What is the characteristic of the gastrula stage of embryo development? select one of the options below as your
a. formation of the neural tube and nervous system
b. formation of thethree germinal layers and the primitive gut
c. formation of the amniotic cavity and archenteron?

List two limitations of natural selection

Match the following terms describing electrical events with the correct phases of the cardiac cycle. the ventricular muscle cells depolarize at the start of this phase. during this phase, na+ entry through the funny channels causes the pacemaker potential of sa nodal cells to gradually become less negative until it reaches threshold. the ventricular muscle cells repolarize right before this phase. the cytosolic concentration of calcium in the contractile cells of the ventricle is highest during this phase. a. isovolumetric relaxation b. ventricular ejection c. isovolumetric contraction d. ventricular filling

Question 1 of 102 pointswhich best describes adaptive radiation? oa. geographical isolation caused by an adaptationob. biodiversity resulting from few ancestorsoc. a decrease in the rate of speciationd. adaptations that organisms teach each other