Discuss embryological evidences of evolution.

Explanation

Evidences from embryology The similarities in the embryonic development process of different groups of animals and their embryos provide most conclusive evidences supporting organic evolution. These similarites indicate that evolution of organisms occurs through a common pathway. These studies also suggest a degree of intimacy in the relationships among different groups of animals. The following conclusions are derived from the study of comparative embryology. Common pattern of development In the process of sexual reproduction, all multicellular animals produce a diploid zygote. After fertilisation, the zygote undergoes cleavage to form a solid ball of cells called morula. The morula then forms a single-layered embryo called blastula which then develops into a two or three-layered gastrula. Differentiation of tissues and organogenesis occur after the formation of gastrula. This results in the formation of various organs. This is a common pattern of development in the animal kingdom with similar stages. This justifies presence of a common ancestry. Similarity in early embryos of vertebrates A comparative study of the early embryos of different vertebrates, such as fish, salamander, lizard, opposum, monkey and human reveals a striking similarities in the early embryos. These similarities are so alike that it becomes difficult to distinguish them from each other. They all possess external gills, notochord, tail-like structures and other similar organs. Development of organs like heart, brain, lungs, ear, alimentary canal, etc. in the vertebrates occurs essentially in the same manner. As development progresses, the embryos develop specialised characters and they gradually appear different. Similarities like these in early embryos suggest that all these animals share common ancestry. Embryological Evidence in Plants
Protonema, a moss is similar to certain green algae suggests that the mosses might has evolved from the later. Primitive gymnosperms like Cycas and Ginkgo possess have ciliated sperms like those of pteridophytes. It is therefore, believed that gymnosperms have evolved from pteridophytes.