level 2 Flashcards
- symmetry - di & triploblastic organisation - coelom - segmentation - notochord
what is asymmetrical symmetry?
Any plane that passes through the center doesn’t divide it into equal halves. its called asymmetrical
ex, sponges
what is radical symmetry?
Any plane passing through the central axis of the body divides the organism into two identical halves, it’s called radial symmetry.
ex, Coelenterates, ctenophores, and echinoderms.
what is bilateral symmetry?
where the body can be divided into identical left and right halves in only one plane.
ex, annelids, arthropods, etc.
what are diploblastic animals?
animals in which the cell are arranged in two embryonic layers, external “ectoderm” and internal “endoderm”, are called diploblastic animals.
ex, coelenterates
what are triploblastic animals?
animals in which the developing embryo has a third germinal layer, “mesoderm”. in between, the ectoderm and endoderm, are called triploblastic animals
ex, (Platyhelminthes to chordates)
what is coelom?
body cavity, which is lined by mesoderm
animals possessing coelom are called ___________ . its examples? (any two)
coelomates
ex, annelids molluscs, arthropods echinoderms, hemichordates, and chordates
what is pseudocoelom?
the body cavity is lined with endoderm and ectoderm
instead of mesoderm.
animals possessing pseudocoelom are called _______________ . example?
pseudocoelomates
ex, aschelminthes.
what is acoelomates?
the animals which the body cavity is absent is called acoelomates
ex, Platyhelminthes
segmentation?
the body is externally and internally divided into segments with a serial repetition of at least some organs,
Do earthworms show segmentation?
yes, they do!
their body shows the pattern called metameric segmentation, and the phenomenon is known as metamerism.
what is Notochord?
- its rod-like structure
- formed on the dorsal side
- animals with notochord are called chordates and without this structure are called non-chordates.
ex, Porifera to echinoderms
