Lecture 5

Water and Ice Effect on Cells

• Water can turn into ice, which can burst cells and cause death.

• This is particularly problematic for animal cells.

• Example: Ice on feet can create bubbles, leading to cell disruption.

Adaptations of Animals in Cold Conditions

Short Extremities

• Animals in colder climates, such as the caribou, tend to have shorter extremities (tails, legs, ears).

• Short extremities are advantageous for cold conditions to reduce the risk of frostbite.

Allen's Rule

• This principle states that animals adapted to cold environments often have smaller extremities to conserve heat.

• Allen's rule contrasts with other rules focused on adaptation based on body coloration or other features.

Surface Area to Volume Ratio

Understanding the Concept

• Surface area refers to the outer contact exposed to the environment.

• Volume is the internal space of the animal.

• Example: Snakes have a high surface area with low volume, while more compact shapes (like balls) have higher volume and relatively lower surface area.

Bergman's Rule

• Bergman's rule states that animals living in colder regions generally have a lower surface area to volume ratio compared to those in warmer regions.

• This adaptation helps them retain heat more effectively.

Countercurrent Heat Exchange Mechanism

• The blood vessels in certain animals exhibit a countercurrent heat exchange system.

• Arteries and veins are positioned close together with blood flowing in opposite directions.

• This arrangement allows for efficient heat transfer; warm blood from arteries heats the cooler blood in veins.