Character evolution is the process by which a

character Character or Characters may refer to: Arts, entertainment, and media Literature * ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk * ''Characters'' (Theophrastus), a classical Greek set of character sketches attributed to Theoph ...

or trait (a certain body part or property of an organism) evolves along the branches of an evolutionary tree. Character evolution usually refers to single changes within a lineage that make this lineage unique from others. These changes are called character state changes and they are often used in the study of evolution to provide a record of common ancestry. Character state changes can be phenotypic changes,

nucleotide Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...

substitutions, or

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

substitutions. These small changes in a species can be identifying features of when exactly a new lineage diverged from an old one. Current location in evolution

Phylogenetics

In the study of

phylogenetics In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

cladistics Cladistics ( ; from Ancient Greek 'branch') is an approach to Taxonomy (biology), biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesiz ...

, researchers can look at the characters shared by a collection of species and then group them into what is called a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

. The term clade was coined in 1957 by the biologist

Julian Huxley Sir Julian Sorell Huxley (22 June 1887 – 14 February 1975) was an English evolutionary biologist, eugenicist and Internationalism (politics), internationalist. He was a proponent of natural selection, and a leading figure in the mid-twentiet ...

to refer to the result of

cladogenesis Cladogenesis is an evolutionary splitting of a parent species into two distinct species, forming a clade. This event usually occurs when a few organisms end up in new, often distant areas or when environmental changes cause several extinctions, ...

, a concept Huxley borrowed from

Bernhard Rensch Bernhard Rensch (21 January 1900 – 4 April 1990) was a German evolutionary biologist and ornithologist who did field work in Indonesia and India. Starting his scientific career with pro- Lamarckian views, he shifted to selectionism and became ...

. A clade is by definition

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

, meaning it contains one ancestor (which can be an organism, a

population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

, or a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

) and all its descendants.

Natural selection

Natural Selection is the process by which organisms that are better adapted to their environment are selected to survive and reproduce more offspring. Natural selection selects for the phenotype or the characteristics of an organism that gives the organism a reproductive advantage in which it becomes the gene pool of a population. In addition, mutations also arise in the genome of an individual organism and offspring(s) can inherit such mutations. This genetic variation allows more organisms to adapt to a changing environment.

Maximum parsimony

It is often the case in the study of phylogenies that the vast majority of organisms of interest are long

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

. It is therefore a matter of speculation to reconstruct what ancestral organisms existed long before the present time, and how the evolutionary process led from one organism to another, and which present-day organisms are most closely related. Character evolution and the character state changes that drive this type of evolution are what help researchers construct these trees in a fashion referred to as

maximum parsimony In phylogenetics and computational phylogenetics, maximum parsimony is an optimality criterion under which the phylogenetic tree that minimizes the total number of character-state changes (or minimizes the cost of differentially weighted charact ...

. When talking about phylogenetics, maximum parsimony refers to a method of inferring a phylogenetic tree in a way that minimizes the number of implied character state transformations in the observed data (hence ''maximally parsimonious''). The basic ideas were presented by James S. FarrisFarris, J. S. (1970). Methods for computing Wagner trees. ''Systematic Zoology'' 19, 83-92. in 1970. Although fairly effective, maximum parsimony (like any method of phylogenetic inference) may not recover the true course of evolution for a given feature. For a number of reasons, two organisms can possess a trait not present in their last common ancestor. The phenomena of

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...

parallel evolution Parallel evolution is the similar development of a trait in distinct species that are not closely related, but share a similar original trait in response to similar evolutionary pressure.Zhang, J. and Kumar, S. 1997Detection of convergent and pa ...

, and evolutionary reversals (collectively termed ''homoplasy'') are evolutionary forces that may disrupt the effectiveness of the maximum parsimony method of inferring phylogenetic relationships. However, Rindal and Brower Rindal, E. and Brower A.V.Z. (2010) Do model-based phylogenetic analyses perform better than parsimony? A test with empirical data. ''Cladistics'' 27, 331-334. showed that the vast majority of the time, parsimony and model-based phylogenetic analyses of the same data sets gave results that were not significantly different from one another, implying that if parsimony is producing false hypotheses of relationships due to homoplasy, then the Maximum Likelihood or Bayesian methods are doing so as well.

Theory of Inheritance of Acquired Characteristics

Lamarck is best known for his ''Theory of Inheritance of Acquired Characteristics'' in 1801. His theory states that the characteristics an organism acquires throughout its life in order to adapt to its environment are passed down to its offspring. For example, Lamarck believed that the long necks of giraffes evolved as generations of giraffes reached for ever higher leaves of a tree. Their offspring and later generations inherited the resulting long necks.

References

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External links

Character Evolution research group
of

Naturalis Biodiversity Center Naturalis Biodiversity Center () is a national museum of natural history and a research center on biodiversity in Leiden, Netherlands. It was named the European Museum of the Year 2021. Although its current name and organization are relatively ...

Evolution