In cross-sectional studies, the midlife period is characterized by

increases in environmental mastery.

Explanation:

Cross-sectional study is defined by observational research, which analyzes data collected over a period of time. This survey can be in a sample population or in a predefined subset. This type of study is also known as cross-sectional study, cross-sectional study and prevalence study. The data collected in the cross-sectional study are from similar people in all variables. Except for the variable being studied.

Regarding middle age, cross-sectional studies are characterized by increases in the environmental domain as a shared feature among participants and research in this approach.

in 1972 the fluid—mosaic membrane model of membrane structure was proposed based on thermodynamic principals of organization of membrane lipids and proteins and available evidence of asymmetry and lateral mobility within the membrane matrix [s. j. singer and g. l. nicolson, science 175 (1972) 720–731].