Determine the Derived Characteristics

Oct 13, 2025 by leolavanderia.com.br 148 views

A cladogram is a diagram that shows the evolutionary relationships between organisms. It is a tool used in biology to visualize the shared characteristics and differences between species. By analyzing the characteristics of different organisms, biologists can create a cladogram that illustrates their evolutionary history.

What is a Cladogram?

A cladogram is a type of phylogenetic tree that shows the relationships between organisms based on their shared characteristics. It is a diagram that uses branches to represent the different species and their relationships to each other. The cladogram is constructed by analyzing the characteristics of different organisms and grouping them together based on their similarities.

How to Create a Cladogram

To create a cladogram, you need to follow these steps:

Identify the Organisms: Choose the organisms you want to include in your cladogram. This can be a group of species that you are interested in studying or a set of organisms that you want to compare.
List the Characteristics: Make a list of the characteristics that you want to use to create the cladogram. This can include physical characteristics such as body shape, size, color, and texture, as well as behavioral characteristics such as diet, habitat, and behavior.
Determine the Derived Characteristics: Determine which characteristics are derived and which are ancestral. Derived characteristics are those that have evolved from a common ancestor and are unique to a particular group of organisms. Ancestral characteristics are those that are shared by all organisms and are not unique to a particular group.
Create the Cladogram: Use the derived characteristics to create the cladogram. Start with the most ancestral characteristic and work your way down to the most derived characteristic. Each time you add a new characteristic, you will create a new branch on the cladogram.
Analyze the Cladogram: Once you have created the cladogram, analyze it to see what it tells you about the evolutionary relationships between the organisms.

Example: Creating a Cladogram for Earthworms and Cod Fish

Let's create a cladogram for earthworms and cod fish. We will use the following characteristics:

Backbone: The presence or absence of a backbone.
Legs: The presence or absence of legs.
Hair/Fur: The presence or absence of hair or fur.

Here is the data for the two organisms:

Organism	Backbone	Legs	Hair/Fur
Earthworm
Cod fish	X

To create the cladogram, we will start with the most ancestral characteristic, which is the presence or absence of a backbone. Since both earthworms and cod fish have a backbone, we will not create a branch for this characteristic.

Next, we will look at the presence or absence of legs. Earthworms do not have legs, while cod fish have fins that are similar to legs. We will create a branch for this characteristic, with the earthworms on one side and the cod fish on the other.

Finally, we will look at the presence or absence of hair or fur. Earthworms do not have hair or fur, while cod fish have scales that are similar to hair or fur. We will create a branch for this characteristic, with the earthworms on one side and the cod fish on the other.

Here is the resulting cladogram:

          +---------------+
          |  Backbone  |
          +---------------+
                  |
                  |
                  v
+---------------+---------------+
|  No Legs    |  Legs        |
|  (Earthworm) |  (Cod fish)  |
+---------------+---------------+
                  |
                  |
                  v
+---------------+---------------+
|  No Hair/Fur |  Hair/Fur    |
|  (Earthworm) |  (Cod fish)  |
+---------------+---------------+

Interpreting the Cladogram

The cladogram shows that earthworms and cod fish share a common ancestor that had a backbone. From this common ancestor, two distinct lineages evolved: one that led to the earthworms and one that led to the cod fish. The earthworms lost their legs and developed a worm-like body, while the cod fish developed fins and scales.

The cladogram also shows that the earthworms and cod fish have distinct characteristics that are not shared by their common ancestor. The earthworms do not have hair or fur, while the cod fish have scales that are similar to hair or fur.

Conclusion

Creating a cladogram is a powerful tool for understanding the evolutionary relationships between organisms. By analyzing the characteristics of different organisms and grouping them together based on their similarities, biologists can create a cladogram that illustrates their evolutionary history. The cladogram can be used to identify the derived characteristics of a particular group of organisms and to understand the evolutionary relationships between different species.

References

Mayr, E. (1969). Principles of Systematic Zoology. New York: McGraw-Hill.
Simpson, G. G. (1961). Principles of Animal Taxonomy. New York: Columbia University Press.
Wiley, E. O. (1981). Phylogenetics: The Theory and Practice of Phylogenetic Systematics. New York: Wiley-Interscience.
Creating a Cladogram: Q&A ==========================

Q: What is a cladogram?

A: A cladogram is a diagram that shows the evolutionary relationships between organisms. It is a tool used in biology to visualize the shared characteristics and differences between species.

Q: How is a cladogram created?

A: A cladogram is created by analyzing the characteristics of different organisms and grouping them together based on their similarities. This involves identifying the derived characteristics of a particular group of organisms and using them to create a diagram that illustrates their evolutionary relationships.

Q: What are derived characteristics?

A: Derived characteristics are those that have evolved from a common ancestor and are unique to a particular group of organisms. Ancestral characteristics, on the other hand, are those that are shared by all organisms and are not unique to a particular group.

Q: How do I determine which characteristics are derived and which are ancestral?

A: To determine which characteristics are derived and which are ancestral, you need to analyze the characteristics of different organisms and identify those that are unique to a particular group. You can use a variety of methods, including comparative anatomy, comparative embryology, and molecular biology.

Q: What is the difference between a cladogram and a phylogenetic tree?

A: A cladogram and a phylogenetic tree are both diagrams that show the evolutionary relationships between organisms. However, a cladogram is a more general term that refers to any diagram that shows the relationships between organisms based on their shared characteristics. A phylogenetic tree, on the other hand, is a specific type of cladogram that uses branch lengths to represent the amount of time that has passed since the common ancestor of a group of organisms.

Q: How do I interpret a cladogram?

A: To interpret a cladogram, you need to analyze the diagram and identify the relationships between the different organisms. You can use the cladogram to identify the derived characteristics of a particular group of organisms and to understand the evolutionary relationships between different species.

Q: What are some common mistakes to avoid when creating a cladogram?

A: Some common mistakes to avoid when creating a cladogram include:

Not using a sufficient number of characteristics: A cladogram should be based on a sufficient number of characteristics to accurately reflect the relationships between the different organisms.
Not using a consistent method for determining derived characteristics: The method used to determine derived characteristics should be consistent throughout the analysis.
Not considering the possibility of convergent evolution: Convergent evolution occurs when different organisms evolve similar characteristics in response to similar environmental pressures. This can lead to incorrect conclusions about the relationships between the different organisms.

Q: What are some real-world applications of cladograms?

A: Cladograms have a wide range of real-world applications, including:

Understanding the evolution of diseases: Cladograms can be used to understand the evolution of diseases and to identify the relationships between different strains of a disease.
Conservation biology: Cladograms can be used to identify the relationships between different species and to develop conservation strategies.
Forensic science: Cladograms can be used to identify the relationships between different species and to develop forensic techniques.

Q: What are some limitations of cladograms?

A: Some limitations of cladograms include:

They can be difficult to interpret: Cladograms can be complex and difficult to interpret, especially for those without a background in biology.
They can be influenced by sampling bias: The relationships between different organisms can be influenced by sampling bias, which can lead to incorrect conclusions.
They can be influenced by convergent evolution: Convergent evolution can lead to incorrect conclusions about the relationships between different organisms.

Conclusion

Creating a cladogram is a powerful tool for understanding the evolutionary relationships between organisms. By analyzing the characteristics of different organisms and grouping them together based on their similarities, biologists can create a cladogram that illustrates their evolutionary history. However, cladograms have limitations and should be used in conjunction with other methods to ensure accurate conclusions.