Comparative anatomy

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Comparative anatomy studies similarities and differences in organisms. The image shows homologous bones in the upper limb of various vertebrates. Homology vertebrates-en.svg
Comparative anatomy studies similarities and differences in organisms. The image shows homologous bones in the upper limb of various vertebrates.

Comparative anatomy is the study of similarities and differences in the anatomy of different species. It is closely related to evolutionary biology and phylogeny [1] (the evolution of species).

Contents

The science began in the classical era, continuing in Early Modern times with work by Pierre Belon who noted the similarities of the skeletons of birds and humans.

Comparative anatomy has provided evidence of common descent, and has assisted in the classification of animals. [2]

History

Skeletons of humans and birds compared by Pierre Belon, 1555 Belon Oyseaux.jpg
Skeletons of humans and birds compared by Pierre Belon, 1555

The first specifically anatomical investigation separate from a surgical or medical procedure is associated by early commentators with Alcmaeon of Croton. [3] Leonardo da Vinci made notes for a planned anatomical treatise in which he intended to compare the hands of various animals including bears. [4] Pierre Belon, a French naturalist born in 1517, conducted research and held discussions on dolphin embryos as well as the comparisons between the skeletons of birds to the skeletons of humans. His research led to modern comparative anatomy. [5]

Andreas Vesalius Andreas Vesalius-Pierre Poncet.jpg
Andreas Vesalius

Around the same time, Andreas Vesalius was also making some strides of his own. A young anatomist of Flemish descent made famous by a penchant for amazing charts, he was systematically investigating and correcting the anatomical knowledge of the Greek physician Galen. He noticed that many of Galen's observations were not even based on actual humans. Instead, they were based on animals such as apes, monkeys, and oxen. [6] In fact, he entreated his students to do the following, in substitution for human skeletons, as cited by Edward Tyson : "“If you cant happen to see any of these, dissect an Ape, carefully view each Bone, &c. …” Then he advises what sort of Apes to make choice of, as most resembling a Man : And conclude “One ought to know the Structure of all the Bones either in a Humane Body, or in an Apes ; ‘tis best in both ; and then to go to the Anatomy of the Muscles.”" (Edward Tyson, Orang-Outang..., 1699, p. 59.) Up until that point, Galen and his teachings had been the authority on human anatomy. The irony is that Galen himself had emphasized the fact that one should make one's own observations instead of using those of another, but this advice was lost during the numerous translations of his work. As Vesalius began to uncover these mistakes, other physicians of the time began to trust their own observations more than those of Galen. An interesting observation made by some of these physicians was the presence of homologous structures in a wide variety of animals which included humans. These observations were later used by Darwin as he formed his theory of Natural Selection. [7]

A drawing by Edward Tyson Affe-tyson.jpg
A drawing by Edward Tyson

Edward Tyson is regarded as the founder of modern comparative anatomy. He is credited with determining that whales and dolphins are, in fact, mammals. Also, he concluded that chimpanzees are more similar to humans than to monkeys because of their arms. Marco Aurelio Severino also compared various animals, including birds, in his Zootomia democritaea, one of the first works of comparative anatomy. In the 18th and 19th century, great anatomists like George Cuvier, Richard Owen and Thomas Henry Huxley revolutionized our understanding of the basic build and systematics of vertebrates, laying the foundation for Charles Darwin's work on evolution. An example of a 20th-century comparative anatomist is Victor Negus, who worked on the structure and evolution of the larynx. Until the advent of genetic techniques like DNA sequencing, comparative anatomy together with embryology were the primary tools for understanding phylogeny, as exemplified by the work of Alfred Romer.[ citation needed ]

Concepts

Two major concepts of comparative anatomy are:

  1. Homologous structures - structures (body parts/anatomy) which are similar in different species because the species have common descent and have evolved, usually divergently, from a shared ancestor. They may or may not perform the same function. An example is the forelimb structure shared by cats and whales.
  2. Analogous structures - structures similar in different organisms because, in convergent evolution, they evolved in a similar environment, rather than were inherited from a recent common ancestor. They usually serve the same or similar purposes. An example is the streamlined torpedo body shape of porpoises and sharks. So even though they evolved from different ancestors, porpoises and sharks developed analogous structures as a result of their evolution in the same aquatic environment. This is known as a homoplasy. [8]

Uses

Comparative anatomy has long served as evidence for evolution, now joined in that role by comparative genomics; [9] it indicates that organisms share a common ancestor.

It also assists scientists in classifying organisms based on similar characteristics of their anatomical structures. A common example of comparative anatomy is the similar bone structures in forelimbs of cats, whales, bats, and humans. All of these appendages consist of the same basic parts; yet, they serve completely different functions. The skeletal parts which form a structure used for swimming, such as a fin, would not be ideal to form a wing, which is better-suited for flight. One explanation for the forelimbs' similar composition is descent with modification. Through random mutations and natural selection, each organism's anatomical structures gradually adapted to suit their respective habitats. [10] The rules for development of special characteristics which differ significantly from general homology were listed by Karl Ernst von Baer as the laws now named after him.

See also

Related Research Articles

Anatomy The study of the structure of organisms and their parts

Anatomy is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science which deals with the structural organization of living things. It is an old science, having its beginnings in prehistoric times. Anatomy is inherently tied to developmental biology, embryology, comparative anatomy, evolutionary biology, and phylogeny, as these are the processes by which anatomy is generated, both over immediate and long-term timescales. Anatomy and physiology, which study the structure and function of organisms and their parts respectively, make a natural pair of related disciplines, and are often studied together. Human anatomy is one of the essential basic sciences that are applied in medicine.

Andreas Vesalius Flemish anatomist

Andreas Vesalius was a 16th-century Flemish anatomist, physician, and author of one of the most influential books on human anatomy, De Humani Corporis Fabrica Libri Septem. Vesalius is often referred to as the founder of modern human anatomy. He was born in Brussels, which was then part of the Habsburg Netherlands. He was a professor at the University of Padua (1537–1542) and later became Imperial physician at the court of Emperor Charles V.

Zoology is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems. The term is derived from Ancient Greek ζῷον, zōion, i.e. "animal" and λόγος, logos, i.e. "knowledge, study".

History of anatomy

The history of anatomy extends from the earliest examinations of sacrificial victims to the sophisticated analyses of the body performed by modern scientists. The study of human anatomy can be traced back thousands of years, at least to the Egyptians, but the science of anatomy, as we know it today, did not develop until far later. The development of the study of anatomy gradually built upon concepts that were understood during the time of Galen and slowly became a part of the traditional medical curriculum. It has been characterized, over time, by a continually developing understanding of the functions of organs and structures in the body.

Homology (biology) Shared ancestry between a pair of structures or genes in different taxa

In biology, homology is similarity due to shared ancestry between a pair of structures or genes in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats and birds, the arms of primates, the front flippers of whales and the forelegs of four-legged vertebrates like dogs and crocodiles are all derived from the same ancestral tetrapod structure. Evolutionary biology explains homologous structures adapted to different purposes as the result of descent with modification from a common ancestor. The term was first applied to biology in a non-evolutionary context by the anatomist Richard Owen in 1843. Homology was later explained by Charles Darwin's theory of evolution in 1859, but had been observed before this, from Aristotle onwards, and it was explicitly analysed by Pierre Belon in 1555.

Anatomical terms of location Standard terms for unambiguous description of relative placement of body parts

Standard anatomical terms of location deal unambiguously with the anatomy of animals, including humans. Terms used generally derive from Latin or Greek roots and used to describe something in its standard anatomical position. This position provides a standard definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and anatomical axes.

The history of zoology before Charles Darwin's 1859 theory of evolution traces the organized study of the animal kingdom from ancient to modern times. Although the concept of zoology as a single coherent field arose much later, systematic study of zoology is seen in the works of Aristotle and Galen in the ancient Greco-Roman world. This work was developed in the Middle Ages by Islamic medicine and scholarship, and in turn their work was extended by European scholars such as Albertus Magnus.

Vestigiality

Vestigiality is the retention during the process of evolution of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on comparison with homologous features in related species. The emergence of vestigiality occurs by normal evolutionary processes, typically by loss of function of a feature that is no longer subject to positive selection pressures when it loses its value in a changing environment. The feature may be selected against more urgently when its function becomes definitively harmful, but if the lack of the feature provides no advantage, and its presence provides no disadvantage, the feature may not be phased out by natural selection and persist across species.

Realdo Colombo

Matteo Realdo Colombo was an Italian professor of anatomy and a surgeon at the University of Padua between 1544 and 1559.

Moulage

Moulage is the art of applying mock injuries for the purpose of training emergency response teams and other medical and military personnel. Moulage may be as simple as applying pre-made rubber or latex "wounds" to a healthy "patient's" limbs, chest, head, etc., or as complex as using makeup and theatre techniques to provide elements of realism to the training simulation. The practice dates to at least the Renaissance, when wax figures were used for this purpose.

Dissection

Dissection is the dismembering of the body of a deceased animal or plant to study its anatomical structure. Autopsy is used in pathology and forensic medicine to determine the cause of death in humans. Less extensive dissection of plants and smaller animals preserved in a formaldehyde solution is typically carried out or demonstrated in biology and natural science classes in middle school and high school, while extensive dissections of cadavers of adults and children, both fresh and preserved are carried out by medical students in medical schools as a part of the teaching in subjects such as anatomy, pathology and forensic medicine. Consequently, dissection is typically conducted in a morgue or in an anatomy lab.

<i>De humani corporis fabrica</i>

De humani corporis fabrica libri septem is a set of books on human anatomy written by Andreas Vesalius (1514–1564) and published in 1543. It was a major advance in the history of anatomy over the long-dominant work of Galen, and presented itself as such.

Forelimb

A forelimb is an anterior limb on a terrestrial vertebrate's body. With reference to quadrupeds, the term foreleg is often used instead.

Evidence of common descent Evidence that a given group of organisms have a common ancestor, and therefore that evolution has taken place.

Evidence of common descent of living organisms has been discovered by scientists researching in a variety of disciplines over many decades, demonstrating that all life on Earth comes from a single ancestor. This forms an important part of the evidence on which evolutionary theory rests, demonstrates that evolution does occur, and illustrates the processes that created Earth's biodiversity. It supports the modern evolutionary synthesis—the current scientific theory that explains how and why life changes over time. Evolutionary biologists document evidence of common descent, all the way back to the last universal common ancestor, by developing testable predictions, testing hypotheses, and constructing theories that illustrate and describe its causes.

John Struthers (anatomist)

Sir John Struthers MD FRCSEd FRSE was the first Regius Professor of Anatomy at the University of Aberdeen. He was a dynamic teacher and administrator, transforming the status of the institutions in which he worked. He was equally passionate about anatomy, enthusiastically seeking out and dissecting the largest and finest specimens, including whales, and troubling his colleagues with his single-minded quest for money and space for his collection. His collection was donated to Surgeon's Hall in Edinburgh.

Osteoderm Bony structures in the dermis

Osteoderms are bony deposits forming scales, plates or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls, various groups of dinosaurs, phytosaurs, aetosaurs, placodonts, and hupehsuchians.

A cadaver or corpse is a dead human body that is used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue to repair a defect in a living human being. Students in medical school study and dissect cadavers as a part of their education. Others who study cadavers include archaeologists and artists.

Medical Renaissance

The Medical Renaissance, from 1400 to 1700 CE, is the period of progress in European medical knowledge, and a renewed interest in the ideas of the ancient Greek and Roman civilizations, along with Arabic-Persian medicine, after the Latin translation movement. Such medical discoveries during the Medical Renaissance are credited with paving the way for modern medicine.

Matthew Bonnan is an American paleobiologist and a Professor of Biological Sciences at Stockton University. His research combines traditional descriptive and anatomical study with computer-aided morphometric analysis and modeling of vertebrate skeletons. See also Dr. Bonnan's blog on his research and teaching at The Evolving Paleontologist.

Hand

A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala are often described as having "hands" instead of paws on their front limbs. The raccoon is usually described as having "hands" though opposable thumbs are lacking.

References

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Further reading