One of the pictures has a great blue sky but the green tree is very dark and the other one has the green tree and very bright sky?

That is a very difficult situation but if you meter more toward the edge of the light and dark area you can get them both right. You can fix an underexposed shot but not one that the highlites are blown. I use spot meter to achieve that ..but here is the dark photo adjusted.

The two pictures were shot at dramatically different exposures - the "dark" one at 1/1600 shutter speed, f7.3, the "light" one at 1/320 shutter speed, f4.0. This accounts for the great difference, as the exposure conditions for the "light" one allowed much more light into the image during the exposure period. You didn't tell the whole story of how you set this up, I think you were shooting in a "spot" metering mode, where the particular exposure conditions the camera uses would vary considerably whether you were aiming at a dark area (making the picture light) or a light area (making the picture dark). I would make two recommendations: Switch your metering mode to "center weighted" (the mode labeled "[(•)]"), and also change your ISO setting to AUTO, as there would be no reason for shooting these photos at ISO 200 that I can think of.