The diagram illustrates the different stages involved in the life of a frog.
Frogs emerge from embryos laid in the water and start their life as tadpoles, slowly developing into adult frogs after passing through multiple stages in the process of development.
Frogs begin their life as embryos laid in eggs in the water. The first stage of a frog's existence begins when the embryo develops into a tadpole. The second stage of development takes place when the tadpole starts developing appendages and the front legs start developing. The process of the development of the front legs is called breaking through. The next phase happens when the tadpole develops pulmonary breathing, enabling it to breathe both on land and water. It then further develops into a tadpole frog, wherein only a tail-like protrusion is present from the first phase. The frog then matures into an adult frog and the protrusion disappears. 
The diagram illustrates the  
different
  stages
 involved in the life of a frog.
Frogs emerge from embryos laid in the water and  
start
 their life as  
tadpoles
,  
slowly
 developing into adult  
frogs
 after passing through multiple  
stages
 in the process of development.
Frogs  
begin
 their life as embryos laid in eggs in the water. The  
first
  stage
 of a frog's existence  
begins
 when the embryo develops into a  
tadpole
. The second  
stage
 of development takes place when the  
tadpole
  starts
 developing appendages and the front legs  
start
 developing.  
The
 process of the development of the front legs  
is called
 breaking through.  
The
  next
 phase happens when the  
tadpole
 develops pulmonary breathing, enabling it to breathe both on land and water. It then  
further
 develops into a  
tadpole
  frog
, wherein  
only
 a tail-like protrusion is present from the  
first
 phase. The  
frog
 then matures into an adult  
frog
 and the protrusion disappears.