Question

Short-spined sea urchin fossils were found directly above long spined sea urchin fossils in a layer of rock. What do the differences between the two sets of sea urchin fossils suggest about them?

a)The longer spines developed as the shorter-spined sea urchins grew older.

b)The longer-spined sea urchins existed before the shorter-spined sea urchins.

c)The shorter-spined sea urchins stretched their spines to ward off predators.

d)The shorter spines did not protect the sea urchins well enough and they died off.

Answer 1

Answer: b) is correct.

Step-by-step explanation:

As the animals die, they get covered in layers. The lowest being the oldest. The difference is showing us a direct link between the two fossils. This means that the longer-spined sea urchins existed before the shorter-spined sea urchins. And evolved to have shorter spines rather than long ones.

Answer 2

The correct option is B (The longer-spined sea urchins existed before the shorter-spined sea urchins.)

Step-by-step explanation:

The more drawn out spined ocean urchins existed before the shorter-spined ocean urchins.

Since the shorter spined urchins are higher up, that demonstrates that they developed from the more drawn out spined urchins, implying that having the shorter spines was useful to them as an animal types, so the shorter spines came AFTER the more extended spines.