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A typical precocial mammal has a gestation period almost four times longer than a typical altricial mammal of the same body size. [20] Precocial mammal species generally have greater adult body weights than altricial mammals as precocial mammals have markedly longer gestation periods than altricial mammals. [21]
1 - morula, 2 - blastula 1 - blastula, 2 - gastrula with blastopore; orange - ectoderm, red - endoderm. Embryology (from Greek ἔμβρυον, embryon, "the unborn, embryo"; and -λογία, -logia) is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses.
For most species, the amount a fetus grows before birth determines the length of the gestation period. Smaller species normally have a shorter gestation period than larger animals. [2] For example, a cat's gestation normally takes 58–65 days while an elephant's takes nearly 2 years (21 months). [3]
My fourth son defied the timelines of the previous three sons, not taking his first steps until 20 months. (According to the Centers for Disease Control and Prevention, it's typical for a child to ...
Members of the rodent family Cricetidae can reach sexual maturity in 1–2 months, e.g. the Norway lemming (Lemmus lemmus) in 39 days. Many dogs ( family Canidae ) and bovids ( Bovidae ) take about a year to reach maturity while primates (including humans ) and dolphins ( Delphinidae ) require more than 10 years.
With few exceptions, animals consume organic material, breathe oxygen, are able to move, reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described —of which around 1 million are insects —but it has been estimated there are over 7 million ...
[20] There is no sharp limit of development, age, or weight at which a fetus automatically becomes viable. [21] According to data from 2003 to 2005, survival rates are 20–35% for babies born at 23 weeks of gestation (5 + 3 ⁄ 4 months); 50–70% at 24–25 weeks (6 – 6 + 1 ⁄ 4 months); and >90% at 26–27 weeks (6 + 1 ⁄ 2 – 6 + 3 ...
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