How to ensure validity in a investigation​

Alaska and northern canada have a diet rich in vitamin d and their skin color is darker than predicted on the basis of iv intensity at their latitude. explain the observation:

How does buring fossil fuels impact does carbon cycle? what large impact does this have on the envirnment?

Pls need ! in your opinion, what are the limiting factors that might affect the growth or diversity of our ecosystem? respond to this question in claim, evidence, reasoning format. 1. make your claim (i are the limiting factors that might affect the growth or diversity of our 2. follow the claim with 3 pieces of evidence. evidence may be taken from the reading, the videos, previous lessons, or googled answers. site sources, too. 3. use reasoning to explain why you chose your evidence.