Question

which experiments led to changes to the original cell theory?
○ experiments that showed that blood cells transport gases, waste, and nutrients throughout the body
○ experiments that showed that all cells are similar in how they metabolize and in their composition
○ experiments that transplanted synthetic chromosomes into bacterial cells to create a new species
○ experiments that established the existence of single-celled organisms and microbes

Explanation:

The original cell theory stated all living things are made of cells, cells are basic units, and cells come from pre - existing cells. Experiments showing single - celled organisms (like bacteria, protozoa) and microbes exist expanded the theory, as the original focused on larger organisms. Other options: blood cell transport is about function, not theory change; cell similarity in metabolism/composition is about cell properties, not theory change; synthetic chromosome transplants are modern, not about original theory changes.

Answer:

D. experiments that established the existence of single - celled organisms and microbes