Developmental Biology

Embryology: 

                                          Study of the embryo is called embryology.

     Embryo:
                     It is the juvinile stage of animal which it is continued within egg or in maternal body.

                                                              Type of  Development

                                                  there are two types of Development
                  1.Onto genetic Development
                  2.Phylogenetic Development


                                                           1. Organic Development
This development based on the individuality such as environmental experiences,observations,emotional etc.
               
                                                          2. Phylogenetic Development
This developmental based on evolutionary perspective .what is phylogentic line of that individual.


                                       Stages of ONTO GENETIC DEVELOPMENT 
 i)            Gametogensis
 ii)           Fetilization
 iii)          Cleavage
 iv)          Gastrulation
  v)          Organogensis
 vi)          Histological  Differentiation

                                                             Embryogenesis
                            It is depend upon the SEXUAL DEVELOPMENT
    
                                                             Blastogenesis
                            It is depend upon the ASEXUAL DEVELOPMENT


                                        HISTORY OF DEVELOPMENT
1. Aristotle
2.Karl Ernst Von Baer

1.Aristotle
              had describe the development of CHICK in the EGG as early as 340 BC

2.Karl Ernst Von Baer
             Later data is presented by VON BAER in 1828.
             and base on following FEATURES.

   i)        General features appear earlier.
  ii)        Specific features appear later.
  iii)       Embryo cleavage by time.
  iv)       Common features appear earlier and Uncommon feature appear later
  
                                      THEORIES ABOUT  DEVELOPMENT
                           1.Theory of Subst ance and Form
                           2.Theory of Pre-formation
                           3.Theory of Epigensis
                                       1.THEORY OF SUBSTANCE AND FORM
i)    This theory was given by the Aristotle.
ii)   Substance or medium given by Mother
       Form is given by Father
                 SO BIOGENESIS (FERTILIZAION IS OCCUR) 

                                      2.THEORY OF PRE-FORMATION
     i). Animals are produce by EGGS and always present in the EGG (pre-form)
     ii). It is same as FLOWER BUDS after cutting it grow into FLOWER.

OVISTS:
          Who beleived that EGG contained EMBRYO.
ANIMAL UULISTS
          Who beleived that SPERM contained EMBRYO.

                                              3.THEORY OF EPIGENSIS
                                        This theory given by the Fredrick Wold
 i). It describe that both EGG and SPERM is necessary for DEVELOPMENT

                                             TYPES OF EMBRYOLOGY
i).    Descriptive embryology
ii).   Experimental embryology
iii).  Comparative embryology
iv).  General embryology
v).   Specific embryology
vi).  Modern embryology