The document traces the evolution of the heart from simple to complex organisms. It begins with unicellular and simple multicellular organisms that lacked specialized cells, tissues, and organs. More complex invertebrates first developed specialized cells and muscular pumping in structures like sponges and jellyfish, representing early precursors to cardiac muscle cells. Vertebrates evolved with the first two-chambered hearts in fish and amphibians. Reptiles developed three-chambered hearts with two atria and one ventricle. Birds and mammals further evolved four-chambered hearts with two atria and two ventricles allowing for double circulation.

1. EVOLUTION OF HEART
By
Qudrat ullah
Student of uos subcampus
bhakkar

2. Two types of invertebrates
i. Simple invertebrates
ii. Complex invertebrates

3. Unicellular
Simple multicellular
No specialized cells
No tissues
No organs

4. Specialized cells
Muscular pumping
Presence of organs

5.  First organism with specialized cells
 Contain layers of specialized cells
 Amoebocytes:
Move with in walls of sponge
and carry food to other cells.

These amoebocytes are considered as
precursors to Cardiac muscle cells or
myocardiocytes.

7.  First organism with muscular tissues.
 Presence of muscles in oral cavity as
pump for one way flow of water.
 Due to this the origins of the heart
pump are believed to have started
with the pumping of a jellyfish.

9.  First organism with
organs
 No typical circulatory
system found
 Breath through skin

10.  Dorsal vessel (heart) muscular areas
for pumping.
 Open circulatory system.
 No blood vessels or very few.
Accessory heart:
In addition to the dorsal vessel
insects have accessory heart that
supply body appendages with
hemolymph.

11.  No actual heart.
 These muscular regions are
the precursors to our
complex human heart.

13. first animals with a two-
chamber heart consisting
of a ventricle and an
atrium.

15. All vertebrates stem
from a common
chordate ancestor.
Like lancelets.

18.  Closed circulatory system.
 two chamber heart.
 Oxygen transported by only
one vessel via gills.
 Single circulation.

20.  Three chamber heart
 Two atria and one ventricle

21.  Two atria.
 Two ventricles partially
divided.
 Incomplete septum.

23.  Four chamber heart
 Two atria and two
ventricles
 Double circulation.

26. 1. Displacement of structures.

27. 1. Formation of septum between
atria(amphibians).
2. Formation of septum between
ventricle(crocodiles)
3. Disappearance of the sinus
venosus and the conus
arteriosus (birds and
mammals).