Question | Answer |
Von Baer,1828 | "on the development of Animals".embryos develop from general to specific.he first described mammalian egg and notochord |
Garstang,1922 | started the theory of paleogenesis.descendant ontogenies(development) tend to preserve ancestral ontogenies.ex:humans do not go through a "fish" stage, but they do have pharyngeal slits(not gills) in early embryology,like fish embroys |
paleogenesis | appearance of ancestral characteristics in successive generations |
Ancestor development | zygote-structure a,b,c,d, |
descendant development | zygote-structure a,b,c,d,e,f,g. More complex= longer development time.shorter development is better for organisms. |
what are the solutions to the long development plan? | accleration,abreviation,toleration |
acceleration | heat(environment), catalyst(enzymes). internal body heat(endothermy). |
abbreviation | retain juvenile features in to adult hood(neoteny). ex Nectural salamander(still has gills slits) |
toleration | behavioral ways to help embryo if cant shorten time. ex;bigger yolk in developing egg,switching from egg birth to live birth(VIVIPARITY)(able to provide more food). |
Altricial | are helpless at birth (baby mice,kangaroos) |
precocial | well developed at birth.lessens the degree of parental care. |
blastula | hollow ball of cells |
gastrulation | formaulation of gut tube |
enrocoel | hollow gut tube |
lumen | hollow part of an organ |
what are the mesoderm regions | chordamesoderm,epimere,mesomere,hypomere |
chordamesoderm | becomes notochord,induces neurulation(formation of nerve cord) |
epimere | in blocks=somites. separates into 3 layers(skin dermis,skeletal muscle,vertebrae) |
skin dermis | outer somites |
skeletal muscle | middle somite |
vertebrae | inner somite |
mesomere | kidneys |
hypomere | not segmented. splits into 2 layers.coelom lining(peritoneum).smooth muscle around gut tube.heart/circulatory system(vessels).skeleton of body wall/limbs.gonads |
ectoderm | skin-epidermis.nervous system,sense organs(eye+ears),pigments |
endoderm | lining of gut(hollow organs).liver,pancreas,lungs.gut tube(anything that buds from it). |