BioScience.pk App
www.bioscience.pk
Put vital info into the palm of your hand.
ASH Job Center
www.jobcenter.hematology.org
By American Society of Hemotology

EMBRYOLOGICAL EVIDENCES FOR ORGANIC EVOLUTION

Published in Zoology
Saturday, 10 June 2017 13:03
The Study of the developmental stages of an organism is called If we observe the embryos of different animals, there is a similarity. This similarity tells us that there is a relationship between the animals. The embryological evidences show support to organic evolution.
 
SEQUENCE OF DEVELOPMENTAL STAGES
 
All multi cellular organisms begin their life as a single celled stage, namely Zygote. It undergoes cleavage to produce the first embryo, called morula. It develops into a single layered second embryo, called blastula. This embryo develops into a third embryo called gastrula. This embryo develops into adult. The Zygote represents the unicellular stage. Morula and blastula represent the colonial protozoan stages. Whereas gastrula represents the coelenterate stage. The embryos of organisms differ after the gastrula stage. The sequence of embryos shows that every multi cellular organism passes through the above stages representing their ancestors.
 
Zygote -------> Morula-------> Blastula -------> gastrula ------->adult.
(protozoan (colonial protozoan (coelenterate stage) stage) stage)
 
EMBRYOLOGICAL PRINCIPLES
 
Von Baer proposed these principles by studying the embryology of Fish, Frog, Tortoise, Pigeon, Chimpanzee and Man. The early embryos of above animals resemble with each other closely. That it is impossible to separate if the embryos were mixed. But the embryos differ in the final stages clue to the formation of specialized characters. The similarity of early embryos tells that the above animals have common ancestors. The embryological principles are
 
  1. General characters appear in the early embryos.
  2. The special character appear in the last embryos.
  3. The embryos of closely related individuals are almost similar up to the end with small differences.
  4. The embryos of one organism resembles to the embryos o f its ancestors but not with adults.
 
BIOGENETIC LAW
 
It was proposed by Earnest Haeckel . The Study of the sequence of embryos or life history of an organism is called ontogeny. The evolutionary history of an individual is called phylogeny.
 
Biogenetic law states that every organism recapitulates its ancestors through the embryos. In other words the ontogeny of an individual repeats its phylogeny. The biogenetic law is also called recapitulation theory. Earnst Haeckel is considered as the father of embryology. Von Baer is considered as the father of modern embryology.
 
Biogenetic Law - Examples:
 
I. Tad pole larva of Frog:
 
The tad pole larva resembles fish both externally and internally. It contains two chambered heart, respires with gills like Fish. Later tad pole larva metamorphoses into adult Frog. Frog recapitulates its closet ancestor, fish through the tad pole larva. It also indicates that the Frog was evolved, from fish.
 
ii. Cater pillar larva of Butter fly:
 
This larva resembles to annelid. Butterfly recapitulates its closest ancestor, annelid through the caterpillar larva. It alsc tells us that the Butter fly was evolved from annelid.
 
iii. Development of ‘4’ chambered heart in the embryos of Birds and Mammals:
 
ontogeny repeats phylogeny18
 
In the embryos of Birds and Mammals, the heart is ‘2’ chambered, then ‘3’ chambered and incompletely ‘4’ chambered before developing into complete ‘4’ chambered heart. This shows that the Birds and Mammals recapitulate even the development of heart also.
 
Likewise the recapitulation is also observed in the development of brain, aortic arches, kidneys etc.
 
iv. Temporary embryonic nonfunctional organs:
 
The embryos consist of some temporary embryonic organs. These are present only in their ancestors but absent in adults. Such organs are called temporary embryonic vestigial organs. But these disappear when the embryo develops into adult. Some of the temporary embryonic vestigial organs are
 
  1. Formation of gill slits in the embryos of reptiles, birds and mammals.
  2. Formation of teeth in the embryos of pigeon and whale.
  3. Formation of limbs in the embryos of snakes.
  4. Formation of tail in the embryo of human beings.
 
These structures are of no use in the embryos. But their presence explains the biogenetic law.
 
These are the remains impressions of past lived organisms.

Useful Sites

  • NCBI

    National Center for Biotechnology Information
  • LTO

    Lab Tests Online® by AACC
  • ASCP

    American Society for Clinical Pathology
  • ASM

    American Society for Microbiology
  • The Medical Library®

    Project of BioScience.pk

Sponsored Links

ASH Job Center
www.jobcenter.hematology.org
By American Society of Hemotology
BioScience.pk App
www.bioscience.pk
Put vital info into the palm of your hand.
Online Digital Library
www.bioscience.pk
Free Downloads Medical Books.
Advertisement

Sponsored Links

SiteGround
www.siteground.com
Web Hosting Services Crafted with Care!
Make money online!
www.adf.ly
Use a URL shortener service that pays.
ASH Job Center
www.jobcenter.hematology.org
By American Society of Hemotology
BioScience.pk App
www.bioscience.pk
Put vital info into the palm of your hand.
Online Digital Library
www.bioscience.pk
Free Downloads Medical Books.
Daily Science
www.bioscience.pk
The Science News app that will get you to the breaking news.

Connect With Us

Contact Us

All comments and suggestions about this web site are very welcome and a valuable source of information for us. Thanks!

Tel: +(92) 302 970 8985-6

Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

Website: https://www.bioscience.pk

Our Sponsors

The Physio ClubB2BPakistan.com

By using BioScience.pk you agree to our use of cookies to enhance your experience on this website.