(Last Updated On: April 15, 2021)

Monotremes are one of the three major groups of living mammals, including placental and marsupials. Compared to the types, they are typed by structural differences in the brain, jaw, digestive tract, reproductive tract, and other body parts. In addition, they lay eggs instead of lactating, but like all mammals, female monotremes give their baby milk. This article will share facts about Monotremes Mammals.

Monotremes Mammals

Monotremes are traditionally known as mammalian subclass Prototheria. The only surviving examples of monotremes are indigenous to Australia and New Guinea, although there is evidence that they were once more widespread, including some extinct species in South America.

Common monotreme species are Platypus and four species Echidnas. There is currently some debate about the taxation of monopoly.

General features

Like other mammals, monotremes are endothermic with a higher metabolic rate (although not higher than other mammals; see below); They have hair in their bodies; Produces milk through the mammary gland to feed their babies; They have a bone in the lower jaw, and the middle ear has three bones.

Common to reptiles and marsupials, there is a deficiency in the monotreme connective structure (corpus callosum), which is the primary contact pathway between the right and left cerebral hemispheres in placental mammals.

The anterior committee provides an alternative communication pathway between the two hemispheres, however, and in monotremes and marsupialis it carries all commissural fibers originating from the neocortex, whereas in the placement mammals the anterior commissure carries only a few of these fibers.

Diagram of a monotreme egg. 1) Shell; 2) rinse; 3) saffron sack; 4) Atlantis; 5) the fetus; 6) Amniotic fluid; 7) Amniotic membrane, and 8) membranes

As an adult, the extra monotreme lacks teeth. The fossil form and the modern platypus young molasses have a “tribosphenic” form (the shaped surface arranged in a triangle by three casks), which is one of the characteristics of existing mammals.

Some recent work suggests that monotremes took the form of molasses individually from mammals and marsupials, although this hypothesis remains controversial. Tooth loss in modern monotremes may be related to the development of their electrolyte.

Monotreme jaws are somewhat different than other mammals, and the jaw opening muscles are different. Like all true mammals, the tiny bones that sound to the ear are fully synthesized in the skull, rather than lying in the jaws like synodonts and other pre-mammalian synapeptides; This feature has also been claimed to have evolved independently between monotremes and therians, although this hypothesis, such as the Tryptophanic longitudinal evolution, is controversial.

Nevertheless, explorations of the extinct species of tinolophos confirm that the bones of the cane suspension were developed independently of the ankle and the Therians. The external opening of the ear is still at the jaw.

Sequencing of the platypus genome has provided insight into a number of monotreme features such as the evolution and evolution of electronic retention, as well as some new unique features, such as monotremes containing 5 pairs of sex chromosomes, and similar to the Z chromosome of birds among the X chromosomes, suggesting that marsupial.

And placental mammals The two sex chromosomes split from wife after manotrima seed was developed. Additional reconstitution through shared genes on the sex chromosomes supports this hypothesis of independent evolution.

This feature, along with some other genetic similarities to birds, is the recent common ancestor of the snoopsid lineage to mammals and to the sauerpside lineage of birds and modern. Surrey is thought to provide some insight Rpa, during the Carboniferous, about 315 million years ago is thought to have been broken.

The presence of the vitellogenin gene (a protein required for egg formation) is shared with the bird; The presence of these simplexiomorphies suggests that the common ancestors of monotremes, marsupials, and placental mammals were ovaries, and this trait was retained in one form but all but cheaply lost in the mammalian group.

DNA analysis suggests that although this trait is shared and synthesized with birds, the platypuses are still mammals and the common ancestor of existing mammals. L-ascorbic acid is only synthesized in the kidney.

In monotremes, there is an excess bone in the wrist of the shoulder, not found in other mammals, including an interclavial and choruside. The monotremes hold gait like a reptile, with neither foot nor two under the body. In the ankle region, the monotreme leg carries an inclination; Spar is not viable in Echidnas, but there is a strong poison in the male platypus.

This toxin is derived from B -deficins, proteins that are present in mammals that create pores of viral and bacterial microbes. Some reptile venom is also made up of a variety of B-defensins, which is another trait shared with reptiles considered to be an ancient mammalian feature, as many non-mainstream archaeological mammals also contain toxic spores.

monotremes mammals

Reproductive system

The key physical difference between monotremes and other mammals is their name; MonTrim means “single opening” in Greek, referring to a single drain (cloaca) for their urethra, rectum, and reproductive system. Monotremes, like reptiles, also have a single cloaca.

The marsupials also have separate genitalia; Although most placental mammals are open to reproductive (vaginal), urinary (renal) and rectum (rectum).

In monotremes only the semen passes through the cartilage; Urine is released through the cloaca monotream is similar to penis turtle and is covered in a preschool pouch.

Monotream eggs are retained for some time in the mother and are fed directly from them, and they usually become much shorter than the incubation period of the sauropacid egg within 10 days after laying eggs.

Much like newborn marsupials (and probably all non-native mammals) and relatively similar to them which enables them to crawl around nnata nozzle.

In fact, the breasts that lack monotone seeds, their pugs crawl more often than marsupial winches in search of milk; This difference raises questions about the supposed development constraints in marsupial forelimbs.

From mammals to mammals through mammals through mammals rather than mammals, all five species show long-term parental care in children with low rates of reproduction and relatively long lifetimes.

Monotremes are also noticeable in their zygotic development. Most mammalian zygotes undergo holoblastic cleavage, that is, after fertilization, the ovary divides into multiple, differentiated daughter cells.

In contrast, zygotes of monotremes, such as birds and reptiles, are moving into the meroblastic (partial) category. This means that the cells on the edge of the yolk have a continuous cytoplasm with the egg, which allows the yolk and embryo to exchange waste and nutrients with the surrounding cytoplasm.

Description

The monotreme is the female reproductive organ

The rate of metabolism of monotreme by mammalian levels is significantly lower than that of marsupials on the low platypus, with an average body temperature of 5 ° C (5 ° F) and placental mammals not 5 ° C (1 ° F).

Research suggests that it has adapted slowly to the strict, marginal environmental niche where some The general characteristics of extinct species manootrimagulira stitbaprana somehow managed to survive.

Although monotremes may have less developed thermoregulation than other mammals, recent studies show that they easily maintain different body conditions such as body ice temperature, such as the platypus of ice mountain flow.

Early researchers were distracted by two factors: first, monotremes maintain lower average temperatures than most mammals.

Keeps; Second, the short-baked Echidna, much easier to study than the recurrent platypus, only maintains a normal temperature when activated; During cooler weather, it saves energy by “switching off” its temperature control.

The burden of this process is then to target thermal control over the reduced hermetics, which are placental mammals.

Monotreme milk contains a highly expressed antibacterial protein that is not found in other mammals, probably to compensate for the more septic mode of milk intake associated with the absence of breast levels.

Both Platypus and Achidna species have urine in their back organs. Echidna sparrows are detectable and have no known efficacy, while poisonous platypus spores contain.

Molecular data suggest that the main component of platypus toxin originated before the deviation of platypus and echidnas, indicating that the most recent common ancestor of this taxon is also a poisonous one. Was.

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