symmetry, tissues, and body cavities Flashcards
what organisms are asymmetrical?
sponges
radial symmetry
arrangement of parts around a single axis with no true head, contains oral and aboral sides
bilateral symmetry
organism can be divided into equal parts along central axis, includes anterior/posterior ends and dorsal and ventral surfaces
what are true tissues?
tissues isolated from others by a membranous layer, sponges lack this
diploblastic and triploblastic
organisms have ectoderm and endoderm (diplo) + mesoderm (triplo)
what do the ectoderm, endoderm, and mesoderm give rise to?
ecto: outer covering and CNS
endo: digestive tract and organs
meso: muscles, skeletons, organs b/w digestive tract and outer covering
what are coeloms?
fluid/air filled space located b/w digestive tract and outer body wall
coelomates
posses a true coelom derived from mesoderm
mesenteries
layers of tissue that connect and form structures to suspend organs in coelomates
pseudocoelomates
posses a pseudocoelom formed from mesoderm and endoderm where organs lie freely
acoelomates
lack body cavity so organs are encased within the body tissue
what do body cavities help faciliate?
larger body size, hydrostatic skeleton, room for organ development, greater area for exchange
how are modes of development distinguished by?
differences in cleavage, coelom, fate of blastopore
protostome development cleavage planes
8 cell stage with plans offset to the cells above (spiral and determinate)
protostome development steps (3)
1) 8 cell stage leads to coelom when mesoderm splits
2) blastopore forms after grastulation
3) opening becomes mouth
deuterostome cleavage planes
perpendicular or parallel to vertical axis of embryo (radial and indeterminate)
deuterostome development steps (2)
1) coelom forms from gastrulation
2) blastopore becomes anus
trends in animal evolution
1) simple to complex body
2) asymmetrical to radial symmetry to bilateral organisms
3) sessile to gentle stirring to running
4) filter feeders to herbivores to predators
