what are two ways organisms can be compared to provide evidence of evolution from a common ancestor

Chapter eleven: Evolution and Its Processes

Evidence of Evolution

Learning Objectives

By the end of this section, you lot will be able to:

  • Explicate sources of evidence for development
  • Ascertain homologous and vestigial structures

The evidence for development is compelling and extensive. Looking at every level of organization in living systems, biologists encounter the signature of past and present development. Darwin defended a large portion of his book, On the Origin of Species, identifying patterns in nature that were consequent with development and since Darwin our understanding has go clearer and broader.

Fossils

Fossils provide solid bear witness that organisms from the by are not the same equally those establish today; fossils evidence a progression of evolution. Scientists determine the age of fossils and categorize them all over the earth to decide when the organisms lived relative to each other. The resulting fossil record tells the story of the past, and shows the evolution of form over millions of years ([Effigy one]). For case, highly detailed fossil records have been recovered for sequences of species in the evolution of whales and modern horses. The fossil record of horses in North America is especially rich and many contain transition fossils: those showing intermediate anatomy between before and later forms. The fossil record extends back to a dog-like ancestor some 55 1000000 years ago that gave rise to the start horse-like species 55 to 42 million years agone in the genus Eohippus. The series of fossils tracks the alter in anatomy resulting from a gradual drying trend that changed the landscape from a forested i to a prairie. Successive fossils evidence the evolution of teeth shapes and foot and leg anatomy to a grazing habit, with adaptations for escaping predators, for example in species of Mesohippus plant from xl to xxx million years ago. After species showed gains in size, such as those of Hipparion, which existed from about 23 to 2 million years agone. The fossil tape shows several adaptive radiations in the equus caballus lineage, which is now much reduced to only ane genus, Equus, with several species.


A series of paintings on a timeline from 55 million years ago to today showing 4 of the ancestors to the modern horse. The first in the series is Eohippus, which lived from 55 to 45 million years ago. It was a small, dog-sized, animal with 4 toes on the front feet and 3 on the back, a long tail, and a brown spotted coat. The second is Mesohippus, which lived from 40 to 30 million years ago. It was slightly larger than Eohippus with longer legs. It had 3 toes on the front and back feet. The third is Hipparion, which lived from 23 to 2 million years ago. It walked on its middle toe on each foot (now a hoof), but it still had vestiges of the remaining toes. It was much larger than Hipparion. The fourth is Przewalski's horse, a recent but endangered horse. It is smaller and stockier than the domesticated horse with one toe (hoof) on each foot.
Figure one: This illustration shows an creative person's renderings of these species derived from fossils of the evolutionary history of the equus caballus and its ancestors. The species depicted are but 4 from a very diverse lineage that contains many branches, dead ends, and adaptive radiations. One of the trends, depicted here is the evolutionary tracking of a drying climate and increase in prairie versus forest habitat reflected in forms that are more adapted to grazing and predator escape through running. Przewalski's horse is one of a few living species of equus caballus.

Beefcake and Embryology

Some other type of prove for evolution is the presence of structures in organisms that share the aforementioned basic form. For example, the bones in the appendages of a human, dog, bird, and whale all share the same overall construction ([Effigy ii]). That similarity results from their origin in the appendages of a common ancestor. Over time, evolution led to changes in the shapes and sizes of these bones in dissimilar species, just they accept maintained the aforementioned overall layout, testify of descent from a mutual ancestor. Scientists phone call these synonymous parts homologous structures. Some structures be in organisms that have no apparent function at all, and appear to be residual parts from a past ancestor. For instance, some snakes accept pelvic bones despite having no legs because they descended from reptiles that did accept legs. These unused structures without role are called vestigial structures. Other examples of vestigial structures are wings on flightless birds (which may have other functions), leaves on some cacti, traces of pelvic bones in whales, and the sightless eyes of cave animals.

Illustration compares a human arm, dog and bird legs and a whale flipper. All appendages have the same bones, but the size and shape of these bones vary.
Figure ii: The similar construction of these appendages indicates that these organisms share a common antecedent.

Click through the activities at this interactive site to guess which bone structures are homologous and which are analogous, and to see examples of all kinds of evolutionary adaptations that illustrate these concepts.

Another bear witness of evolution is the convergence of grade in organisms that share similar environments. For instance, species of unrelated animals, such as the arctic fox and ptarmigan (a bird), living in the arctic region accept temporary white coverings during winter to blend with the snow and ice ([Figure iii]). The similarity occurs not because of common beginnings, indeed one roofing is of fur and the other of feathers, simply because of like selection pressures—the benefits of not being seen by predators.

Photo (a) depicts an arctic fox with white fur sleeping on white snow. Photo (b) shows a ptarmigan with white feathers standing on white snow.
Figure 3: The white winter coat of (a) the arctic fox and (b) the ptarmigan's plume are adaptations to their environments. (credit a: modification of work by Keith Morehouse)

Embryology, the study of the evolution of the anatomy of an organism to its adult form as well provides evidence of relatedness between now widely divergent groups of organisms. Structures that are absent-minded in some groups oftentimes announced in their embryonic forms and disappear past the time the adult or juvenile grade is reached. For example, all vertebrate embryos, including humans, showroom gill slits at some signal in their early on evolution. These disappear in the adults of terrestrial groups, simply are maintained in adult forms of aquatic groups such equally fish and some amphibians. Great ape embryos, including humans, have a tail construction during their development that is lost by the fourth dimension of nascence. The reason embryos of unrelated species are oft similar is that mutational changes that impact the organism during embryonic evolution can cause amplified differences in the adult, even while the embryonic similarities are preserved.

Biogeography

The geographic distribution of organisms on the planet follows patterns that are all-time explained by evolution in conjunction with the move of tectonic plates over geological fourth dimension. Broad groups that evolved before the breakup of the supercontinent Pangaea (well-nigh 200 million years agone) are distributed worldwide. Groups that evolved since the breakup appear uniquely in regions of the planet, for case the unique flora and fauna of northern continents that formed from the supercontinent Laurasia and of the southern continents that formed from the supercontinent Gondwana. The presence of Proteaceae in Australia, southern Africa, and South America is best explained by the plant family's presence at that place prior to the southern supercontinent Gondwana breaking up ([Effigy 4]).

Map shows the supercontinent Gondwana from 220 million years ago, with South America, Africa, India, Arabia, Antarctica, Australia, New Zealand, New Guinea and parts of southeast Asia in close proximity. A modern day map shows the areas from Gondwana highlighted to show the regions where Proteacea plants are found today. Inset photo shows a Proteacea flower, Banksia spinulosa, a tall spike with many small orange flowers.
Figure 4: The Proteacea family of plants evolved before the supercontinent Gondwana broke up. Today, members of this institute family unit are plant throughout the southern hemisphere (shown in red). (credit "Proteacea flower": modification of piece of work past "dorofofoto"/Flickr)

The peachy diversification of the marsupials in Commonwealth of australia and the absence of other mammals reflects that island continent'due south long isolation. Australia has an affluence of endemic species—species found nowhere else—which is typical of islands whose isolation by expanses of water prevents migration of species to other regions. Over fourth dimension, these species diverge evolutionarily into new species that look very unlike from their ancestors that may exist on the mainland. The marsupials of Commonwealth of australia, the finches on the Galápagos, and many species on the Hawaiian Islands are all plant nowhere else but on their island, yet display distant relationships to ancestral species on mainlands.

Molecular Biology

Like anatomical structures, the structures of the molecules of life reverberate descent with modification. Testify of a common ancestor for all of life is reflected in the universality of DNA equally the genetic material and of the near universality of the genetic lawmaking and the machinery of DNA replication and expression. Primal divisions in life between the three domains are reflected in major structural differences in otherwise conservative structures such equally the components of ribosomes and the structures of membranes. In general, the relatedness of groups of organisms is reflected in the similarity of their Deoxyribonucleic acid sequences—exactly the design that would be expected from descent and diversification from a common antecedent.

Deoxyribonucleic acid sequences have also shed light on some of the mechanisms of evolution. For case, information technology is clear that the evolution of new functions for proteins commonly occurs after gene duplication events. These duplications are a kind of mutation in which an entire gene is added as an extra copy (or many copies) in the genome. These duplications allow the gratuitous modification of i copy past mutation, option, and drift, while the 2nd copy continues to produce a functional protein. This allows the original part for the protein to be kept, while evolutionary forces tweak the copy until it functions in a new style.

Section Summary

The show for evolution is constitute at all levels of arrangement in living things and in the extinct species we know about through fossils. Fossils provide testify for the evolutionary change through at present extinct forms that led to modern species. For instance, there is a rich fossil record that shows the evolutionary transitions from horse ancestors to modernistic horses that document intermediate forms and a gradual adaptation o changing ecosystems. The beefcake of species and the embryological development of that beefcake reveal common structures in divergent lineages that have been modified over fourth dimension by evolution. The geographical distribution of living species reflects the origins of species in particular geographic locations and the history of continental movements. The structures of molecules, like anatomical structures, reflect the relationships of living species and match patterns of similarity expected from descent with modification.

Multiple Choice

The wing of a bird and the arm of a human are examples of ________.

  1. vestigial structures
  2. molecular structures
  3. homologous structures
  4. analogous structures

[reveal-answer q="298505″]Show Respond[/reveal-answer]
[hidden-answer a="298505″]3[/hidden-answer]

The fact that Deoxyribonucleic acid sequences are more similar in more closely related organisms is evidence of what?

  1. optimal design in organisms
  2. adaptation
  3. mutation
  4. descent with modification

[reveal-answer q="527050″]Show Answer[/reveal-answer]
[hidden-answer a="527050″]iv[/hidden-answer]

Free Response

Why do scientists consider vestigial structures evidence for development?

A vestigial structure is an case of a homologous structure that has apparently been reduced through development to a not-functional state because its role is no longer utilized by the species exhibiting it; therefore, any mutations which might reduce its construction are non selected against. The fact that the species has vestiges of the structure rather than no construction at all is prove that it was nowadays in an antecedent and evolved to non-functionality through accumulation of random mutations.

Glossary

vestigial structure
a physical structure present in an organism but that has no apparent function and appears to exist from a functional structure in a distant ancestor

keeganstrue1970.blogspot.com

Source: https://opentextbc.ca/conceptsofbiologyopenstax/chapter/evidence-of-evolution/

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