What is immigration in population structure

The table shows dates and appearance of index fossils. which rock layers can be dated most precisely? a) a layer containing both a fossil 4 and a fossil 3 b) a layer containing both a fossil 2 and a fossil 3 c) a layer containing both a fossil 1 and a fossil 4 d) a layer containing both a fossil 1 and a fossil 2

Which kind of worm has a closed circulatory system? a planarian b fluke c pinworm d an earthworm

What does the splanchnic nerve innervate?