How would removing your umbrella in a rainstorm affect your ability to stay dry? The definition of a keystone species is a species that has a crucial role in an ecosystem. Removing one gear from a clock would stop the clock from working. Removing/changing a major contributer to a balance and natural ecosystem can potentially collapse the entire system altogether.
There are many human activities that could contribute significantly to the creation of dead zones, and here are some of them:
1. the use of chemical fertilizers
2. urban land use
3. coastal littering, as well as runoff from sewage
4. use of harmful phosphates in detergents
Dead zones are places in waters on Earth where there is so little oxygen left due to pollution that marine life cannot survive there.
The correct answer of the given question above would be the third option: INVOLUNTARY MOVEMENT. The function of the musculatory system that is best illustrated by the heart pumping blood throughout the body is an involuntary movement. The heart has specialized muscles which are called cardiac muscles and these are only found in the heart. It is an involuntary, striated muscle.