BIOL 1020U Lecture Notes - Lecture 8: Triploblasty, Diploblasty, Body Cavity
Animal Diversity (Part 1) Lecture
Textbook Reference: Chapter 44 in Biology How Life Works (2nd ed.)
Sections 44.1 – 44.2; pp.946 to 956
Animal “Body Plans”
•Four major patterns in body plans useful in classifying animals:
1. Symmetry
2. Tissue orientation
3. Body cavity
4. Orientation of mouth and anus
Symmetry
Radial symmetry – seen in jellyfish – left and right side look the same difficult to see
what is top, bottom, left and right
Bilateral – one plane that separates left and right planes into mirror sides (left and right)
– different body form to radial symmetry
–Dorsal – top side
–Ventral – bottom side
–Anterior - front
–Posterior - back
–Oral – top or where the mouth is found
–Aboral – bottom or where the mouth isn’t found (radially specific animals)
Tissue Organization of Cnidarians and Bilaterians
How are diploblasts and triploblasts distinguished from each other?
oDiploblasts: animals that develop from embryos with 2 germ layers
(cnidarians)
oTriploblasts: animals that develop from embryos with 3 germ layers
(bilaterians)
1
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Triploblast Body Cavities
•Most triploblastic animals can be further subdivided based type of body cavity or
coelom
•Define coelom = space inside body, usually fluid filled, where organs,
move, and are cushioned from outside shocks
•Aceolomates -
•Pseudocoleomates – body cavity derived from the blastocoel, rather than
from mesoderm
•Coelomates -
Draw diagrams to distinguish an acoelomate from a pseudocoelomate from a
coelomate:
Protostomes and Deuterostomes
Protostomes Deuterostomes
Cleavage pattern Spiral – planes of cell division
diagonal to vertical axis of
embryo
Determinate – each cell
designed, early on, to become
particular part of body
Radical – planes are parallel or
perpendicular to vertical axis of
egg
Indeterminate – fate of each cell
not determined early in
development – early cleavage
retains capacity to develop into
complete embryo – stem cell
diversity
Coelom Formation Forms solid layer – splits to form
coelomic cavity
-Mesoderm forms outpockets
from archenteron
-Cavity of outpockets becomes
coelom
Fate of Blastopore Blastopore become mouth and
second opening becomes anus
Blastopore becomes anus and
second opening become mouth
Animal Phylogeny
2
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Document Summary
Textbook reference: chapter 44 in biology how life works (2nd ed. ) Sections 44. 1 44. 2; pp. 946 to 956. Animal body plans : four major patterns in body plans useful in classifying animals, symmetry, tissue orientation, body cavity, orientation of mouth and anus. Radial symmetry seen in jellyfish left and right side look the same difficult to see what is top, bottom, left and right. Bilateral one plane that separates left and right planes into mirror sides (left and right) Oral top or where the mouth is found. Aboral bottom or where the mouth isn"t found (radially specific animals) How are diploblasts and triploblasts distinguished from each other? o. Diploblasts: animals that develop from embryos with 2 germ layers (cnidarians) o. Triploblasts: animals that develop from embryos with 3 germ layers (bilaterians) Draw diagrams to distinguish an acoelomate from a pseudocoelomate from a coelomate: Spiral planes of cell division diagonal to vertical axis of embryo.
