Although the actual questions are missing from your ask, here's how you can tell.
If the study will be messed up (added bias) through interaction with the subjects the study should be observational. For example if a biologists wanted to study the eating habits of wild birds in the tropics, they would need to do an observational study. if they did a controlled experiment, the birds will change their eating habits based on human interaction, thus making the study invalid.
If the study requires specific measurements, close monitoring, or contact and interaction with the subjects the study should be a controlled experiment. For example, if a scientist wanted to test out a new drug, the health of patients would need to be closely monitored.
Eukaryote cells are single I’m pretty sure like it’s 1 thing
things that we do daily such as driving for example, has an effect on our ecosystem. Driving pollutes the air in our ecosystem and uses up gas and diesel resources.
They would eventually die out because they don’t have the correct adaptations, or they could breed together to make more of the adapted versions. Basically survival of the fittest
