定义：Single birth offspring quantity. The proportion or number of offspring produced from a single pregnancy (mammals) or ovulation (fish) or nesting (birds).
定义：The duration of the development from fertilized, deposited or implanted egg to hatching/birth. Corresponds to egg incubation duration in oviparous animals and to gestation period duration in viviparous animals.
定义：Because of the difference in refractive index between air and water (or corneal tissue), a curved cornea is an image-forming lens in its own right. Its focal length is determined by the radius of curvature of the cornea. Many corneal eyes (eg: in land vertebrates) also have lenses, but the lens is flattened and weakened compared with an aquatic lens; most of the refractive power is provided by the cornea. Corneal eyes cannot focus in aquatic habitat.
