In general, colder temperatures would tend to reduce the fluidity of membranes. In response, cells can adjust the composition of their membranes to maintain the proper degree of fluidity. How would the membrane change in response to colder temperatures?

Many organisms can adapt to colder temperatures by changing the lipids of their membrane.

Explanation:

The cells membrane are a phospholipid bilayer and the fluidity is given by characteristics of the phospholipids. Saturated fatty acids have a rigid structure and in cold temperatures, they solidify (like butter) and the membrane gest rigid. Phospholipids with unsaturated fatty acids have a more flexible structure making the membrane more flexible maintaining the fluidity in colder temperatures (like some oils). An organism that can adapt to temperatures can change the saturated lipids for unsaturated lipids of their membranes maintaining the fluidity of the membrane in cold temperatures.