Have you ever wondered how different species evolve and how they are related to each other? Well, scientists use a method called phylogeny to answer these questions. Phylogeny helps us understand which species or groups share the same ancestors. It's like a family tree for different species! By reconstructing the phylogeny, we can learn more about the evolution of different species and their relationships with each other.

What is phylogeny?

Have you ever heard of the word "phylogeny"? It's all about the evolutionary history and relationships of different organisms. Basically, it tells us how different species are related to each other and how they evolved over time. Let's take an example of mammal phylogeny to understand it better. To reconstruct the phylogeny of mammals, scientists use lines of evidence such as fossils, DNA, and morphology. By combining all this evidence, they can create a family tree of mammals that shows their relationships and evolution. It's pretty cool, isn't it? In the following discussion, we will learn more about the definition of phylogeny, how it works, and the different methods used to reconstruct it.

What Is the Definition of Phylogeny?

Evolution is a gradual change in the traits of a population of organisms that takes place over many generations. Scientists study patterns of evolutionary changes to understand how new species are formed.

Phylogeny refers to the evolutionary history and relationships of a species or group of species. It is often shown using a diagram called a phylogenetic tree. This tree shows how organisms are related to each other through common ancestors.

Organisms are grouped into categories in taxonomy, ranging from species to domain. Taxonomists group organisms with similar traits and features into increasingly broader categories. For example, the leopard, jaguar, African lion, and tiger are all part of the Panthera genus, which includes all big cats.

Besides taxonomy, phylogeny can also be shown through cladistics, which groups organisms based on common ancestry. Clades consist of a common ancestor and its descendant species.

Taxonomy is a systematic approach to naming and classifying organisms.

An Example of Animal Phylogeny

Let's take a closer look at mammal phylogeny as an example of animal phylogeny.

The evolutionary history and relationships of mammals can be shown through a phylogenetic tree, as illustrated in Figure 1. We can see how the class Mammalia, which diverged from other tetrapods due to unique anatomical features such as specific jawbones and differentiated teeth, gave rise to two orders: Monotremata, which includes egg-laying mammals, and Theria.

Theria, a subclass of mammals, further diverged into two infraclasses:ialacentalia.upials mammals that use external pouches to raise their newborn offspring, while Placentalia are mammals that have a placenta, a temporary organ that connects the embryo to the mother's uterus.

This example shows how phylogeny can be used to infer common ancestry from similar traits and how divergence can be inferred from the emergence of new traits. By analyzing the traits of different species, scientists can create a family tree illustrating the evolutionary history and relationships of different groups of animals.

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Phylogenies are not definitive–they are hypotheses that can be revised or updated based on available evidence. They are also presented in different ways. For example, Figure 2 is another phylogenetic tree of Mammalia. This version shows the phylogeny of families under Mammalia. It also shows other information, such as the geographic distribution of these groups of mammals indicated by the points on a map.

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What Evidence Is Used to Determine Phylogeny?

Phylogenies are inferred based on different lines of evidence, including fossils, homology, and molecular biology. Let's discuss each of these briefly.

Fossils

Fossils are the preserved remains or traces of organisms from past geological periods, often found in sedimentary rocks. The fossil record is used to document the history of life on Earth based on the arrangement of fossils in strata. This arrangement gives us an idea of what organisms existed in a particular geological time.

use fossils to construct the both ext the fossil record shows that cetaceans, an order of marine mammals that includes whales, dolphins, and porpoises, evolved from terrestrial mammals similar to modern-day hippopotamuses, pigs, and cows. Fossils also show that the pelvis and hind limb bones of extinct cetacean ancestors became smaller, eventually disappearing completely and developing into flukes and flippers.

By studying fossils, scientists can construct a timeline of the evolution of different species and understand how they became what they are today. The fossil record provides an important tool for understanding the history of life on Earth and how different species have evolved over time.

Homology

Homology plays critical role in determining the evolutionary relationships organisms The degree to which species share traits and features indicates how closely they are related. There are three types of homology: morphological, molecular, and developmental.

Morphological homology refers to similar structures found in different species that share the same basic form due to common ancestry. For example, mammals are divided into monotremes, placentals, and marsupials based on how they produce offspring.

Molecular homology refers to similar genes or DNA sequences found in different species that were inherited from a common ancestor. By comparing these sequences, scientists can determine how closely related different species are to each other.

Developmental or ontological homology refers to similar structures found in various stages of development across different species. For example, all vertebrate embryos have gill slits and tails, but these disappear when they are born.

When inferring phylogenies, scientists distinguish between analogous and homologous traits. Analogous traits are structures that are similar due to common selection pressures, rather than common ancestry. Only homologous features can be used to determine the evolutionary relationships between organisms. By analyzing homologous traits, scientists a family that illustrates the evolutionary history and relationships of different groups of organisms.

How Are DNA and rRNA Used in Phylogeny?

Although many phylogenies have been constructed using morphological and fossil evidence, molecular evidence has helped scientists build more accurate phylogenetic trees. DNA and rRNA (ribosomal RNA) are useful for studying the evolutionary relationship of organisms because all living organisms–from bacteria to humans–have them.

DNA and rRNA molecules are made up of four chemical bases that pair as follows:

Adenine (A) pairs with thymine (T)Cytosine (C) always pairs with guanine (G).

DNA sequencing is the process of determining the order of these chemical bases. Scientists use DNA sequencing to determine the evolutionary relationship of organisms by aligning comparable sequences.

If the sequences are different at only one or a few sites, the species are likely very closely related. If there are different bases of various lengths at many sites, the species are likely distantly related.

Figure 3 below demonstrates how two DNA sequences might be aligned.

Insertions and deletions in DNA sequences can alter the sequence and make it challenging to align sequences. Scientists have developed computer programs and statistical tools to accurately align DNA sequences and determine if the alignment is due to hom DNA be used in dating, similar to fossils and. Mitochondrial DNA has high mutation rates and can be used to determine the evolutionary relationships among closely related species. Ribosomal RNA has low mutation rates and can be aligned more accurately for distantly related species.

"Ontogeny recapitulates phylogeny" is a phrase that encapsulates the recapitulation theory by Ernst Haeckel, stating that the development of individual organisms replays the evolutionary development of the species from its ancestral species. While the statement is not entirely true, it implies that similarities shared by organisms in various stages of development could mean that they evolved from a common ancestor. This is why all vertebrates, at some point in their development, have gill slits and tails.

Phylogenies are inferred based on different lines of evidence, including fossils, homology, and molecular biology. DNA sequencing has helped scientists build more accurate phylogenetic trees, and molecular evidence has complemented morphological and fossil evidence to construct more accurate evolutionary relationships among different species.

Phylogeny

What is phylogeny?

Phylogeny is the evolutionary history and relationship of a species or a group of species. 

How can dna be useful in phylogeny?

DNA and rRNA (ribosomal RNA) are useful for studying the evolutionary relationship of organisms because all living organisms–from bacteria to humans–have them. Scientists use DNA sequencing to determine the evolutionary relationship of organisms by aligning comparable sequences. 

What is used to determine phylogeny?

Phylogenies are determined based on different lines of evidence including fossils, homology, and molecular biology. 

What is a phylogeny based on? 

Phylogenies are inferred based on different lines of evidence including fossils, homology, and molecular biology. 

Why is rrna used for phylogeny?

Ribosomal RNA has low mutation rates, so its sequence and structure can be aligned more easily and accurately, even for distantly related species.

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