What first walks with 4 legs, then 2 legs, then 3 legs?

Which list shows the levels of organization of an organism in hierarchical order from left to right, from the smallest to the most complex?

Why do we perceive objects as retaining their brightness under different lighting levels?

Ras is a g-protein that is activated when a growth factor attaches to egfr. its activation results in the replacement of a gdp molecule with a gtp molecule, thus allowing a signal transduction pathway to be activated. considering the signal pathway illustrated on this page, what is one potential outcome of a mutation in the ras gene that leads to ras protein hyperactivity. be specific.