What is the smallest level on the hierarchy of organization that is considered living?

The biological levels of organization of living things are arranged from the simplest to most complex. Here is a list.

organelle, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystem, and biosphere.

So organelle would be the smallest.

Movement toward a stimulus is considered a positive response, while ... Describe the biological levels of organization from the smallest to highest level ... to the entire biosphere, living organisms are part of a highly structured hierarchy.