How is a Petrarchan sonnet constructed in contrast to a Shakespearean sonnet? (formal structure)

A Petrarchan (or Italian) sonnet is constructed in the
following way:

This particular sonnet is divided into two
sections and contains two distinctively different rhyming patterns. The first section is
called the octave because it consists of eight lines ("oct" is Latin for
eight).

These eight lines have the rhyming
pattern:

-a b b a a b b a.

The
second section of the Petrarchan sonnet is called the sestet (consists of six
lines-Latin for sixth). These lines do not rhyme with the preceding octave; instead,
they contain a new rhyme scheme using the one of the following
patterns:

-cdcdcd

-cddcdc

-cdecde

-cdeced

-cdcedc

The
change in the rhyming pattern announces a change in the "plot" or subject matter of the
poem. This change is notated by the "volta" in the ninth line of the
sonnet.

The Shakespearean Sonnet (or the English Sonnet) is
unlike the Petrarchan Sonnet in regards to the "plot"/meaning of the poem. In the
Shakespearean Sonnet, the plot remains the same throughout the entire poem with each
stanza building on the content which supports and defines the main idea of the poem- all
stanzas are linked closely. The plot does not contain a major shift in subject matter.
Both types of sonnets include the use of fourteen
lines.

The Shakesperean Sonnet is constructed in the
following way:

This sonnet consists of three quatrains (a
stanza which consists of four lines and a couplet (a two line stanza). The rhyme scheme
of this sonnet is the
following:

abab

cdcd

efef

gg

A
volta does exist within the Shakespearean Sonnet, but typically can appear at any point
throughout the poem.