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Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Developmenta ...

biology
that studies the
animal kingdom
animal kingdom
, including the
structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A ...

structure
,
embryology Embryology (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 mi ...
,
evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolution
,
classification Classification is a process related to categorization Categorization is the human ability and activity of recognizing shared features or similarities between the elements of the experience of the world (such as Object (philosophy), objects, eve ...
,
habits A habit (or wont as a humorous and formal term) is a routine of behavior that is repeated regularly and tends to occur Subconscious, subconsciously.
, and distribution of all animals, both living and
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the endling, last individual of the species, although the Functional extin ...

extinct
, and how they interact with their
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
s. The term is derived from
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages () ...
, ('animal'), and , ('knowledge', 'study'). Although humans have always been interested in the natural history of the animals they saw around them, and made use of this knowledge to domesticate certain species, the formal study of zoology can be said to have originated with
Aristotle Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , translit ...

Aristotle
. He viewed animals as living organisms, studied their structure and development, and considered their adaptations to their surroundings and the function of their parts. The Greek physician
Galen Aelius Galenus or Claudius Galenus ( el, Κλαύδιος Γαληνός; September 129 – c. AD 216), often Anglicized Linguistic anglicisation (or anglicization, occasionally anglification, anglifying, or Englishing) is the practice of modify ...
studied human anatomy and was one of the greatest surgeons of the ancient world, but after the fall of the
Western Roman Empire The Western Roman Empire comprises the western provinces of the Roman Empire at any time during which they were administered by a separate independent Imperial court; in particular, this term is used in historiography to describe the period from ...

Western Roman Empire
and the onset of the
Early Middle Ages The Early Middle Ages or Early Medieval Period, sometimes referred to as the Dark Ages (historiography), Dark Ages, is typically regarded by historians as lasting from the late 5th or early 6th century to the 10th century. They marked the start ...
, the Greek tradition of medicine and scientific study went into decline in Western Europe, although it continued in the medieval Islamic world. Modern zoology has its origins during the
Renaissance The Renaissance ( , ) , from , with the same meanings. is a period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in m ...

Renaissance
and early modern period, with
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomia ...
,
Antonie van Leeuwenhoek Antonie Philips van Leeuwenhoek ( ; ; 24 October 1632 – 26 August 1723) was a Dutch Republic, Dutch businessman and scientist in the Dutch Golden Age, Golden Age of Dutch science and technology. A largely self-taught man in science, he is ...
,
Robert Hooke Robert Hooke FRS FRS may also refer to: Government and politics * Facility Registry System, a centrally managed Environmental Protection Agency database that identifies places of environmental interest in the United States * Family Resources ...
,
Charles Darwin Charles Robert Darwin (; ; 12 February 1809 – 19 April 1882) was an English natural history#Before 1900, naturalist, geologist and biologist, best known for his contributions to the science of evolution. His proposition that all spe ...

Charles Darwin
,
Gregor Mendel Gregor Johann Mendel (; cs, Řehoř Jan Mendel; 20 July 1822 – 6 January 1884) was a meteorologist, mathematician, biologist, Augustinian friar and abbot of St. Thomas' Abbey in Brno, Margraviate of Moravia. Mendel was born in a Germa ...

Gregor Mendel
and many others. The study of animals has largely moved on to deal with form and function, adaptations, relationships between groups, behaviour and ecology. Zoology has increasingly been subdivided into disciplines such as
classification Classification is a process related to categorization Categorization is the human ability and activity of recognizing shared features or similarities between the elements of the experience of the world (such as Object (philosophy), objects, eve ...

classification
,
physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, B ...
,
biochemistry Biochemistry or biological chemistry, is the study of chemical process In a scientific Science (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. La ...

biochemistry
and
evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolution
. With the discovery of the structure of
DNA The structure of part of a DNA double helix Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings ...
by
Francis Crick Francis Harry Compton Crick (8 June 1916 – 28 July 2004) was a British molecular biologist, biophysicist, and neuroscientist A neuroscientist (or neurobiologist) is a scientist A scientist is a person who conducts Scientific method, scie ...

Francis Crick
and
James Watson James Dewey Watson KBE (born April 6, 1928) is an American molecular biologist, geneticist and zoologist. In 1953, he co-authored with Francis Crick the academic paper proposing the double helix structure of the DNA molecule File:Pent ...

James Watson
in 1953, the realm of
molecular biology Molecular biology is the branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, molecular synthesis, modification, mechanisms, and interactions ...
opened up, leading to advances in
cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, ...
,
developmental biology Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of Regeneration (biology), regeneration, asexual reproduction, metamorphosis, and the growth and dif ...
and
molecular genetics Molecular genetics is a sub-field of biology that addresses how differences in the structures or expression of DNA molecules manifests as variation among organisms. Molecular genetics often applies an "investigative approach" to determine the ...
.


History

The
history of zoology The history of zoology had a key moment in 1859 with the publication of Darwin's ''On the Origin of Species ''On the Origin of Species'' (or, more completely, ''On the Origin of Species by Means of Natural Selection, or the Preservation of Fav ...
traces the study of the
animal kingdom
animal kingdom
from ancient to modern times. Prehistoric man needed to study the animals and plants in his environment in order to exploit them and survive. There are cave paintings, engravings and sculptures in France dating back 15,000 years showing bison, horses and deer in carefully rendered detail. Similar images from other parts of the world illustrated mostly the animals hunted for food but also the savage animals. The
Neolithic Revolution The Neolithic Revolution, or the (First) Agricultural Revolution, was the wide-scale transition of many human culture Culture () is an umbrella term which encompasses the social behavior Social behavior is behavior Behavior (Americ ...
, which is characterized by the domestication of animals, continued over the period of Antiquity. Ancient knowledge of wildlife is illustrated by the realistic depictions of wild and domestic animals in the Near East, Mesopotamia and Egypt, including husbandry practices and techniques, hunting and fishing. The invention of writing is reflected in zoology by the presence of animals in Egyptian hieroglyphics. Although the concept of ''zoology'' as a single coherent field arose much later, the zoological sciences emerged from
natural history Natural history is a domain of inquiry involving organisms, including animals, fungus, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history ...

natural history
reaching back to the biological works of Aristotle and
Galen Aelius Galenus or Claudius Galenus ( el, Κλαύδιος Γαληνός; September 129 – c. AD 216), often Anglicized Linguistic anglicisation (or anglicization, occasionally anglification, anglifying, or Englishing) is the practice of modify ...
in the ancient
Greco-Roman world Roman Theatre of Mérida, Spain. The term "Greco-Roman world" (also "Greco-Roman culture" or ; spelled Graeco-Roman in the Commonwealth), as understood by modern scholars and writers, refers to geographical regions and countries that cultura ...
. Aristotle, in the fourth century BC, looked at animals as living organisms, studying their structure, development and vital phenomena. He divided them into two groups, animals with blood, equivalent to our concept of vertebrates, and animals without blood (invertebrates). He spent two years on
Lesbos Lesbos or Lesvos (, also ; el, Λέσβος, Lésvos ) is a Greek island located in the northeastern Aegean Sea, often called Mytilene () in Greece, after its capital. It has an area of with of coastline, making it the third largest island in ...
, observing and describing the animals and plants, considering the adaptations of different organisms and the function of their parts. Four hundred years later, Roman physician Galen dissected animals to study their anatomy and the function of the different parts, because the dissection of human cadavers was prohibited at the time. This resulted in some of his conclusions being false, but for many centuries it was considered
heretical Heresy is any belief or theory that is strongly at variance with established beliefs or customs, in particular the accepted beliefs of a church or religious organization. The term is usually used in reference to violations of important religi ...
to challenge any of his views, so the study of anatomy stultified. During the post-classical era, Middle Eastern science and medicine was the most advanced in the world, integrating concepts from Ancient Greece, Rome, Mesopotamia and Persia as well as the ancient Indian tradition of
Ayurveda Ayurveda () is an alternative medicine system with historical roots in the Indian subcontinent. The theory and practice of Ayurveda is pseudoscience, pseudoscientific. The Indian Medical Association (IMA) characterises the practice of modern me ...

Ayurveda
, while making numerous advances and innovations. In the 13th century,
Albertus Magnus Albertus Magnus (c. 1200 – November 15, 1280), also known as Saint Albert the Great or Albert of Cologne, was a German Catholic The Catholic Church, often referred to as the Roman Catholic Church, is the List of Christian denominat ...

Albertus Magnus
produced commentaries and paraphrases of all Aristotle's works; his books on topics like botany, zoology, and minerals included information from ancient sources, but also the results of his own investigations. His general approach was surprisingly modern, and he wrote, "For it is he taskof natural science not simply to accept what we are told but to inquire into the causes of natural things." An early pioneer was
Conrad Gessner Conrad Gessner (; la, Conradus Gesnerus 26 March 1516 – 13 December 1565) was a Swiss Swiss may refer to: * the adjectival form of Switzerland ,german: Schweizer(in),french: Suisse(sse), it, svizzero/svizzera or , rm, Svizzer/Svizra , g ...

Conrad Gessner
, whose monumental 4,500-page encyclopedia of animals, ''
Historia animalium ''History of Animals'' ( grc-gre, Τῶν περὶ τὰ ζῷα ἱστοριῶν, ''Ton peri ta zoia historion'', "Inquiries on Animals"; la, Historia Animalium, "History of Animals") is one of the major texts on biology by the ancient Gree ...
'', was published in four volumes between 1551 and 1558. In Europe, Galen's work on anatomy remained largely unsurpassed and unchallenged up until the 16th century. During the
Renaissance The Renaissance ( , ) , from , with the same meanings. is a period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in m ...

Renaissance
and early modern period, zoological thought was revolutionized in
Europe Europe is a continent A continent is one of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven regions are commonly regarded as continents. Ordered from largest ...

Europe
by a renewed interest in
empiricism In philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, ...
and the discovery of many novel organisms. Prominent in this movement were
Andreas Vesalius Andreas Vesalius (; 31 December 1514 – 15 October 1564) was a 16th-century Flemish people, Flemish anatomist, physician, and author of one of the most influential books on human anatomy, ''De humani corporis fabrica, De Humani Corporis Fabrica ...

Andreas Vesalius
and
William Harvey William Harvey (1 April 1578 – 3 June 1657) was an English physician who made influential contributions in anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organis ...

William Harvey
, who used experimentation and careful observation in
physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, B ...
, and naturalists such as
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomia ...
,
Jean-Baptiste Lamarck Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck (1 August 1744 – 18 December 1829), often known simply as Lamarck (; ), was a French naturalist Natural history is a domain of inquiry involving organisms, including animals, fu ...

Jean-Baptiste Lamarck
, and
Buffon
Buffon
who began to classify the diversity of life and the
fossil record A fossil (from Classical Latin: , literally 'obtained by digging') is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, Seashell, shells, exoskeletons, stone imprints of a ...
, as well as studying the development and behavior of organisms.
Antonie van Leeuwenhoek Antonie Philips van Leeuwenhoek ( ; ; 24 October 1632 – 26 August 1723) was a Dutch Republic, Dutch businessman and scientist in the Dutch Golden Age, Golden Age of Dutch science and technology. A largely self-taught man in science, he is ...
did pioneering work in
microscopy Microscopy is the technical field of using microscope A microscope (from grc, μικρός ''mikrós'' 'small' and ''skopeîn'' 'to look (at); examine, inspect') is a laboratory instrument used to examine objects that are too small to b ...

microscopy
and revealed the previously unknown world of
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms ar ...
s, laying the groundwork for
cell theory In biology, cell theory is a scientific theory first formulated in the mid-nineteenth century, that living organisms are made up of Cell (biology), cells, that they are the basic structural/organizational unit of all organisms, and that all cells ...
. van Leeuwenhoek's observations were endorsed by
Robert Hooke Robert Hooke FRS FRS may also refer to: Government and politics * Facility Registry System, a centrally managed Environmental Protection Agency database that identifies places of environmental interest in the United States * Family Resources ...
; all living organisms were composed of one or more cells and could not generate spontaneously. Cell theory provided a new perspective on the fundamental basis of life. Having previously been the realm of gentlemen naturalists, over the 18th, 19th and 20th centuries, zoology became an increasingly professional
scientific discipline The branches of science, also referred to as science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes knowledge in the form of Tes ...
. Explorer-naturalists such as
Alexander von Humboldt Friedrich Wilhelm Heinrich Alexander von Humboldt (14 September 17696 May 1859) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * F ...

Alexander von Humboldt
investigated the interaction between organisms and their environment, and the ways this relationship depends on geography, laying the foundations for
biogeography Biogeography is the study of the distribution of species and ecosystems in geography, geographic space and through evolutionary history of life, geological time. Organisms and biological community (ecology), communities often vary in a regular f ...

biogeography
,
ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms In biology ...
and
ethology Ethology is the scientific method, scientific study of animal behaviour, usually with a focus on behaviour under natural conditions, and viewing behaviour as an evolutionarily Adaptive behavior (ecology), adaptive trait. Behaviourism as a t ...
. Naturalists began to reject
essentialism Essentialism is the view that objects have a set of attributes that are necessary to their identity Identity may refer to: Social sciences * Identity (social science), personhood or group affiliation in psychology and sociology Group e ...
and consider the importance of
extinction Extinction is the termination of a kind of organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by ...

extinction
and the mutability of species. These developments, as well as the results from
embryology Embryology (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 mi ...
and
paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (geology), epoch (roughly 11,700 years before present). It includes th ...
, were synthesized in the 1859 publication of
Charles Darwin Charles Robert Darwin (; ; 12 February 1809 – 19 April 1882) was an English natural history#Before 1900, naturalist, geologist and biologist, best known for his contributions to the science of evolution. His proposition that all spe ...

Charles Darwin
's theory of
evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolution
by
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the Heredity, heritable Phenotypic trait, traits characteristic of a populatio ...
; in this Darwin placed the theory of organic evolution on a new footing, by explaining the processes by which it can occur, and providing observational evidence that it had done so. Darwin's theory was rapidly accepted by the scientific community and soon became a central axiom of the rapidly developing science of biology. The basis for modern genetics began with the work of
Gregor Mendel Gregor Johann Mendel (; cs, Řehoř Jan Mendel; 20 July 1822 – 6 January 1884) was a meteorologist, mathematician, biologist, Augustinian friar and abbot of St. Thomas' Abbey in Brno, Margraviate of Moravia. Mendel was born in a Germa ...

Gregor Mendel
on peas in 1865, although the significance of his work was not realized at the time. Darwin gave a new direction to
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
and
physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, B ...
, by uniting them in a common biological theory: the theory of organic evolution. The result was a reconstruction of the classification of animals upon a
genealogical Genealogy (from el, γενεαλογία ' "the making of a pedigree") is the study of families, family history, and the tracing of their lineages. Genealogists use oral interviews, historical records, genetic analysis, and other records to ob ...

genealogical
basis, fresh investigation of the development of animals, and early attempts to determine their genetic relationships. The end of the 19th century saw the fall of
spontaneous generation Spontaneous generation is a body of thought on the ordinary formation of living organisms without descent from similar organisms. The theory of spontaneous generation held that living creatures could arise from nonliving matter and that such process ...
and the rise of the
germ theory of disease The germ theory of disease is the currently accepted scientific theory A scientific theory is an explanation of an aspect of the natural world and universe that has been repeatedly tested and verified in accordance with the scientific method ...
, though the mechanism of
inheritance Inheritance is the practice of passing on private property, Title (property), titles, debts, entitlements, Privilege (law), privileges, rights, and Law of obligations, obligations upon the death of an individual. The rules of inheritance differ ...

inheritance
remained a mystery. In the early 20th century, the rediscovery of
Mendel's
Mendel's
work led to the rapid development of
genetics Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) Though heredity had been observed for millennia, Gregor Mendel, Moravia, Moravian scientist and Augustinian ...

genetics
, and by the 1930s the combination of
population genetics Population genetics is a subfield of genetics Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) Though heredity had been observed for millennia, Gregor Men ...
and natural selection in the modern synthesis created
evolutionary biology Evolutionary biology is the subfield of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interaction ...
. Research in cell biology is interconnected to other fields such as genetics,
biochemistry Biochemistry or biological chemistry, is the study of chemical process In a scientific Science (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. La ...

biochemistry
,
medical microbiology Medical microbiology, the large subset of microbiology Microbiology (from Greek , ''mīkros'', "small"; , ''bios'', "life Life is a characteristic that distinguishes physical entities that have biological processes, such as signaling ...
,
immunology Immunology is a branch of biology and Medicine that covers the study of immune systems in all organisms. Immunology charts, measures, and contextualizes the Physiology, physiological functioning of the immune system in states of both health and d ...
, and
cytochemistry Cytochemistry is the branch of cell biology dealing with the detection of cell constituents by means of biochemical analysis and visualization techniques. The term is also used to describe a process of identification of the biochemical content of ...
. With the sequencing of the
DNA The structure of part of a DNA double helix Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings ...
molecule by
Francis Crick Francis Harry Compton Crick (8 June 1916 – 28 July 2004) was a British molecular biologist, biophysicist, and neuroscientist A neuroscientist (or neurobiologist) is a scientist A scientist is a person who conducts Scientific method, scie ...

Francis Crick
and
James Watson James Dewey Watson KBE (born April 6, 1928) is an American molecular biologist, geneticist and zoologist. In 1953, he co-authored with Francis Crick the academic paper proposing the double helix structure of the DNA molecule File:Pent ...

James Watson
in 1953, the realm of
molecular biology Molecular biology is the branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, molecular synthesis, modification, mechanisms, and interactions ...
opened up, leading to advances in
cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, ...
,
developmental biology Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of Regeneration (biology), regeneration, asexual reproduction, metamorphosis, and the growth and dif ...
and
molecular genetics Molecular genetics is a sub-field of biology that addresses how differences in the structures or expression of DNA molecules manifests as variation among organisms. Molecular genetics often applies an "investigative approach" to determine the ...
. The study of
systematics Biology, Biological systematics is the study of the diversification of living forms, both past and present, and the Correlation and dependence, relationships among living things through time. Relationships are visualized as evolutionary trees (syn ...
was transformed as
DNA sequencing DNA sequencing is the process of determining the nucleic acid sequence A nucleic acid sequence is a succession of bases signified by a series of a set of five different letters that indicate the order of nucleotides Nucleotides are organic ...

DNA sequencing
elucidated the degrees of affinity between different organisms.


Scope

Zoology is the branch of science dealing with
animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, ...

animal
s. A
species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

species
can be defined as the largest group of organisms in which any two individuals of the appropriate sex can produce fertile offspring; about 1.5 million species of animal have been described and it has been estimated that as many as 8 million animal species may exist. An early necessity was to identify the organisms and group them according to their characteristics, differences and relationships, and this is the field of the
taxonomist In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxon, taxa (singular ...

taxonomist
. Originally it was thought that species were immutable, but with the arrival of Darwin's theory of evolution, the field of
cladistics Cladistics (; ) is an approach to biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular ...

cladistics
came into being, studying the relationships between the different groups or
clade A clade (), also known as a monophyletic group or natural group, is a group of organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell t ...

clade
s.
Systematics Biology, Biological systematics is the study of the diversification of living forms, both past and present, and the Correlation and dependence, relationships among living things through time. Relationships are visualized as evolutionary trees (syn ...
is the study of the diversification of living forms, the evolutionary history of a group is known as its
phylogeny , based on completely sequenced genomes. A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolution ...

phylogeny
, and the relationship between the clades can be shown diagrammatically in a
cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics Cladistics (, from Greek language, Greek , ''kládos'', "branch") is an approach to Taxonomy (biology), biological classification in whi ...

cladogram
. Although someone who made a scientific study of animals would historically have described themselves as a zoologist, the term has come to refer to those who deal with individual animals, with others describing themselves more specifically as physiologists, ethologists, evolutionary biologists, ecologists, pharmacologists, endocrinologists or parasitologists.


Branches of zoology

Although the study of animal life is ancient, its scientific incarnation is relatively modern. This mirrors the transition from
natural history Natural history is a domain of inquiry involving organisms, including animals, fungus, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history ...

natural history
to
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Developmenta ...

biology
at the start of the 19th century. Since
Hunter Hunting is the practice of seeking, pursuing and capturing or killing wildlife A ground pangolin Wildlife traditionally refers to undomesticated animal Animals (also called Metazoa) are multicellular eukaryotic organisms that ...
and
Cuvier
Cuvier
, comparative
anatomical Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, mo ...

anatomical
study has been associated with morphography, shaping the modern areas of zoological investigation:
anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual conti ...

anatomy
,
physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, B ...
,
histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Mol ...

histology
,
embryology Embryology (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 mi ...
,
teratology Teratology is the study of abnormalities of physiological development in all organisms including plants during the entire life span. A sub discipline in Medical Genetics Medical genetics is the branch of medicine that involves the diagnosis and ...
and
ethology Ethology is the scientific method, scientific study of animal behaviour, usually with a focus on behaviour under natural conditions, and viewing behaviour as an evolutionarily Adaptive behavior (ecology), adaptive trait. Behaviourism as a t ...
. Modern zoology first arose in German and British universities. In Britain,
Thomas Henry Huxley Thomas Henry Huxley (4 May 1825 – 29 June 1895) was an English biologist Francesco Redi, the founder of biology, is recognized to be one of the greatest biologists of all time A biologist is a professional who has specialized knowledge ...

Thomas Henry Huxley
was a prominent figure. His ideas were centered on the
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
of animals. Many consider him the greatest comparative anatomist of the latter half of the 19th century. Similar to
Hunter Hunting is the practice of seeking, pursuing and capturing or killing wildlife A ground pangolin Wildlife traditionally refers to undomesticated animal Animals (also called Metazoa) are multicellular eukaryotic organisms that ...
, his courses were composed of lectures and laboratory practical classes in contrast to the previous format of lectures only.


Classification

Scientific classification in zoology, is a method by which zoologists group and categorize
organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into groups such as Multice ...

organism
s by
biological type In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cel ...
, such as
genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biolog ...
or
species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

species
. Biological classification is a form of
scientific taxonomy Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes knowledge in the form of Testability, testable explanations and predictions about the u ...
. Modern biological classification has its root in the work of
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomia ...
, who grouped species according to shared physical characteristics. These groupings have since been revised to improve consistency with the
Darwinian Darwinism is a theory A theory is a reason, rational type of abstraction, abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as obser ...

Darwinian
principle of
common descent Common descent is a concept in evolutionary biology Evolutionary biology is the subfield of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chem ...
.
Molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny , based on completely sequenced genomes. A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a ...
, which uses
nucleic acid sequence A nucleic acid sequence is a succession of bases signified by a series of a set of five different letters that indicate the order of nucleotides Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monom ...
as data, has driven many recent revisions and is likely to continue to do so. Biological classification belongs to the science of zoological systematics. Many scientists now consider the
five-kingdom system In biology, kingdom (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...
outdated. Modern alternative classification systems generally start with the
three-domain system The three-domain system is a biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, ...
:
Archaea Archaea ( ; singular archaeon ) constitute a domain Domain may refer to: Mathematics *Domain of a function, the set of input values for which the (total) function is defined **Domain of definition of a partial function **Natural domain of a pa ...

Archaea
(originally Archaebacteria);
Bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a Bacte ...

Bacteria
(originally Eubacteria);
Eukaryota Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), tax ...

Eukaryota
(including
protist A protist () is any eukaryotic organism (that is, an organism whose Cell (biology), cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a Common descent, common ancestor (the last eukaryo ...
s,
fungi A fungus (plural: fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as ...

fungi
,
plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions o ...

plant
s, and
animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, ...

animal
s) These domains reflect whether the cells have nuclei or not, as well as differences in the chemical composition of the cell exteriors. Further, each kingdom is broken down recursively until each species is separately classified. The order is:
Domain Domain may refer to: Mathematics *Domain of a function, the set of input values for which the (total) function is defined **Domain of definition of a partial function **Natural domain of a partial function **Domain of holomorphy of a function *Doma ...
;
kingdom Kingdom may refer to: Monarchy * A type of monarchy * A realm ruled by: **A king, during the reign of a male monarch **A queen regnant, during the reign of a female monarch Taxonomy * Kingdom (biology), a category in biological taxonomy Arts an ...
;
phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a q ...
;
class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently f ...
;
order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and the habit of achieving a ...
;
family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same Politics, ...
;
genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biolog ...
;
species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

species
. The scientific name of an organism is generated from its genus and species. For example, humans are listed as ''
Homo sapiens Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal ...

Homo sapiens
''. ''Homo'' is the genus, and ''sapiens'' the specific epithet, both of them combined make up the species name. When writing the scientific name of an organism, it is proper to capitalize the first letter in the genus and put all of the specific epithet in lowercase. Additionally, the entire term may be italicized or underlined. The dominant classification system is called the
Linnaean taxonomy Linnaean taxonomy can mean either of two related concepts: # the particular form of biological classification (taxonomy) set up by Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblemen ...
. It includes ranks and
binomial nomenclature In taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only ...
. The classification,
taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only about biological ...
, and nomenclature of zoological organisms is administered by the
International Code of Zoological Nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention Convention may refer to: * Convention (norm), a custom or tradition, a standard of presentation or conduct ** Treaty, an agreement in international law * Co ...
. A merging draft, BioCode, was published in 1997 in an attempt to standardize nomenclature, but has yet to be formally adopted.


Vertebrate and invertebrate zoology

Vertebrate zoology is the
biological Biology is the natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes knowl ...

biological
discipline Discipline is action ACTION is a bus operator in Canberra Canberra ( ) is the capital city of Australia. Founded following the Federation of Australia, federation of the colonies of Australia as the seat of government for the new na ...

discipline
that consists of the study of
vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic ma ...
animals, that is animals with a
backbone The backbone is the vertebral column of a vertebrate. Arts, entertainment, and media Film * Backbone (1923 film), ''Backbone'' (1923 film), 1923 lost silent film starring Alfred Lunt * Backbone (1975 film), ''Backbone'' (1975 film), 1975 Yugoslavi ...

backbone
, such as
fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...

fish
,
amphibian Amphibians are ectothermic, tetrapod vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial animal, terr ...
s,
reptile Reptiles, as most commonly defined, are the animals in the Class (biology), class Reptilia , a paraphyletic grouping comprising all amniotes except synapsids (mammals and their extinct relatives) and Aves (birds). Living reptiles comprise turtle ...

reptile
s,
bird Birds are a group of warm-blooded vertebrates constituting the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of indiv ...

bird
s and
mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian female, females produce milk ...
s. The various taxonomically oriented disciplines such as
mammalogy In zoology, mammalogy is the study of mammals – a Class (biology), class of vertebrates with characteristics such as Homeothermy, homeothermic metabolism, fur, four-chambered hearts, and complex nervous systems. Mammalogy has also been known as "m ...
,
biological anthropology Biological anthropology, also known as physical anthropology, is a scientific discipline concerned with the biological and behavioral aspects of human beings, their extinct hominin ancestors, and related non-human primates, particularly from an ...
,
herpetology Herpetology (from Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is the branch of zoology Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, though it is not uncommon. is the branc ...

herpetology
,
ornithology Ornithology is a branch of zoology that concerns the "methodological study and consequent knowledge of birds with all that relates to them". Several aspects of ornithology differ from related disciplines, due partly to the high visibility and th ...

ornithology
, and
ichthyology Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of October 2 ...
seek to identify and classify
species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

species
and study the structures and mechanisms specific to those groups. The rest of the animal kingdom is dealt with by
invertebrate zoologyInvertebrate zoology is the subdiscipline of zoology Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the anatomy, stru ...
, a vast and very diverse group of animals that includes
sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the Diploblasts. They are Multicellular organism, multicellular organisms that have bodies full of pores and channels allowing water ...

sponge
s,
echinoderm An echinoderm () is any member of the phylum Echinodermata (; ) of marine life, marine animals. The adults are recognizable by their (usually five-point) radial symmetry, and include starfish, sea urchins, sand dollars, and sea cucumbers, as wel ...
s,
tunicate A tunicate is a marine invertebrate Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This includes all animals apart from the subphylum ...
s,
worm Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limb Limb can refer to: *Limb (anatomy), an appendage of a human or animal *Limb Music, a record label *Limb (album), an a ...

worm
s,
mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. The members are known as molluscs or mollusks (). Around 85,000 extant taxon, extant species of molluscs are recognized. The number of fossil species is es ...
s,
arthropod An arthropod (, (gen. ποδός)) is an invertebrate Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This includes all animals apart fr ...
s and many other phyla, but single-celled organisms or
protist A protist () is any eukaryotic organism (that is, an organism whose Cell (biology), cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a Common descent, common ancestor (the last eukaryo ...
s are not usually included.


Structural zoology

Cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, ...
studies the structural and
physiological Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, B ...
properties of
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse lives * Prison cell, a room used to hold peopl ...
, including their
behavior Behavior (American English) or behaviour (British English; American and British English spelling differences#-our, -or, see spelling differences) is the Action (philosophy), actions and mannerisms made by individuals, organisms, systems or Arti ...
, interactions, and
environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

environment
. This is done on both the
microscopic The microscopic scale (from , ''mikrós'', "small" and σκοπέω, ''skopéō'' "look") is the scale of objects and events smaller than those that can easily be seen by the naked eye, requiring a lens or microscope to see them clearly. In phys ...

microscopic
and
molecular A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atom An atom is the smallest unit of ordinary matter In ...

molecular
levels for single-celled organisms such as
bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a Bacte ...

bacteria
as well as the specialized cells in
multicellular organisms Multicellular organisms are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties of life. It is a synonym for "Out ...
such as
human Humans (''Homo sapiens'') are the most populous and widespread species of primates, characterized by bipedality, opposable thumbs, hairlessness, and intelligence allowing the use of culture, language and tools. They are the only Extant taxon, ...

human
s. Understanding the structure and function of cells is fundamental to all of the biological sciences. The similarities and differences between cell types are particularly relevant to molecular biology.
Anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual conti ...

Anatomy
considers the forms of macroscopic structures such as
organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly categorized as parenchyma Parenchyma () is the bulk of functional ...
and organ systems. It focuses on how organs and organ systems work together in the bodies of humans and animals, in addition to how they work independently. Anatomy and cell biology are two studies that are closely related, and can be categorized under "structural" studies.
Comparative anatomy Comparative anatomy is the study of similarities and differences in the anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Anc ...
is the study of similarities and differences in the
anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual conti ...

anatomy
of different groups. It is closely related to
evolutionary biology Evolutionary biology is the subfield of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interaction ...
and
phylogeny , based on completely sequenced genomes. A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolution ...

phylogeny
(the
evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolution
of species).


Physiology

Physiology studies the mechanical, physical, and biochemical processes of living organisms by attempting to understand how all of the structures function as a whole. The theme of "structure to function" is central to biology. Physiological studies have traditionally been divided into
plant physiology Plant physiology is a subdiscipline of botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds ...

plant physiology
and
animal physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, B ...
, but some principles of physiology are universal, no matter what particular
organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into groups such as Multice ...

organism
is being studied. For example, what is learned about the physiology of
yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom (biology), kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are esti ...

yeast
cells can also apply to human cells. The field of animal physiology extends the tools and methods of
human physiology The human body is the structure of a human being Humans (''Homo sapiens'') are the most populous and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an ...
to non-human species. Physiology studies how for example ,
immune In biology, immunity is the capability of multicellular organisms to resist harmful microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμό ...
,
endocrine The endocrine system is a messenger system comprising feedback loops of the hormone A hormone (from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Re ...

endocrine
,
respiratory The respiratory system (also respiratory apparatus, ventilatory system) is a biological system A biological system is a complex network which connects several biologically relevant entities. Biological organization spans several scales and are ...

respiratory
, and circulatory systems, function and interact.


Developmental biology

Developmental biology Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of Regeneration (biology), regeneration, asexual reproduction, metamorphosis, and the growth and dif ...
is the study of the processes by which animals and plants reproduce and grow. The discipline includes the study of
embryonic development An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism that consists of more than one cell (biology), cell, in contrast to a unicellular organism. All species of animals, Embryophyte, la ...
,
cellular differentiation Cellular differentiation is the process in which a cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or re ...
,
regeneration Regeneration may refer to: Science and technology * Regeneration (biology), the ability to recreate lost or damaged cells, tissues, organs and limbs * Regeneration in humans, the ability of humans to recreate, or induce the regeneration of, lost ...
, asexual and sexual
reproduction Reproduction (or procreation or breeding) is the biological process Biological processes are those processes that are vital for an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is ...

reproduction
,
metamorphosis Metamorphosis is a biological process Biological processes are those processes that are vital for an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous syst ...
, and the growth and differentiation of
stem cell In multicellular organisms Multicellular organisms are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties o ...
s in the adult organism. Development of both animals and plants is further considered in the articles on
evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolution
,
population genetics Population genetics is a subfield of genetics Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) Though heredity had been observed for millennia, Gregor Men ...
,
heredity Heredity, also called inheritance or biological inheritance, is the passing on of traits Trait may refer to: * Phenotypic trait in biology, which involve genes and characteristics of organisms * Trait (computer programming), a model for str ...

heredity
,
genetic variabilityGenetic variability is either the presence of, or the generation of, genetic differences. It is defined as "the formation of individuals differing in genotype Here the relation between genotype and phenotype is illustrated, using a Punnett square ...
,
Mendelian inheritance Mendelian inheritance is a type of biological Biology is the natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific me ...

Mendelian inheritance
, and
reproduction Reproduction (or procreation or breeding) is the biological process Biological processes are those processes that are vital for an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is ...

reproduction
.


Evolutionary biology

Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. Evolutionary research is concerned with the origin and descent of
species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

species
, as well as their change over time, and includes scientists from many taxonomically oriented disciplines. For example, it generally involves scientists who have special training in particular
organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into groups such as Multice ...

organism
s such as
mammalogy In zoology, mammalogy is the study of mammals – a Class (biology), class of vertebrates with characteristics such as Homeothermy, homeothermic metabolism, fur, four-chambered hearts, and complex nervous systems. Mammalogy has also been known as "m ...
,
ornithology Ornithology is a branch of zoology that concerns the "methodological study and consequent knowledge of birds with all that relates to them". Several aspects of ornithology differ from related disciplines, due partly to the high visibility and th ...

ornithology
,
herpetology Herpetology (from Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is the branch of zoology Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, though it is not uncommon. is the branc ...

herpetology
, or
entomology upright=1.2, A Phyllium, Phyllium sp., mimicry, mimicking a leaf Entomology () is the science, scientific study of insects, a branch of zoology. In the past the term "insect" was less specific, and historically the definition of entomology would a ...
, but use those organisms as systems to answer general questions about evolution. Evolutionary biology is partly based on
paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (geology), epoch (roughly 11,700 years before present). It includes th ...
, which uses the
fossil A fossil (from Classical Latin Classical Latin is the form of Latin language Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the a ...

fossil
record to answer questions about the mode and tempo of evolution, and partly on the developments in areas such as
population genetics Population genetics is a subfield of genetics Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) Though heredity had been observed for millennia, Gregor Men ...
and evolutionary theory. Following the development of
DNA fingerprinting DNA profiling (also called DNA fingerprinting) is the process of determining an individual's DNA The structure of part of a DNA double helix Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning ...
techniques in the late 20th century, the application of these techniques in zoology has increased the understanding of animal populations. In the 1980s,
developmental biology Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of Regeneration (biology), regeneration, asexual reproduction, metamorphosis, and the growth and dif ...
re-entered evolutionary biology from its initial exclusion from the modern synthesis through the study of
evolutionary developmental biology Evolutionary developmental biology (informally, evo-devo) is a field of biological research that compares the developmental processes of different organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''org ...
. Related fields often considered part of evolutionary biology are
phylogenetics In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, ...

phylogenetics
,
systematics Biology, Biological systematics is the study of the diversification of living forms, both past and present, and the Correlation and dependence, relationships among living things through time. Relationships are visualized as evolutionary trees (syn ...
, and
taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only about biological ...
.


Ethology

Ethology is the scientific method, scientific and objective study of animal behavior under natural conditions, as opposed to behaviorism, which focuses on behavioral response studies in a laboratory setting. Ethologists have been particularly concerned with the
evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolution
of behavior and the understanding of behavior in terms of the theory of
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the Heredity, heritable Phenotypic trait, traits characteristic of a populatio ...
. In one sense, the first modern ethologist was
Charles Darwin Charles Robert Darwin (; ; 12 February 1809 – 19 April 1882) was an English natural history#Before 1900, naturalist, geologist and biologist, best known for his contributions to the science of evolution. His proposition that all spe ...

Charles Darwin
, whose book, ''The Expression of the Emotions in Man and Animals,'' influenced many future ethologists. A subfield of ethology is behavioral ecology which attempts to answer Nikolaas Tinbergen's Tinbergen's four questions, four questions with regard to animal behavior: what are the proximate causes of the behavior, the ontogeny, developmental history of the organism, the Adaptation, survival value and phylogeny of the behavior? Another area of study is animal cognition, which uses laboratory experiments and carefully controlled field studies to investigate an animal's intelligence and learning.


Biogeography

Biogeography studies the spatial distribution of organisms on the Earth, focusing on topics like plate tectonics, climate change, Biological dispersal, dispersal and Animal migration, migration, and
cladistics Cladistics (; ) is an approach to biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular ...

cladistics
. It is an integrative field of study, uniting concepts and information from
evolutionary biology Evolutionary biology is the subfield of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interaction ...
, taxonomy (biology), taxonomy,
ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms In biology ...
, physical geography, geology,
paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (geology), epoch (roughly 11,700 years before present). It includes th ...
and climatology. The origin of this field of study is widely accredited to Alfred Russel Wallace, a British biologist who had some of his work jointly published with
Charles Darwin Charles Robert Darwin (; ; 12 February 1809 – 19 April 1882) was an English natural history#Before 1900, naturalist, geologist and biologist, best known for his contributions to the science of evolution. His proposition that all spe ...

Charles Darwin
.


Molecular biology

Molecular biology studies the common genetics, genetic and developmental mechanisms of animals and plants, attempting to answer the questions regarding the mechanisms of Heredity, genetic inheritance and the structure of the gene. In 1953,
James Watson James Dewey Watson KBE (born April 6, 1928) is an American molecular biologist, geneticist and zoologist. In 1953, he co-authored with Francis Crick the academic paper proposing the double helix structure of the DNA molecule File:Pent ...

James Watson
and
Francis Crick Francis Harry Compton Crick (8 June 1916 – 28 July 2004) was a British molecular biologist, biophysicist, and neuroscientist A neuroscientist (or neurobiologist) is a scientist A scientist is a person who conducts Scientific method, scie ...

Francis Crick
described the structure of DNA and the interactions within the molecule, and this publication jump-started research into molecular biology and increased interest in the subject. While researchers practice techniques specific to molecular biology, it is common to combine these with methods from
genetics Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) Though heredity had been observed for millennia, Gregor Mendel, Moravia, Moravian scientist and Augustinian ...

genetics
and
biochemistry Biochemistry or biological chemistry, is the study of chemical process In a scientific Science (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. La ...

biochemistry
. Much of molecular biology is quantitative, and recently a significant amount of work has been done using computer science techniques such as bioinformatics and computational biology. Molecular genetics, the study of gene structure and function, has been among the most prominent sub-fields of molecular biology since the early 2000s. Other branches of biology are informed by molecular biology, by either directly studying the interactions of molecules in their own right such as in
cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, ...
and
developmental biology Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of Regeneration (biology), regeneration, asexual reproduction, metamorphosis, and the growth and dif ...
, or indirectly, where molecular techniques are used to infer historical attributes of populations or
species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

species
, as in fields in
evolutionary biology Evolutionary biology is the subfield of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interaction ...
such as
population genetics Population genetics is a subfield of genetics Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) Though heredity had been observed for millennia, Gregor Men ...
and
phylogenetics In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, ...

phylogenetics
. There is also a long tradition of studying biomolecules "from the ground up", or molecularly, in biophysics.


See also

* Animal science, the biology of domesticated animals * Astrobiology * Animal cognition, Cognitive zoology * Evolutionary biology * List of zoologists * Outline of zoology * Palaeontology * Timeline of zoology * Zoological distribution


Notes


References


External links


Books on Zoology
at Project Gutenberg *
Online Dictionary of Invertebrate Zoology
' {{Authority control Zoology, Branches of biology