Identify the structure labeled Y

Centrioles
Centromere
Chromosome
Spindle Fibers

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?

Aplant may open end close its stomata to prevent excess water loss and maintain