bluuebunny/crossref_metadata_2025 huggingface dataset:
Reptilia (Reptiles)
Authors: Benton Michael J
Published: September 2006

Reptiles are a diverse group of vertebrates, including turtles, crocodiles, lizards and snakes, as well as the extinct dinosaurs, pterosaurs, plesiosaurs and ichthyosaurs. Reptiles lay cleidoic eggs (adapted to dry land), and they include the ancestors of birds and mammals.
Synapsida (‘Mammal‐like Reptiles’)
Authors: Sues Hans‐Dieter
Published: September 2006

In the phylogenetic system, the Synapsida include Mammalia and all other amniotes more closely related to Mammalia than to Reptilia. Nonmammalian synapsids form an extensive series of taxa that are successively more closely related to mammals and are often collectively referred to as ‘mammal‐like reptiles’. This vernacular term alludes to the superficially ‘reptilian’ appearance of many primitive synapsids. It has become scientifically meaningless because Synapsida and Reptilia are now interpreted as two entirely distinct evolutionary lineages of Amniota.
Palaeognathae (Flightless Birds)
Authors: Dyke Gareth J
Published: September 2006

There are two broad subdivisions within living birds represented by the neognathous birds (Neognathae) and palaeognathous birds (Palaeognathae). The palaeognaths are characterized by a primitive internal skull morphology and the absence of a keel on the sternum (they are, therefore, flightless). Palaeognathae comprises a number of well‐known flightless birds: the ostrich, rhea, emu, cassowaries, kiwis and tinamous.
Mammalia
Authors: Shoshani Jeheskel
Published: September 2006

Mammalia is a monophyletic taxon whose diagnostic features include a dentary bone in its lower jaw (for living and extinct members), hair (for living and some extinct members), and mammary glands (for living taxa). Earliest mammals lived in the late Triassic period (Mesozoic era) coexisting with dinosaurs; they were small (rat‐size), nocturnal, insectivorous, plantigrade, possessing a muscular prehepatic diaphragm (inferred), had developed senses of hearing and smell, enlarged brains, and were endotherms (inferred).
Marsupialia (Marsupials)
Authors: Croft David B
Published: September 2006

There are around 250 species of marsupials found predominantly in Australia and South America. Many are convergent in form to placental mammals but they differ in reproduction, physiology and behaviour offering an alternative view on mammalian adaptation and lifestyles to their more diverse placental counterparts.
Edentata and Pholidota (Armadillos, Anteaters and Tree Sloths)
Authors: Rose Kenneth D
Published: September 2006

The mammalian order Edentata includes the armadillos, sloths and anteaters, and the extinct glyptodonts; the mammalian order Pholidota comprises the pangolins or scaly anteaters.
Carnivora (Carnivores)
Authors: Anyonge William N
Published: September 2006

Carnivores are terrestrial or aquatic predators that usually consume other animals as a major part of their diet.
Scandentia (Tree Shrews)
Authors: Beard Chris
Published: September 2006

Tree shrews constitute an order of placental mammals known as Scandentia, represented by about 18 living species native to southern and southeastern Asia. Roughly similar in appearance to squirrels, tree shrews are scansorial omnivores that are equally adept on the ground and in the trees. Although tree shrews have often been considered the nearest living relatives of primates, this distinction may belong to dermopterans instead.
Dermoptera (Flying Lemurs)
Authors: Beard Chris
Published: September 2006

Dermopterans are an order of placental mammals represented by only two living species confined to Southeast Asia. Numerous anatomical specializations for arboreal climbing and gliding distinguish dermopterans from other mammals. Competing phylogenetic reconstructions place dermopterans as the nearest relatives of either primates or bats.
Chiroptera (Bats)
Authors: Jones Kate E
Published: September 2006

Bats are the second largest order of placental mammals after rodents, consisting of over 900 species in at least 17 families and 177 genera. They are unique among mammals as they are the only group to have evolved truly powered flight. Bats have a worldwide distribution with extremely diverse ecologies, life histories, morphologies and unique sensory adaptations.
Perissodactyla (Odd‐Toed Ungulates Including Horses, Rhinoceroses and Tapirs)
Authors: Prothero Donald R
Published: September 2006

The mammalian order Perissodactyla, or ‘odd‐toed’ ungulates, includes the living horses, rhinoceroses and tapirs, and two extinct groups, the brontotheres and chalicotheres. Over their 55 million years, they evolved into an amazing variety of forms, and about 40 million years ago, they were the dominant hoofed mammals on the planet. Since then, they have been largely replaced by the even‐toed artiodactyls, and today most wild perissodactyl species are on the brink of extinction.
Artiodactyla (Even‐Toed Ungulates Including Sheep and Camels)
Authors: Theodor Jessica M
Published: September 2006

The Artiodactyla are the even‐toed ungulates, one of the most diverse groups of living mammals, including many game and domestic animals, such as sheep and camels. There are over 200 species living worldwide, and many more extinct forms.
Human Evolution: Overview
Authors: Wood Bernard A
Published: September 2006

The fossil evidence for human evolution can be traced from close to 4.5 Ma to the present. The new term for modern humans and the human clade is ‘hominin’, which replaces the older name ‘hominid’.
Hyracoidea (Hyraxes)
Authors: Shoshani Jeheskel
Published: September 2006

Hyracoidea (hyraxes) appear to have originated in Africa from ungulate mammals. Despite their rabbit size, lack of visible tail, and absence of trunk, hyraxes are the closest land relatives of elephants.
Tubulidentata (Aardvarks)
Authors: Shoshani Jeheskel
Published: September 2006

Tubulidentata is the only mammalian order that contains a single living species, the aardvark,Orycteropus afer. It has been called a ‘living fossil’ because it exhibits primitive anatomical characters that have shown little or no morphological change over about 20 million years. The ordinal name Tubulidentata is derived from tiny dentinal tubules found in the chewing surfaces of its teeth. Tubulidentata probably originated in Africa and has its roots in a group of extinct archaic ungulates known as the condylarths.
Mesozoa (Dicyemids)
Authors: Furuya Hidetaka
Published: September 2006

The dicyemid mesozoan is a unique multicellular animal found in the kidney of benthic cephalopod molluscs. The life cycle is complex, but the body organization is the simplest among multicellular animals.
Nemertea (Ribbon Worms)
Authors: Moore Janet , Gibson Ray
Published: September 2006

Nemerteans form a phylum of predominantly marine soft‐bodied, often elongate, worms with no general body cavity. They are characterized by an eversible proboscis separate from the gut, a gut with separate mouth and anus, and a closed blood system.
Gnathostomulida (Unsegmented Marine Worms)
Authors: Sterrer Wolfgang
Published: September 2006

Gnathostomulida are microscopic, free‐living, unsegmented, entirely monociliated marine worms most likely related to Rotifera, Acanthocephala and Micrognathozoa.
Kinorhyncha
Authors: Kristensen Reinhardt Møbjerg
Published: September 2006

The kinorhynchs (mud dragons) are a small phylum of microscopic, free‐living, segmented acoelomate or pseudocoelomate invertebrates belonging exclusively to the marine meiofauna. Some 150 species have been described from polar to tropical environments. The kinorhynchs have their phylum, but they are related to the phyla Loricifera and Priapulida. Cambrian microfossils may belong to the stemgroup of both Kinorhyncha and Priapulida.
Loricifera
Authors: Kristensen Reinhardt Møbjerg
Published: September 2006

The loriciferans are a group of newly discovered microscopic marine animals with a complex life cycle and worldwide distribution. Despite their small size, they have complex alimentary, reproductive, excretory, nervous and muscle systems. The head of the adult can have more than two hundred appendages, and the larvae always have terminal toes. The loriciferans have their own phylum, which is related to the phyla Kinorhyncha and Priapulida.
Priapulida
Authors: Wallace Robert Lee
Published: September 2006

Priapulida is a very small phylum of free‐living worms that inhabit marine sediments from the littoral zone to abyssal waters. The phylum name (Greek,
priapus
, phallus), given by Lamarck in 1816, comes from the fact that these worms resemble a small penis.
Nematoda (Roundworms)
Authors: Poinar George
Published: September 2006

The Nematoda are a group of non‐segmented worm‐like invertebrates that occur worldwide in a wide range of habitats.
Nematomorpha (Horsehair Worms)
Authors: Poinar George
Published: September 2006

The phylum Nematomorpha, the hairworms, are parasitic worms that occur worldwide. While one genus,
Nectonema
, is marine, all of the remaining species occur in fresh or brackish water as adults, and as parasites of aquatic or terrestrial invertebrates during their developmental stage.
Acanthocephala (Thorny‐Headed Worms)
Authors: Crompton DWT
Published: September 2006

The Acanthocephala or thorny‐headed worms constitute a group of about 1100 species of endoparasites. Sexual maturity occurs in the gut of a vertebrate and development in the body cavity of an arthropod.
Entoprocta
Authors: Nielsen Claus
Published: September 2006

The entoprocta are a small phylum of minute, solitary or colonial, sessile, aquatic animals. About 150 species have been described worldwide, with only one species occurring in freshwater. The colonial species encrust stones, shells and algae, and species have been described from all oceans. The solitary species are mostly associated with water‐current‐producing hosts, such as polychaetes, sponges and bryozoans; these species are not conspicuous and most of the reported distributions reflect specialists' searches.
Annelida (Segmented Worms)
Authors: Rouse Greg W
Published: September 2006

Annelida contains a large assemblage of mainly marine animals that are commonly referred to as segmented worms. It also contains terrestrial groups such as earthworms and leeches.
Arthropoda (Arthropods)
Authors: Blackstone Neil W
Published: September 2006

The Arthropoda is a phylum of ecdysozoan animals in which the epidermis produces a segmented, jointed, and hardened exoskeleton, which has internal musculature.
Chelicerata (Arachnids, Including Spiders, Mites and Scorpions)
Authors: Shultz Jeffrey W
Published: September 2006

Chelicerata is the group of arthropods that includes the marine sea‐spiders and horseshoe crabs and the terrestrial arachnids (spiders, mites, scorpions and their relatives). They have two main body regions, and the arachnids typically have eight walking legs. They are covered by a jointed exoskeleton and grow by periodic moulting. Chelicerates are typically predaceous and most terrestrial forms ingest only liquefied food. Next to insects, they are the most diverse and numerous animals.
Myriapoda (Including Centipedes and Millipedes)
Authors: Wright Jonathan C
Published: September 2006

The Myriapoda comprise four classes of terrestrial arthropods: Chilopoda or centipedes, Diplopoda or millipedes, Symphyla and Pauropoda. Myriapods are generally found in soil and litter and have a worldwide distribution.
Insecta (Insects)
Authors: Jarzembowski EA
Published: September 2006

Insects are the most diverse organisms on Earth with a long evolutionary history and are one of the most successful groups of organisms to have existed.
Pentastomida
Authors: Riley John
Published: September 2006

Pentastomids comprise an ancient taxon of about 110 species of vermiform endoparasites which attain maturity in the respiratory tracts of terrestrial tetrapods. About 85% of species inhabit the lungs of reptiles. Life cycles usually involve an intermediate host, although a few are direct. An unprecedented fossil record, dating from the late Cambrian, indicates a long association with vertebrates.
Onychophora (Velvet Worms)
Authors: Wright Jonathan C
Published: September 2006

The phylum Onychophora, also known as ‘peripatus’, ‘velvet worms’, or ‘walking worms’, comprises over 100 described species. Long believed to be an evolutionary ‘missing link’ between annelids and arthropods, they are now usually classified within the Arthropoda. Onychophorans are exclusively terrestrial, but are susceptible to desiccation and are restricted to humid microsites. The majority of species inhabit tropical forest litter.
Brachiopoda (Lamp Shells)
Authors: Cohen Bernard L
Published: September 2006

Members of the phylum Brachiopoda are predominantly sessile, filter‐feeding marine invertebrates with a bivalved shell that, in adult life, is functionally divided into inhalant and exhalant chambers by a ciliated, tentaculate curtain‐like feeding organ or lophophore. One subphylum is commonly known as ‘lamp‐shells’.
Neogene Time Scale
Authors: Berggren William A
Published: September 2006

The Neogene Period/System (approximately the past 24 million years) is the younger of a twofold subdivision of the Cenozoic Era which includes as its lower component the Palaeogene Period/System (65–24 Ma). It includes the Miocene, Pliocene and Pleistocene (and in some sources Holocene) Epochs/Series.
Molecular Palaeontology
Authors: Waggoner Ben
Published: September 2006

The traces that organisms of the past have left are not restricted to their bones, shells, imprints, and tracks; biogenic macromolecules may also survive in the fossil record. As techniques for studying fossil macromolecules have expanded, information from molecules has complemented and expanded our knowledge of the history of life as derived from other types of fossils.
Fossil Record: Quality
Authors: Benton Michael J
Published: September 2006

There are divergent opinions about the quality of the fossil record and its ability to give a useful representation of the history of life. Extensive testing, by comparisons of the congruence of morphological and molecular phylogenies suggests that the fossils do tell the story relatively well.
Continental Drift
Authors: Prothero Donald R
Published: September 2006

The old notion that continents have drifted apart over geological time was revived by the scientific revolution of plate tectonics in the 1960s. Geologists now believe that the Earth's crust is made up of about 20 tectonic plates which are constantly shifting with respect to one another at a rate of centimetres per year. These plate motions and interactions are responsible for most of the Earth's volcanoes, earthquakes, mountain belts, and many other geological phenomena.
Palaeoclimatology
Authors: Parrish Judith Totman
Published: September 2006

Palaeoclimatology is the study of climates in the Earth's past.
Ice Ages
Authors: Davis Owen
Published: September 2006

Ice ages are periods of the Earth's history characterized by glacier advance and cold climate. The response of the Earth's systems to ice ages includes extinctions and migrations of the biosphere, expansion and contraction of oceans and lakes, and the waxing and waning of glaciers.
Origin of Life
Authors: Brack André
Published: September 2006

Strategies to understand the origin of life include the search for fossilized terrestrial life as well as the search for a second genesis of life, either artificial in a test tube or natural on another planet.
Terrestrialization (Precambrian–Devonian)
Authors: Selden Paul A
Published: September 2006

The emergence of plants and animals from the sea onto land – terrestrialization – was one of the major advances in the history of life on Earth. Evidence for early colonization is poor, but the fossil record reveals that by mid‐Palaeozoic times complex terrestrial ecosystems had become established.
Mesozoic Marine Revolution
Authors: Gregory F John
Published: September 2006

The Mesozoic is characterized by a dramatic diversification of marine invertebrates and vertebrates. This affected both the existing marine ecosystems and the modern ecosystems that subsequently developed. Causes of the diversification include the end‐Permian and Early Triassic mass extinctions, continental break‐up, oceanic partitioning and sea‐level fluctuations.
Terrestrial Ecosystems in the Past 100 Million Years
Authors: Elias Scott A
Published: September 2006

Terrestrial ecosystems are the large‐scale associations of the biological communities living on land. Although the last 100 million years represent only a small fraction (perhaps 2%) of the earth's history, revolutionary changes in terrestrial life occurred during this period.
Extinction
Authors: MacLeod Norman
Published: September 2006

Extinction is the act or process of dying‐out for a species or evolutionary lineage. It is one of the most common of all ecological/evolutionary processes and represents the inevitable corollary of natural selection. Information on extinction comes from many sources, including laboratory experiments, field studies, and the fossil record. The causes of short‐term extinctions involving few species can, in principle, be well understood. But the causes of long‐term extinction events, such as those preserved in the fossil record, remain controversial.
Extinction: End‐Triassic Mass Extinction
Authors: Wignall Paul B
Published: September 2006

The end of the Triassic period, roughly 201 million years ago, was marked by one of the biggest mass extinction events in the history of life. Estimates of magnitude vary, but recent compilations suggest that it may have been one of the greatest extinction events of the fossil record. It has been estimated that nearly 70 terrestrial families and 60 marine families disappeared at the end of the Triassic, corresponding to 23% and 18% extinction, respectively.
Extinction: K–T Mass Extinction
Authors: MacLeod Norman
Published: September 2006

The K–T mass extinction event occurred at the end of the Cretaceous System (K, for kreta or chalk, a common Cretaceous rock type) and the beginning of the Tertiary System (T), when approximately 60–80% of marine invertebrate species became extinct as a result of climate changes brought about by a sharp fall in global sea level, a major episode of continental flood basalt volcanism, and a large bolide (asteroid or comet) impact.
Origin of Novelties
Authors: Carroll Robert L
Published: September 2006

The term ‘novelty’ in evolutionary biology is applied to structures or processes that evolve within groups without obvious precursors among their probable ancestors. The genetic system that enables the generation of novelties in multicellular animals evolved in the late Precambrian and Early Cambrian. Continuing change within the elements of this system explains how novelties have arisen within the metazoan phyla over the last 600 million years.
Speciation and the Fossil Record
Authors: Pearson Paul N , Harcourt‐Brown Katherine G
Published: September 2006

The fossil records of marine microfossils, shallow marine invertebrates and terrestrial vertebrates permits the study of individual speciations and their consequences over time scales up to millions of years.
Red Queen Hypothesis
Authors: Pearson Paul N
Published: September 2006

Van Valen's Red Queen hypothesis is a model of coevolution driven by competitive interactions between species. It contrasts with the stationary or ‘lost world’ model, in which evolution is driven primarily by environmental change.
Tiering in the Sea – Reefs and Burrows (Late Palaeozoic)
Authors: Wood Rachel A
Published: September 2006

Ancient reefs in the Late Palaeozoic were dominated by microbial communities, together with a variety of calcified algae and suspension‐feeding metazoans. Tiering in epafaunal communities increased significantly in the Ordovician, but infaunal tiering developed slowly, with occupation of deeper depths being achieved only by the Lower Carboniferous.
Plant Cell: Overview
Authors: Doris Fiona , Steer Martin
Published: September 2006

Although plant cells share the same eukaryotic ancestor cells as animal cells, and hence bear strong resemblance to one another, there are many differences between the two. These differences reflect the distinct structural, developmental and environmental pressures which plant cells experience and include the presence of cell walls, differences in membrane structure and changes to the endomembrane system and structures associated with cell division.
Plant Golgi Apparatus
Authors: Hawes Chris , Satiat‐Jeunemaitre Béatrice
Published: September 2006

The plant Golgi apparatus exists as a number of discrete units
known as Golgi bodies distributed in the cytoplasm. Its primary role is the
glycosylation of secretory proteins, the construction of complex cell wall
polysaccharides and the packaging and targeting of such products either to the
vacuole or to the cell surface.
Plant Exocytosis, Endocytosis and Membrane Recycling in Turgid Cells
Authors: Battey Nicholas H
Published: September 2006

In plant cells growth is dependent on cell wall building and plasma membrane growth; secretion of proteins is vital for cell function and cell–cell communication. The fusion of secretory vesicles at the plasma membrane (exocytosis) is a key mechanism because it delivers proteins, wall polysaccharides and membrane; endocytosis retrieves excess membrane. The balance of exocytosis–endocytosis is therefore crucial to plant development, is highly regulated, and is an intriguing subject for future research.
Plant Peroxisomes and Glyoxysomes
Authors: Donaldson Robert Paul , Assadi Masoumeh , Karyotou Konstantina , Olcum Tulin , Qiu Tianqing
Published: September 2006

Peroxisomes and glyoxysomes are membrane enclosures, both referred to as microbodies, which contain oxidative enzymes that participate in photorespiration in leaves, nitrogen metabolism in root nodules, and fat conversions in seeds. The enzymes found within microbodies are brought in from the cytosol by information described as peroxisomal targeting sequences (PTS).
Plant Cells: Plasmodesmata
Authors: Oparka Karl J
Published: September 2006

Plasmodesmata are plasma membrane‐lined pores that span the adjoining walls of plant cells. They permit the intercellular passage of several molecules and signals and play a central role in plant development.
Plant Cell Wall Biosynthesis
Authors: Fry Stephen C
Published: September 2006

Most plant cell wall polymers are synthesized from ‘activated’ precursors by the action of transferases. These enzymes are located in cell membranes (synthesizing polysaccharides and glycoproteins) or in the cell wall itself (synthesizing cutin and suberin). Lignin, in contrast, is synthesized in the wall by oxidative rather than transferase‐catalysed reactions.
Plant cytoskeleton
Authors: Lloyd Clive W
Published: September 2006

The major filamentous elements of the plant cytoskeleton are
microtubules and actin microfilaments. Although essentially similar to those
found in animals, they make different structures that reflect the special
features of plant growth.
Plant Cell Differentiation
Authors: Hülskamp Martin , Ilgenfritz Hilmar
Published: September 2006

During plant cell development cells become specialized for a
particular function. This process is called plant cell differentiation.
Drift: Introduction
Authors: Whitlock Michael C , Phillips Patrick C
Published: September 2006

Genetic drift is the random change in allele frequencies by the chance success of some alleles relative to others.
Multigene Families: Evolution
Authors: Walsh J Bruce , Stephan Wolfgang
Published: September 2006

Groups of genes showing similarity with each other are referred to as a gene family, arising from wholesale or partial gene duplication. The clustering of functionally related members of a gene family reflects their common ancestry and subsequent duplication and divergence. It has been speculated that gene duplication is essential for the creation of major evolutionary novelty. Genome projects will help in understanding the importance of gene duplications underlying macroevolutionary events.
Adaptation and Natural Selection: Overview
Authors: Mitton Jeffry B
Published: September 2006

Adaptation is both an evolutionary process and a product of natural selection: adaptation is a process of evolution in which traits are modified by natural selection; an adaptation is a phenotypic trait moulded by natural selection. In both cases the evolution is driven by natural selection.
Intragenomic Conflict
Authors: Spencer Hamish G
Published: September 2006

Intragenomic conflict is the struggle for survival among different elements of the genome. In this struggle, manifested in a number of different ways, so‐called selfish genetic elements distort the standard rules of inheritance to gain a transmission advantage over other parts of the genome, often at the expense of the host organism itself.
Microevolution and Macroevolution: Introduction
Authors: Callahan Hilary S
Published: September 2006

Microevolution and macroevolution are terms for describing biological patterns and processes observed at short and long time scales, respectively. A deeper question is whether different biological processes account for microevolutionary and macroevolutionary change.
Natural Selection: Sex Ratio
Authors: Seger Jon
Published: September 2006

Natural selection acts strongly on the proportional numbers of male and female offspring among the progeny of adults. The equilibrium is often one at which males and females are produced in roughly equal numbers, but under certain ecological and genetic circumstances there may be dramatic population‐wide biases, and even in populations with balanced sex ratios, parents are often selected to produce strongly male‐ or female‐biased progenies in response to variations in their individual condition.
Mutations and New Variation: Overview
Authors: Johnston Mark O
Published: September 2006

A mutation is a heritable change in the genetic material that is not due to genetic recombination. Mutation alters the structure or number of genes or entire chromosomes.
Adaptation: Genetics
Authors: Travisano Michael
Published: September 2006

Adaptation results from the fixation of alleles that improve fitness. The precise mechanism by which adaptive alleles are fixed and the average phenotypic effect of alleles are as yet unknown.
Geographical Variation
Authors: Mousseau Timothy A , Olvido Alexander E
Published: September 2006

Geographical variation refers to differences among populations of organisms in genetically based traits across the geographical range of that species.
Population Genetics: Overview
Authors: Ewens Warren J
Published: September 2006

Population genetics is concerned with the analysis of factors affecting the genetic composition of a population. Since any presently observed population is the outcome of an evolutionary process, the subject is in large part concerned with evolutionary questions. Since the Darwinian theory is population‐based, population genetics is the description of that theory in genetic terms.
Hardy–Weinberg Theorem
Authors: Hastings Alan
Published: September 2006

The Hardy–Weinberg theorem states what the genotype frequencies are, in terms of the gene frequencies, at a single locus, under the simplest assumptions for the genetic processes in a diploid organism. It is essentially the cornerstone on which much of the theory of population genetics has been built.
Species and Speciation: An Overview
Authors: Otte Daniel
Published: September 2006

A species is the fundamental or basic unit of organic or biological diversity, usually characterized as a set of individuals or populations of individuals that comprise an interbreeding or potentially interbreeding unit. Speciation is the formation or origin of species, usually the formation of several new daughter species from an existing ancestral species.
Species Concepts
Authors: Ghiselin Michael T
Published: September 2006

The species is one of the most fundamental units in biology. However, there are different concepts of what is meant by the term ‘species’ that reflect diverse goals and priorities on the part of scientists.
Isolating Mechanisms
Authors: Butlin Roger K
Published: September 2006

Isolating mechanisms are intrinsic characteristics of species that reduce or prevent successful reproduction with members of other species. Viewed genetically, they are characters that act as barriers to the exchange of genes between populations.
Speciation: Allopatric
Authors: Howard Daniel J
Published: September 2006

Allopatric speciation, the splitting of one species into two as a result of the geographic separation of populations, is regarded by many evolutionists as the predominant mode by which new species are formed and biodiversity generated.
Speciation: Sympatric and Parapatric
Authors: Ritchie Michael G
Published: September 2006

Sympatric and parapatric speciation refer to the origin of species in the absence of complete geographic isolation between the diverging taxa. Until recently, most biologists believed that geographic isolation was an obligatory stage in the development of most species, i.e. most species originated in allopatry. However, new empirical and theoretical studies have shown that speciation may occur despite the incipient species having adjacent or overlapping geographic ranges.
Natural Selection: Introduction
Authors: Reznick David
Published: September 2006

Most organisms have relatively stable populations, so that, of all those born, only some survive to reproduce. Those that survive do so because they are in some way better suited to their environment. This process involves natural selection by environmental pressures among all of the variations present in a population. Over time, those alleles that enhance survival and/or reproductive success will become more common in the population and the genetic composition of the population will change.
Hybrid Zones
Authors: Hewitt Godfrey M
Published: September 2006

A hybrid zone occurs where two distinct genetic forms meet, mate and produce offspring with mixed genomes. Such zones may vary in width, length and patchiness, and are found between species, subspecies, races or forms.
Hybrid Speciation
Authors: Rieseberg Loren H
Published: September 2006

Hybridization between genetically divergent populations may lead to the formation of new evolutionary lineages. This may occur via the duplication of a hybrid's chromosome complement or by the stabilization of a fertile hybrid segregant.
Speciation: Genetics
Authors: Rieseberg Loren H , Ungerer Mark C
Published: September 2006

New species arise when previously interbreeding populations become isolated by reproductive barriers. These barriers are thought to originate as a byproduct of genetic divergence between geographically isolated populations; they may have a complex polygenic basis or be under simple genetic control.
Heterozygous Advantage
Authors: Mitton Jeffry B
Published: September 2006

Heterozygous advantage, also called overdominance, refers to the fitness superiority of heterozygotes over homozygotes. Heterozygote advantage, frequency‐dependent selection and some modes of selection in fluctuating environments are all forms of balancing selection, which actively maintains genetic variation.
Coevolution
Authors: Thompson John N
Published: September 2006

Coevolution is the process of reciprocal evolutionary change between interacting species, driven by natural selection. It is one of the major processes organizing the Earth's biodiversity into interrelated communities of species.
Coevolution: plant–Microorganism
Authors: Thrall Peter H , Watkin Elizabeth LJ , Burdon Jeremy J
Published: September 2006

Plant–microorganism coevolutionary interactions cover a very wide arena involving the interactions between plants and many bacteria, fungi, viruses and nematodes.
Environmental Heterogeneity: Temporal and Spatial
Authors: Pigliucci Massimo
Published: September 2006

Environments experienced by living organisms can be heterogeneous in a variety of ways. Variation in time and in space have distinct consequences for the fitness of plants and animals, and elicit different types of evolutionary responses through natural selection.
Drift: Theoretical Aspects
Authors: Ohta Tomoko
Published: September 2006

Drift is the process by which gene frequency changes erratically in a population.
Coalescence
Authors: Brookfield John FY
Published: September 2006

Coalescence is the process whereby alleles sampled from a population can be traced back to a single ancestor. The structure of this genealogy can reveal whether the population has been constant in size and whether it has been geographically subdivided. It can also suggest whether selection has operated.
Evolution: Shifting Balance Theory
Authors: Tonsor Stephen J , Moore Francisco B‐G
Published: September 2006

The shifting balance is an evolutionary process by which: 1) Drift and selection in small populations drive among‐population epistatic differentiation. 2) The epistatic combinations differ in fitness, and their mean fitnesses are dependent on the joint frequencies of the various epistatic combinations. 3) Epistatic differentiation among populations drives among‐population selection when migration levels depend on population mean fitness. This leads to the replacement of the ancestral epistatic combination throughout the metapopulation, under some circumstances.
Adaptive Radiation
Authors: Murren Courtney J
Published: September 2006

Adaptive radiation is a diversification of a single lineage into morphologically or physiologically distinct taxa that are adapted to a certain set of environmental conditions.
Evolutionary Trends
Authors: McNamara Kenneth J
Published: September 2006

An evolutionary trend can be defined as a persistent, directional change in a character state, or set of character states, resulting in a significant change through time.
Quantitative Genetics
Authors: Walsh Bruce
Published: September 2006

Almost any trait that can be defined shows variation, both within and between populations. Quantitative genetics is concerned with the analysis of the genetic and environmental basis of this variation. Classical genetics typically deals with single genes of large effect, while quantitative genetics often assumes a large number of genes, each with small effects, influence trait variation.
Human Population Genetics: Drift and Migration
Authors: Chakraborty Ranajit
Published: September 2006

Genetic drift is the effect of changes in genetic composition of a finite population, due to random replacement of alleles from one generation to the next. Migration effect specifies alterations caused by exchange of genes between populations.
Industrial Melanism
Authors: Grant Bruce S , Clarke† Sir Cyril A
Published: September 2006

Industrial melanism refers to the evolution of dark body colours in animal species that live in habitats blackened by industrial soot. The phenomenon has been documented notably in species that hide from predators by blending in with their backgrounds.
Natural Selection: Responses to Current (Anthropogenic) Environmental Changes
Authors: Thomas Sean C , Kingsolver Joel G
Published: September 2006

Human‐caused changes in the environment are pervasive, as are evolutionary responses to these changes by living organisms. Selective responses to anthropogenic environmental change have thus been the topic of extensive research, providing hundreds of well‐documented cases of natural selection in action. Many of these responses are also of great importance from an ecological, economic and human health perspective.
Mimicry
Authors: Turner John RG
Published: September 2006

Mimicry is the resemblance of one organism to another (or to an inanimate object), a resemblance that confers an adaptive advantage on at least one of the organisms.
Human Populations: Origins and Evolution
Authors: Harding Rosalind M , Relethford John H
Published: September 2006

The origins of modern human diversity have been debated within a framework set by two hypotheses: ‘Out of Africa’ versus ‘multiregional’ evolution. For a better understanding of how human populations evolved, a new framework for analysis of genetic data is needed.
Molecular Evolution: Techniques
Authors: Mable Barbara K
Published: September 2006

Progress in the field of molecular evolution has been intricately tied to advances in the techniques used to characterize the molecular basis of genetic change. Although DNA sequencing currently provides the most information on evolutionary processes at the molecular level, techniques such as immunological distances, protein sequencing, protein electrophoresis, DNA hybridization, and restriction fragment analyses contributed to the development of more advanced techniques and continue to have important usages.
Molecular Evolution: Patterns and Rates
Authors: Bromham Lindell
Published: September 2006

The pace of DNA evolution varies across the genome and between species, determined by the balance between mutation, selection and drift.
Molecular Evolution: Neutral Theory
Authors: Takahata Naoyuki
Published: September 2006

The neutral theory is shorthand for the theory that at the molecular level evolutionary changes and polymorphisms are mainly due to selectively neutral mutations; thus, their behaviour and fate are determined by mutation and random drift. The theory explains polymorphism as a transient phase of molecular evolution, and demands a dichotomy between molecular and phenotypic evolution.
Molecular Evolution: Nearly Neutral Theory
Authors: Ohta Tomoko
Published: September 2006

Nearly neutral theory is an extension of the neutral theory and contends that the borderline mutations whose effects lie between the selected and the neutral classes are important at the molecular level.
Base Composition Patterns
Authors: Eyre‐Walker Adam
Published: September 2006

The composition of DNA varies between species and within a single genome. The principal patterns are reviewed together with the reasons that variation in base composition might have evolved.
Plant Secondary Metabolism
Authors: Haslam Edwin
Published: September 2006

Plants and microorganisms synthesize an extraordinary array of natural products that, in the majority of cases, appear to play no explicit role in the welfare and economy of the producing organism. For this reason they are commonly referred to as secondary metabolites.
Functional Morphology and Physiology: Comparative Methods
Authors: Westneat Mark W
Published: September 2006

A central goal of biology is to compare organismal structure, function and physiology among a diversity of life forms spanning major evolutionary changes. Special methods now allow the integration of physiology, functional morphology and other traits with evolutionary information to reveal physiological evolution.
Vertebrate Metabolism
Authors: Jones James H
Published: September 2006

Metabolism is the term used to describe all of the transformations and exchanges of chemicals and energy that occur in an organism's body.
Vertebrate Respiration and Circulation in Extreme Conditions
Authors: Lillywhite Harvey B
Published: September 2006

The acquisition and internal transport of respiratory gases and metabolic fuels depend on linked processes, with design and function related to energetic demands and attributes of the environment. Environmental challenges to these processes reflect variation in the density of gases and the pressures that prevail in the environmental medium.
Animal Nutrient Requirements
Authors: Hume Ian D
Published: September 2006

Animals eat to satisfy their need for energy for cellular respiration; carbon skeletons and other elements such as nitrogen for the synthesis of larger organic molecules; and essential nutrients that the animal cannot synthesize from any raw material. The nutrients that animals need include water, carbohydrates, lipids and proteins, essential amino acids, essential fatty acids, vitamins and minerals.
Vertebrate Food Pathway and Gut: Overview
Authors: Hume Ian D
Published: September 2006

The width of an animal's nutritional niche is determined
by (a) the amounts of energy and specific nutrients it requires; and (b)
how successfully it acquires and extracts those nutrients from available food
resources.
Ingestion in Reptiles and Amphibians
Authors: Nishikawa Kiisa , Schwenk Kurt
Published: September 2006

The feeding stages of prey capture, ingestion, processing,
intraoral transport and swallowing are accomplished in different ways in
different species of amphibians (caecilians, salamanders and frogs) and
reptiles (crocodilians, turtles, tuatara, lizards, amphisbaeneans and snakes
– birds have diverged so much from other reptile groups that they can be
considered separately). The structural and ecological diversity of amphibians
and reptiles is reflected in the diversity of their feeding systems.
Digestive System of Fish
Authors: Horn Michael H , Gawlicka Anna
Published: September 2006

Acquisition of nutrients and energy essential for metabolism and
growth in fish involves the processes of secretion, digestion and absorption
and, in some cases, unique structures such as pyloric caeca or a spiral valve.
The digestive tract is also involved in electrolyte and water balance.
Digestive System of Mammals
Authors: Stevens C Edward
Published: September 2006

Mammalian digestive systems share many common characteristics,
but also feature numerous species‐specific adaptations to diet and habitat.
Excretion and Fluid Balance in Vertebrates
Authors: Kokko Juha P
Published: September 2006

Vertebrates have adapted to large variations in environmental
conditions in each of which the internal environment of volume and solute
composition must be maintained within narrow limits. In mammals, some
80–90% of the total osmolality is made up of sodium and chloride
ions. To maintain their highly regulated internal environments, animals must
be ‘in balance’ – a state termed homeostasis that is
achieved through complex positive and negative feedback mechanisms.
Osmoregulation by Vertebrates in Terrestrial Environments
Authors: Hillman Stanley S
Published: September 2006

A terrestrial environment for vertebrates leads to both a passive water loss to the air and solute gain through food. Consequently, terrestrial environments would tend to increase the osmotic concentration of vertebrates. Natural selection has led to a variety of behavioural, physiological and anatomical adaptations to both minimize water loss and excrete solutes in order to maintain a constant osmotic concentration in terrestrial environments.
Coordination and Integration in Vertebrates: Overview
Authors: Gabella Giorgio
Published: September 2006

Integration is the process of combining parts to create a coordinated, or integrated, whole; it is found at all levels of organization of living matter. Every biological function is the expression of some sort of integration of parts, which allows the complexity of a system to grow and new properties to emerge.
Pheromones in Vertebrates
Authors: Faulkes Chris G
Published: September 2006

Pheromones are chemical signals, released from a donor individual, that elicit a specific response in a recipient of the same species. They are generally classified into two types: releaser pheromones produce a relatively rapid, behavioural effect, while primer pheromones lead to longer term physiological or developmental changes in the recipient animal. The use of pheromones as a method of communication is widespread amongst organisms from bacteria to humans.
Reproduction in Amphibians
Authors: Verrell Paul
Published: September 2006

In terms of its most basic components, reproduction in amphibians is similar to that in other vertebrate animals. But, superimposed on this similarity is a level of diversity that is unique among the tetrapods.
Reproduction in Mammals: General Overview
Authors: Harrison Richard M
Published: September 2006

Reproduction in mammals is sexual and, with rare exceptions, fetal nutrition is provided via a placenta. The reproductive and developmental processes are similar in most mammalian species although the time of events can differ greatly.
Reproduction in Monotremes and Marsupials
Authors: Renfree Marilyn , Shaw Geoffrey
Published: September 2006

The three subclasses of mammals are most clearly distinguished from one another by their mode of reproduction and the anatomy of their reproductive tracts. The three species of monotreme are all oviparous, whereas the 276 or more living species of marsupial all give birth to small, altricial young that in most species are retained in the mother's pouch during the extended lactational period.
Reproduction in Eutherian Mammals
Authors: Finn Colin A
Published: September 2006

The eutherians make up the vast majority of extant mammals. They are all viviparous but vary in details of their ovarian cycle, behaviour, placentation and length of gestation.
Biomechanics: Principles
Authors: Lieberman Daniel E
Published: September 2006

Biomechanics is the application of engineering and physics to biology. All biological functions are subject to and constrained by the laws of physics. An understanding of basic physical principles allows one to understand many aspects of animal function, and the relationships between form and function. Of particular importance is the study of how animals generate movement.
Comparative Skeletal Structure
Authors: Rubin Clinton , Alikhani Mani , Rubin Janet
Published: September 2006

The sophisticated organization of the skeleton achieves a structure that can withstand the extremes of functional load‐bearing. The growth, development and repair of the skeletal structure is realized through the tightly regulated remodelling of bone tissue, orchestrated by cells that specifically form or resorb the matrix.
Nervous Control of Movement
Authors: van Leeuwen Johan L , Spierts Igor LY
Published: September 2006

The nervous control of movement involves the neuronal planning of movement trajectories and the maintenance of dynamic stability. It involves various sensory systems (such as muscle spindles) and effectors (such as muscles).
Swimming in Fish
Authors: Fish Frank E
Published: September 2006

Fish swim by a variety of propulsive modes which allow them to operate at different levels of performance. To locomote effectively, fish must be able to reduce drag and maintain stability while efficiently generating thrust.
Vertebrate Peripheral Nervous System
Authors: Thexton AJ
Published: September 2006

The peripheral nervous system can be regarded as all those nerves that fan out from the central nervous system (CNS) and connect with the skin, internal organs, muscles and exocrine glands.
Mendelian Genetic Disorders
Authors: Kennedy Martin Alexander
Published: September 2006

Mendelian disorders occur in families with a pattern that reflects the inheritance of a single causative gene. Studies of families with conditions such as cystic fibrosis, Huntington disease and fragile X syndrome reveal a variety of inheritance patterns that reflect the nature of the underlying gene and the causative genetic lesion.
Haemophilias
Authors: Walter Johannes , High Katherine
Published: September 2006

Haemophilia is a hereditary bleeding disorder caused by a deficiency of one of two plasma clotting factors, factor VIII or factor IX. The clinical symptoms of this X‐linked recessive disease vary depending on the level of activity of the affected factor. Patients may be asymptomatic, except in the face of trauma or surgery, or suffer from mild to severe, often spontaneous, haemorrhage.
Dysmorphism: Syndromes
Authors: Van Esch Hilde , Fryns Jean‐Pierre
Published: September 2006

Dysmorphology is the study of human congenital malformations and combines concepts and knowledge of different medical fields, including embryology, paediatrics and clinical genetics.
Mutation
Authors: Devoret Raymond
Published: September 2006

A mutation is a DNA change that is recorded durably and passed on to the offspring. A number of mutations in germ cells have detrimental effects for they often cause hereditary diseases. Likewise, mutations that accumulate in body cells can generate cancers. Nevertheless, a large number of mutations are neutral in their normal environment. The few advantageous mutations that occur are generally maintained. Mutations that arise at random are constantly sifted through by a selective environment. This dual process works as the driving force of evolution.