The Skull protects the brain.
The hypothalamus synthesizes and secretes certain hormones called releasing hormones which stimulate the secretion of pituitary hormones.
The hypothalamus gland uses the nervous system and secretes hormones which sends messages to the pituitary hormones.
If a zebra mussel is discovered in a lake in Pennsylvania, then the ecologist would be worried because it is an invasive species. The zebra mussel is native to Ukraine and Russia, but if it has been found in Pennsylvania, than it means that it has been introduced in this area. As an invasive species, the zebra mussel can be very dangerous for the native species in the lake. The invasive species usually are more competitive for food sources than the native species, manage to reproduce quicker, bring in diseases, and the native species tend to not have defense mechanisms for them. This leads to rapid decline or even extinction in the native species, while the invasive spreads out quickly and takes over, resulting in dramatic change in the whole ecosystem.
