在初中生物学教学中，经常遇到一些容易分辨不清的概念，应及时诱导，予以辨析。１　胚盘与胎盘胚盘　指动物卵上形成胚胎的盘形区域。凡是含卵黄特别丰富的卵，如鸟卵、爬行类等的卵，其原生质都集中在动物极一端，呈小盘状，卵裂仅在此区内进行，这便是形成胚胎的基础。胎盘? In junior high school biology teaching, often encounter some easily distinguish the concept of indistinguishable, should be promptly induced, to be analyzed. 1 Placenta and placental placenta refer to the disc-shaped area of ​​the embryo formed on the animal's egg. Eggs containing eggs particularly rich egg, such as eggs, reptiles and other eggs, the protoplasm are concentrated in the extreme end of the animal was small disc-shaped, cleavage only in this area, which is the basis for the formation of embryos. placenta?