The bar above a Pokemon represents their CP in a relative range, for that specific species.
The lower end of this bar represents some (still unknown) minimum value for a single species. The higher end of this bar represents the maximum CP this Pokemon can have at your current Trainer level.
For example, Rattatas are rather weak, therefore their CP range is a lot smaller than that of a Drowzee, which explains the bar difference you are seeing.
You may fill the bar up by training your Pokemon. Note that absolutely nothing happens to the Pokemon when you fill the bar -- you've just reached the Pokemon's current CP cap.
The reason you see these, is most likely because of server trouble. They appear around Pokémon that are standing there. Normally you would see a Pokémon standing there in the middle, but because of server issues, you aren't actually seeing the Pokémon. See the following picture.
Best Answer
That symbol means you can complete the research task by evolving a Bunnelby into a Diggersby