hypothesis
observation
no. a hypothesis would be what he proposed is the reason for the declination of the salamanders. the statement you posted is just an observation
observation
The number of tiger salamanders were decreasing.
scientist
Alexander Fleming
It is observation because observsation means what you see.
Scientists did not discover Mars. It was first noticed in the skies by ancient peoples sitting in the open observing the night sky.
If you haven't noticed there are no mountains in the plains so therefore there can be no valleys, You can consider the great plains to be a valley though
Volcanic mountains have been known since pre-historic times, so there is no way to say when the first one was noticed by humans.
Alexander Fleming wanted to be a doctor so he went to St. Mary's hospital medical school. When he was cleaning up he noticed a mold and that's when the discovery happened.Penicillin.
penicillin comes from mold. A scientist was experimenting with bacterial cultures when they were ruined by mold growing on them and he asked why. The result was penicillin. Other scientists had noticed the same thing years previously but had not asked why.