Amniota Flashcards
amniota includes which groups
reptiles, birds, and mammals
why can amniotes inhabit more environments than amphibians
b/c of the amniotic egg
no longer need to rely on water to prevent dessication of eggs and therefore can live in a wider variety of habitats
3 membranes present in amniotes
allantois (storage site of waste products)
chorion (surface for resp gas exchange)
amnion (fluid filled sac around membrane)
*SHELL DOES NOT COUNT AS AN EXTRAEMBRYONIC MEMBRANE
yolk sac
not present in placental mammals
supplies growing embryo with nutritional needs
why are amphibian and fish eggs limited in size
gases directly diffuse from the environment to the embryo
in amniotes, there are membranes that facilitate gas exchange allowing the egg to be larger and for there to be a longer gestation period
T/F Amniotes do not have a larval stage
T; dont have one b/c they develop for a long time inside the amniotic egg
why do amniotes use internal fertilization
water usually mediates the meeting of egg and sperm, without water must evolve another way
amniotes split into 2 groups
synapsida (monophyletic, includes extant mammals and extinct lineages) and sauropsida (birds, dinos, living reptiles, extinct lineages)
purpose of temporal fenestrae
openings in the skull behind the eye which make the skull lighter, provides a surface for muscles to attach to and provides space for increase muscle volume (larger muscle = stronger bite force)
4 skull types
anapsid = no openings; primitive amoniotes, non amniotes, modern turtles (convergent evolution)
synapsid = 1 opening bordered by an upper temporal bar; derived from anapsid; mammalian ancestors, modified in modern mammals
diapsid = 2 openings separated by upper temporal bar; pterosaurs, archosaurs, modified in birds, living reptiles except for turtles
euryapsid = 1 opening bordered by a temporal bar below it; lower temporal bar has been lost; plesiosaurs and ichthyosaurs
