Difference Between Homology and Homoplasy

Main Difference – Homology vs Homoplasy

Homology and homoplasy are two types of similar characteristics between two or more species. The main difference between homology and homoplasy is that homology refers to a similar character emerged by the common ancestry whereas homoplasy refers to a similar character that does not emerge from a common ancestor. Homology results from divergent evolution while homoplasy results from convergent evolution. Vertebrate limbs are an example of homology since they have emerged from a common ancestor but have different functions. Wings of birds, bats and insects, on the other hand, are an example of homoplasy since they did not emerge from a common ancestor though have similar functions.

Key Areas Covered

1. What is Homology
– Definition, Emergence, Examples
2. What is Homoplasy
– Definition, Emergence, Examples
3. What are the Similarities Between Homology and Homoplasy
– Outline of Common Features
4. What is the Difference Between Homology and Homoplasy
– Comparison of Key Differences

Key Terms: Common Ancestor, Convergent Evolution, Divergent Evolution, Homology, Homoplasy, Similar Characters, Vertebrate Limbs, Wings

What is Homology

Homology refers to a similarity between two or more species, which has emerged from a common ancestor. Thus, homology is a result of divergent evolution. The two species in homology were once the same species, which is known as the most recent common ancestor. Over time, two populations of the common ancestor diverge as a result of adaptation to the environmental factors. However, the diverged species retain the characteristics of the common ancestor. The anatomy of the limbs of vertebrates is an example of homology. The homology of vertebrate wings is shown in figure 1. Each homologous character is shown by a unique color.

Figure 1: Vertebrate Limbs

The form of construction, as well as the number of bones, are identical in vertebrate limbs. But, these structures represent the adaptive modifications as well. This means they are modified to perform different functions based on the requirements of the environment each type of vertebrates used to live. Vertebrate limbs are adapted either to fly, swim, climb or run. The specialized leaves in trees are an example of homology in plants.

What is Homoplasy

Homoplasy is the opposite of homology. Homoplasy occurs when characters are similar but are not derived from a common ancestor. This means homoplasy emerges independently, but not from a common ancestor. Thus, it is a result of convergent evolution. Homoplasy occurs in species that live in the same environment. Therefore, homology is referred to as analogy in which functionally similar characters emerge in evolutionary-unrelated species as an adaptation to the living environment. The wings of birds, bats, and insects are an example of homoplasy.

Difference Between Homology and Homoplasy

Figure 2: Homoplasious Wings

The wings of birds, bats, and insects are developed to fly. Though the function of the wings is similar, birds, bats nor insects emerge from a common ancestor. Therefore, each type of wing is structurally different from each other.

Similarities Between Homology and Homoplasy

Both homology and homoplasy are two types of similar characters shared by two or more species.
Both homology and homoplasy arise from evolution.

Definition

Homology: Homology refers to a similarity between two or more species that emerged from a common ancestor.

Homoplasy: Homoplasy refers to a shared character between two or more species that did not arise from a common ancestor.

Common Ancestor

Homology: Homology arises from a common ancestor.

Homoplasy: Homoplasy does not arise from a common ancestor.

Type of Evolution

Homology: Homology results from divergent evolution.

Homoplasy: Homoplasy results from convergent evolution.

Structure

Homology: The basic structure of the homologies is similar.

Homoplasy: The basic structure of the homoplasies are different.

Function of the Similar Characters

Homology: The homologous characters perform different functions.

Homoplasy: The homoplasious characters perform similar functions.

Genetics

Homology: Homologous characters share a high degree of genetic similarity.

Homoplasy: Homoplasious characters do not share a genetic similarity.

Course

Homology: Homology occurs as a result of the evolutionary relationship.

Homoplasy: Homoplasy occurs as a result of an adaptation to the environmental conditions.

Describing Evolutionary Relationship

Homology: Homology can be used to describe the evolutionary relationship of different species.

Homoplasy: Homoplasy cannot be used to describe the evolutionary relationship between species.

Examples

Homology: Vertebrate limbs are an example of homology.

Homoplasy: The wings of birds, bats, and insects are an example of homoplasy.

Conclusion

Homology and homoplasy are two types of similar characters that occur in different species. Homology emerges from a common ancestor while homoplasy does not emerge from a common ancestor. This relationship through a common ancestor is the main difference between homology and homoplasy.

Reference:

1. “Homology.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 8 Sept. 2016, Available here.
2. Homologies, evolution. Available here.
3. “Homoplasy – Definition and Examples.” Biology Dictionary, 28 Apr. 2017, Available here.
4. “Evolution – A-Z – Homoplasies.” Blackwell Publishing, Available here.

Image Courtesy:

1. “Homology vertebrates-en” By Волков Владислав Петрович – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Big-eared-townsend-fledermaus” By PD-USGov (Public Domain) via Commons Wikimedia and
“2829563” (Public Domain) via Pixabay and “985432” (Public Domain) via pxhere (Merged)