What is Phylogeny?
Phylogeny is the evolutionary history of a species or group. There are about 100 million species living on earth today.
The morphological and biochemical evidence suggests that all the organisms are genetically related.
The genealogical relationships of the organisms can be represented in the form of an evolutionary tree known as the phylogenetic tree. In this, the species or groups are organized in such a way that helps to know how they evolved from the common ancestors.
Phylogeny helps us know how the genes, genomes and species evolve. It is useful for fundamental and numerical applications.
The phylogenetic tree is also known as the cladogram. The species or the groups are found at the tips of the lines known as the tree branches.
The evolution of species evolved from a common ancestor is exhibited by how the branches connect.
The branch points represent the most recent common ancestor of all the groups descended from that common point.
Some cladograms are blocky, while the others are diagonal. However, the orientation of the tree does not change the information.
In a phylogenetic tree, if two species have the more common recent ancestor, they are more related than those with a less recent common ancestor.
Also read: Evolution
Applications of Phylogenetics
Phylogenetics has the following applications:
The Linnaean classification of species is known with the help of phylogeny. Based on the sequence data, more accurate descriptions of patterns of relatedness are available.
The DNA in case of a crime scene or paternity disputes is assessed by phylogeny.
Identification of the origin of Pathogens
Phylogenetic approaches can be used to know about a new pathogen outbreak. It helps to know the species the pathogen is related to and the source of its transmission.
Phylogeny helps the conservation biologists to make decisions about which species they should try to prevent from extinction.
Computing and Bioinformatics
The algorithms developed for phylogenetics are also used in software development in other fields.
Ontogeny and Phylogeny
Ontogeny is the course of development of an individual organism. It begins at the time of fertilization and includes all the developmental events at the time of birth and thereafter.
The ancestral characters are often preserved in the development of an organism. For eg., the human and chick embryos undergo a stage during their development where they have slits and arches in their neck similar to the gill slits and arches of a fish. This suggests that humans and chicks share a common ancestor with fish. These developmental characters can be used to create phylogenetic trees.
It is believed that during development, an organism progresses through each of the adult stages of evolutionary history. This states that “ontogeny recapitulates phylogeny”. For instance, a chick goes through the following stages of evolutionary history during the development- a single cell, a multicellular invertebrate, fish, reptile, bird, and then forms the chick. However, the statement is controversial and cannot be proved in all the organisms.
Over the years, the organisms have evolved into more derived forms. The new generations retain most of their ancestral features. These features get modified with additional novel traits which helps them to adjust in the environment they live in.
Phylogeny helps us to know the similarities and differences between plants, animals, and microorganisms.
Difference Between Ontogeny And Phylogeny
Ontogeny refers to the development of an organism while phylogeny refers to how the organisms have evolved.
Let us take an example of a chicken, the ontogeny will explain the entire development cycle of the chicken right from the single cell.
Now if we consider the example of an ostrich and assume that it descended from the family of chickens, phylogeny will explain how the chicken evolved into an ostrich, i.e., it will explain the evolutionary process.
Also read: Origin and Evolution of Man
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Frequently Asked Questions
What do you mean by phylogeny?
Phylogeny refers to the evolutionary history of a group of organisms. A phylogenetic tree is used to depict the relationship between different organisms.
Why is studying phylogeny important?
Phylogeny is important because it enriches our knowledge about how the organisms evolved. It also strengthens our understanding about genes, genomes and species.
What are the advantages of phylogenetic classification over Linnaean classification?
The phylogenetic classification has two major advantages:
- It tells us about the evolutionary history of an organism.
- It does not attempt to rank the organisms.
What is ontogeny?
Ontogeny refers to the development of an individual from the time of fertilization of the egg until the organism matures.
What is meant by “ontogeny recapitulates phylogeny”?
The phrase “ontogeny recapitulates phylogeny” means that all the evolutionary forms of an organism are expressed in its developmental stages.