T16 Flashcards
invertebrates vs vertebrates
invertebrataes = no backbone - majority of animals are
vertebrates = backbone
diploblastic
2 layers are formed during development, after gastrulation
endoderm and ectoderm
include jellyfish/cnidaria
no mesoderm
triploblastic
3 layers form, endoderm,ectoderm, mesoderm
a tube forms - two types of these, protosome or a deuterostome
protosome
includes - molluscs, annelids, arthropods
In the eight cell stage of development, cells are spiral, no symmetrical, have a development direction - which means cannot split the cell in half and have 2 identical embryos
the blastopore develops into the mouth
deutrosomes
in eight cell stage - radial, symmetrical, and not determined in development direction so the cells can split in half and form an identical embryo- twins
the original blastopore becomes the anus
body cavity - coelom
it is a space or fluid that separates the digestive tract from the outer body wall- between the endo and ectoderm
what function does a body cavity have?
- it cushions organs to prevent injury
- organs can be suspended so can move independently
- allows room for organs to grow
- can be filled with non-compressible fluid in hydrostatic skeletons
true coelom - coelomate
the body cavity - space is completely lined by tissue from the mesoderm
false coelom - psuedocoelomate
body cavity lined by the mesoderm and the endoderm
no coelom - acoelomates
no body cavity at all - just goes undo,meso,ecor
radial symmetry
top and a bottom
- no left or right
bilaterial symmetry
top and bottom, left right, front and back
Porifera - sponges
first separation in the metazoa tree
- no symmetry
- no gut
- no germ layers - no cleavage pattern in development
-mainly marine
-a basal group of animals
-choanocytes - create water current for filter feeding
- sexual or asexual
- fiercely competitive for space
- can reform from constituent parts because they are so simple
Cnidaria - jellyfish, coral
in the eumetoza group
- diploblastic
- radial symmetry - related to sediternary lifestyle
- have specialised stinging cells called cnidocytes
- polyp - sessile - stationary - coral
- medusa - motile - jellyfish
lophotrochozoa - protostomes
triploblastic
- lophphore feeding appartus or trochophore larva
includes annedlida, mollusca, brachiopoda, platyhelminthes, syndermata