Embryology is the study of development of an egg into the adult. Evidences from Embryology based on comparative developmental studies of embryos of various organisms. Some examples are: All multicellular start their life as a Zygote. Zygote is a single celled and comparable to Protozoa. Zygote undergoes a series of events like morula, blastula and gastrula. Cell of blastula organize to differentiate into two germ layers i.e. Ectoderm and Endoderm (in diploblastic animals). Blastula changes into gastrula. During gastrula stage (in triploblastic) the third germ layers mesoderm originates. According to Evidences from Embryology the developmental stages upto gastrula stage in all metazoans are similar i.e. Monophyltic origin. The development of heart in embryos of fish is two chambered and same condition of the heart retained in adult stage. The development of heart starts as two chambered in amphibia, reptiles, birds and mammals but become three chambered in adult amphibia, three and half in reptile (in crocodile 4 chambered), in aves and mammals four chambered. The presence of gills slits is one of salient characters of chordates; which remains as such in primitive characters (protochordata). The gill pouch and gill slits develops into gills in fish for aquatic respiration. But in adult amphibia, reptiles, aves and mammals replaced by lungs for Aerial respiration.
Von Baer (1828)
Von Baer suggests basic principles of Evidences from Embryology development, which are as follows: During development general characters appear before special characters. From more general, the less general and finally the special characters appear. During development, an animal develops progressively from the form of other animals. Young stages are like young stage of ancestors or embryonic stages of lower animal, but not like adults of those animals.
Biogenetic Law
Biogenetic Law was proposed by Ernest Haeckel (1866), also called Recapitulation Theory. He studied a lot about Evidences from Embryology. It states that ontogeny repeats phylogeny. It means all organisms during their development receives ancestral characters (ontogeny). This historical evolution is called phylogeny. Ontogeny: It means development of organs, Phylogeny: It means ancestral characters. Example: Gills, gill slits, tail, tail fin, lateral line, sense organs, etc. in the tadpole larva of frog.
Von Baer (1828)
Von Baer suggests basic principles of Evidences from Embryology development, which are as follows: During development general characters appear before special characters. From more general, the less general and finally the special characters appear. During development, an animal develops progressively from the form of other animals. Young stages are like young stage of ancestors or embryonic stages of lower animal, but not like adults of those animals.
Biogenetic Law
Biogenetic Law was proposed by Ernest Haeckel (1866), also called Recapitulation Theory. He studied a lot about Evidences from Embryology. It states that ontogeny repeats phylogeny. It means all organisms during their development receives ancestral characters (ontogeny). This historical evolution is called phylogeny. Ontogeny: It means development of organs, Phylogeny: It means ancestral characters. Example: Gills, gill slits, tail, tail fin, lateral line, sense organs, etc. in the tadpole larva of frog.
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