deuterostomes I; starfish, sea squirts and amphioxus Flashcards
echinoderms classes
starfish sea urchins brittle stars sea cucumbers sea lillise
cleavage types
spiral cleavage
radial cleavage
spiral cleavage
new cells in cell division sit above grooves of old 4 cells
radial cleavage
new cells in cell division sit directly on top of four old cells
gastrulation
hollow ball of cells forms (blastula) and then moves inwards create a blastopore. This then develops further into an indented tube that will form the gut
animals with spiral cleavage
the blastopore will form the mouth at the end of the gut and create a mouth and anus end
- are protostomes; ‘first mouth’
animals with radial cleavage
blastopore marks the rear end of embryo where anus forms
- are deuterostomes; ‘second mouth ‘
bilaterian animals
protostome mode of development; lophotrochozoa and ecdysozoa
bilateria without protostome development
insects and nematodoes; have neither radial or spiral cleavage
deuterostomia grouping
some but not all animals with radial cleavage and secondary mouth formation
three major groups of deteurostomia
echinodermata
hemichordata
chordata
basal animals: chindaria
jellyfish in cnidaria
- no obvious left or right symmetry
- four fold symmetry
echinoderms evolution
- ‘number five’ pattern evlution
- include starfish and brittle stars and sea urchins and sea cucumbers and crinoid/sea lillies
has fluid filled canal in body called water vascular system
starfish evolution
five aerms moves with tiny tub efeed are predatory and hunt bivalve molluscs stomach secretes enzymes to weaken clam has fluid filled canal in body called water vascular system
brittle stars
graze on debris and detritus
