar at very early stages. Fishlike structures still form in early embryos of reptiles, birds, and mammals. In fish embryos, a two-chambered heart, some veins, and parts of arteries develop and persist in adult fishes. The same structures form early in human embryos but do not persist as such in adults.

Evidence from comparative physiology and biochemistry

Serological studies

Evolution of widely distributed proteins and molecules

Almost all living organisms make use of DNA and ATP molecules. Furthermore, the codon codes of the DNA are the same for every organism, meaning that a piece of RNA in a bacteria codes for the same protein as in a human cell. The general structure of a section of DNA Deoxyribonucleic acid (DNA) is a nucleic acid —usually in the form of a double helix— that contains the genetic instructions specifying the biological development of all cellular forms of life, and most viruses. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide primarily known in biochemistry as the molecular currency of intracellular energy transfer. ... RNA codons. ... The general structure of a section of DNA Deoxyribonucleic acid (DNA) is a nucleic acid —usually in the form of a double helix— that contains the genetic instructions specifying the biological development of all cellular forms of life, and most viruses. ... Ribonucleic acid (RNA) is a nucleic acid polymer consisting of covalently bound nucleotides. ... ‹ The template below has been proposed for deletion. ... Cells in culture, stained for keratin (red) and DNA (green). ...

Cytochrome c

A classic example of biochemical evidence for evolution is the variance of the protein Cytochrome c in living cells. The variance of cytochrome c of different organisms is measured in the number of differing amino acids, each differing amino acid being a result of a base pair substitution (mutation). If each differing amino acid is assumed to be the result of one base pair substitution, it can be calculated how long ago the two species diverged by multiplying the number of base pair substitutions by the estimated time it takes for a substituted base pair of the cytochrome c gene to be successfully passed on. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Cytochrome c (horse heart: PDB 1HRC) is a small heme protein found loosely associated with the inner membrane of the mitochondrion. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... In biology, mutations are changes to the genetic material (usually DNA or RNA). ...

Example:
Assume the time it takes for a base pair of the cytochrome c gene is 4 million years*, the number of amino acids making up the cytochrome c protein in monkeys differ by one from that of humans, this leads us to believe that the two species diverged 4 million years ago.

*Figures may be inaccurate

See also: Molecular evolution Molecular evolution is the process of the genetic material in populations of organisms changing over time. ...

Haemoglobin

Evidence from studies of complex iteratation

"It has taken more than five decades, but the electronic computer is now powerful enough to simulate evolution" [2] assisting bioinformatics in its attempt to solve biological problems. Making sense of the huge amounts of DNA data (pictured) produced by gene sequencing projects is just one of the tasks faced by bioinformatics. ...

Computer science allows the iteration of self changing complex systems to be studied, allowing a mathematically exact understanding of the nature of the processes behind evolution; providing evidence for the hidden causes of known evolutionary events. The evolution of specific cellular mechanisms like spliceosomes that can turn the cell's genome into a vast workshop of billions of interchangeable parts that can create tools that create tools that create tools that create us can be studied for the first time in an exact way. Computer science is the study of the theoretical foundations of information and computation and their implementation and application in computer systems. ... Iteration is the repetition of a process, typically within a computer program. ... Many natural phenomena can be considered to be complex systems, and their study (complexity science) is highly interdisciplinary. ... A spliceosome is a complex of RNA and many protein subunits, that remove the non-coding introns from unprocessed mRNA. The mRNA of prokaryotes is simpler, and they do not have introns, so only eukaryotes have spliceosomes. ...

For example, Christoph Adami et. al. make this point in Evolution of biological complexity:

To make a case for or against a trend in the evolution of complexity in biological evolution, complexity needs to be both rigorously defined and measurable. A recent information-theoretic (but intuitively evident) definition identifies genomic complexity with the amount of information a sequence stores about its environment. We investigate the evolution of genomic complexity in populations of digital organisms and monitor in detail the evolutionary transitions that increase complexity. We show that, because natural selection forces genomes to behave as a natural "Maxwell Demon," within a fixed environment, genomic complexity is forced to increase. [3]

For example, David J. Earl and Michael W. Deem make this point in Evolvability is a selectable trait: Maxwells demon is a character in an 1867 thought experiment by the Scottish physicist James Clerk Maxwell, meant to raise questions about the second law of thermodynamics. ...

Not only has life evolved, but life has evolved to evolve. That is, correlations within protein structure have evolved, and mechanisms to manipulate these correlations have evolved in tandem. The rates at which the various events within the hierarchy of evolutionary moves occur are not random or arbitrary but are selected by Darwinian evolution. Sensibly, rapid or extreme environmental change leads to selection for greater evolvability. This selection is not forbidden by causality and is strongest on the largest-scale moves within the mutational hierarchy. Many observations within evolutionary biology, heretofore considered evolutionary happenstance or accidents, are explained by selection for evolvability. For example, the vertebrate immune system shows that the variable environment of antigens has provided selective pressure for the use of adaptable codons and low-fidelity polymerases during somatic hypermutation. A similar driving force for biased codon usage as a result of productively high mutation rates is observed in the hemagglutinin protein of influenza A. [4]

"Computer simulations of the evolution of linear sequences have demonstrated the importance of recombination of blocks of sequence rather than point mutagenesis alone. Repeated cycles of point mutagenesis, recombination, and selection should allow in vitro molecular evolution of complex sequences, such as proteins." [5] Evolutionary molecular engineering, also called directed evolution or in vitro molecular evolution involves the iterated cycle of mutation, multiplication with recombination, and selection of the fittest of individual molecules (proteins, DNA, and RNA). Natural evolution can be relived showing us possible paths from catalytic cycles based on proteins to based on RNA to based on DNA. [6] [7] [8] [9] Influenzavirus A is a genus of a family of viruses called Orthomyxoviridae in virus classification. ...

Evidence from fossils

Tiktaalik roseae fish fossil

Paleontologists have found fossils of a newly-discovered species on Canada’s Ellesmere Island, located in the Nunavut Providence, that provide a key look at the evolution of fish into land animals. The fossils were found by Edward Daeschler of the Academy of Natural Sciences in Philadelphia, Neil Shubin of the University of Chicago, Farish Jenkins Jr. of Harvard and their colleagues. They found the fossils in the rocks of Ellesmere Island in 2004 after a four-year search in the area. Their findings appeared in the journal Nature on April 6, 2006.

The creature, which lived 375 million years ago during the Devonian time period, has been dubbed Tiktaalik roseae, and represents a long-sought link to the time when animals were first moving out of the primordial ocean and onto land, say scientists. The name Tiktaalik comes from a word in the Inuktitut language, meaning large, shallow water fish. The name was supplied by Inuit elders in Nunavut.

The three well-preserved specimens each have a head that looks like a crocodile and a body like a fish, and they range in length from one metre to 2.5 metres. The new animal shows both fish and animal traits, with the scales and fins of a fish, but the ribs, neck, head and appendage bones are like those of a land animal. Primitive joints and fingers were also noted. The researchers said Tiktaalik was probably a poor swimmer, but would have been able push its body off the ground, moving on land like a seal to hunt for land-based food.

Fossil of creatures having both fish and land animals features have been found before, but Tiktaalik falls into a gap between 385 million and 365 million years ago, giving researchers more details of the transition, and a critical piece of the evolutionary puzzle that directly links sea creatures to land animals.

Source: Fish fossils found in Nunavut bridge evolution gap, Wed, 05 Apr 2006, CBC News

Ethiopia pre-human species fossils

The latest fossil unearthed from a human ancestral hot spot in Africa allows scientists to link together the most complete chain of human evolution so far. The 4.2 million-year-old fossil discovered in northeastern Ethiopia helps scientists fill in the gaps of how human ancestors made the giant leap from one species to another.

That's because the newest fossil, the species Australopithecus anamensis, was found in the region of the Middle Awash -- where seven other human-like species spanning nearly 6 million years and three major phases of human development were previously discovered.

"We just found the chain of evolution, the continuity through time," study co-author and Ethiopian anthropologist Berhane Asfaw said in a phone interview from Addis Ababa. "One form evolved to another. This is evidence of evolution in one place through time."

Source: Fossil connects human evolution dots Wed, 12 Apr 2006, CNN

References

• Darwin, Charles November 24, 1859. On the Origin of Species by means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life. London: John Murray, Albemarle Street. 502 pages. Reprinted: Gramercy (May 22, 1995). ISBN 0517123207
• Mayr, Ernst. What Evolution Is. Basic Books (October, 2002). ISBN 0465044263
• Gigerenzer, Gerd, et al., The empire of chance: how probability changed science and everyday life (New York: Cambridge University Press, 1989).
• Williams, G.C. (1966). Adaptation and Natural Selection: A Critique of some Current Evolutionary Thought. Princeton, N.J.: Princeton University Press.
• Biological science, Oxford, 2002.
• CJ Clegg, 1999, Genetics and Evolution, John Murray. ISBN 0-7195-7552-4
• Y.K. Ho, 2004, Advanced-level Biology for Hong Kong, Manhattan Press. ISBN 962-990-635-X

November 24 is the 328th day (329th on leap years) of the year in the Gregorian Calendar. ... 1859 is a common year starting on Saturday. ... The 1859 edition of On the Origin of Species First published in 1859, The Origin of Species (full title On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life) by British naturalist Charles Darwin is one of the pivotal...

External links

• 29+ Evidences for Macroevolution: The Scientific Case for Common Descent
• National Academies Evolution Resources
• Evolution by Natural Selection — An introduction to the logic of the theory of evolution by natural selection
• Evolution — Provided by PBS.
• Howstuffworks.com — How Evolution Works
• Evolution News from Genome News Network (GNN)
• National Academy Press: Teaching About Evolution and the Nature of Science
• Transitional Vertebrate Fossils FAQ