Biogenetic Law: Definition, Meaning, Ontogeny, Phylogeny, Applications
The Biogenetic Law, proposed by Ernst Haeckel in the late 19th century, The law states that “ontogeny recapitulates phylogeny,” meaning the development of an individual organism retraces its species’ evolutionary history. The evolutionary history of a species is the cause of its embryonic development, therefore, during embryonic development an organism passes through the stages of its evolution. Biogenetic law was influenced by Meckel-Serres law which was given by Etienne Serres based on the work of Johann Friedrich Meckel.
This Story also Contains
- What is Biogenetic Law?
- Ontogeny
- Phylogeny
- Assumptions of Biogenetic Law
- Applications Of Biogenetic Law
- Criticism and Modern Perspective
- Biogenetic Law NEET MCQs
- FAQs on Biogenetic Law
Though it was rejected by the biologists in the 1920s as it was incompatible with the understanding of genetics. But, the concept still holds historical significance. It highlights how embryo development can show in evolutionary patterns. This has encouraged scientists to study embryos to understand the history of the species.
What is Biogenetic Law?
Biogenetic Law, also known as the theory of recapitulation, was introduced by German scientist Ernst Harckel after reading Darwin’s Theory of Natural Selection. It suggests that the development of an organism from fertilization to maturity retraces the evolutionary history of its species. This means that an animal embryo passes through various stages during its development that resembles the adult forms of its ancestors. This idea is also known as “ontogeny recapitulates phylogeny”, indicating a link between embryology and evolutionary biology.
Ontogeny
Ontogeny is the beginning and development of an entity. It starts with fertilization and ends with the development of an adult. It suggests the path an organism followed during its lifespan. As individuals develop and species change, developmental processes can affect the following evolutionary stages. Ontogeny is used to describe how different cell types develop within an organism. It is important to understand ontogeny as it helps scientists trace genetic interactions, identify developmental abnormalities, and relate embryonic stages to evolutionary history.
Commonly Asked Questions
Ontogeny refers to the developmental history of an organism from fertilization to maturity. It encompasses all the changes that occur during an individual's lifespan, including embryonic development, growth, and differentiation of cells and tissues.
Ontogenetic depth refers to the number of cell divisions and developmental steps required to reach a particular stage of development. This concept challenges the Biogenetic Law by showing that evolutionary changes can occur at various points in development, not just through the addition of new stages at the end.
The study of gene expression patterns during development has revealed that while some genes are expressed in patterns that might suggest recapitulation, the overall process is much more complex. This research has helped to refine our understanding of the relationship between ontogeny and phylogeny beyond the simplistic view of the Biogenetic Law.
The discovery of developmental toolkit genes, which are highly conserved across diverse species, has shown that similarities in embryonic development are often due to shared genetic mechanisms rather than recapitulation of ancestral forms. This finding has helped to refine our understanding of the relationship between ontogeny and phylogeny.
The study of developmental sequences across species has revealed both conserved and divergent patterns. While some sequences show similarities that might suggest recapitulation, others show significant variations. This research has led to a more nuanced understanding of the relationship between ontogeny and phylogeny than the Biogenetic Law proposed.
Phylogeny
Phylogeny refers to the evolutionary history and relationships among species. It shows how organisms are related through common ancestors. These relationships are often represented using a phylogenetic tree, a diagram that shows connections based on physical and genetic similarity. In simple words, it is similar to a family tree. Closely related species show more similarities than distant ones. Studying phylogeny is important to understand how species, genes, and traits have evolved over time. It helps scientists trace the origin of organisms and predict how they might change in the future. Phylogeny is very helpful and has application in various fields:
Classification: Helps in classifying organisms more accurately by showing how closely they are related.
Finding the origin of pathogens: Helps to trace the origin and spread of new diseases and viruses, useful for developing public health policies.
Conservation: Helps in identifying the biodiversity that can go extinct based on their evolutionary uniqueness.
Forensics: DNA analysis based on phylogenetic data can be used in cases involving criminal activity, tainted food, unidentified fathers of children, etc.
Bioinformatics & computing: Used to create software and algorithms to analyze biological data using evolutionary relationships.
Commonly Asked Questions
Phylogeny is the evolutionary history and relationships among species or groups of organisms. It describes how different species have evolved from common ancestors over time and is often represented in the form of a phylogenetic tree.
Comparative embryology, which examines similarities and differences in embryonic development across species, was initially used to support the Biogenetic Law. However, it now provides evidence for common ancestry and evolutionary relationships without adhering to the strict recapitulation proposed by Haeckel.
Evolutionary developmental biology, or evo-devo, recognizes that while the Biogenetic Law is an oversimplification, there are important connections between ontogeny and phylogeny. Evo-devo focuses on how developmental processes evolve and how these changes lead to the evolution of new features and body plans.
Some features that appear to support the law include pharyngeal arches in vertebrate embryos (resembling fish gills), and the temporary appearance of a tail-like structure in human embryos. However, these features are now understood as shared developmental patterns rather than direct recapitulations of adult ancestral forms.
Homologous structures in embryos, such as pharyngeal arches in vertebrates, were once seen as evidence for the Biogenetic Law. Now, they are understood as shared developmental features that reflect common ancestry rather than a recapitulation of adult ancestral forms.
Assumptions of Biogenetic Law
Biogenetic Law, proposed by Haeckel, is based on how embryonic development reflects in evolutionary history. It helps explain why embryos of different species look similar in the early stages of development and how new traits appear as development progresses. Haeckel made the following assumptions:
Law of Correspondence: It states that early developmental stages in higher animals resemble the adult stages in lower species. Example: Human embryos show gill slits in early development, similar to adult fish. This shows common ancestry.
New Traits in Later Stages: Haeckel believed that as embryos grow, they pass through stages similar to other organisms and then develop new features that are unique to their own species. All embryos initially have a similar appearance, but differences appear as they grow and develop.
Principle of Truncation: According to this, the development of higher animals becomes faster over time. Some early stages are short and more new traits are added. This means that although higher animals have longer gestation periods, the early stages appear more quickly compared to lower organisms.
Applications Of Biogenetic Law
Although modern science has revised many aspects of Haekel’s theory, these applications continue to provide perspectives in several fields such as science as well as humanities. It helps scientists trace changes during evolution and understand how traits are evolved. Here is list of applications of biogenetic law:
Evolutionary Biology: It provides a framework for studying how traits evolve by observing embryonic development.
Field of Art: In art history, the biogenetic principle has been used to trace the development of artistic styles.
Cognitive Development: Some researches related the development of a child’s mental and emotional growth to the evolutionary stages of human development
Paleontology and Fossil Interpretation: It helps to interpret the fossil records by linking developmental stages in modern organisms and population to features of ancient species.
Commonly Asked Questions
This phrase, central to the Biogenetic Law, means that an organism's individual development (ontogeny) repeats the evolutionary stages of its species (phylogeny). In other words, it suggests that embryos go through stages resembling their evolutionary ancestors during development.
The Biogenetic Law was initially used to support evolutionary theory by suggesting that embryonic development provides evidence for evolutionary relationships between species. However, modern understanding shows that while some developmental stages reflect evolutionary history, the law oversimplifies the complex relationship between ontogeny and phylogeny.
The Biogenetic Law is now considered an oversimplification and is not accepted as a universal principle in modern biology. While some aspects of embryonic development do reflect evolutionary history, the relationship between ontogeny and phylogeny is much more complex than Haeckel's original theory suggested.
Criticism and Modern Perspective
Karl Ernst von Baer objected to the embryological justification for evolution. He rejected the idea that the morphological stages experienced by embryos of more sophisticated animals were similar to those of adult forms of species lower in the food chain. Von Baer's law states that general features of a group of animals appear earlier in embryonic development than specialized features. Unlike the Biogenetic Law, it doesn't claim that organisms recapitulate their evolutionary history but rather emphasizes the divergence of embryos from a common form as development progresses.
Critics also argued that the law oversimplifies embryonic development, ignores the influence of environmental factors, and fails to account for evolutionary adaptations in early developmental stages. Additionally, Haeckel's embryo drawings, used to support the law, were later found to be inaccurate.
Biogenetic Law NEET MCQs
Q1. The biogenetic law states that:
Ontogeny repeats phylogeny
Phylogeny repeats ontogeny
Both ontogeny and phylogeny are unrelated
Ontogeny is independent of phylogeny
Answer: 1) Ontogeny repeats phylogeny
Explanation:
The biogenetic law, proposed by Ernst Haeckel, suggests that ontogeny (the development of an individual organism) goes through stages that resemble the evolutionary history (phylogeny) of its species. For example, during embryonic development, humans exhibit features like gill slits, which are found in ancestral aquatic organisms like fish. Hence, the statement "Ontogeny repeats phylogeny" correctly summarizes the concept.
Hence the correct answer is option 1) Ontogeny repeats phylogeny.
Q2. In the context of the biogenetic law, ontogeny refers to:
The evolutionary history of a species
The development of an individual organism
The study of fossils
The process of natural selection
Answer: 2) The development of an individual organism
Explanation:
Ontogeny is the biological term for the entire sequence of events in the development of an organism, from fertilization of the egg to its mature form. In biogenetic law, ontogeny is compared to phylogeny (the evolutionary development of the species), implying that individual development mirrors ancestral evolution.
Hence the correct answer is option 2) The development of an individual organism.
Q3. Human embryos showing gill slits during early development is an example of:
Phylogeny
Ontogeny
Law of Correspondence
Truncation
Correct answer: 2) Ontogeny
Explanation:
The appearance of gill slits in human embryos during early development is a classic example of ontogeny recapitulating phylogeny, as described by Haeckel’s biogenetic law. Ontogeny refers to the individual development of an organism from zygote to adult, while phylogeny refers to the evolutionary history of the species. The transient presence of gill slits in embryos does not mean humans develop into fishes, but it indicates an ancestral connection with aquatic vertebrates. This feature provides strong evidence for common ancestry and supports the theory of evolution. Thus, it is an example from ontogeny that reflects stages of phylogenetic history.
Hence, the correct answer is option 2) Ontogeny.
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FAQs on Biogenetic Law
What is the biogenetic law?
The Biogenetic Law, also known as the Theory of Recapitulation was proposed by Ernst Haeckel in the 19th century. It states that an organism's embryonic development (ontogeny) repeats or recapitulates its evolutionary history (phylogeny). For example, early embryos of vertebrates show similar features such as gill slits and tails, reflecting their common ancestry.
Who proposed the biogenetic law?
The Biogenetic Law was proposed by Ernst Haeckel, a German biologist and philosopher, in 1866. Haeckel was a prominent advocate of Darwinism and used this law to support evolutionary theory.
What are the three assumptions of biogenetic law?
Early developmental stages in higher animals resemble the adult stages in lower species. Example: Human embryos show gill slits in early development, similar to adult fish. This shows common ancestry.
All embryos initially have a similar appearance, but differences appear as they grow and develop.
The development of higher animals becomes faster over time. Some early stages are short and more new traits are added.
What are the applications of biogenetic law?
It provides evidence for evolution by showing similarities in embryonic stages across species.
It helps in understanding comparative embryology and tracing evolutionary relationships.
It is applied in taxonomy and systematics for classifying organisms based on developmental features.
It explains why embryonic features like gill slits in humans point to a fish-like ancestry.
Frequently Asked Questions (FAQs)
Developmental systems drift refers to the phenomenon where the underlying developmental mechanisms can change over evolutionary time while maintaining a similar end result. This concept challenges the Biogenetic Law by showing that similar developmental outcomes can be achieved through different evolutionary pathways, rather than through strict recapitulation.
Developmental burden refers to the constraints placed on evolutionary change by the need to maintain functional developmental processes. This concept challenges the Biogenetic Law by showing that evolutionary changes are limited by the need to preserve essential developmental functions, rather than simply recapitulating ancestral forms.
The study of regeneration in different species has revealed diverse mechanisms and capabilities, challenging the idea of a universal pattern of development as proposed by the Biogenetic Law. It shows that developmental processes can be reactivated and modified in various ways across different species and life stages.
The discovery of microRNAs and their role in regulating gene expression during development has revealed another layer of complexity in the relationship between ontogeny and phylogeny. This finding demonstrates that developmental processes are regulated at multiple levels, beyond the simple recapitulation proposed by the Biogenetic Law.
Developmental bias refers to the tendency of developmental systems to produce certain variations more readily than others. This concept challenges the Biogenetic Law by showing that evolutionary changes are constrained and guided by developmental processes, rather than simply recapitulating ancestral forms.
The discovery of induced pluripotent stem cells, which can be reprogrammed to an embryonic-like state, challenges the unidirectional view of development implied by the Biogenetic Law. It demonstrates that developmental potential is more flexible than previously thought, further complicating the relationship between ontogeny and phylogeny.
The study of cell lineages during development has revealed both conserved and divergent patterns across species. While some lineages show similarities that might suggest recapitulation, others show significant variations. This research has contributed to a more nuanced understanding of the relationship between ontogeny and phylogeny than the Biogenetic Law proposed.
The phylotypic stage is a period in early development when embryos of different species within a phylum appear most similar. While this concept might seem to support the Biogenetic Law, it actually demonstrates that the relationship between ontogeny and phylogeny is more complex, with both conserved and divergent features at different stages of development.
The study of heterochrony, or changes in the timing of developmental events during evolution, has shown that evolutionary changes can occur through alterations in the rate or timing of developmental processes. This concept provides a more flexible and accurate view of the relationship between ontogeny and phylogeny than the rigid recapitulation proposed by the Biogenetic Law.
The discovery of deeply conserved non-coding elements in genomes across diverse species has revealed that some aspects of development are regulated by highly conserved genetic mechanisms. This finding provides a more nuanced understanding of the relationship between ontogeny and phylogeny than the simplistic view proposed by the Biogenetic Law.