What slippery, watery membrane is next to the surface of the heart?

How many chromosomes are in a gold fish?

(drag each tile to the correct location.) categorize each term as something that is typical of a scientific theory, a scientific hypothesis, or both. - a tentative statement used to guide scientific investigations. - makes predictions about future events. - can be tested by many independent researchers. - based on observations of natural phenomena. - a well-established, highly reliable explanation.

The organelle pictured is found in cells of and is theorized to have once been an independent organism.