Answer to Question 1
A meta-analytic study of exercise interventions in advanced-age participants without clinical disorders found that the effect size for psychological well-being was three times greater than for control groups; aerobic exercise was the type and moderate intensity activity was the activity level that were the most beneficial. The study's authors noted that physical activity had a significant effect on self-efficacy and that well-being was linked to indicators of cardiovascular fitness.
Answer to Question 2
Although there are some mixed findings, when examining the studies with better methodology, it appears that it does. For example, using a large scale community sample from the Alameda County Study, epidemiologists were able to determine that physical activity was protective against developing later depression both through cross-sectional and longitudinal analysis even after controlling for potentially confounding variables.
The effects of emphysema.
The effects of elevated atmospheric CO2 on insect herbivores.
Horses require room to exercise
Types of infections and their Effects on host cells
Effects of a Placebo on μ-Opioid Neurotransmission
Effects of Differences in Solute Concentration on the Movement of Water Molecules