sexual dimorphism

sexual dimorphism . It occurs in most species and is nothing more than the set of morphological and physiological differences that characterize and differentiate the two sexes of the same species to a greater or lesser degree, it is the physical difference between males and females and the degree of sexual dimorphism usually varies a lot between some species and others, it is defined as the variations in the external physiognomy such as: shape, coloration or size, between males and females of the same species.


[ hide ]

  • 1 General characteristics
  • 2 Sexual dimorphism in humans
  • 3 Presence in various species
    • 1 Mammals
    • 2 Aves
    • 3Peces
    • 4 Invertebrates
  • 4 Difference between males and females of different species
  • 5 Sources

General characteristics

The sexes are differentiated by the shape of the genitalia, this is called primary sexual dimorphism as opposed to secondary, which groups the differences that are not physically necessary for the transport of gametes (sex cells).

Secondary sexual dimorphism can affect size, shape, color , voice, and the presence or absence of certain attributes.

When talking about sexual dimorphism, it is usually understood that we are talking about secondary sexual dimorphism. Charles Darwin proposed the theory of sexual selection to explain secondary sexual dimorphism.

sexual dimorphism in humans

In the human species, the differences are physical (body size, muscle mass, etc.) and behavioral. Presence of characters of both sexes in the same individual, as occurs during a certain time in the development of the embryo or in hermaphrodites .

Sexual dimorphism in favor of the female is moderate in most species, without missing of course some exceptions where males are larger than females.

It is also the case that individuals of the same sex have different morphological appearances, which is called sexual polymorphism.

Now, it is convenient to clarify that not all animal species have sexual dimorphism. Many reptiles, for example, with internal sexual organs, do not show noticeable external differences between specimens of different sexes.

Presence in various species

Sexual Dimorphism occurs in different species of:

  • mammals
  • Aves
  • Pieces
  • invertebrates


In the case of Mammals , where the male sexual organs (penis and scrotum) are manifested externally, sexual dimorphism is very clear. Let us see, for example, the example of the human being, where the male presents his genitals externally, while the female has them internal; on the other hand, as in other adult mammals, the females show well-marked mammary glands.

However, in other mammalian species, this sexual dimorphism shows other distinctive features. A clear example is that of the lion, a species in which the male shows a larger size and profuse hair in the form of a mane, which the female lacks.


In the case of Birds , it is very common to speak of sexual dimorphism referring fundamentally to the plumage, as in the Mandarin diamond (Taeniopygia guttata), the House Sparrow (Passer domesticus) or the Black-headed (Carduelis magellanica), the males in general present a more striking plumage than that of the females. That is why it expresses itself with or without sexual dimorphism, depending on whether males and females share the color of their plumage.

But it is often the case that the plumage shows seasonal dimorphism, a different plumage for male and female, during the breeding season and similar in both sexes during the winter or non-breeding season. These plumages are common in migratory birds. In general, the species of birds that present marked sexual dimorphism in color, etc., also present great dimorphism in behavior; while those species in which the males and females differ little morphologically usually share the activities of building the nest and caring for the young.


In fish , there are also clear examples of sexual dimorphism. A clear example of this is the Siamese fighter (Betta splendens), being the male endowed with brighter colors and broader fins.<


In the Invertebrates , we find many cases of sexual dimorphism. Although, in these animals, the differences are given, in most of the species where it occurs, due to size (for example, the female of the tarantula (genus Grammostola) is much larger than the male), it can also be found chromatic variations (as in certain lepidoptera) or appearance (as in some cephalopods).


by Abdullah Sam
I’m a teacher, researcher and writer. I write about study subjects to improve the learning of college and university students. I write top Quality study notes Mostly, Tech, Games, Education, And Solutions/Tips and Tricks. I am a person who helps students to acquire knowledge, competence or virtue.

Leave a Comment