Content
- what is sexual dimorphism
- Factors that cause sexual dimorphism in animals
- Examples of sexual dimorphism in animals
- Examples of sexual dimorphism in polygynous animals
- Examples of sexual dimorphism in animals to differentiate themselves
- Examples of sexual dimorphism in animals by sexual performance
- Examples of sexual dimorphism in animals where females are larger
- Other examples of sexual dimorphism in animals
- sexual dimorphism in humans
Procreation through sexual reproduction is, in most cases, highly beneficial, but the main feature of this reproductive strategy is the necessary presence of two sexes. The competition for resources, the risk of predation, the energy costs involved in finding and courting a partner make many species animals have evolved to facilitate this process.
In this article by PeritoAnimal we will talk about sexual dimorphism - definition, trivia and examples addressing which factors cause it and what their function has according to the different species. Good reading.
what is sexual dimorphism
The sexual dimorphism are the characteristics that differentiate one sex from another between animals and plants. As a concept defined by man, only species whose males and females we can differentiate with the naked eye will have sexual dimorphism. If this dimorphism is determined only by pheromones or odors emitted by different genders and not by a visual characteristic, it will not be called dimorphism.
Sexual dimorphism expressed as differences in size and morphology between the sexes is widespread in the animal kingdom. Charles Darwin noticed this and tried to provide an explanation through various hypotheses. On the one hand, he said that the sexual dimorphism it was intended for sexual selection, dimorphism being an advantage, for example, for males competing with each other for females. Another hypothesis that complements the previous one is that sexual dimorphism, in addition to serving sexual selection, may have evolved as a competition for food or resources in general.
It should be taken into account that in many cases this sexual dimorphism makes the individual who carries it more flashy and therefore more likely to fall prey.
Factors that cause sexual dimorphism in animals
The main factor that causes sexual dimorphism is genetics, usually expressed by the sex chromosomes. In most cases of sexual dimorphism in vertebrate animals, females have two X chromosomes and males have an X and a Y chromosome, which determines whether they are born male or female. In many invertebrate species, females will have only one sex chromosome and males will have two.
Another important factor is hormones. Each sex differs from one another by different concentrations of certain hormones. Also, during the fetal developIn certain species, a high concentration of testosterone in the brain will cause her to develop as a female.
THE food is also essential for the correct development of the secondary sexual characteristics that will give rise to dimorphism. A sick and malnourished animal will have poorer dimorphism and will most likely not attract the opposite sex.
THE seasons and mating season causes dimorphism to appear in certain species where the characteristics of sexual dimorphism are not as evident during the rest of the year. This is the case for some birds.
Examples of sexual dimorphism in animals
To understand the different types of sexual dimorphism, the easiest way is to observe the procession of different species and their way of life.
Examples of sexual dimorphism in polygynous animals
In many cases, sexual dimorphism can be explained as a competition for females. This occurs in polygynous animals (groups of females with one or few males). In these cases, males have to compete to be able to mate with females, which makes them bigger, sturdier and stronger than them. Also, they usually have some body that serves as a defense or offense. This is the case, for example, with the following animals:
- Deer
- Elephant
- Antelope
- Chimpanzee
- Gorilla
- Peacock
- great grouse
- Boar
Examples of sexual dimorphism in animals to differentiate themselves
In other animals, dimorphism exists so that females and males of the same species can be distinguished from one another. This is the case with parakeets. O sexual dimorphism in these birds is found in the beak, in a specific area called "wax". Females have this browner and rougher part and males have it softer and bluer. Thus, if a female's wax is painted blue, she will be attacked by males, and if a male is painted brown, he will be courted as a female.
Examples of sexual dimorphism in animals by sexual performance
Another example of sexual dimorphism is given by sexual performance in the species. Thus, frogs that tend to hug females during copulation have stronger, more developed arms, and may have thorns in the hands to hold on better.
Dimorphism can also be used as an element of courtship. This is the case with birds of paradise. these birds have no natural predators in their place of origin, therefore, having a very strong plumage, long feathers on the tail or head does not make them more susceptible to predation, but it is a good attraction for females. This plumage is not only attractive to females, but also gives information about the male's health status and the possibility of having healthy offspring.
Examples of sexual dimorphism in animals where females are larger
Female birds of prey, such as eagles, owls or hawks, are larger than males, sometimes much larger. That's because it's usually the female that spends more time in the nest incubating the eggs, therefore, being bigger will help it defend the nest. Also, these females are generally more aggressive and territorial than males, so their large size helps.
In the arthropod group, females tend to be infinitely larger than males, as is the case with spiders, praying mantises, flies, mosquitoes, etc. The same happens with amphibians and reptiles, where females are also larger.
Other examples of sexual dimorphism in animals
There are also very specific cases, such as hyenas. Females, before giving birth, are almost indistinguishable from males. They have a clitoris as big as a man's penis, their lips are extended and look like a scrotum. After giving birth, the nipples are visible so they can be recognized. Also, they are much larger than males, that's because they are cannibal animals and any male could try to eat a newborn calf. To avoid this, greater female bulk and strength is needed.
sexual dimorphism in humans
Humans also have sexual dimorphism, although some studies suggest that there is no severe feminization or masculinization and that human beings tend to unify sexual characteristics, that is, in our species there are more or less masculine men and more or less women feminized. They are the cultural standards and beauty standards that lead us to a culture of sexual differentiation.
At puberty, women and men begin to develop their sexual organs, visually different from each other. Hair appears on the armpits, pubis, face, legs and other parts of the body. Men, genetically, tend to have more hair on their faces and other areas of the body, but many men don't. Women also have hair on their upper lip.
A unique characteristic of women is the development of mammary glands, regulated by genetics and hormones, although not all women have the same degree of development.
Now that you know the meaning of sexual dimorphism and have seen several examples, you might be interested in this other article where we explain whether there are homosexual animals. Don't miss it.
If you want to read more articles similar to Sexual Dimorphism - Definition, Trivia and Examples, we recommend that you enter our Curiosities section of the animal world.