Phylogeny Flashcards
taxon
named group of organisms
comparative morphology
looking @ similar structures to determine relationships between taxa
homologous structures
originating from the same structure
convergent evolution
similar selective pressures causing different species to evolve similar but non homologous traits
determining which species have a more recent common ancestor looking at a phylogenetic tree
look at TIME NOT # of nodes!!!!! if closer to extant species on tree, less time has passed
divergence
different selective pressures cause homologous characters to appear very different
ancestral character state (aka…)
plesiomorphic - trait that arose before the most recent common ancestor diverged
**present in ingroup AND outgroup
derived character state (aka…)
apomorphic - trait that arose in the most recent common ancestor
**present ONLY in ingroup
synapomorphy
a derived character shared by 2 or more taxa and their most recent common ancestor
monophyletic group
an ancestor and ALL of it’s descendents
paraphyletic group
doesn’t include all descendents
protostomes vs deuterostome differentiation
LOOK AT EARLY EMBRYONIC DEVELOPMENT
proto - blastopore gives rise to mouth region **‘FIRST MOUTH’
deut - blastopore gives rise to anus region **‘SECOND MOUTH’
chordate characters
post-anal tail
pharyngeal slits
notochord
dorsal HOLLOW nerve chord
endostyle (homologous to thyroid gland in vertebrates)
**all present in all chordates at some stage stage in development
dorsal hollow nerve chord
hollow, fluid filled tube dorsal to digestive tract
arrises from ectoderm (invagination during neurulatoin), forms the central nervous system
FUNCTION - sends and receives electrical impulses
notochord
arrises from mesoderm
rod with a core of cells and fluid surrounded by a fibrous sheath
FUNCTIONS: 1. provides structure support as it can withstand axial compression, 2. signals ectodermal cells to differentiate into neural plate ectoderm during neurulation
pharyngeal slits
DEUTEROSTOME synapomorphy
series of openings in the walls of the pharynx
endostyle
arrises from ventral region of the pharynx
STRUCTURE - groove filled with glandular tissue, produces mucus and processes iodine
**HOMOLOGOUS to thyroid gland in vertebrates
post-anal tail
muscular extension of the body past the anus, with myomeres separated by myosepta and the notochord extending into it
thyroid gland function
produces T4 hormones to regulate metabolic rate
what taxa are included in deuterostomes
echinodermata, hemichordata, chordates
what taxa are included in chordates
cephalochordata, urochordata, vertebrata
echinodermata
sea stars, sea cucumbers, sea urchins, sand dollars, basket stars, feather stars
as larvae have bilateral symmetry but develop pentaradial symmetry
hemichordata
acorn worms and pterobranchs
body regions: probosis, collar, pharynx, trunk
cephalochordata
** have all 5 chordate characters throughout life (post anal tail, dorsal hollow nerve chord, notochord, pharynx w/ slits, endosytle
see diagram in summary
