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Ecophenotypic variation ("ecophenotype") refers to phenotypical variation as a function of life station. In wide-ranging species, the contributions of heredity and environment are not always certain, but their interplay can sometimes be determined by experiment.
Plants display the most obvious examples of ecophenotypic variation. One example are trees growing in the woods developing long straight trunks, with branching crowns high in the canopy, while the same species growing alone in the open develops a spreading form, branching much lower to the ground. Genotypes often have much flexibility in the modification and expression of phenotypes; in many organisms these phenotypes are very different under varying environmental conditions. The plant Hieracium umbellatum is found growing in two different habitats in Sweden. One habitat is rocky sea-side cliffs, where the plants are bushy with broad leaves and expanded inflorescences; the other is among sand dunes where the plants grow prostrate with narrow leaves and compact inflorescences. These habitats alternate along the coast of Sweden and the habitat that the seeds of H. umbellatum land in determines the phenotype that grows. [1] Invasive plants such as the honeysuckle can thrive by altering their morphology in response to changes in the environment, [2] which gives them a competitive advantage. Another example of a plants phenotypic reaction and adaptation with its environment is how Thlaspi caerulescens can absorb the metals in the soil to use to its advantage in defending against harmful microbes and bacteria in its leaves. [3] The more immediate responses shown by vascular plants to their environment, for instance a vine's ability to conform to the wall or tree upon which it grows, are not usually considered ecophenotypic, even though the mechanisms may be related. [4]
Since animals are far less plastic than plants, ecophenotypic variation is noteworthy. When encountered, it can cause confusion in identification if it is not anticipated. The most obvious examples are again common observations, as the dwarfing of aquarium fish living in a restricted environment. [5] In asexual reproduction, the parent passes on the entire genome to the next generation. Mutations to the genes are the only source of genetic variation. In sexual reproduction, each parent contributes half of his or her genome to the offspring; thus the offspring contain a mixture of genetic material. Adaptations are traits that increase fitness, the driving force for natural selection. The level of fitness associated with an allele can only be ascertained by comparison with alternate alleles. Traits that increase the survival rate of a species contribute to an animal's fitness, but selection will only favor such traits insofar as survival improves the reproductive success of the organism. More interesting are examples where causation is less clear. Among mollusks, examples include the muricid snail species Nucella lamellosa , which in rough, shallow waters is generally less spiny than in deeper, quiet waters. [6] In unionid freshwater bivalves, there are lake, small river, and large river forms of several species. [7] In vertebrates, experiments on mice show reduced length of ears and tails in response to being reared in a lower temperature, a phenomenon known as Allen's rule. [8]
In humans, environmental differences due to lifestyle choices are a consideration, for instance the differences between someone who spends much time on the sofa before the television, beer in hand, and an individual who spends his time in the gym or the soccer field can be pronounced. Franz Boas found that cephalic index was to some degree dependent on where a child was born, independent of the child's genetic or cultural heritage. [9] Another way in which environmental differences can cause physical and/or behavioral alterations is in being put under great levels of stress, causing a wide range of effects. Chronic Stress has been proven to cause health issues in many individuals. "Early childhood attempts to cope with fear or rejection ... set up psychological patterns of behavior for the person's later life. Those behaviors in turn affect the biochemical imbalances in the brain's neuronal systems. Those altered imbalances in turn reinforce the behaviors, and the cycle feeds upon itself." "The body reacts biochemically to excessive stress as it attempts to regain its healthy dynamic balance"; "In psychologically stressful situations, hormones may be brought into play to remedy the imbalance the body finds itself in." [10]
In the General Adaption Syndrome, which is the biological response to stress, there are three stages. 1.) The "Alarm Action" - heart rate increases, blood sugar levels rise, pupils dilate, and digestion slows. 2.) The "Resistance" or "Adaptive" stage - The body attempts to repair the damage which caused the emergency arousal 3.) The "Exhaustion Stage" - The body grows ill; Mentally, possibly by neurosis or even psychotic disturbances, or physically, having the possibility to trigger several kinds of cardiovascular and kidney diseases, and Quite commonly, certain forms of asthma. [10]
In genetics, the phenotype is the set of observable characteristics or traits of an organism. The term covers the organism's morphology, its developmental processes, its biochemical and physiological properties, its behavior, and the products of behavior. An organism's phenotype results from two basic factors: the expression of an organism's genetic code and the influence of environmental factors. Both factors may interact, further affecting the phenotype. When two or more clearly different phenotypes exist in the same population of a species, the species is called polymorphic. A well-documented example of polymorphism is Labrador Retriever coloring; while the coat color depends on many genes, it is clearly seen in the environment as yellow, black, and brown. Richard Dawkins in 1978 and then again in his 1982 book The Extended Phenotype suggested that one can regard bird nests and other built structures such as caddisfly larva cases and beaver dams as "extended phenotypes".
Heritability is a statistic used in the fields of breeding and genetics that estimates the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population. The concept of heritability can be expressed in the form of the following question: "What is the proportion of the variation in a given trait within a population that is not explained by the environment or random chance?"
A maternal effect is a situation where the phenotype of an organism is determined not only by the environment it experiences and its genotype, but also by the environment and genotype of its mother. In genetics, maternal effects occur when an organism shows the phenotype expected from the genotype of the mother, irrespective of its own genotype, often due to the mother supplying messenger RNA or proteins to the egg. Maternal effects can also be caused by the maternal environment independent of genotype, sometimes controlling the size, sex, or behaviour of the offspring. These adaptive maternal effects lead to phenotypes of offspring that increase their fitness. Further, it introduces the concept of phenotypic plasticity, an important evolutionary concept. It has been proposed that maternal effects are important for the evolution of adaptive responses to environmental heterogeneity.
Human variability, or human variation, is the range of possible values for any characteristic, physical or mental, of human beings.
In biology, polymorphism is the occurrence of two or more clearly different morphs or forms, also referred to as alternative phenotypes, in the population of a species. To be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population.
Stabilizing selection is a type of natural selection in which the population mean stabilizes on a particular non-extreme trait value. This is thought to be the most common mechanism of action for natural selection because most traits do not appear to change drastically over time. Stabilizing selection commonly uses negative selection to select against extreme values of the character. Stabilizing selection is the opposite of disruptive selection. Instead of favoring individuals with extreme phenotypes, it favors the intermediate variants. Stabilizing selection tends to remove the more severe phenotypes, resulting in the reproductive success of the norm or average phenotypes. This means that most common phenotype in the population is selected for and continues to dominate in future generations.
Gene–environment interaction is when two different genotypes respond to environmental variation in different ways. A norm of reaction is a graph that shows the relationship between genes and environmental factors when phenotypic differences are continuous. They can help illustrate GxE interactions. When the norm of reaction is not parallel, as shown in the figure below, there is a gene by environment interaction. This indicates that each genotype responds to environmental variation in a different way. Environmental variation can be physical, chemical, biological, behavior patterns or life events.
In ecology and genetics, a reaction norm, also called a norm of reaction, describes the pattern of phenotypic expression of a single genotype across a range of environments. One use of reaction norms is in describing how different species—especially related species—respond to varying environments. But differing genotypes within a single species may also show differing reaction norms relative to a particular phenotypic trait and environment variable. For every genotype, phenotypic trait, and environmental variable, a different reaction norm can exist; in other words, an enormous complexity can exist in the interrelationships between genetic and environmental factors in determining traits. The concept was introduced by Richard Woltereck in 1909.
A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions. It is therefore a special case of phenotypic plasticity.
Phenotypic plasticity refers to some of the changes in an organism's behavior, morphology and physiology in response to a unique environment. Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompasses all types of environmentally induced changes that may or may not be permanent throughout an individual's lifespan.
Canalisation is a measure of the ability of a population to produce the same phenotype regardless of variability of its environment or genotype. It is a form of evolutionary robustness. The term was coined in 1942 by C. H. Waddington to capture the fact that "developmental reactions, as they occur in organisms submitted to natural selection...are adjusted so as to bring about one definite end-result regardless of minor variations in conditions during the course of the reaction". He used this word rather than robustness to consider that biological systems are not robust in quite the same way as, for example, engineered systems.
In biology, a cline is a measurable gradient in a single characteristic of a species across its geographical range. Clines usually have a genetic, or phenotypic character. They can show either smooth, continuous gradation in a character, or more abrupt changes in the trait from one geographic region to the next.
In genetics, transgressive segregation is the formation of extreme phenotypes, or transgressive phenotypes, observed in segregated hybrid populations compared to phenotypes observed in the parental lines. The appearance of these transgressive (extreme) phenotypes can be either positive or negative in terms of fitness. If both parents' favorable alleles come together, it will result in a hybrid having a higher fitness than the two parents. The hybrid species will show more genetic variation and variation in gene expression than their parents. As a result, the hybrid species will have some traits that are transgressive (extreme) in nature. Transgressive segregation can allow a hybrid species to populate different environments/niches in which the parent species do not reside, or compete in the existing environment with the parental species.
Developmental noise or stochastic noise is a concept within developmental biology in which the observable characteristics or traits (phenotype) varies between individuals even though both individuals share the same genetic code (genotypes) and the other environmental factors are completely the same. Factors that influence the effect include stochastic, or randomized, gene expression and other cellular noise.
Phenotypic Integration is a metric for measuring the correlation of multiple functionally-related traits to each other. Complex phenotypes often require multiple traits working together in order to function properly. Phenotypic integration is significant because it provides an explanation as to how phenotypes are sustained by relationships between traits. Every organism's phenotype is integrated, organized, and a functional whole. Integration is also associated with functional modules. Modules are complex character units that are tightly associated, such as a flower. It is hypothesized that organisms with high correlations between traits in a module have the most efficient functions. The fitness of a particular value for one phenotypic trait frequently depends on the value of the other phenotypic traits, making it important for those traits evolve together. One trait can have a direct effect on fitness, and it has been shown that the correlations among traits can also change fitness, causing these correlations to be adaptive, rather than solely genetic. Integration can be involved in multiple aspects of life, not just at the genetic level, but during development, or simply at a functional level.
Genetic variance is a concept outlined by the English biologist and statistician Ronald Fisher in his fundamental theorem of natural selection. In his 1930 book The Genetical Theory of Natural Selection, Fisher postulates that the rate of change of biological fitness can be calculated by the genetic variance of the fitness itself. Fisher tried to give a statistical formula about how the change of fitness in a population can be attributed to changes in the allele frequency. Fisher made no restrictive assumptions in his formula concerning fitness parameters, mate choices or the number of alleles and loci involved.
Countergradient variation is a type of phenotypic plasticity that occurs when the phenotypic variation determined by a biological population's genetic components opposes the phenotypic variation caused by an environmental gradient. This can cause different populations of the same organism to display similar phenotypes regardless of their underlying genetics and differences in their environments.
This glossary of genetics and evolutionary biology is a list of definitions of terms and concepts used in the study of genetics and evolutionary biology, as well as sub-disciplines and related fields, with an emphasis on classical genetics, quantitative genetics, population biology, phylogenetics, speciation, and systematics. Overlapping and related terms can be found in Glossary of cellular and molecular biology, Glossary of ecology, and Glossary of biology.
Urban evolution refers to the heritable genetic changes of populations in response to urban development and anthropogenic activities in urban areas. Urban evolution can be caused by mutation, genetic drift, gene flow, or evolution by natural selection. Biologists have observed evolutionary change in numerous species compared to their rural counterparts on a relatively short timescale.
Temporal plasticity, also known as fine-grained environmental adaptation, is a type of phenotypic plasticity that involves the phenotypic change of organisms in response to changes in the environment over time. Animals can respond to short-term environmental changes with physiological (reversible) and behavioral changes; plants, which are sedentary, respond to short-term environmental changes with both physiological and developmental (non-reversible) changes.