What is the structure called, found in Agnathans, which will become the endoskeleton in more evolutionary advanced organisms?

Acommon kind of mechanical weathering is called

At the age of 6 months, caleb was diagnosed with tay-sachs disease. as his primary care physician, what would you tell his parents about this disease?

10 points a population of mice have tails. over time those mice with either really short tails or really long tails have a higher rate of survival. this will probably lead to what type of selection? a. disruptiveb. directionalc. stabilizingd. evological