Lecture 41: Biology in Winter Summary. The tilt of the Earth’s rotational axis causes the Earth’s northern and southern hemispheres to experience seasons. Winter is characterized by colder temperatures, shorter days, and drier conditions, even though precipitation, in the form of snow, may be high. Colder temperatures mean that water in organisms can freeze. Water expands when it freezes, which represents the danger of ice crystals tearing plasma membranes and bursting cells. Organisms have evolved three basic strategies to deal with this: migrate away, remain in the habitat and be dormant, or remain be active. We discussed migration in lecture 40, so in this final lecture, we will discuss physiological, behavioral and morphological adaptations that animals and plants use to make it through the winter. Reading Assignment Campbell, N. A. and Reece, J. B. (2008). Chapter 40 (p. 872). Objectives
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