Monotremes vs Marsupials
单人群和有袋动物通常是许多普通人的困惑,因为它们在哺乳动物中的独特性。这两个哺乳动物的动物群是独一无二的,应该明确地理解它们,因为它们提供了非常有趣的研究。在许多领域的单人和有袋动物之间存在许多有趣的差异,包括多样性,地理范围以及其他生物学和生态方面。本文试图通过对其特征提出简洁明了的说明来简化这些差异,并进行比较。
Monotremes
单人是所有动物中的独特群体之一,是产卵的哺乳动物。这些独特的动物仅在澳大利亚和新几内亚发现。根据生物学分类,单体属于秩序:Monotremata, which contains two suborders and five species described under three genera. Those five species include four echidna species and one platypus species. Monotremes are warm-blooded animals, and their metabolic rate is higher than cold-blooded animals but lower than other mammals. Monotremes have hairs on their bodies and produce milk in their mammary glands as in other mammals. However, they do not have teats but only the openings called milk patches to secrete milk in females to feed the young during lactation periods. Monotremes do not have a corpus callosum, the nerve bridge seen in mammals to connect the left and right sides of the brain. Usually, most of the mammals have an anus for defecation and urethra for expulsion of urine and reproductive discharges, but monotremes have a common opening called cloaca for all those purposes. In echidnas, there are more than 2,000 electro receptors inside the mouth of one animal. The usual body temperature in monotremes ranks slightly subnormal among mammals, which is about 32 °C. They demonstrate a great parental care, which continues for a prolonged period like in most of the primates and elephants. The newborn animals from the eggs live inside the mothers pouch. However, they have a lower rate of reproduction compared to many other mammalians.
Marsupials
Marsupials are one of the three major mammalian groups with about almost 500 extant species. Predominantly, the marsupials are found in Australia and the rest are ranging in South America with very few in North America. Marsupials give birth to an undeveloped young following a small gestation period. The undeveloped young are known as Joey. The Joey comes out of mother, and its development takes place inside an external body pouch that has milk secreting mammary glands. Joeys do not have hairs on their body when they are newly born. In addition, Joeys are tiny; in the size of a jellybean, and they cannot open their eyes, or in other words, they are blind. Depending on the species and their relative body sizes, the time inside the mother’s pouch varies, but the completed development has to take place inside the pouch. However, during the short gestation period, there is a placenta between foetus and mother, but it is a very simple structure. One of the noticeable absences in marsupials is the lack of the corpus callosum or the bridge of neurons between left and right hemispheres of the brain. Kangaroo, wallaby, and Tasmanian devil are few of the most well known marsupials.
What is the difference between Monotremes and Marsupials? •所有有袋动物都有小袋,但并非所有的单人都有它。 •单孔目动物产卵而不是有袋动物。 • Monotremes have a subnormal temperature and a lower metabolic rate compared to marsupials. • There are almost 500 species of marsupials, but the number of monotreme species is only five. • Marsupials are distributed mainly in Australia and some in Americas, whereas monotremes are only found in Australia and New Guinea. |
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