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Phylogeny and Cladistics Study Guide

Phylogeny and Cladistics are a method of classifying organisms based on common traits evolved within them to trace their evolutionary relations.

Table of content

Introduction:

We have an infinite number of species in our environment. To organize these species, many botanists started classifying species on different bases in the past.

The major contribution came from Carl Linnaeus. He gave various theories of the classification of organisms. In this section, we will talk about one of his most important contributions to biology, i.e., phylogeny and cladistics classification of organisms.

What is phylogeny?

Are you aware that we are related to several organisms? Not only that, we have similar characteristics as them as well. Many animals were found to be our ancestors. But how can we say that? Linnaeus gave a classification theory to the world, known as Phylogeny.

Phylogeny is a kind of classification in which organisms can be classified with the help of their basic physical traits. In simple words, those organisms who have a similar kind of body structure will be grouped.
The motive of grouping organisms together was to show that they had common ancestors in the past.
Phylogeny is presented with the help of a tree diagram known as a phylogenetic tree. It's a pattern in use to show the evolutionary past of organisms.
The organisms placed near branches are considered to have a common ancestral past. In modern times, phylogenetic trees are made with the help of clades.

What is cladistics?

Cladistics classification includes the comparison of traits of one species with another and finding similarities among the ancestors and their descendants to create a relationship among them. Cladistics theory creates clades of organisms that are represented with the help of a cladogram. What is a clade?

Cladogram Source

A clade is a group of organisms that includes an ancestor and its descendants. Clades are based on cladistics classification.
Cladistics is a classification that represents phylogenetic classification related to evolutionary relationships.
Clades are formed with organisms with shared and unique traits.

Types of clades:

Clades are of these three types:

Monophyletic: monophyletic clades means a group of organisms with a single clade in it. Here you will find only one ancestor for many descendants.

Paraphyletic: this clade includes an ancestor and multiple descendants, removing some 2-3 groups.

Polyphyletic: in this clade, organisms possess homoplasy traits. It means organisms in a group show similar characteristics, but they don't.

We hope now you are aware of the basic meaning of Phylogeny and cladistics. Now, we'll discuss some points that make cladistics and Phylogeny different from each other.

Phylogeny vs cladistics

Phylogeny and cladistics are a part of each other because phylogenetic trees are made using cladistics. However, these are some points on which we can differentiate between Phylogeny and cladistics:

Phylogenetic classification represents the historical evolutionary relationship of organisms, whereas cladistics classification deals with the recent ancestor and descendants relationship of organisms.
Phylogeny involves making groups with the help of physical characteristics of organisms, but cladistics talks about the actual traits of the organisms.
Phylogenetic representation is done with the help of a phylogenetic tree, and cladistics representation is done using a cladogram.

Cladistic tree/cladogram based on phylogenetic clades

Cladogram and a phylogenetic tree Source

As discussed, Phylogeny is shown by a diagrammatic representation called a phylogenetic tree. Here are some most common terminologies related to the Phylogenetic/cladistics tree:

Nodes: Nodes represent a place in a phylogenetic tree where one species gets separated from another. Here branching occurs.

Branches: It is a line that represents ancestors and their descendants. It starts from nodes.

Monophyletic clades: It represents the relationship of descendants with their most common ancestors. Presented by a single line in the phylogenetic tree.

Taxa: A specific group of organisms. Tips of phylogenetic trees end in taxa.

Assumptions of phylogenetic trees:

Phylogenetic tree Source

The diagram of phylogenetic trees are based on the following assumptions:

Every ancestor had a common ancestor.
New organisms come into existence when old ones get separated into two groups.
As time passes, changes will occur in characteristics within the same group.

Conclusion:

Phylogeny is a classification that creates a relationship between ancestors and descendants of species based on their physical traits. Phylogeny is represented with the help of phylogenetic trees.
Cladistics shows the evolutionary relationship of recent ancestors and descendants or the pathway of evolution from the very start. It can be represented with the help of a cladogram.
Phylogenetic trees are based on clades; hence cladistics is a part of the Phylogeny. These clades act as branches of three, representing different groups of species with similar characteristics.T

FAQs:

1. What is the relationship between phylogeny and cladistics?

Phylogeny deals with the historical relationships of ancestors and descendants. Cladistics helps Phylogeny present a reconstructed evolutionary relationship between descendants and their most recent ancestors.

2. Is cladistics a branch of phylogeny?

Yes, cladistics helps prepare phylogenetic trees, and cladistics is a branch of it that shows the evolutionary relationship of descendants and their recent ancestors.

3. What is phylogeny based on?

Phylogeny is based on the basic physical traits of organisms. Carl Linnaeus grouped living organisms of the same physical characteristics in the same groups to present that those organisms must've had a common ancestor.

4. What is an example of cladistics?

Reptiles, fishes, and birds can be an example of cladistics. Because they had common ancestors in the past, and evolution resulted in differences among them.

5. What does cladistics mean?

A grouping of organisms based on their shared and unique traits is known as cladistics. It's a path that shows the evolution of organisms over a while. Cladistics can be represented with the help of cladograms.

6. What are autapomorphic traits?

Alin phylogeny, autapomorphic traits are unique traits that can only be found in one particular taxon. These traits are also known as derived traits. Autapomorphic traits are only present in a particular species; you can't find these traits in any other group of species or clades.

7. What are phenetics and cladistics?

Phenetics is also referred to as taximeters. It is a classification of organisms based on the similarities found in their visible traits, irrespective of their evolutionary relationships. At the same time, cladistics involves evolutionary characters as well.

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