protochordates and its significance

1. PROTOCHORDATES AND IT’S
SIGNIFICANCE
CREATED BY : AMAN SINGH
Course : B.Sc (ZBC) iii sem.
STUDENT ID : BZBC2019026
INSTITUTE : INVERTIS UNIVERSITY
BAREILLY
Department: Invertis institute of applied
science and humanities.

2. Protochordates :
The organisms belonging to the Protochordata are
generally known as the lower chordates. They don’t form a
“proper” taxonomic group and are only classified as such
for convenience purposes. However, they do form a major
division of Chordata. They are also known as Acraniata
because they lack a true skull. They are divided into three
sub-phyla- Hemichordata, Urochordata, Cephalochordata
CHARACTERISTICS OF
PROTOCHORDATA
1. They are generally found in marine water.
2. Their body is bilaterally symmetrical, triploblastic, and
coelomated.
3. At a certain stage of their lives, their body develops a
long, rod-like structure for support called the
notochord.
4. They exhibit organ system level of organization.
E.g. Herdmania, Amphioxus.

3. CLASSIFICATIONS OF PROTOCHORDATA
HEMICHORDATA
1. They are found in marine water.
2. Some live solitarily, and some stay in colonies.
3. The body is cylindrical, unsegmented, and stout.
4. The body is divided into proboscis, collar, and trunk.
5. The collar bears arms and tentacles.
6. They have a complete digestive system.
7. They respire through gills or general body surface.
8. The circulatory system comprises a heart with two
longitudinal vessels.
9. The blood has no colour and corpuscles.
10. The proboscis gland or glomerulus make up the
excretory system.
11. Sexes may be separate or united and fertilization is
either internal or external.
E.g.Cephalodiscus, Rhabdopeura.

4. UROCHORDATA OR TUNICATA
1. They are found in the marine environment.
2. They are sessile and filter-feeders.
3. They are also known as tunicates because their body
is surrounded by a leathery sheath composed of
tunicin (cellulose).
4. The notochord appears in the larval stage in the tail of
the larva and disappears in the adult. This is known as
retrogressive metamorphosis.
5. The neural tube in the larva is replaced by a dorsal
ganglion in the adults.
6. Respiration occurs through gills.
7. They have an open circulatory system.
8. The excretory organs are absent.
9. They reproduce asexually by budding.
E.g. Herdmania, Selpa

5. CEPHALOCHORDATA
1. They are marine and filter-feeders.
2. The notochords remain throughoutlife and extend up
to the head region.
3. The nerve cord and the tail also remain throughout life.
4. Solenocyts are the excretory organs.
5. They respire through gills which open in the atrium.
6. The body wall comprises myotomes.
E.g. Amphioxus
Significance of Protochordates :
The protoehordates are of little economic importance
But they have great phylogenetic significance to the
zoologists.
They show great affinities and perhaps, common origin
with the living vertebrates. They retain the three basic
chordate features (notochord, hollow dorsal nerve cord
and pharyngeal gill-slits) throughout life. As such, they
are considered most primitive and borderline chordates
closer to the ancestor which probably gave rise to the
final and the largest group of chordates, the vertebrates.
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6. REFRENCES :-
1. Modern Text Book Of Zoology Vertibrates.
By R . L KOTPAL
2. Internet.