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Evidence of Evolution
Evidence of Evolution
The evidence for evolution is compelling and extensive. Looking at every level of organization in
living systems, biologists see the signature of past and present evolution. Darwin dedicated a large
portion of his book, On the Origin of Species, to identifying patterns in nature that were consistent
with evolution. Since Darwin, our understanding has become clearer and broader.
The evidence for evolution is compelling and extensive. Looking at every level of organization in
living systems, biologists see the signature of past and present evolution. Darwin dedicated a large
portion of his book, On the Origin of Species, to identifying patterns in nature that were consistent
with evolution. Since Darwin, our understanding has become clearer and broader.
Fossils, Anatomy, and Embryology
Fossils, Anatomy, and Embryology
Fossils provide solid evidence that organisms from the past are not the same as those found today;
they show a progression of evolution. Scientists calculate the age of fossils and categorize them to
determine 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. The whale flipper shares a similar
morphology to appendages of birds and mammals, indicating that these species share a common
ancestor. Over time, evolution led to changes in the shapes and sizes of these bones in different
species, but they have maintained the same overall layout. Scientists call these synonymous parts
homologous structures. They have a similar anatomy, but serve different functions in each
organism because they have experienced different selective pressures in different environments.
This is an example of divergent evolution.
Fossils provide solid evidence that organisms from the past are not the same as those found today;
they show a progression of evolution. Scientists calculate the age of fossils and categorize them to
determine 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. The whale flipper shares a similar
morphology to appendages of birds and mammals, indicating that these species share a common
ancestor. Over time, evolution led to changes in the shapes and sizes of these bones in different
species, but they have maintained the same overall layout. Scientists call these synonymous parts
homologous structures. They have a similar anatomy, but serve different functions in each
organism because they have experienced different selective pressures in different environments.
This is an example of divergent evolution.
Some structures exist in organisms that have no apparent function at all, appearing to be residual
parts from a common ancestor. These unused structures (such as wings on flightless birds, leaves
on some cacti, and hind leg bones in whales) are vestigial.
Some structures exist in organisms that have no apparent function at all, appearing to be residual
parts from a common ancestor. These unused structures (such as wings on flightless birds, leaves
on some cacti, and hind leg bones in whales) are vestigial.
Another form of evidence of evolution is the convergence of form in organisms that share similar
environments. For example, species of unrelated animals, such as butterflies and bats have evolved
wings. These similarities occur not because of common ancestry, but because of similar
(analogous) selection pressures in their environments: the benefits of flight. These types of similar
structures are analogous structures.
Another form of evidence of evolution is the convergence of form in organisms that share similar
environments. For example, species of unrelated animals, such as butterflies and bats have evolved
wings. These similarities occur not because of common ancestry, but because of similar
(analogous) selection pressures in their environments: the benefits of flight. These types of similar
structures are analogous structures.
Embryology, the study of the development of the anatomy of an organism to its adult form,
provides evidence for evolution. Structures that are absent in the adults of some groups often
appear in their embryonic forms, disappearing by the time the adult or juvenile form is reached. For
example, all vertebrate embryos exhibit gill slits and tails at some point in their early development.
These disappear in the adults of terrestrial groups, but are maintained in adults of aquatic groups,
such as fish and some amphibians. Great ape embryos have a tail structure during their
development that is lost by birth.
Embryology, the study of the development of the anatomy of an organism to its adult form,
provides evidence for evolution. Structures that are absent in the adults of some groups often
appear in their embryonic forms, disappearing by the time the adult or juvenile form is reached. For
example, all vertebrate embryos exhibit gill slits and tails at some point in their early development.
These disappear in the adults of terrestrial groups, but are maintained in adults of aquatic groups,
such as fish and some amphibians. Great ape embryos have a tail structure during their
development that is lost by birth.
Molecular Biology
Molecular Biology
Like anatomical structures, the structures of the molecules of life provide evidence of an
evolutionary relationship between organisms. Evidence of a common ancestor for all of life is
reflected in the universality of DNA as the genetic material. In general, closely related organisms
share a larger percent of DNA sequences, chemical processes, and proteins. For example: ferns
are more closely related to grasses than mushrooms, because ferns and grasses go through
photosynthesis, mushrooms do not. Dogs and bears have more similar DNA sequences with each
other than they do with fish.
Like anatomical structures, the structures of the molecules of life provide evidence of an
evolutionary relationship between organisms. Evidence of a common ancestor for all of life is
reflected in the universality of DNA as the genetic material. In general, closely related organisms
share a larger percent of DNA sequences, chemical processes, and proteins. For example: ferns
are more closely related to grasses than mushrooms, because ferns and grasses go through
photosynthesis, mushrooms do not. Dogs and bears have more similar DNA sequences with each
other than they do with fish.
Text adapted from: Boundless. “Evidence of Evolution.” Boundless Biology. Boundless, 08 Jan. 2016. Retrieved 14 Mar. 2016
from https://www.boundless.com/biology/textbooks/boundless-biology-textbook/evolution-and-the-origin-of-species18/understanding-evolution-124/evidence-of-evolution-498-11724/
Text adapted from: Boundless. “Evidence of Evolution.” Boundless Biology. Boundless, 08 Jan. 2016. Retrieved 14 Mar. 2016
from https://www.boundless.com/biology/textbooks/boundless-biology-textbook/evolution-and-the-origin-of-species18/understanding-evolution-124/evidence-of-evolution-498-11724/