Zoology ()
[The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon.] is the branch of
biology that studies the
animal kingdom, including the
structure,
embryology
Embryology (from Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, '' -logia'') is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embr ...
,
evolution,
classification,
habits, and distribution of all animals, both living and
extinct, and how they interact with their
ecosystems. The term is derived from
Ancient Greek , ('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. 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 studied human anatomy and was one of the greatest surgeons of the ancient world, but after the fall of the
Western Roman Empire 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 and early modern period, with
Carl Linnaeus,
Antonie van Leeuwenhoek,
Robert Hooke,
Charles Darwin,
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,
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. With the discovery of the structure of
DNA by
Francis Crick and
James Watson in 1953, the realm of
molecular biology opened up, leading to advances in
cell biology,
developmental biology and
molecular genetics.
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 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, 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 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, while making numerous advances and innovations. In the 13th century,
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 task
He or HE may refer to:
Language
* He (pronoun), an English pronoun
* He (kana), the romanization of the Japanese kana へ
* He (letter), the fifth letter of many Semitic alphabets
* He (Cyrillic), a letter of the Cyrillic script called ''He'' ...
of 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, whose monumental 4,500-page encyclopedia of animals, ''
Historia animalium'', 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 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 Continent#Subcontinents, subcontinent of Eurasia ...
by a renewed interest in
empiricism and the discovery of many novel organisms. Prominent in this movement were
Andreas Vesalius and
William Harvey, who used experimentation and careful observation in
physiology, and naturalists such as
Carl Linnaeus,
Jean-Baptiste Lamarck, and
Buffon who began to
classify the diversity of life and the
fossil record, 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. 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
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 ext ...
and the
mutability of species.
These developments, as well as the results from
embryology
Embryology (from Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, '' -logia'') is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embr ...
and
paleontology, were synthesized in the 1859 publication of
Charles Darwin's theory of
evolution by
natural selection; 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 on peas in 1865, although the significance of his work was not realized at the time.
Darwin gave a new direction to
morphology 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 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, and by the 1930s the combination of
population genetics and natural selection in the
modern synthesis
Modern synthesis or modern evolutionary synthesis refers to several perspectives on evolutionary biology, namely:
* Modern synthesis (20th century), the term coined by Julian Huxley in 1942 to denote the synthesis between Mendelian genetics and ...
created
evolutionary biology.
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
Medical microbiology, the large subset of microbiology that is applied to medicine, is a branch of medical science concerned with the prevention, diagnosis and treatment of infectious diseases. In addition, this field of science studies vario ...
,
immunology, and
cytochemistry. With the sequencing of the
DNA molecule by
Francis Crick and
James Watson in 1953, the realm of
molecular biology opened up, leading to advances in
cell biology,
developmental biology and
molecular genetics. 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 biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage ...
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 appropriat ...
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. Originally it was thought that species were immutable, but with the arrival of Darwin's theory of evolution, the field of
cladistics 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.
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 at the start of the 19th century. Since
Hunter and
Cuvier
Jean Léopold Nicolas Frédéric, Baron Cuvier (; 23 August 1769 – 13 May 1832), known as Georges Cuvier, was a French naturalist and zoologist, sometimes referred to as the "founding father of paleontology". Cuvier was a major figure in nat ...
, comparative
anatomical study has been associated with
morphography, shaping the modern areas of zoological investigation:
anatomy,
physiology,
histology,
embryology
Embryology (from Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, '' -logia'') is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embr ...
,
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 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
organisms by
biological type, such as
genus 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 appropriat ...
. Biological classification is a form of
scientific taxonomy. Modern biological classification has its root in the work of
Carl Linnaeus, who grouped species according to shared physical characteristics. These groupings have since been revised to improve consistency with the
Darwinian 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 outdated. Modern alternative classification systems generally start with the
three-domain system:
Archaea (originally Archaebacteria);
Bacteria (originally Eubacteria);
Eukaryota (including
protists,
fungi,
plants, and
animal
Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage ...
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
* ...
;
kingdom;
phylum;
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 ...
;
order
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
;
family;
genus;
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 appropriat ...
. 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. It includes ranks and
binomial nomenclature
In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name compos ...
. 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 is the
biological discipline that consists of the study of
vertebrate animals, that is animals with a
backbone, such as
fish,
amphibians,
reptiles,
birds and
mammals. The various taxonomically oriented disciplines such as
mammalogy,
biological anthropology,
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 appropriat ...
and study the structures and mechanisms specific to those groups. The rest of the animal kingdom is dealt with by
invertebrate zoology Invertebrate zoology is the subdiscipline of zoology that consists of the study of invertebrates, animals without a backbone (a structure which is found only in fish, amphibians, reptiles, birds and mammals).
Invertebrates are a vast and very ...
, a vast and very diverse group of animals that includes
sponges,
echinoderms,
tunicates,
worms,
molluscs,
arthropods and many other
phyla Phyla, the plural of ''phylum'', may refer to:
* Phylum, a biological taxon between Kingdom and Class
* by analogy, in linguistics, a large division of possibly related languages, or a major language family which is not subordinate to another
Phy ...
, but
single-celled organisms or
protists are not usually included.
Structural zoology
Cell biology studies the structural and
physiological properties of
cells
Cell most often refers to:
* Cell (biology), the functional basic unit of life
Cell may also refer to:
Locations
* Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...
, including their
behavior, 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 ...
. This is done on both the
microscopic and
molecular levels for single-celled organisms such as
bacteria as well as the specialized cells in
multicellular organisms such as
humans. 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 and
phylogeny (the
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 and
animal physiology
Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical a ...
, but some principles of physiology are universal, no matter what particular
organism 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 to non-human species. Physiology studies how, for example, the
nervous,
immune,
endocrine,
respiratory, and
circulatory
The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, t ...
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 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,
population genetics,
heredity,
genetic variability,
Mendelian inheritance, 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 appropriat ...
, as well as their change over time, and includes scientists from many
taxonomically
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 given ...
oriented disciplines. For example, it generally involves scientists who have special training in particular
organisms 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 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
DNA profiling (also called DNA fingerprinting) is the process of determining an individual's DNA characteristics. DNA analysis intended to identify a species, rather than an individual, is called DNA barcoding.
DNA profiling is a forensic t ...
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
Modern synthesis or modern evolutionary synthesis refers to several perspectives on evolutionary biology, namely:
* Modern synthesis (20th century), the term coined by Julian Huxley in 1942 to denote the synthesis between Mendelian genetics and ...
through the study of
evolutionary developmental biology. Related fields often considered part of evolutionary biology are
phylogenetics,
systematics, and
taxonomy.
Ethology
Ethology is the
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 of behavior and the understanding of behavior in terms of the theory of
natural selection. In one sense, the first modern ethologist was
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
Nikolaas "Niko" Tinbergen (; ; 15 April 1907 – 21 December 1988) was a Dutch biologist and ornithologist who shared the 1973 Nobel Prize in Physiology or Medicine with Karl von Frisch and Konrad Lorenz for their discoveries concerning the ...
's
four questions
Ma Nishtana ( he, מה נשתנה) are the first two words in a phrase meaning "Why is tonight different from all other nights?" The phrase appears at the beginning of each line of The Four Questions, traditionally asked via song by the youngest ...
with regard to animal behavior: what are the
proximate causes of the behavior, the
developmental history of the organism, the
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
dispersal and
migration,
plate tectonics,
climate change, and
cladistics. It is an integrative field of study, uniting concepts and information from
evolutionary biology,
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.
Molecular biology
Molecular biology studies the common
genetic and developmental mechanisms of animals and plants, attempting to answer the questions regarding the mechanisms of
genetic inheritance 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 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, 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
population
Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction usi ...
s 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 appropriat ...
, as in fields in
evolutionary biology such as
population genetics and
phylogenetics. There is also a long tradition of studying
biomolecules "from the ground up", or molecularly, in
biophysics.
See also
*
Animal science
Animal science is described as "studying the biology of animals that are under the control of humankind". It can also be described as the production and management of farm animals. Historically, the degree was called animal husbandry and the ...
, the biology of domesticated animals
*
Astrobiology
*
Cognitive zoology
*
Evolutionary biology
*
List of zoologists
This is a list of notable zoologists who have published names of new taxa under the International Code of Zoological Nomenclature.
A
* Abe – Tokiharu Abe (1911–1996)
* Abeille de Perrin, Ab. – Elzéar Abeille de Perrin (1843–1910)
* A ...
*
Outline of zoology
*
Palaeontology
*
Timeline of zoology
*
Zoological distribution
Notes
References
External links
Books on Zoologyat
Project Gutenberg
*
Online Dictionary of Invertebrate Zoology'
{{Authority control
Branches of biology