Examples of rudiments. Atavisms and rudiments: examples

Atavisms and rudiments, examples of which will be considered in this article, are irrefutable proofs of the evolutionary theory of the development of living organisms. What do these concepts mean and what is the significance of their discovery for modern science?

Evidence of Evolution

Evolution is the irreversible process of the development of all life from the simple to the complex. This means that over time, organisms succeeded each other. Each subsequent generation had more progressive features of the structure, which conditioned their adaptation to new living conditions. And this means that organisms that belong to different systematic units should have similar features.

For example, the forelimbs of birds and pinnipeds of mammals consist of the same parts. This shoulder, forearm and hand. But since birds are adapted to flight, this limb in them turns into wings, and in aquatic inhabitants is modified into flippers. Such organs are called homologous.

Another proof of the theory of evolution are analogies. So, both insects and bats have wings. But in the former they are derived from epithelial tissue, while in the latter they represent a skin fold between the anterior and posterior extremities. These organs have different origins, but they have common features of structure and functioning. This phenomenon arose from a divergence of signs, or divergence.

Atavisms and rudiments, examples of which are studied by comparative anatomy, are also direct evidence of the relationship of all living things to each other.

What is a rudiment?

Some organs are said to be "developed rudimentary". This means - not enough to fully implement the intended functions. Indeed, the rudiments are called organs, which in the process of evolution lost their original meaning. On the one hand, they are to some extent developed, and on the other hand they are at the stage of disappearance. Typical examples of rudiments are a change in the shape of the auricle and the degree of development of the muscles that surround it. Every day our ancestors needed to listen to the approach of danger or long-awaited prey. Therefore, the shape of the shell was more acute, and the muscles ensured its movement. Modern man's ability to wiggle his ears is hardly useful in everyday life. Therefore, individuals with such skills can be met very rarely.

Examples of rudiments in humans and animals

Insufficiently developed organs, inherent in ancestors, are found in animals quite often. Examples of rudiments are the presence of a coccyx in a person, which is the tail of the spine, as well as the wisdom teeth needed for chewing rough and unprocessed food. At this stage, we practically do not use these parts of the body. The appendix is a rudiment that a person supposedly inherited from herbivores. This part of the digestive system secrete enzymes and participates in the cleavage processes, but is considerably shortened in comparison with the ancestors. For comparison: a person has an average length of about 10 cm, and a sheep or a camel - a few meters.

The list of rudiments of man continues the third eyelid. In reptiles, this structure moisturizes and cleanses the outer shell of the eye. In humans, it is motionless, has a small size, and the above functions are performed by the upper eyelid. The rudiment is also the scar in the upper sky of man - these are the rudiments of the next row of teeth, in which a person does not need.

The animal's rudiments are the hind legs of the whales hidden inside the body, and the buzzing of the Diptera insects, which are a modified pair of wings. But the snakes have not developed limbs, because due to the peculiarities of their oborono-motor system, the need for them is completely absent.

Rudiments: photos of plants

Rudimentary organs are also found in plants. For example, the weed weed has a well-developed rhizome, which is an underground shoot with elongated interstices. It is well marked by small scales that are rudimentary leaves. Since under the ground it can not perform its basic function - the implementation of photosynthesis, then there is no need in their development. The rudiment is also an embryonic pestle in the form of a tubercle in a stamen flower of cucumbers.

What is atavism?

Atavisms are another proof of evolution. We can say that this concept is the opposite of rudiments. Atavisms are the manifestation in individuals of the traits characteristic of distant ancestors. Their presence also indicates a certain degree of kinship among generations. In the early stages of embryo development, there is a tail, and gill sacks. If embryogenesis occurs correctly, these structures cease to develop. If the development process is violated, individuals with disparate features of the structure may appear on the light. Therefore, a tailed boy and an amphibian man are not just fantasies.

Atavisms of man

In addition to the appearance of the tail, typical atavisms in humans are excessive body hair. Sometimes it considerably exceeds the norm. There are cases when hair covered the entire body of a person, except for the palms and feet. Atavism is the appearance of additional mammary glands on the body, and this can occur both in women and in men. This sign is inherited from mammals, who had many children. At the same time, there was a need to feed all of them at the same time. A person does not have such a need.

The second row of teeth is also a feature inherent in our distant ancestors. For example, a shark has several rows. This is necessary for predators for effective capture and retention of prey. There is an opinion that atavism can be considered and microcephaly. This is a genetic disease that manifests itself in a decrease in the size of the brain and skull. In this case, all other body proportions remain normal. This entails mental retardation.

Man spices some signs of animals and in the form of reflexes. For example, hiccups are a typical feature of ancient amphibians. This reaction was necessary for them to pass water through the respiratory system. And the grasping reflex, which is especially strong in children, is a manifestation of that in mammals. They grabbed the wool of their parents, so as not to get lost.

Atavisms of animals and plants

Examples of manifestations of ancestral features in animals are the appearance of wool or hind limbs in cetaceans. This is proof of the origin of these animals from extinct ungulate mammals. Atavisms are also the development of additional fingers in modern horses, moving limbs in snakes and legless lizards. In primroses, an increase in the number of stamens is sometimes observed up to 10. It was precisely the ancestors of modern plants that had the same number. Although modern species have only 5 stamens.

Causes of evolutionary changes

As you can see, rudiments and atavisms are manifested in many species of plants and animals. This indicates a certain degree of kinship between representatives of different systematic units within the same kingdom. Evolutionary changes always occur in the direction of their complication, as a result of which living organisms have the opportunity to better adapt to these or other conditions of habitation.

After examining examples of rudiments and atavisms, we were convinced of the generality of the system of the organic world and the consistency of the theory of evolution.