Zoology ()
[The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon.] is the branch of
biology
Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...
that studies the
animal kingdom, including the
structure,
embryology,
evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
,
classification,
habits
A habit (or wont as a humorous and formal term) is a routine of behavior that is repeated regularly and tends to occur subconsciously. , and distribution of all animals, both living and
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 ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...
, ('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 and polymath during the Classical period in Ancient Greece. Taught by Plato, he was the founder of the Peripatetic school of ph ...
. 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 as Galen () or Galen of Pergamon, was a Greek physician, surgeon and philosopher in the Roman Empire. Considered to be one ...
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 comprised 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 ...
and the onset of the
Early Middle Ages, 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 in European history
The history of Europe is traditionally divided into four time periods: prehistoric Europe (prior to about 800 BC), classical antiquity (800 BC to AD ...
and early modern period, with
Carl Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...
,
Antonie van Leeuwenhoek,
Robert Hooke,
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
,
Gregor Mendel
Gregor Johann Mendel, OSA (; cs, Řehoř Jan Mendel; 20 July 1822 – 6 January 1884) was a biologist, meteorologist, mathematician, Augustinian friar and abbot of St. Thomas' Abbey in Brünn (''Brno''), Margraviate of Moravia. Mendel was ...
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,
physiology,
biochemistry
Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...
and
evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
. With the discovery of the structure of
DNA by
Francis Crick and
James Watson in 1953, the realm of
molecular biology
Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and physi ...
opened up, leading to advances in
cell biology,
developmental biology 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 traces the study of the
animal kingdom from ancient to modern times. Prehistoric people needed to study the animals and plants in their 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, 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 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 as Galen () or Galen of Pergamon, was a Greek physician, surgeon and philosopher in the Roman Empire. Considered to be one ...
in the ancient
Greco-Roman world. 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 ( el, Λέσβος, Lésvos ) is a Greek island located in the northeastern Aegean Sea. It has an area of with approximately of coastline, making it the third largest island in Greece. It is separated from Asia Minor by the nar ...
, 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
In world history, post-classical history refers to the period from about 500 AD to 1500, roughly corresponding to the European Middle Ages. The period is characterized by the expansion of civilizations geographically and development of trade ...
,
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, while making numerous advances and innovations. In the 13th century,
Albertus Magnus
Albertus Magnus (c. 1200 – 15 November 1280), also known as Saint Albert the Great or Albert of Cologne, was a German Dominican friar, philosopher, scientist, and bishop. Later canonised as a Catholic saint, he was known during his li ...
produced commentaries and paraphrases of all Aristotle's works; his books on topics like
botany
Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...
, 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 physician, naturalist, bibliographer, and philologist. Born into a poor family in Zürich, Switzerland, his father and teachers quickly realised his tale ...
, 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 Gr ...
'', 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 in European history
The history of Europe is traditionally divided into four time periods: prehistoric Europe (prior to about 800 BC), classical antiquity (800 BC to AD ...
and early modern period, zoological thought was revolutionized in
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...
by a renewed interest in
empiricism and the discovery of many novel organisms. Prominent in this movement were
Andreas Vesalius
Andreas Vesalius (Latinized from Andries van Wezel) () was a 16th-century anatomist, physician, and author of one of the most influential books on human anatomy, ''De Humani Corporis Fabrica Libri Septem'' (''On the fabric of the human body'' ' ...
and
William Harvey
William Harvey (1 April 1578 – 3 June 1657) was an English physician who made influential contributions in anatomy and physiology. He was the first known physician to describe completely, and in detail, the systemic circulation and propert ...
, who used experimentation and careful observation in
physiology, and naturalists such as
Carl Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...
,
Jean-Baptiste Lamarck, and
Buffon who began to
classify the diversity of life and the
fossil record
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
, as well as studying the development and behavior of organisms.
Antonie van Leeuwenhoek did pioneering work in
microscopy and revealed the previously unknown world of
microorganisms, 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 cells, that they are the basic structural/organizational unit of all organisms, and that all cells come from pre ...
. van Leeuwenhoek's observations were endorsed by
Robert Hooke; 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. Explorer-naturalists such as
Alexander von Humboldt investigated the interaction between organisms and their environment, and the ways this relationship depends on geography, laying the foundations for
biogeography,
ecology and
ethology. Naturalists began to reject
essentialism and consider the importance of
extinction and the
mutability of species.
These developments, as well as the results from
embryology and
paleontology, were synthesized in the 1859 publication of
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
's theory of
evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
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 heritable traits characteristic of a population over generations. Cha ...
; 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, OSA (; cs, Řehoř Jan Mendel; 20 July 1822 – 6 January 1884) was a biologist, meteorologist, mathematician, Augustinian friar and abbot of St. Thomas' Abbey in Brünn (''Brno''), Margraviate of Moravia. Mendel was ...
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, 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 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 superseded scientific theory that held that living creatures could arise from nonliving matter and that such processes were commonplace and regular. It was hypothesized that certain forms, such as fleas, could arise f ...
and the rise of the
germ theory of disease, though the mechanism of
inheritance remained a mystery. In the early 20th century, the rediscovery of
Mendel's work led to the rapid development of
genetics
Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...
, and by the 1930s the combination of
population genetics and natural selection in the
modern synthesis created
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. It is also defined as the study of the history of life ...
.
Research in cell biology is interconnected to other fields such as genetics,
biochemistry
Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...
,
medical microbiology,
immunology, and
cytochemistry
Cytochemistry is the branch of cell biology dealing with the detection of cell constituents by means of biochemical analysis and visualization techniques. This is the study of the localization of cellular components through the use of staining me ...
. With the sequencing of the
DNA molecule by
Francis Crick and
James Watson in 1953, the realm of
molecular biology
Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and physi ...
opened up, leading to advances in
cell biology,
developmental biology 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 was transformed as
DNA sequencing elucidated the degrees of affinity between different organisms.
Scope
Zoology is the branch of science dealing with
animal
Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
s. A
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
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 ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are give ...
. 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 which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived cha ...
came into being, studying the relationships between the different groups or
clades.
Systematics is the study of the diversification of living forms, the evolutionary history of a group is known as its
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 to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
.
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 to
biology
Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...
at the start of the 19th century. Since
Hunter and
Cuvier, comparative
anatomical study has been associated with
morphography, shaping the modern areas of zoological investigation:
anatomy,
physiology,
histology,
embryology,
teratology and
ethology. Modern zoology first arose in German and British universities. In Britain,
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, 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 living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
s by
biological type, such as
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
or
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
. Biological classification is a form of
scientific taxonomy. 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 in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...
, who grouped species according to shared physical characteristics. These groupings have since been revised to improve consistency with the
Darwinian
Darwinism is a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others, stating that all species of organisms arise and develop through the natural selection of small, inherited variations that ...
principle of
common descent.
Molecular phylogenetics, which uses
nucleic acid sequence 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, a kingdom is the second highest taxonomic rank, just below domain. Kingdoms are divided into smaller groups called phyla.
Traditionally, some textbooks from the United States and Canada used a system of six kingdoms (Animalia, Plan ...
outdated. Modern alternative classification systems generally start with the
three-domain system
The three-domain system is a biological classification introduced by Carl Woese, Otto Kandler, and Mark Wheelis in 1990 that divides cellular life forms into three domains, namely Archaea, Bacteria, and Eukaryota or Eukarya. The key difference ...
:
Archaea (originally Archaebacteria);
Bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
(originally Eubacteria);
Eukaryota (including
protists,
fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
,
plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...
s, and
animal
Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
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;
kingdom
Kingdom commonly refers to:
* A monarchy ruled by a king or queen
* Kingdom (biology), a category in biological taxonomy
Kingdom may also refer to:
Arts and media Television
* ''Kingdom'' (British TV series), a 2007 British television drama s ...
;
phylum;
class;
order;
family;
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
;
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
. The scientific name of an organism is generated from its genus and species. For example, humans are listed as ''
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, as set forth in his ''Systema Naturae'' (1735) and subsequent works. In the taxonomy of Linnaeus t ...
. It includes ranks and
binomial nomenclature. The classification,
taxonomy, and nomenclature of zoological organisms is administered by the
International Code of Zoological Nomenclature. 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
The State Museum of Zoology (german: Staatliches Museum für Tierkunde) in Dresden is a natural history museum that houses 10,000–50,000 specimens, including skeletons and large insect collections. Many are types. The collection suffered war ...
is the
biological discipline that consists of the study of
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...
animals, that is animals with a
backbone
The backbone is the vertebral column of a vertebrate.
Arts, entertainment, and media Film
* ''Backbone'' (1923 film), a 1923 lost silent film starring Alfred Lunt
* ''Backbone'' (1975 film), a 1975 Yugoslavian drama directed by Vlatko Gilić
...
, such as
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...
,
amphibians,
reptiles,
birds and
mammals. The various taxonomically oriented disciplines such as
mammalogy,
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 e ...
,
herpetology,
ornithology, and
ichthyology seek to identify and classify
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
and study the structures and mechanisms specific to those groups. The rest of the animal kingdom is dealt with by
invertebrate zoology, a vast and very diverse group of animals that includes
sponges,
echinoderms,
tunicates,
worms,
molluscs,
arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
s and many other
phyla, but
single-celled organisms or
protists are not usually included.
Structural zoology
Cell biology studies the structural and
physiological properties of
cells, including their
behavior, interactions, and
environment. This is done on both the
microscopic and
molecular levels for single-celled organisms such as
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
as well as the specialized cells in
multicellular organisms
A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism.
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni ...
such as
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...
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 considers the forms of macroscopic structures such as
organs 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 is the study of similarities and differences in the
anatomy of different groups. It is closely related to
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. It is also defined as the study of the history of life ...
and
phylogeny (the
evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
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 and
animal physiology, but some principles of physiology are universal, no matter what particular
organism
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
is being studied. For example, what is learned about the physiology of
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. It is composed of many different types of cells that together create tissues and subsequently organ systems. They ensure homeostasis and the viability of the human body.
It comprises a head ...
to non-human species. Physiology studies how, for example, the
nervous,
immune,
endocrine,
respiratory
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies gre ...
, and
circulatory systems function and interact.
Developmental biology
Developmental biology is the study of the processes by which animals and plants reproduce and grow. The discipline includes the study of
embryonic development,
cellular differentiation,
regeneration,
asexual and
sexual
Sex is the biological distinction of an organism between male and female.
Sex or SEX may also refer to:
Biology and behaviour
*Animal sexual behaviour
**Copulation (zoology)
**Human sexual activity
**Non-penetrative sex, or sexual outercourse
** ...
reproduction,
metamorphosis, and the growth and differentiation of
stem cells in the adult organism. Development of both animals and plants is further considered in the articles on
evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
,
population genetics,
heredity,
genetic variability
Genetic variability is either the presence of, or the generation of, genetic differences.
It is defined as "the formation of individuals differing in genotype, or the presence of genotypically different individuals, in contrast to environmentally i ...
,
Mendelian inheritance
Mendelian inheritance (also known as Mendelism) is a type of biological inheritance following the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, and later popularize ...
, and
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, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
, 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 living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
s such as
mammalogy,
ornithology,
herpetology, or
entomology, but use those organisms as systems to answer general questions about evolution.
Evolutionary biology is partly based on
paleontology, which uses the
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
record to answer questions about the mode and tempo of evolution,
and partly on the developments in areas such as
population genetics and evolutionary theory. Following the development of
DNA fingerprinting 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 re-entered evolutionary biology from its initial exclusion from the
modern synthesis through the study of
evolutionary developmental biology. Related fields often considered part of evolutionary biology are
phylogenetics
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...
,
systematics, and
taxonomy.
Ethology
Ethology is the
scientific
Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe.
Science may be as old as the human species, and some of the earliest archeological evidence for ...
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 characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
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 heritable traits characteristic of a population over generations. Cha ...
. In one sense, the first modern ethologist was
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
, 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
four questions with regard to animal behavior: what are the
proximate cause
In law and insurance, a proximate cause is an event sufficiently related to an injury that the courts deem the event to be the cause of that injury. There are two types of causation in the law: cause-in-fact, and proximate (or legal) cause. Ca ...
s of the behavior, the
developmental history of the organism, the
survival value and
phylogeny of the behavior? Another area of study is
animal cognition
Animal cognition encompasses the mental capacities of non-human animals including insect cognition. The study of animal conditioning and learning used in this field was developed from comparative psychology. It has also been strongly influen ...
, 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
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
, focusing on topics like
dispersal and
migration
Migration, migratory, or migrate may refer to: Human migration
* Human migration, physical movement by humans from one region to another
** International migration, when peoples cross state boundaries and stay in the host state for some minimum le ...
,
plate tectonics,
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
, and
cladistics. It is an integrative field of study, uniting concepts and information from
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. It is also defined as the study of the history of life ...
,
taxonomy,
ecology,
physical geography,
geology,
paleontology 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 naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
.
Molecular biology
Molecular biology
Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and physi ...
studies the common
genetic and developmental mechanisms of animals and plants, attempting to answer the questions regarding the mechanisms of
genetic inheritance
Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic informa ...
and the structure of the
gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
. In 1953,
James Watson and
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 the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...
and
biochemistry
Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...
. 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
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 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 and
developmental biology, or indirectly, where molecular techniques are used to infer historical attributes of
populations or
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
, as in fields in
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. It is also defined as the study of the history of life ...
such as
population genetics and
phylogenetics
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...
. There is also a long tradition of studying
biomolecules "from the ground up", or molecularly, in
biophysics
Biophysics is an interdisciplinary science that applies approaches and methods traditionally used in physics to study biological phenomena. Biophysics covers all scales of biological organization, from molecular to organismic and populations. ...
.
See also
*
Animal science, the biology of domesticated animals
*
Astrobiology
*
Cognitive zoology
*
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. It is also defined as the study of the history of life ...
*
List of zoologists
*
Outline of zoology
The following outline is provided as an overview of and topical guide to zoology:
Zoology – study of animals. Zoology, or "animal biology", is the branch of biology that relates to the animal kingdom, including the identification, structu ...
*
Palaeontology
*
Timeline of zoology
*
Zoological distribution
Notes
References
External links
Books on Zoologyat
Project Gutenberg
*
Online Dictionary of Invertebrate Zoology'
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Branches of biology