How many cells does a unicellular organism have?

In general, characteristics that an organism survive and reproduce become more common over time. what mechanism of evolution causes this?

What characteristic does giardia have that makes it a protist, a characteristic that all other protists have? a. it is a unicellular eukaryote. b. it is a eukaryote that is not an animal, a plant, or a fungus. c. it is parasitic and has flagella. d. it spends part of its time in a body of water.

If all prokaryotes on earth suddenly vanished, which of the following would be the mostlikely and most direct result? a) the number of organisms on earth would decrease by 10—20%.b) human populations would thrive in the absence of disease.c) bacteriophage numbers would dramatically increase.d) the recycling of nutrients would be greatly reduced, at least initially.e) there would be no more pathogens on earth.