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48-463: Bloodline most commonly refers to heredity. Bloodline , bloodlines , blood line or blood lines may also refer to: Bloodline In humans, eye color is an example of an inherited characteristic: an individual might inherit the "brown-eye trait" from one of the parents. Inherited traits are controlled by genes and the complete set of genes within an organism's genome is called its genotype . The complete set of observable traits of

96-451: A broader notion of an evolutionary process, one that it shares with some other evolutionary biologists. Although the advocate agrees that there is a useful distinction to be made between processes that modify gene frequencies directly, and factors that play different roles in evolution... The skeptics probably represent the majority position: evolutionary processes are those that change gene frequencies. Advocates of NCT, in contrast, are part of

144-460: A mode of inheritance is also achieved primarily through statistical analysis of pedigree data. In case the involved loci are known, methods of molecular genetics can also be employed. An allele is said to be dominant if it is always expressed in the appearance of an organism (phenotype) provided that at least one copy of it is present. For example, in peas the allele for green pods, G , is dominant to that for yellow pods, g . Thus pea plants with

192-506: A mutation occurs within a gene, the new allele may affect the trait that the gene controls, altering the phenotype of the organism. However, while this simple correspondence between an allele and a trait works in some cases, most traits are more complex and are controlled by multiple interacting genes within and among organisms. Developmental biologists suggest that complex interactions in genetic networks and communication among cells can lead to heritable variations that may underlie some of

240-439: A new niche in which sophisticated cognition was beneficial. While the fact that niche construction occurs is non-contentious, and its study goes back to Darwin's classic books on earthworms and corals , the evolutionary consequences of niche construction have not always been fully appreciated. Researchers differ over to what extent niche construction requires changes in understanding of the evolutionary process. Many advocates of

288-411: A part of early Lamarckian ideas on evolution. During the 18th century, Dutch microscopist Antonie van Leeuwenhoek (1632–1723) discovered "animalcules" in the sperm of humans and other animals. Some scientists speculated they saw a "little man" ( homunculus ) inside each sperm . These scientists formed a school of thought known as the "spermists". They contended the only contributions of the female to

336-473: A particular DNA molecule) specifies the genetic information: this is comparable to a sequence of letters spelling out a passage of text. Before a cell divides through mitosis , the DNA is copied, so that each of the resulting two cells will inherit the DNA sequence. A portion of a DNA molecule that specifies a single functional unit is called a gene ; different genes have different sequences of bases. Within cells ,

384-523: A sizable minority of evolutionary biologists that conceive of evolutionary processes more broadly, as anything that systematically biases the direction or rate of evolution, a criterion that they (but not the skeptics) feel niche construction meets." The authors conclude that their disagreements reflect a wider dispute within evolutionary theory over whether the modern synthesis is in need of reformulation, as well as different usages of some key terms (e.g., evolutionary process). Further controversy surrounds

432-410: A striking example is people with the inherited trait of albinism , who do not tan at all and are very sensitive to sunburn . Heritable traits are known to be passed from one generation to the next via DNA , a molecule that encodes genetic information. DNA is a long polymer that incorporates four types of bases , which are interchangeable. The Nucleic acid sequence (the sequence of bases along

480-403: A variety of ideas about heredity: Theophrastus proposed that male flowers caused female flowers to ripen; Hippocrates speculated that "seeds" were produced by various body parts and transmitted to offspring at the time of conception; and Aristotle thought that male and female fluids mixed at conception. Aeschylus , in 458 BC, proposed the male as the parent, with the female as a "nurse for

528-553: Is a related but non-evolutionary concept referring to structural changes brought about in the environment by organisms. The following are some examples of niche construction: As creatures construct new niches, they can have a significant effect on the world around them. Niche construction theory (NCT) has been anticipated by diverse people in the past, including by the physicist Erwin Schrödinger in his What Is Life? and Mind and Matter essays (1944). An early advocate of

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576-558: Is generating some pressing current problems (e.g. climate change , deforestation , urbanization ). However, human scientists have been attracted to the niche construction perspective because it recognizes human activities as a directing process, rather than merely the consequence of natural selection . Cultural niche construction can also feed back to affect other cultural processes, even affecting genetics. Niche construction theory emphasizes how acquired characters play an evolutionary role, through transforming selective environments. This

624-404: Is growing evidence that there is transgenerational inheritance of epigenetic changes in humans and other animals. The description of a mode of biological inheritance consists of three main categories: These three categories are part of every exact description of a mode of inheritance in the above order. In addition, more specifications may be added as follows: Determination and description of

672-416: Is known as gene-culture coevolution . There is now little doubt that human cultural niche construction has co-directed human evolution. Humans have modified selection, for instance, by dispersing into new environments with different climatic regimes, devising agricultural practices or domesticating livestock. A well-researched example is the finding that dairy farming created the selection pressure that led to

720-542: Is of considerable importance. For instance, niche construction can: Niche construction theory has had a particular impact in the human sciences, including biological anthropology , archaeology , and psychology . Niche construction is now recognized to have played important roles in human evolution , including the evolution of cognitive capabilities. Its impact is probably because it is immediately apparent that humans possess an unusually potent capability to regulate, construct and destroy their environments, and that this

768-601: Is particularly relevant to human evolution, where our species appears to have engaged in extensive environmental modification through cultural practices. Such cultural practices are typically not themselves biological adaptations (rather, they are the adaptive product of those much more general adaptations, such as the ability to learn, particularly from others, to teach, to use language, and so forth, that underlie human culture). Mathematical models have established that cultural niche construction can modify natural selection on human genes and drive evolutionary events. This interaction

816-410: Is that developmental biology (' evo-devo ') played little part in the synthesis, but an account of Gavin de Beer 's work by Stephen Jay Gould suggests he may be an exception. Almost all aspects of the synthesis have been challenged at times, with varying degrees of success. There is no doubt, however, that the synthesis was a great landmark in evolutionary biology. It cleared up many confusions, and

864-514: The Moravian monk Gregor Mendel who published his work on pea plants in 1865. However, his work was not widely known and was rediscovered in 1901. It was initially assumed that Mendelian inheritance only accounted for large (qualitative) differences, such as those seen by Mendel in his pea plants – and the idea of additive effect of (quantitative) genes was not realised until R.A. Fisher 's (1918) paper, " The Correlation Between Relatives on

912-574: The Origin of Species and his later biological works. Darwin's primary approach to heredity was to outline how it appeared to work (noticing that traits that were not expressed explicitly in the parent at the time of reproduction could be inherited, that certain traits could be sex-linked , etc.) rather than suggesting mechanisms. Darwin's initial model of heredity was adopted by, and then heavily modified by, his cousin Francis Galton , who laid

960-501: The Supposition of Mendelian Inheritance " Mendel's overall contribution gave scientists a useful overview that traits were inheritable. His pea plant demonstration became the foundation of the study of Mendelian Traits. These traits can be traced on a single locus. In the 1930s, work by Fisher and others resulted in a combination of Mendelian and biometric schools into the modern evolutionary synthesis . The modern synthesis bridged

1008-444: The alleles in an organism. Niche construction Niche construction is the ecological process by which an organism alters its own (or another species') local environment. These alterations can be a physical change to the organism’s environment, or it can encompass the active movement of an organism from one habitat to another where it then experiences different environmental pressures. Examples of niche construction include

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1056-417: The application of niche construction theory to the origins of agriculture within archaeology. In a 2015 review, archaeologist Bruce Smith concluded: "Explanations [for domestication of plants and animals] based on diet breadth modeling are found to have a number of conceptual, theoretical, and methodological flaws; approaches based on niche construction theory are far better supported by the available evidence in

1104-500: The building of nests and burrows by animals, the creation of shade, the influencing of wind speed, and alternations to nutrient cycling by plants. Although these modifications are often directly beneficial to the constructor , they are not necessarily always. For example, when organisms dump detritus , they can degrade their own local environments. Within some biological evolutionary frameworks, niche construction can actively beget processes pertaining to ecological inheritance whereby

1152-784: The claim that niche construction is an evolutionary process has excited controversy. A collaboration between some critics of the niche-construction perspective and one of its advocates attempted to pinpoint their differences. They wrote: "NCT argues that niche construction is a distinct evolutionary process, potentially of equal importance to natural selection. The skeptics dispute this. For them, evolutionary processes are processes that change gene frequencies , of which they identify four ( natural selection , genetic drift , mutation , migration [ie. gene flow ])... They do not see how niche construction either generates or sorts genetic variation independently of these other processes, or how it changes gene frequencies in any other way. In contrast, NCT adopts

1200-436: The direct control of genes include the inheritance of cultural traits , group heritability , and symbiogenesis . These examples of heritability that operate above the gene are covered broadly under the title of multilevel or hierarchical selection , which has been a subject of intense debate in the history of evolutionary science. When Charles Darwin proposed his theory of evolution in 1859, one of its major problems

1248-515: The environmental modification. The first two criteria alone provide evidence of niche construction. Recently, some biologists have argued that niche construction is an evolutionary process that works in conjunction with natural selection . Evolution entails networks of feedbacks in which previously selected organisms drive environmental changes, and organism-modified environments subsequently select for changes in organisms. The complementary match between an organism and its environment results from

1296-476: The first to make the argument that ‘niche construction’ and ‘ ecological inheritance ’ should be recognized as evolutionary processes. Over the next decade research into niche construction increased rapidly, with a rush of experimental and theoretical studies across a broad range of fields. Mathematical evolutionary theory explores both the evolution of niche construction, and its evolutionary and ecological consequences. These analyses suggest that niche construction

1344-467: The framework for the biometric school of heredity. Galton found no evidence to support the aspects of Darwin's pangenesis model, which relied on acquired traits. The inheritance of acquired traits was shown to have little basis in the 1880s when August Weismann cut the tails off many generations of mice and found that their offspring continued to develop tails. Scientists in Antiquity had

1392-403: The fundamental unit of life is the cell, and not some preformed parts of an organism. Various hereditary mechanisms, including blending inheritance were also envisaged without being properly tested or quantified, and were later disputed. Nevertheless, people were able to develop domestic breeds of animals as well as crops through artificial selection. The inheritance of acquired traits also formed

1440-463: The gap between experimental geneticists and naturalists; and between both and palaeontologists, stating that: The idea that speciation occurs after populations are reproductively isolated has been much debated. In plants, polyploidy must be included in any view of speciation. Formulations such as 'evolution consists primarily of changes in the frequencies of alleles between one generation and another' were proposed rather later. The traditional view

1488-434: The laws of heredity through compiling data on family phenotypes (nose size, ear shape, etc.) and expression of pathological conditions and abnormal characteristics, particularly with respect to the age of appearance. One of the projects aims was to tabulate data to better understand why certain traits are consistently expressed while others are highly irregular. The idea of particulate inheritance of genes can be attributed to

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1536-520: The long strands of DNA form condensed structures called chromosomes . Organisms inherit genetic material from their parents in the form of homologous chromosomes , containing a unique combination of DNA sequences that code for genes. The specific location of a DNA sequence within a chromosome is known as a locus . If the DNA sequence at a particular locus varies between individuals, the different forms of this sequence are called alleles . DNA sequences can change through mutations , producing new alleles. If

1584-493: The mechanics in developmental plasticity and canalization . Recent findings have confirmed important examples of heritable changes that cannot be explained by direct agency of the DNA molecule. These phenomena are classed as epigenetic inheritance systems that are causally or independently evolving over genes. Research into modes and mechanisms of epigenetic inheritance is still in its scientific infancy, but this area of research has attracted much recent activity as it broadens

1632-490: The next generation were the womb in which the homunculus grew, and prenatal influences of the womb. An opposing school of thought, the ovists, believed that the future human was in the egg, and that sperm merely stimulated the growth of the egg. Ovists thought women carried eggs containing boy and girl children, and that the gender of the offspring was determined well before conception. An early research initiative emerged in 1878 when Alpheus Hyatt led an investigation to study

1680-410: The niche construction perspective in biology was the developmental biologist, Conrad Waddington . He drew his attention to the many ways in which animals modify their selective environments throughout their lives, by choosing and changing their environmental conditions, a phenomenon that he termed "the exploitive system". The niche construction perspective was subsequently brought to prominence through

1728-571: The niche-construction perspective align themselves with other progressive elements in seeking an extended evolutionary synthesis , a stance that other prominent evolutionary biologists reject. Laubichler and Renn argue that niche construction theory offers the prospect of a broader synthesis of evolutionary phenomena through "the notion of expanded and multiple inheritance systems (from genomic to ecological, social and cultural)." Niche construction theory (NCT) remains controversial, particularly amongst orthodox evolutionary biologists. In particular,

1776-497: The organism in question “constructs” new or unique ecologic, and perhaps even sociologic environmental realities characterized by specific selective pressures . For niche construction to affect evolution it must satisfy three criteria: 1) the organism must significantly modify environmental conditions, 2) these modifications must influence one or more selection pressures on a recipient organism, and 3) there must be an evolutionary response in at least one recipient population caused by

1824-400: The pair of alleles either GG (homozygote) or Gg (heterozygote) will have green pods. The allele for yellow pods is recessive. The effects of this allele are only seen when it is present in both chromosomes, gg (homozygote). This derives from Zygosity , the degree to which both copies of a chromosome or gene have the same genetic sequence, in other words, the degree of similarity of

1872-411: The process of niche construction is defined by the regular and repeated activities of organisms in their environment. This generates a legacy of effect that modifies and feeds back into the selection regime of subsequent generations. Descendants inherit genes plus environmental characteristics generated by the ecological actions of ancestors. Other examples of heritability in evolution that are not under

1920-439: The scope of heritability and evolutionary biology in general. DNA methylation marking chromatin , self-sustaining metabolic loops , gene silencing by RNA interference , and the three dimensional conformation of proteins (such as prions ) are areas where epigenetic inheritance systems have been discovered at the organismic level. Heritability may also occur at even larger scales. For example, ecological inheritance through

1968-710: The spread of alleles for adult lactase persistence. Analyses of the human genome have identified many hundreds of genes subject to recent selection, and human cultural activities are thought to be a major source of selection in many cases. The lactase persistence example may be representative of a very general pattern of gene-culture coevolution. Niche construction is also now central to several accounts of how language evolved. For instance, Derek Bickerton describes how our ancestors constructed scavenging niches that required them to communicate in order to recruit sufficient individuals to drive off predators away from megafauna corpses. He maintains that our use of language, in turn, created

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2016-476: The structure and behavior of an organism is called its phenotype . These traits arise from the interaction of the organism's genotype with the environment . As a result, many aspects of an organism's phenotype are not inherited. For example, suntanned skin derives from the interaction between a person's genotype and sunlight; thus, suntans are not passed on to people's children. However, some people tan more easily than others, due to differences in their genotype:

2064-483: The two processes of natural selection and niche construction. The effect of niche construction is especially pronounced in situations where environmental alterations persist for several generations, introducing the evolutionary role of ecological inheritance . This theory emphasizes that organisms inherit two legacies from their ancestors: genes and a modified environment. A niche constructing organism may or may not be considered an ecosystem engineer . Ecosystem engineering

2112-418: The writings of Harvard evolutionary biologist, Richard Lewontin . In the 1970s and 1980s Lewontin wrote a series of articles on adaptation, in which he pointed out that organisms do not passively adapt through selection to pre-existing conditions, but actively construct important components of their niches. Oxford biologist John Odling-Smee (1988) was the first person to coin the term 'niche construction', and

2160-525: The young life sown within her". Ancient understandings of heredity transitioned to two debated doctrines in the 18th century. The Doctrine of Epigenesis and the Doctrine of Preformation were two distinct views of the understanding of heredity. The Doctrine of Epigenesis, originated by Aristotle , claimed that an embryo continually develops. The modifications of the parent's traits are passed off to an embryo during its lifetime. The foundation of this doctrine

2208-413: Was based on the theory of inheritance of acquired traits . In direct opposition, the Doctrine of Preformation claimed that "like generates like" where the germ would evolve to yield offspring similar to the parents. The Preformationist view believed procreation was an act of revealing what had been created long before. However, this was disputed by the creation of the cell theory in the 19th century, where

2256-515: Was directly responsible for stimulating a great deal of research in the post- World War II era. Trofim Lysenko however caused a backlash of what is now called Lysenkoism in the Soviet Union when he emphasised Lamarckian ideas on the inheritance of acquired traits . This movement affected agricultural research and led to food shortages in the 1960s and seriously affected the USSR. There

2304-418: Was the lack of an underlying mechanism for heredity. Darwin believed in a mix of blending inheritance and the inheritance of acquired traits ( pangenesis ). Blending inheritance would lead to uniformity across populations in only a few generations and then would remove variation from a population on which natural selection could act. This led to Darwin adopting some Lamarckian ideas in later editions of On

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