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.
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Key concepts and summary. A supernova occurs on average once every 25 to 100 years in the Milky Way Galaxy.
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Meiosis and Genetic Variation. ... When cells divide during meiosis, homologous chromosomes are randomly distributed during anaphase I, separating and segregating independently of each other. This is called independent assortment. It results in gametes that have unique combinations of chromosomes.
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A wolf can be considered as both a secondary and primary consumer because they feed on both primary and primary and secondary consumers. As a secondary consumer, wolves can feed on plant eaters [primary consumers] such as elk which is an herbivore. As a tertiary consumer, wolf feed on secondary consumers such as deer.
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