hi friends we discuss evidence from embryology .always we are interested to know about evolution then this information is able to know about evolution lets get started.
simple meaning: embryology is the study of the development of an organism from zygote to adult .. it may also provide evidence for evolution .. the evidence based on the comparative study of the embryos of various animals are as follows.
HOMOLOGY IN EARLY DEVELOPMENT :
a common pattern of development is found in all the multicellular organism .. the development of embryos start from a unicellular zygote or fertilized egg.. the zygote undergoes repeated cleavage or call division to form solid ..structure call as a morula. (maybe fruit like structure ) the morula la divide to form blastula it means a single hollow structure, which finally developed into gastrula it means two or three-layered structure.
animals which two-layered are termed as diploblastic .. and the example is coelenterate and next is the animals which three-layered gastrula is found are known as triploblastic and the example is frog and lizard and after this, the process gives rise to an entire body or animals ..thus the similar early embryological development shows the close relationship among all the organism ..
RESEMBLANCE AMONG VERTEBRATE EMBRYOS:
it the comparative study of embryos of vertebrate at the same age is done, it is observed that they resemble one another same similarities in the early embryonic stage are as follow
1: present of gills clefts, notochord, tail, rudimentary eyes, etc. in all vertebrates from fishes to mammals.
2:after the notochord is replaced by a vertebral column in all adult vertebrates..
3: gill are replaced by lung in adult amphibian , reptile and mammals
RESEMBLANCE AMONE INVERTEBRATE LARVAG
this process that , in larval stages of invertebrates has common ancestor . it simple means that the larval stages of some invertebrates has same in starting state but has development after maturity this animals are look like a different but they same in origin hence this call as common ancestry ..
[ this common ancestry shoes above image see this images and get understand .. ] example : annelids and molluscum passes a similar type of larva it called as trochophore .. similarly echinoderm and hemichordate also have a similar larva it indicate common ancestry..
this are come example shoes common ancestry in invertebrates in larval stages ..
PROGRESSIVE METAMORPHOSIS :
progressive metamorphosis : in process of metamorphosis animals growth are done progressive in the flow of evolution .
example: ammonocete larva of a lamprey resembles the adult of the amphioxus or group of branchiostoma in most of the details ..this is possible only if presume only that lamprey has evolved from branchiostoma loke animals ..
RETROGRESSIVE METAMORPHOSIS :
retrogressive metamorphosis : in the process of retrogressive metamorphosis degenerative changes of active larva metamorphosis to a new adult it simple mean that the chordate characters are also in a larva stages ..
the adult ascidian { ex. herdmania } are derived the a retrogressive metamorphosis of tadpole larva .. due to this the most of the chordate are lost ..they may show some chordate affinities .. in those organism larva has helped in phylogenetic relationship .. this ascidian tadpole larva is free swimming and asses all the three characters this is notochord , nerve chord and myotome .. thus , it may be place in group chordate..
NEOTENY:
the condition in which larval fail to undergo metamorphosis , instead develop gonads and attain sexual maturity .. in simple mean sexual maturity of animals in development stage is decline or the grown of the organism body part development is slow in maturing sate it call is neoteny .. reproduction in such larval form is call as paedogenesis ..
example : axolotl larva of ambystoma..
TEMPORARY EMBRYONIC STRUCTURE :
some structure are temporary in embryos , which remain absent in adults ..
example :
1 : birds embyo has tooth buds and gill clefts , which remain absent in adult ..this shows , that the birds may have evolved from toothed ancestors , which ware lost during evolution ..
2 : the embryo of whale possesses hairs , which remain absence in adult ..this hears are shed before birth ..
RECAPITULATION THEORY OR BIOGENETIC LAW :
in this process the development of embryo in development stage to maturing stage stats that as below_____
karl ernst von baer { father of modern embryology } in 1828 publish the bears law or von brars law of embryology to explain the details and development of embryo.
this important statement proposes in this law are as follow
[1]:during development , general characters appear before specialised characters in following manners .
more general to less general to specialised ..
[2]:during development , animals progressive depart from the form of animals ..
[3] :organism of different group share resemblance among thaire embryonic form ..
in 1866 , earn haeckel postulate biogenetic law or recapitulation theory by coming the idea of darwine evolution and bears law ..biogenetic law states that the ontogeny .. i.e . development of embryo in the recapitulation of phylogeny ..
some examples of development evidence of evolution ..
[1] presence of fish , like characters eg. gill ,gill slits, tail ,tail fin , lateral line and sense organs in tadpole larva of frog
[2]presence of filamentous green algae like structure , i.e protonema during development stage of funaria { moss} ...
[3] pteridophytes , primitive gymnosperms and animals having flagellated sperm and they depend on the water for fertilisation
[4] adult frog excreta urea , whereas tadpole excreate ammonia as in fishes ..
[5] birds generally secret uric acid , but embryo excreat ammonia first and urea later on ..
[6] in south american mouse secret uric acid as apest from this bird excreata as in the pest formate ..
