2. Bilateria
• Most animals have
bilateral symmetry.
• The vast majority of
animal species belong to
the clade Bilateria, ﺛ
ﻧ
ﺎ
ﺋ
ﯾ
ﺔ
ا
ﻟ
ﺗ
ﻣ
ﺎ
ﺛ
ل which consists of
animals with bilateral
symmetry and
triploblastic ﺛ
ﻼ
ﺛ
ﯾ
ﺔ
ا
ﻟ
ط
ﺑ
ﻘ
ﺎ
ت
development.
DR-ALSAQABI-2013INVERTEBRATE 2
3. There can be two
Ectoderm
Endoderm
or three
Mesoderm
Diploblastic ﺛ
ﻧ
ﺎ
ﺋ
ﯾ
ﺔ
ا
ﻟ
ط
ﺑ
ﻘ
ﺎ
ت Triploblastic ﺛ
ﻼ
ﺛ
ﯾ
ﺔ
ا
ﻟ
ط
ﺑ
ﻘ
ﺎ
ت
Tissue Layers
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4. Body Cavities ﺗ
ﺟ
و
ﯾ
ف
ا
ﻟ
ﺟ
ﺳ
م
Coelomate - the coelom is lined on both
sides with mesoderm
Pseudocoelomate - the
coelom (= pseudocoelom) is
lined on one side with
mesoderm
Acoelomate - there is no body cavity
between the digestive tract and body wall
Body Cavities - There are three different kinds
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