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Difference between Homologous and Analogous

Biology is a vivid subject covering various parts of the human body. Biology gives explanations regarding the working of the systems in the body.

We have heard many terms like homozygous, heterozygous, the nervous system, respiratory system, etc. There are several terms that we study in biology. But today, we will be discussing about two significant terms, i.e., homologous and analogous. We might not have studied them, but they hold importance in biology. So, without further ado, let us begin by knowing the primary meaning of these homologous and analogous.


Homologous or homology is a distinctive term in biology. Homologous is defined as the similarity in physiology and structure of an organism. In this condition, the development of various species takes place with common ancestors, i.e., the ancestors of a particular organism are the same. The homologous is categorized into three significant categories, namely developmental homology, molecular homology, and structural homology. The major characteristic of homologous is that the organism has evolved from a common ancestor. The term homologous first came into being in the year 1859. Many researchers and scientists like Geoffroy, Richard Owen, Darwin used the term. One of the common examples of homologous can be dogs and crocodiles because they have evolved from tetrapod structures (ancestors).

Homologous vs Analogous


Analogous is also called analogy in biology. Analogous is defined as the organisms that perform the same functions. The analogous organisms have different evolutionary ancestors. One of the most common examples of analogous organisms is the wings of birds and insects. They might seem to be different, but they have the same ancestors. There are four main types of analogous, i.e., opposite analogy, object and classification analogy, object and related analogy, cause and effect analogy, etc. There are several other types of analogies that we will be discussing later. Now, let us take a look at some of the fundamental differences between homologous and analogous.

1. Homologous is defined as the similarity of physiology and structure in an organism. Analogous is defined as the similarity of functions in an organism.
2. The evolutionary ancestors in homologous organisms are the same. The evolutionary ancestors are different in analogous organisms.
3. The internal structure of homologous organisms is the same. The internal structure of analogous organisms is different.
4. The developmental stages are the same. The developmental stages are different in organisms.
5. Divergent evolution is shown in homologous organisms. Convergent evolution is shown in analogous organisms.
6. Homologous is developed in organisms that are related to one another. Analogous is developed in organisms that are not related to one another.
7. Homologous organisms have the same anatomy. Analogous organisms have different anatomy.
8. Homologous traits are adapted in response to a different environment. Analogous traits are adapted in response to the same environment.
9. Homologous organisms look different externally. Analogous organisms look the same externally.
10. Examples:
  • Human Arm
  • Wings of a bird
  • Legs of crocodile/ dogs
  • Dolphin and Whale
  • Wings of insects and birds.
  • Fins of a fish or a penguin.

So, these are some of the primary differences between homologous and analogous organisms. It is important to note that the defining difference between homologous and analogous organisms is the ancestral evolution, i.e., homologous organisms have the same ancestors, unlike analogous organisms. Now, there are several types of analogous and homologous. So, let us discuss them briefly.

Types of Homologous

There are three significant kinds of homology. They are:

  1. Structural Homology: Structural homology is defined as the homology in which the structures of the organisms are compared with one another. For instance, the vertebrate forelimbs might appear to be the same, but they perform different functions.
  2. Developmental Homology: Developmental homology is defined as the homology in which the embryos of various organisms are compared. For instance, the embryos of cat, human, and snake are similar to one another in the initial phases of development. In the later stages, the organisms take a different shape, like some organisms develop a tail, while some develop wings. As the development progresses, the organisms take on a completely different look. Thus, developmental homology is seen in several organisms during the early stages.
  3. Molecular Homology: Molecular homology is defined as the homology in which the similarity among the molecules is focused upon. This type of homology aims at the organisms having a similar molecular level. In molecular homology, the DNA of various species are compared with one another.

So, these are the three major types of homologous. With the help of these three types of homologous, researchers and scientists are able to establish connections among various species. Now, let us look at some types of analogous as well.

Types of Analogous

Analogous or analogy is not only seen in organisms; rather, it is seen in various aspects of life. So, let us take a look at some of the day-to-day types of analogous.

  1. Opposite Analogy: In opposite analogy, the things/ organisms are opposite to one another. For instance, laughing and crying, sunrise and sunset, etc.
  2. Object & Classification Analogy: In object and classification analogy, many things are classified into different groups. For instance, knives and spoons are classified under kitchenware, computer and phones are classified under gadgets, etc.
  3. Object & Related Analogy: There are various objects that are related to one another. This is called object and related analogy. For instance, dogs and puppies are related, cats and kittens are related, seed and plant are related, etc.
  4. Cause & Effect Analogy: When an action is a cause, it leads to an effect, i.e., reaction; it is called cause and effect analogy. Examples of this analogy are fire and burn, reading and learning, etc.
  5. Effort and Result analogy: In effort and result analogy, an effort has to be made in order to achieve the desired result. For example, when we put effort into painting, a beautiful portrait comes as a result. Similarly, when we put effort into building, the result is a beautiful house. This is how effort and result analogy works.
  6. Object & Function Analogy: When an object performs several functions, it is categorized under object and function analogy. For instance, the keyboard has the function of typing; the telephone has the function of calling, etc.

So, these are some of the types of analogous apart from the biological context. Both homologous and analogous have different meanings in biological and generic terms. However, in biology, the major difference between them is that of their ancestors. It is essential to note that both analogous and homologous organisms exist, and they have distinctive features. Thus, both homologous and analogous are important parts of biology.

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