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Phylogeny is the history of evolution and the relationship between species and groups. There are around 100 million species living on Earth. Phylogeny is the study of how all these species evolved over millions of years and how they are related to each other.
- Earth is supposed to have been formed nearly about 4.5 billion years back.
- Life didn’t exist on early Earth as there was no atmosphere and the planet was still hot.
- Slowly, as Earth cooled and water and atmosphere formed, life on Earth appeared almost 4 billion years back.
- Oparin and Haldane proposed that the formation of life was preceded by chemical evolution.
- Later in 1953, Miller’s experiment evidenced that proposition.
- With such limited pieces of evidence, chemical evolution was accepted.
Phylogeny is used to know how genes, genomes, and species evolve. It is also important for various fundamental and numerical applications.
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Key Terms: Phylogeny, Allele, Genes, Genomes, Ancestors, Species, Phylogenetic Tree, Evolution, Organisms
What is Phylogeny?
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Phylogeny is the history of the evolution of various species or groups that are closely related to each other among the broad groups of organisms.
- It suggests that plants and animals of different species or groups are descendants of a common ancestral organism.
- Morphological and biochemical evidence says that all organisms are genetically related.
- Phylogenetic Tree is an evolutionary tree in which the genealogical relationships of the organisms can be represented.
- In this, the species or groups are organized in such a manner that explains how they evolved from their common ancestors.
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Phylogenetic Tree
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Phylogenetic Tree is the visualization of the results of Phylogeny. It is a diagram that represents the evolutionary relationship among various organisms.
- Phylogenetic Tree is rather hypothetical than definitive facts.
- All life on Earth is part of a single Phylogenetic Tree which indicates that all the organisms on Earth share a common ancestor.
- The branches of the tree represent the evolutionary relationship between various organisms.
Phylogenetic Trees are of various types such as:
- Dendrogram
- Cladogram
- Phylogram
- Dahlgrenogram
- Spindle Diagram
Evidence of Evolution
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Evidences that suggest the occurrence of Evolution are as follows:
Fossils
- Fossils are the remains of animals and plants found in sedimentary rocks formed over thousands of years due to heat and pressure.
- They form important evidence of evolution as they verify that there had been a variety of living things on Earth that are now extinct.
- These animals show features that are similar to many animals found today.
- For example, the 150 million-year-old fossil of Archaeopteryx found in southern Germany had jaws with teeth, a long bony tail like dinosaurs, and broad wings and feathers like a bird which suggests that birds had reptilian ancestors.
Chemical and Anatomical Similarities
- All living organisms begin as single cells that reproduce, grow old and die.
- Every organism on Earth shares the ability to create complex molecules out of Carbon and a few other elements.
- 99% of all the molecules of living things are made from only 6 out of 92 most common elements.
- Many organisms even share the same type of body structures which suggests they have inherited them from a common ancestor thus proving the possibilities of evolution.
Geographic Distribution of Related Species
Geographic distribution of various related species also hints at the possibilities of evolution.
For example,
- Australia had more than 100 species of kangaroos, koalas, and other marsupials before humans arrived.
- A great number of birds, plants, and insect species were found in New Zealand and Hawaii which were found in no other places in the world.
Applications of Phylogeny
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Phylogeny has numerous practical applications in the medical field such as:
- Forensics: Phylogeny is used by forensic experts to assess DNA in crime scenes or paternity disputes.
- Identification of Origin of Pathogens: Phylogeny can be used to identify the origination of pathogens to search for a cure effectively.
- Conservation purposes: Phylogeny helps biologists in making decisions as to which species should be conserved and saved from extinction.
- Computing and Bioinformatics: Algorithms developed for Phylogeny are used in developing software in other fields.
- Classification: Phylogeny helps in classifying organisms on the basis of their evolutionary history.
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Things to Remember
- Phylogeny represents the evolutionary relationships among a group or set of organisms.
- The tips of a phylogenetic tree represent species and the nodes of the tree represent common ancestors.
- Phylogenies include an outgroup which means a member outside the group of interest who are not closely related to others.
- New groups develop when existing populations spilt into two groups.
- Lineages experience changes in characteristics over the period of time.
Sample Questions
Ques. What do you understand by Phylogeny? (2 Marks)
Ans. Phylogeny is the evolutionary history of a species. Phylogeny or Phylogenetics is the broad study of the evolutionary relationship in biological entities- often individuals or species or genes.
Ques. What is a Phylogenetic Tree? (3 Marks)
Ans. Phylogenetic Tree is basically the visualization diagram of the phylogeny. Phylogenetic Trees are mostly hypothetical. All life on Earth is part of a single Phylogenetic Tree which indicates that all the organisms on Earth share a common ancestor.
It is characterized as a diagrammatic portrayal of living organisms' evolutionary links. This diagrammatic representation represents how different species evolved from a species of common ancestors
Ques. What are the applications of Phylogeny? (5 Marks)
Ans. Phylogeny is extremely useful in numerous applications like
- Classification: More accurate descriptions of relatedness are provided. Phylogenesis also helps in the Linnaean classification of any new species.
- Identifying the Origin of Pathogens: The new species of pathogens that are related to and are subsequently the source of transmission which can further be helpful for public health policy.
- Conservation: Conservation policies are there in cases of tough decisions about which species to prevent from getting extinct.
- Forensics: Assessment of DNA evidence is presented in court for the situations like crime, food contamination, the father of a child is unknown and etc.
- Bioinformatics & Computing: Various Algorithms are developed for the use of phylogenetics to develop software in other fields.
Ques. What are the different types of Phylogenetic Trees? (2 Marks)
Ans. Phylogenetic Trees may be of the following types:
- Dendogram
- Cladogram
- Phylogram
- Dahlgrenogram
- Spindle Diagram
Ques. What is the evidence of evolution? Elaborate. (5 Marks)
Ans. The evidences of evolution are as follows:
- Fossils of Ancient Animals: Fossils show a pattern of evolution and provide solid evidence that creatures from the past are not the same as those living now. Scientists assess the age of fossils and classify them from around the world in order to identify when creatures existed in relation to one another. For example, horse lineage has yielded some of the most well-studied fossils.
- Chemical and Anatomical Similarities of Species: The chemical composition of most species is identical which suggests them having a common ancestor. Some animals also have similar anatomical features to adapt to a specific region. For example, in the polar area, unrelated animals such as arctic fox and ptarmigan have been chosen for seasonal white phenotypes to blend in with snow and ice. These commonalities occur due to comparable selection pressures— advantages of not being spotted by predators—rather than common ancestry.
- Geographical Distribution of Species of Same Types: Throughout Geological time, the distribution pattern of life on Earth follows patterns best characterized by evolution in conjunction with tectonic plate movement. Australia's abundance of marsupials and the rarity of other mammals are a result of the country's historical isolation.
Ques. What is Adaptive Radiation? (3 Marks)
Ans. Adaptive Radiation is a divergence in species through changes in morphological and anatomical structures and taking different forms with a common ancestor. Organisms go through these changes in order to adapt themselves to changing environments and to increase their chance of survival according to Darwin’s Theory of Evolution.
Ques. State the Hardy-Weinberg Principle. (2 Marks)
Ans. The Hardy-Weinberg Principle says that the genetic variation in a population will remain constant from one generation to the next in the absence of various disturbing factors that affect the equilibrium.
Ques. What are the factors that affect the Hardy-Weinberg equilibrium? (2 Marks)
Ans. The factors affecting the Hardy-Weinberg equilibrium are
- Gene Migration,
- Genetic Drift,
- Mutation,
- Genetic Recombination,
- Natural Selection.
Ques. What is Genetic Equilibrium? (1 Mark)
Ans. The total number of genes and their alleles in a genetic pool or population remains constant which is 1. This is known as Genetic Equilibrium.
Ques. Give some instances of Adaptive Radiation. (2 Marks)
Ans. Some instances of Adaptive Radiation are
- Diversity of finches in the Galapagos Islands
- Variety of marsupials such as kangaroos and koalas in Australia
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