[Dave]

Biology is particularly badly served.

Plant life is almost always depicted by Flowering Plants - which only developed on Earth very recently. Either that, or they are particularly barren rocky planets without plants at all, but still with an Oxygen atmosphere.

Aliens are usually humanoid with recognisable human-like faces, or else it is a parasite peculiarly adapted to attack a species (us) that it has never even met before.

Anything to do with Aging or Cloning is never correct. Have you noticed how Clones are always the same age as the donor, with his/her memories and skills, even with very different upbringings and environmental factors?

Accelerated aging is always reversible!

De-evolution is possible!

Creatures can be enlarged or miniturised!

If you can't explain it, it must be a virus!