Search results
Results from the WOW.Com Content Network
Large mammals develop at an absolute slower rate compared to small mammals. Thus, the large mammal tend have longer gestation periods than small mammal as they tend to produce larger neonate. [18] Large mammals require a longer period of time to attain any proportion of adult mass compared to small mammals. [19]
A pregnant lioness. In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once it leaves the uterus.
Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). [1] It is typical for mammals, but also occurs for some non-mammals. Mammals during pregnancy can have one or more gestations at the same time, for example in a multiple birth. [2]
Gestation, called pregnancy in humans, is the period of time during which the fetus develops, dividing via mitosis inside the female. During this time, the fetus receives all of its nutrition and oxygenated blood from the female, filtered through the placenta , which is attached to the fetus' abdomen via an umbilical cord .
Mammals that have menstrual cycles shed the endometrium through menstruation instead. Humans, elephant shrews , and a few other species have menstrual cycles rather than estrous cycles. Humans, unlike most other species, have concealed ovulation , a lack of obvious external signs to signal estral receptivity at ovulation (i.e., the ability to ...
In mammals, the term refers chiefly to the early stages of prenatal development, whereas the terms fetus and fetal development describe later stages. [2] [4] The main stages of animal embryonic development are as follows: The zygote undergoes a series of cell divisions (called cleavage) to form a structure called a morula.
Unusual among placental mammals, the rectum and urogenital tracts of tenrecs share a common opening, or cloaca which is a feature more commonly seen in birds, reptiles, and amphibians. They have a low body temperature, sufficiently low that they do not require a scrotum to cool their sperm as do most other mammals. [13] [22]
The class Mammalia is divided into two subclasses based on reproductive techniques: monotremes, which lay eggs, and therians, mammals which give live birth, which has two infraclasses: marsupials/metatherians and placentals/eutherians. See List of monotremes and marsupials, and for the clades and families, see Mammal classification ...