BIOL 1011 Lecture Notes - Lecture 14: Endoskeleton, Ecdysis, Notochord
3 Oct 2016
School
Department
Course
Professor
Document Summary
Animals: eukaryotes, multicellular heterotrophs, most are diploids and reproduce sexually. Fuses during fertilization to form a zygote. Zygote divides by the process of mitosis and later forms a hallow ball known as the blastula. When one side of the blastula folds in, (forming either the mouth or anus) this stage is called the glastula. Many animals develop directly into adults at this stage. Endoderm forms a lining of the future digestive tract. Ectoderm forms an outer layer that will give rise to the skin and nervous system. Mesoderm forms a middle layer that will give rise to muscles and most internal organs: clusters of master control homeotic genes control transformation of the zygote into an adult animal. Homeotic genes- genes activated for certain characterstics. Much diversity in body form is associated with when and where homeotic genes are activated in developing embryos: flagellated unikont ancestor is believed to give rise to animals more than 1 billion years ago.
