Phys Eco Exam 2 Section 5: Cold Hardiness & Freezing Strategies

What is cold hardiness?

Ability to survive body temperatures below freezing.

What are the two major cold-hardiness strategies?

Freeze tolerance and freeze avoidance.

What is freeze tolerance?

Ability to tolerate ice formation within the body.

What is freeze avoidance?

Surviving very low temperatures, potentially down to −50°C, without freezing.

What are the freezing points of marine and freshwater?

Marine water: approximately −1.86°C. Freshwater: approximately −0.6°C.

Why does marine water freeze at a lower temperature?

Salt lowers the freezing point.

What freezing problem do freshwater fish face?

Their body fluids have a higher freezing point than the surrounding water.

What are the two general approaches to freeze avoidance?

Lowering the freezing point of tissues and supercooling.

What is supercooling?

Tissues drop below their freezing point without ice forming.

How is supercooling promoted?

Removal of ice-nucleating agents.

Why is supercooling unstable?

Ice crystals can induce freezing.

What is the supercooling point?

The temperature at which a solution spontaneously freezes within a short time.

What are colligative cryoprotectants?

High-concentration solutes that lower freezing point by increasing solute concentration.

What are non-colligative cryoprotectants?

Low-concentration antifreezes, such as polypeptides and glycopeptides.

How does freeze tolerance protect cells?

Controlled extracellular ice formation protects the interior of cells.

What is the role of osmotic concentration in freeze tolerance?

Extracellular ice formation concentrates solutes and promotes water movement out of cells, helping protect them from intracellular freezing.