In general, yes, the dorsal blood vessel of a worm be seen from the worm's exterior because a worm's "skin" is very thin. Although of course there are exceptions.
Answer:
This is called wind shear, and it can induce a spinning movement in the air. At first this creates a spinning cylinder of air that is parallel to the surface. But as with any thunderstorm, the convective cells in a hurricane create strong updrafts. These can tilt the spinning air upright; a tornado is born.
Answer:
D. Selection has led to decreases in the size of fish at the age of reproductive maturity.
Explanation:
The larger body size of the fishes is not an adaptive trait as it reduces the survival chances of these fishes. The process of natural selection tends to increase the frequency of the traits that increase the survival fitness of the organisms. Here, the fishes with smaller body size at the reproductive age have greater chances of survival and would reproduce more to leave more progeny. Over the generations, the selection pressure would increase the proportion of fishes that are smaller during reproductive age.
