Which flexible structure that supports the nerve cord and led to the backbone

The observations of hooke and van leeuwenhoek documenting the existence of microscopic cells formed the basis of what important theory? a. the cell theory stating that all living things are composed of cellsb. the theory of spontaneous generation, which held that life forms could arise spontaneouslyc. the theory of chemotherapy, or use of antimicrobials to destroy pathogenic organismsd. the germ theory of disease and causative agents

Identify the various levels of atmosphere. troposphere mesosphere exosphere stratosphere thermosphere

Coral reefs support more species per unit area than any other marine environment on earth. what is one way coral reefs are important to the health of the biosphere