6. INTRODUCTION
◈ The term “Chordata” was coined by “Frances Balfour”
◈ The term chordata is originated from two words of
Greek language ‘Chorda’ and ‘Ata’. Meaning of Chorda
is ‘at thick string’ and meaning of ata is ‘to have’ and
over all meaning of chordata is animals having
notochord.
◈ Chordates are the animal in which notochord is
present in any stage of their life – span.
◈ Most population in the fishes followed by the
amphibians.
8. OTHER FEATURES
◈ These animals are aquatic, terrestrial or aerial, free
living.
◈ Body is bilaterally symmetrical.
◈ Body wall is triploblastic.
◈ Metamerism is found in the arrangement of muscles in
embyonic stage and in adults it is found in
arrangement of vertebrae and ribs.
9. OTHER FEATURES
◈ Chordates may be cold blooded (Poikilothermous) e.g.
Amphibians, Reptiles and fishes are warm blooded
(Hemothermous) e.g. Birds and Mammals.
◈ Notochord is mesodermal in origin. It forms a primary
endoskeleton which gives support to central nervous
system and muscles.
13. RESPIRATION
◈ In higher chordate animals, paired pharyngeal gill
clefts are found only in embryonal stage,these are
absent in adults.
◈ In aquatic chordates (pisces) and lower chordates,
pharyngeal gill clefts are present throughout their
life span for respiration.
◈ In terrestrial chordates, gill clefts are absent in
adults, because main respiratory organ is lung for
adults.
18. NERVOUS SYSTEM
◈ In these animals, a hollow,
tubular structure is present
which is situated just
beneath the bodywall and
just above the notochord in
the dorsal side.
◈ Ganglia are absent in the
nerve cord of chordates.
20. REPRODUCTION
◈ Sexual reproduction is dominant.
◈ Males are females are separate.
◈ Metamorphosis or development of embryo is direct i.e.
without any larval stage (few exceptions)
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