Answer:
This atomic model has changed over time. Scientists used the model to make predictions. Sometimes the results of their experiments were a surprise and they did not fit with the existing model. Scientists changed the model so that it could explain the new evidence.
Answer:
Simple organisms, such as theamoeba and earthworm, have a moist, permeable external surface. Oxygencan pass into them through this surface by diffusion. A large surface area is needed for effective gas exchange - so larger, more complex, organisms have special organs such as gills and lungs.
Explanation:
Quite simple really.... The CNS actually doesn't receive as much nutrients or key components from the blood... The blood actually dumps it into the Cerebrospinal fluid. The Cerebrospinal fluid therefore is directly in contact with the brain and if you want to find an infection you take from a source as close to thing as you can.
