Evidence of common descent

Special cases like the seasonal changes in the plumage of the ptarmigan, camouflaging it against snow in winter and against brown moorland in summer provide compelling evidence that selection is at work.

Other overarching similarities between all lineages of extant organisms, such as DNA, RNA, amino acids, and the lipid bilayer, give support to the theory of common descent.

As there is no functional advantage to right- or left-handed molecular chirality, the simplest hypothesis is that the choice was made randomly by early organisms and passed on to all extant life through common descent.

Rather than evolving eukaryotic organelles slowly, this theory offers a mechanism for a sudden evolutionary leap by incorporating the genetic material and biochemical composition of a separate species.

][citation needed] Evidence for the evolution of Homo sapiens from a common ancestor with chimpanzees is found in the number of chromosomes in humans as compared to all other members of Hominidae.

The different existing configurations of amino acids do not significantly affect the functionality of the protein, which indicates that the base pair substitutions are not part of a directed design, but the result of random mutations that are not subject to selection.

This evolutionary sequence starts with a small animal called Hyracotherium (commonly referred to as Eohippus), which lived in North America about 54 million years ago then spread across to Europe and Asia.

The major trends seen in the development of the horse to changing environmental conditions may be summarized as follows: Fossilized plants found in different strata show that the marshy, wooded country in which Hyracotherium lived became gradually drier.

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, when these regions were united as a single landmass called Gondwana.

Examples of endemic organisms living in isolated areas include the kagu of New Caledonia,[145] cloud rats of the Luzon tropical pine forests of the Philippines,[146][147] the boojum tree (Fouquieria columnaris) of the Baja California peninsula,[148] and the Baikal seal.

Members range from the silverswords that flower spectacularly on high volcanic slopes to trees, shrubs, vines and mats that occur at various elevations from mountain top to sea level, and in Hawaiian habitats that vary from deserts to rainforests.

[156][157] The history of metatherians (the clade containing marsupials and their extinct, primitive ancestors) provides an example of how evolutionary theory and the movement of continents can be combined to make predictions concerning fossil stratigraphy and distribution.

Radiotrophic fungi appears to use the pigment melanin to convert gamma radiation into chemical energy for growth and were first discovered in 2007 as black molds growing inside and around the Chernobyl Nuclear Power Plant.

To rule out alternative possibilities, Endler set up a highly controlled experiment to mimic the natural habitat by constructing ten ponds within a laboratory greenhouse at Princeton University.

[196][197] The two islands have similar size, elevation, microclimate, and a general absence of terrestrial predators[197] and the P. sicula expanded for decades without human interference, even out-competing the (now locally extinct[196]) Podarcis melisellensis population.

[196] The cecal valves, which occur in less than 1 percent of all known species of scaled reptiles,[196] have been described as an "adaptive novelty, a brand new feature not present in the ancestral population and newly evolved in these lizards".

Genetic analysis found that in the population of tomcods in the four southernmost rivers, the gene AHR2 (aryl hydrocarbon receptor 2) was present as an allele with a difference of two amino acid deletions.

[203][204] Other examples of urban wildlife are rock pigeons and species of crows adapting to city environments around the world; African penguins in Simon's Town; baboons in South Africa; and a variety of insects living in human habitations.

A wealth of information about natural selection, genotypic, and phenotypic variation;[207][208] adaptation and ecomorphology;[209] and social signaling[210] has been acquired from the studies of three species of lizards located in the White Sands desert of New Mexico.

This result could be due to varying factors relating to sand temperature or visual acuity; however, regardless of the cause, "...failure of mismatched lizards to sprint could be maladaptive when faced with a predator".

[213] Speciation occurs as the result of the latter (allopatry); however, a variety of differing agents have been documented and are often defined and classified in various forms (e.g. peripatric, parapatric, sympatric, polyploidization, hybridization, etc.).

[217] Extensive investigation of the fossil record has led to numerous theories concerning speciation (in the context of paleontology) with many of the studies suggesting that stasis, punctuation, and lineage branching are common.

[217] For example, extensive research documenting rates of morphological change, evolutionary trends, and speciation patterns in small mammals has significantly contributed to the scientific literature.

In another study concerning morphological trends and rates of evolution found that the European arvicolid rodent radiated into 52 distinct lineages over a time frame of 5 million years while documenting examples of phyletic gradualism, punctuation, and stasis.

"[244] Studies of snapping shrimp in the genus Alpheus have provided direct evidence of allopatric speciation events,[246] and contributed to the literature concerning rates of molecular evolution.

Studies have also suggested that, due to "the sessile nature of plants... [it increases] the relative importance of ecological speciation...."[250] Hybridization between two different species sometimes leads to a distinct phenotype.

Professor Doug Soltis of the University of Florida said, "We caught evolution in the act...New and diverse patterns of gene expression may allow the new species to rapidly adapt in new environments".

[287] Darwinists such as Alfred Russel Wallace and Edward Bagnall Poulton, and in the 20th century Hugh Cott and Bernard Kettlewell, sought evidence that natural selection was taking place.

Computational evolutionary biology has enabled researchers to trace the evolution of a large number of organisms by measuring changes in their DNA, rather than through physical taxonomy or physiological observations alone.

It has also helped build complex computational models of populations to predict the outcome of the system over time and track and share information on an increasingly large number of species and organisms.

Figure 1a: While on board HMS Beagle , Charles Darwin collected numerous specimens, many new to science, which supported his later theory of evolution by natural selection .
Figure 1b: Fusion of ancestral chromosomes left distinctive remnants of telomeres, and a vestigial centromere.
Figure 2a: In July 1919, a humpback whale was caught by a ship operating out of Vancouver that had legs 4 ft 2 in (1.27 m) long. [ 42 ] This image shows the hindlegs of another humpback whale reported in 1921 by the American Museum of Natural History.
Figure 2b: Skeleton of a baleen whale with the hind limb and pelvic bone structure circled in red. This bone structure stays internal during the entire life of the species.
Figure 3e: Evolution of the horse showing reconstruction of the fossil species obtained from successive rock strata. The foot diagrams are all front views of the left forefoot. The third metacarpal is shaded throughout. The teeth are shown in longitudinal section. The linear sequence is just one of many paths in the equine phylogenetic tree.
Figure 4a: Four of the 13 finch species found on the Galápagos Archipelago , have evolved by an adaptive radiation that diversified their beak shapes to adapt them to different food sources.
In a ring species , gene flow occurs between neighboring populations, but at the ends of the "ring", the populations cannot interbreed.
Figure 5a: The Chihuahua mix and Great Dane illustrate the range of sizes among dog breeds.
Figure 5b: Endler's Trinidadian guppies ( Poecilia reticulata )
Figure 5c: H. m. ruthveni , a White Sands ecotonal variant of Holbrookia maculata
Figure 6a: Morphologic change of Globorotalia crassaformis, G. tosaensis, and G. truncatulinoides over 3.5 Ma. Superimposed is a phylogenetic tree of the group. Adapted from Lazarus et al. (1995).
Figure 6b: A common fruit fly ( Drosophila melanogaster )
Figure 6c: Arabidopsis thaliana (colloquially known as thale cress, mouse-ear cress or arabidopsis)
Figure 6d: Purple salsify, Tragopogon porrifolius
Natural selection has driven the ptarmigan to change from snow camouflage in winter to disruptive coloration suiting moorland in summer. [ 285 ]