Frozen Evolution. Or, that’s not the way it is, Mr. Darwin. A Farewell to Selfish Gene.

see Mutations at the level of the entire DNA section

see Monophyly

The pressure of parasites on a host population can be very intense. In fact, in some cases, it can be the basic element of the feedback regulation mechanism maintaining the size of the host population at a constant level. As the size of a parasite population bound to the population of a certain host is usually larger than the size of the population of a predator, the system is less susceptible to random fluctuations. Consequently, the equilibrium in the parasite-host system is usually more stable than in similar systems based on interactions of the predator-prey type. The greater host specificity of the parasite contributes to the stability of these systems. On the other hand, the frequently low food specificity of a predator allows the population of the predator not to be necessarily bound to the size of the population of a certain species of prey. As a consequence, a momentarily numerous population of a predator can completely exterminate the populations of some kinds of prey.
Similar to the predator-prey system, the parasite-host system also belongs, from the viewpoint of the host, amongst feed-back regulation systems of the turbidostat type (Flegr 1977) (see IV.4.1). This means that, in a system regulated by the action of the parasite, the host population is exposed to r selection, i.e. selection for a faster reproduction rate (and not for more effective use of nutrient sources). As a consequence, the species does not utilize the resources to the extreme of the capacity of the environment, so that a larger or smaller amount is left for other species occurring in the particular environment. Through this mechanism, the phenomenon of parasitism apparently contributes very effectively to maintenance of a high level of biodiversity in real ecosystems.
Maintenance of a high level of biodiversity through the presence of parasites is also augmented by the fact that specialized parasites add a further dimension to the multidimensional ecological environment in which organisms live. In section IV.4.1, we mentioned that two species utilizing a single resource can exist next to one another for a longtime in a single place if one of them is the subject of chemostatic and the other of turbidostatic regulation (see the caption for Fig. IV.4). Similarly, permanent coexistence is possible for two species whose populations are turbidostatically regulated through the action of two different species of parasites.
Overall, it can be stated that, in the absence of parasites, natural ecosystems would have far less biodiversity and would probably make less effective use of the available resources.

see Horisontally transmitted parasites and evolution of virulence

The ability of a parasite to survive and reproduce in the host organism and the ability of the parasite population to survive consistently in the population of the host species are a consequence of gradual evolutionary adaptation of the parasite to the particular host species (Kaltz & Shykoff 1998). If the host species comes into contact with a new range of potential parasites, for example if it invades a new territory, it is generally resistant to parasitization by unspecialized parasites. Escaping from the reach of the original parasites is usually considered to be the most important cause of the ecological success of a great many invasive species (Mitchell & Power 2003; Torchin et al. 2003) (Fig. XIX.5). Only after a longer period of time are some parasites that occur in the given territory able to adapt to a new host sufficiently to survive consistently in the population of new hosts and are thus able to bring the spreading of the invasive species under control.
However, in some cases, the pathogenic manifestations of infection by an unadapted parasite are very drastic, so that in a great many cases it ends with the death of the host organism. These cases are apparently far rarer than cases where an unadapted parasite is not capable of reproducing at all and of substantially damaging the new host. However, from the viewpoint of humans, these cases are more obvious and thus they get far more publicity. If the population of hosts survives the meeting with the new parasite, changes gradually occur in the progress of the infection and, understandably, also in the dynamics of its spreading in the host population. Specifically, the pathogenic manifestations of parasitosis are reduced, so that the originally fatal infection is gradually reduced to a milder sickness and, in extreme cases, can even end up practically free of symptoms (asymptomatic) (Combes 1997). The well-documented history of the intentional introduction of the virus of rabbit myxomatosis into Australia (Fig. XIX.6) is a textbook case of reduction of the pathogenicity of infection that has been well documented.
The phenomenon of gradual reduction in the pathogenicity of parasites, described commonly but rather inaccurately as the phenomenon of reduced virulence (see XIX.4.1), is, on the one hand, influenced by evolution of the host organism and selection of individuals that are more resistant to reproduction of the pathogen and to the pathological manifestations of its action in the organism and, on the other hand, selection within the parasitic species is important here, as parasites that do not excessively damage their hosts can produce more infectious stages and infect more hosts during their existence in a single host organism.
However, it should be pointed out that, in a great many cases, the pathogenic processes that accompany parasitosis are directly connected with the reproduction of the parasite – the more invasive stages it forms during the overall time of infection, the more intense are the pathogenic processes and their consequences (Fig. XIX.7). In this case, to the contrary, the pathogenicity gradually increases with gradually increasing adaptation of the parasite. Even cases where the pathogenic processes are part of manipulative behavior of the parasite and participate substantially in the effectiveness of spreading of the parasite in the host population are not exceptional (see below). Also in these cases, the virulence of the parasite is not reduced; to the contrary, the parasite is able to do more damage to the members of species or populations to which it is adapted in the long term (Ebert 1994; Ebert & Herre 1996).

From the viewpoint of game theory, even the Generous Tit for Tat strategy is not an evolutionarily stable strategy in the stochastic world, because its temporary success enables the always cooperate strategy to spread and this allows the successful return of the always betray strategy. So the game does not have a stable solution, and the representation of individual strategies in the population circulates constantly. It seems so far that the only evolutionarily stable strategies are those that do not direct their behavior according to the opponent’s behavior in the last round, but according to how they behaved in the last round and what profit they got from it. A fairly successful, even though not evolutionarily stable strategy of this kind is a strategy named Pavlov (Nowak & Sigmund 1993). It is directed by a simple rule: repeat your behavior from the last round, if it was successful (i.e. you betrayed and the opponent cooperated or you both cooperated), change your behavior if you lost in the last round (i.e. you cooperated and your opponent betrayed or you both betrayed).  The Pavlov strategy, similar to the Generous Tit for Tat, does not allow the always cooperate strategy to spread in the somewhat unpredictable world, but it enables the always betray strategy to spread. Existing results show that even the simplest so-far described evolutionarily stable theories have to be capable of learning, i.e. they must have memory and the ability to remember the results of a number of previous rounds when choosing a strategy for a new round (Wakano & Yamamura 2001). Experiments performed using experimental games with human volunteers have shown that, actually, in a normal population, people mainly follow strategies similar to the Generous Tit for Tat as well as the Pavlov strategy (Fig. XVI.6). At the same time, it has been shown that the actually used strategies were somewhat complicated and also more successful than the Generous Tit for Tat or Pavlov and that the players used information from a number of previous rounds in the strategies (Wedekind & Milinski 1996).

- The hypothetical model of adaptation of the peptide vocabulary of a parasite to the peptide vocabulary of the host is an example of molecular mimicry. This model could also explain the process of speciation of a host species through development of the host vocabulary and its divergence in various subpopulations. If, for example, a certain subpopulation of hosts achieved a change in its peptide vocabulary, for example, if it removed a certain peptide from its vocabulary through substitution mutations, it would, to a certain degree, escape from the reach of a parasite whose vocabulary is adapted to the original host population. The members of this population would begin to identify the relevant peptide in the parasite proteins as a foreign element. It is apparent that vocabulary differentiation can fulfill a protective function only if crossing does not occur between individuals of the two host subpopulations. The advantageousness of genetic isolation can thus lead to the creation of selection pressure on the formation of reproduction barriers.Thus, pressure from parasites could indirectly lead to the formation of isolated species.
The increased susceptibility of crossed individuals occurring in the hybrid zones of some species could be related to differentiation of the peptide vocabularies of two related species. Such a greater susceptibility has been observed, for example, in mice caught in the hybrid zone of the species Mus musculus and Mus domesticus (Moulia et al. 1991; Sage et al. 1986; Moulia et al. 1995) (Fig. XIX.4). The hybrid mice necessarily have a more extensive peptide vocabulary, so they are unable to identify a great many more peptides as foreign than either of the parent species.

- However, anagenetic changes can complicate the reconstruction of cladogenesis. If anagenesis occurs similarly in two distant phylogenetic lines under the influence of the same selection pressures, even unrelated species of organisms may have similar appearances. Then we could have a tendency to place these organisms close together on the tree. This approach is obviously erroneous; the cladogenesis scheme must express only the degree of mutual relatedness of organisms, while the degree of their phenotype similarity should not have any effect here. If the mutual phenotype similarity of individual groups of organisms is expressed graphically, a phenogram is obtained. The topology of a phenogram allows us to estimate which of the compared species exhibit similar properties and thus were, during their evolution, probably because of a similar life style, exposed to similar selection pressures. In cases where, for some reason, we cannot reconstruct the progress of cladogenesis, for example when all the studied species evolved during a historically short period of adaptive radiation (see XXVI.2.1.1) and did not further undergo speciation, or when all the species were formed gradually but from the same parent species, the phenogram can act as a basis for taxonomic classification of the given group of organisms. If a phenogram is formed on the basis of selectively neutral traits which change in all the phylogenetic branches at approximately a constant rate, i.e. for example on the basis of mutations accumulating in pseudogenes, i.e. in genes that have lost any biological function due to some critical mutation, and, if there is a sufficient amount of data, the topology of the phenogram should be identical with the topology of the graph describing cladogenesis. In this case, the phenogram can also be used for reconstruction of the course of cladogenesis.

During phylogenesis, not only individual species, but entire higher taxa very rapidly emerge and develop to their typical form. G.G. Simpson pointed out this fact in the middle of the last century and proposed the name quantum evolution for this phenomenon, in contrast to phyletic evolution (Simpson 1944). In modern terminology, we would most probably speak of quantum or phyletic anagenesis. While the punctualist model of evolution refers to the fact that a species changes only immediately after the time of its formation, the quantum evolution model refers to the fact that fundamental anagenetic changes typical for the members of a particular taxon also occur very rapidly, almost in a jump on a paleontological scale, in sequences of (punctualistically or gradualistically evolving) species forming a certain phylogenetic line. Simpson explained this by suggesting that the formation of a new taxon is dependent primarily on key anagenetic changes that enable the hosts to occupy a new adaptive zone. However, passage to a new zone frequently has the character of “all or nothing”, so that organisms with transition forms of the particular traits are exposed to very strong selection pressures that cause a very rapid passage to a new adaptive zone. Consequently, species with transition traits practically do not occur in nature or have such short lives that they are not even observed in the paleontological record.
            At the present time, it is not clear whether the quantitative character of anagenesis requires separate explanation or whether it can also be a consequence of the punctualist character of anagenesis of the species.

One of the most obvious properties of life on Earth is that its organisms form a hierarchically ordered system of mutually immersed groups. The lowest level represents species, groups of mutually similar individuals. A separate chapter, Chapter XX, was concerned with the aspect of species and the existence of species. Species can be ordered into higher groups on the basis of similarity of their members and these groups of species can again be classified in groups at higher and higher levels. We are currently aware that the reason for hierarchies in taxa lies in the mechanism through which the individual species emerged during evolution. Species gradually branched off from a common ancestor and the individually established phylogenetic lines subsequently further branched or some of them disappeared as a consequence of extinction of all their species. The lines that branched off only recently contain a number of mutual relative, and thus more similar species than the lines that branched off at an earlier time. The subject of study of phylogenetics consists in phylogenesis, i.e. the formation and evolution of the individual phylogenetic lines. Phylogenetics attempts particularly to reconstruct the course of cladogenesis, i.e. the order and manner of branching of all the phylogenetic lines during evolution. Simultaneously, it must necessarily be based on the study of anagenesis, i.e. on the study of the evolution of the individual properties of organisms within relevant phylogenetic lines. Thus, phylogenetics studies both the mutually interconnected aspects of phylogenesis - the specific history of the evolution of life on the Earth.

- A trait is understood to refer to any structure, function or behavior that occurs in various species in at least two different forms. From an evolutionary standpoint, the individual forms of a certain traits are not equivalent; one of them, the plesiomorphic form, for short plesiomorphy, is evolutionarily older in the particular phylogenetic line and the other forms were formed secondarily all at once or in a certain order as a consequence of anagenetic changes in the original form of the trait. These evolutionarily derived forms are termed apomorphic forms, abbreviated apomorphies.

If point mutations occur in the DNA protein-encoding section, it is possible and frequently useful to classify mutations according to their effect on the structure of that protein.Because of the degeneration of the genetic code, i.e. in relation to the fact that a single aminoacid is encoded by a number of various codons, i.e. nucleotide triplets, replacement of a nucleotide in the codon need not be manifested in the structure of the protein.These are termed synonymous (samesense) mutations.Mutations of this type, similar to most mutations in the area of introns or pseudogenes, i.e. in genes that have lost their functionality and are not rewritten in the cell and translated to proteins, are important in that they are invisible, neutral, from the standpoint of natural selection.However, in actual fact it was found that synonymous mutations are not neutral in the true sense of the word.It can be important for the organism whether a certain triplet-encoded aminoacid is translated by rare or common tRNA.In addition, synonymous mutations also affect the regulation of transcription of the given gene, the secondary structure of the synthesized RNA, its stability and the intensity of the translation.In drosophila, the average selection coefficient acting against mutation in the synonymous site has been estimated at s= 2,3/N_e, where N_e is the effective size of the population (Akashi 1995).In human beings, it has been estimated that approximately 3% of synonymous, 12% of nonsynonymous and 100% of nonsense mutations (see below) are detrimental.

Missense (nonsynonymous) mutations are mutations through which one aminoacid is replaced by a different one.If the aminoacid is replaced by an aminoacid with similar physical-chemical properties, then this is termed a conservative substitution.A conservative substitution need not substantially change the tertiary structure and biological function of the protein.The genetic code is arranged so that most aminoacid substitutions that can occur through mutation of a single nucleotide in the triplet are conservative.For example, 97% of transitions at the third position of the codon are synonymous and the remaining 3% lead to conservative substitutions.Of the less common transversions, 59% of those in the third position are synonymous (Wakeley 1996).It is not currently apparent whether this arrangement of the genetic code is a useful adaptation of organisms preventing drastic changes in the protein structure as a consequence of substitution mutations or whether this is only an indication of the way in which the evolution of the genetic code occurred (see X.3.3).The individual aminoacids differ very substantially in their degree of conservativeness.For example, during evolution in proteins, the aminoacid glycine is substituted by another aminoacid only very rarely, while, in contrast, asparagine is replaced far more frequently.Differences in the rates of evolution of the individual proteins can be explained to a considerable degree by various contents of conservative and nonconservative aminoacids.For example, the differences in the content of glycine alone can explain 39% of the total variability in the rate of development of 27 studied mammal proteins; if we take into account the content of 5 aminoacids with the greatest effect on the rate of evolution, then 73% of the variability can be explained (Graur 1985).

Another type of substitution mutation consists in nonsense mutations.In these mutations, one of the three termination codons is formed from the codon for the aminoacid, so that translation at this site leads to premature termination of synthesis of the protein chain.This is, of course, a drastic change in the protein structure, which mostly leads to the formation of a nonfunctional protein.

Drastic changes also occur through the effect of insertion ordeletion of a nucleotide.These changes, frameshift mutations, lead to a shift (disruption) of the reading frame so that a basically unaltered sequence of nucleotides is translated on the ribosome as a sequence of completely different triplets to a completely different sequence of aminoacids (Fig. III.1).In addition, the shift in the reading frame means that, sooner or later, a termination codon appears in the sequence of new codons, so that protein synthesis is prematurely terminated at the given site.

Most natural populations are characterized by more or less obvious polymorphism. Individuals of the same sex and the same age in the population differ from one another in a number of quantitative and qualitative traits.

Part of this polymorphism is nonhereditary in nature and evolves as a response of the individual to the effects of the external environment that it or its immediate ancestors encountered during their lives or ontogenesis.  However, a large portion of polymorphism is determined genetically and is thus hereditary to various degrees. Genetic polymorphism is a result of the existence of two or more variants (alleles) of the individual genes.

Genes were previously seen as hypothetical factors determining the value of the individual biological traits, the properties of living organisms. In order for the existence of such a gene to be distinguished, the relevant trait for which the particular gene was responsible had to assume at least two values.Monomorphic genes, i.e. the genes occurring in the population in a single variant, could thus not, in principle, be distinguished and described or studied.

Only with the ascendance of molecular biology and following revelation of the material nature of genes, i.e. DNA sections coding proteins or RNA molecules, did it begin to become possible to identify the individual genes without first knowing their phenotype manifestations. This permitted identification of monomorphic genes. Modern methods of molecular genetics, specifically the methods of reverse genetics, permit determination of the biological function of a gene even when only a single variant is known. It is possible to either transfer the relevant gene to the genome of a suitable recipient (through a cell of the germinal line) and thus prepare a transgenic organism or, on the other hand, to employ the gene targeting (knockout) method to inactivate the particular gene in the zygote. Study of the phenotype of these genetically modified organisms then assists in determining which traits a particular gene determines.

While molecular biology has made it possible to also study monomorphic genes, it has simultaneously demonstrated that, strictly speaking, monomorphic genes do not exist. Almost all genes studied in detail occur in populations in a great many variants that differ, at the very least, in the presence of individual point mutations. Most of these mutations are apparently neutral in relation to the phenotype and selection, and occur, e.g., on the third positions of the nucleotide triplets, where their occurrence does not lead to substitution of an aminoacid in the protein chain. Some mutations lead to these substitutions; however, only some substitutions simultaneously lead to changes in the biological functioning of the relevant proteins. A large part of the polymorphism at the DNA level is thus not polymorphism in the true sense of the word and is not manifested externally in any way. This type of “pseudopolymorphism” is important for study of evolutionary and population phenomena, but is of relatively little importance from the viewpoint of biological evolution. It arises from mutation processes and, on the other hand, is being continuously removed by genetic drift, genetic draft andmolecular drive.

If pseudopolymorphism is not taken into consideration, i.e. the presence of neutral mutations, that do not in any way appear in the phenotype of the organisms (i.e. if the location of zones on an electrophoretogram is not considered to constitute part of the phenotype), it is found that two groups of polymorphic genes exist. The first group consists in genes that occur in the population with great frequency in one standard form and in much lower frequency, usually less than 1%, in minority forms. For these alleles, it is generally assumed that they occur only temporarily here or that they are maintained as a result of the dynamic equilibrium of two processes – mutation pressure, i.e. constant formation of new alleles from the majority standard allele during mutagenesis, and selection, i.e. constant disappearance of the mutated alleles from the population.Polymorphism, caused by the temporary presence of rare alleles in the population, will be termed Type I polymorphism and will be discussed primarily in Chapter IX, devoted to the evolution of the DNA sequence and proteins.

However, for the second group of genes, it is difficult to say which allele is standard and which is mutated as they all, or at least a great many of them, occur in the population in high frequency (Fig. VIII.1). This type of polymorphism is maintained over long periods in the population through the action of specific mechanisms and is of incomparably greater importance from the viewpoint of evolutionary and ecological processes. Here, it will be termed Type II polymorphism and will constitute the subject of this chapter.See also Origin of Rh-blood group polymorphism and also Sickle-cell anemia.

The existence of polymorphism within a population is of substantial importance both from the perspective of ecological processes and also from the microevolutionary and macroevolutionary viewpoints. From an ecological perspective, it is important that a polymorphic population is capable of utilizing very varied resources and consequently of utilizing its environment more economically. A polymorphic species is also less vulnerable to random fluctuations in the environmental conditions, as at least part of the population can survive even during drastic changes.

Polymorphism also changes the microevolutionary potential of populations and species, i.e. the ability of populations and species to respond to short-term selection pressures in the environment,as it provides selection with genetic material from which it can choose suitable variants that better correspond to the altered conditions in the environment (Fig.VIII.11).Thus, populations need not wait for the formation of new mutations and can use the already-present variability. As the fate of isolated new mutations immediately after their formation is determined primarily by accident (see V.3.1), it is far more advantageous if potentially suitable variants occur in the population with sufficient frequency right at the beginning. In addition, in case of cyclic changes in the environment, it is ensured that the genetic composition of the population can readily return to the original state after the environmental conditions go back to their original values (Fig. VIII.12). According to some theories, it is this reversibility of microevolutionary changes that is mainly responsible for the greater evolutionary success of sexually reproducing species (Williams 1975, Flegr 2008). In asexual species, the composition of the gene pool of the population follows even temporary environmental changes. Thus, all the alleles that are essential for their bearers under normal conditions can be very easily lost from the population during short-term changes. This can understandably be very disadvantageous for an asexual species in the medium term.

From the perspective of long-term or even permanent changes in the environment, and thus, for example, from the perspective of macroevolutionary processes, the impact of polymorphism on the progress and rate of evolution can be quite the opposite (Flegr 1998). Due to the phenomenon of genetic homeostasis andepistatic interactions, the effectiveness of natural selection is greatly limited in polymorphic sexually reproducing populations (see IV.9.2). Thus, populations and species react to the action of selection pressure only through a shift in the frequencies of individual alleles that are already present in the gene pool, while the fixation of new alleles through selection is greatly limited. Thus, a genetically polymorphic species remains selectionally frozen and anagenetic changes can occur only following a drastic reduction in the polymorphism, for example, in connection with a long-term drastic reduction in population size(see V.2.2).

Essentialist taxonomic systems were mostly monothetic, as they assumed that the presence or absence of a certain trait is decisive for inclusion of a species in a particular taxon. For example, monothetic systems classify angiosperm plants strictly on the basis of the number of individual flower components.
However, most modern systems are polythetic. Polythetic systems allow a taxon to be defined on the basis of a greater number of mutually interchangeable traits. In contrast to monothetic systems, polythetic systems are somewhat harder to use as classification schemes, i.e. as instruments for determination of organisms. On the other hand, only polythetic systems can be truly natural, i.e. can reflect the phylogenesis of the studied organisms.

see Lamarckian microevolution in organisms without Weismann barrier

Preadaptations are biological structures or patterns of behaviour that developed in a different selection context than that in which they later became advantageous. A great many biological structures or patterns of behaviour were formed as a consequence of completely different selection pressures than would follow from their contemporary biological functions and, in some cases, the reason for the formation of the original structure was not selection at all. In this case, evolutionary biologists speak about the formation of the relevant structures on the basis of already existing preadaptation and the relevant traits are mostly not termed adaptation but rather exaptation. For example, The wings of insects apparently developed from structures that originally served the processes of respiration or, according to another theory, for thermoregulation, and thus they emerged and were formed over a long time through the action of selective pressures following from this original function.

see Extinctions types

– see superinfection and virulence

See goal-orientation.

– see Scientific nomenclature

see Neoteny

The emergence of living systems and thus the origin of life are the subject of an independent field of science that is only partly related to evolutionary biology, protobiology. This discipline is faced with two basic question areas. It should tell us how the basic building stones of living organisms were formed, i.e. simple chemical substances of the aminoacid and nucleotide type. These substances are currently formed under terrestrial conditions primarily through the activities of organisms; however, prior to the origin of life, they must necessarily have been formed by some other, abiotic route. Biological evolution must apparently have been preceded by rather complicated chemical evolution, during which the action of various abiotic factors led to the formation and accumulation in the environment of some simple and more complicated organic substances. In the laboratory, it has been possible to copy some of the conditions that could have prevailed on the Earth at the time prior to the origin of life and, under these conditions, scientists have been able to achieve the formation of almost all the important building blocks of present-day biological macromolecules (Fig. X.1).

see Fossils age of

Darwin repeatedly emphasized that evolution (i.e. anagenesis) is basically gradualist, and progresses alternately at greater and lesser rates through the accumulation of minor evolutionary changes. On the basis of these theoretical principles, evolutionary biologists long assumed that most evolutionary changes could occur at any time during the existence of the species, i.e. that anagenesis should not be bound to cladogenesis within the individual phylogenetic lines. Where it seems on the basis of the paleontological record that anagenetic changes occur in sudden jumps, that a new species with fully developed traits appeared instantaneously in the record and that there were no transition forms between it and its predecessor, then this is only a consequence of the imperfectness of the paleontological record, in which the transition forms were not preserved from the key period of the greatest anagenetic changes. It was only in 1972 that N. Eldredge and S. J. Gould pointed out that the absence of transition forms between the individual species is a practically universal phenomenon that cannot be explained by imperfectness of the paleontological record and lack of data (Eldredge & Gould 1972). They contrasted the gradualist concept of evolution with the nongradualist – punctualist concept (Fig. XXVI.8) and demonstrated that the available paleontological data tends to confirm that evolution occurs in the vast majority of cases in a punctualist manner, i.e. the species was formed very rapidly, acquired its characteristic phenotype and then practically did not change throughout the rest of its existence. Like every new theory, this theory of discontinuous progress of anagenesis, mostly termed the punctuated equilibrium theory, encountered considerable skepticism amongst evolutionary biologists and paleontologists. Data was repeatedly collected to test the theory. At the present time, it seems that, in cases where sufficient data is available, these data tend mostly to correspond to the punctualist model. New species appear in the paleontological record completely developed during a period of the order of 10,000 years and then do not change throughout their existence, which is usually 100 – 1000 times longer. They either force out the parent species or coexist for a long time with them until their extinction. The greatest amount of empirical evidence for the punctuated character of evolution is available for marine invertebrates as the best (most numerous and most complete) paleontological data is available for them; this is also confirmed by the available data relating to marine and terrestrial vertebrates (Benton & Pearson 2001). In contrast, the available data related to Foraminifera tend to support the gradualist character of their evolution.