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Boardworks AP Biology Controlling Body Temperature

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1 Boardworks AP Biology Controlling Body Temperature

2 Boardworks AP Biology Controlling Body Temperature
Thermoregulation Boardworks AP Biology Controlling Body Temperature Animals regulate their body temperature using a process called thermoregulation. Thermoregulation is crucial, as it helps to maintain the body at the optimal temperature for its enzymes. Some animals live in thermostable environments, such as the open ocean, and have to do very little to maintain their body temperature. Instead, their enzymes are adapted to work at their environmental temperature. Photo credit (puffer fish): © 2009 Jupiterimages Corporation Environments with fluctuating temperatures provide the greatest challenge for thermoregulation.

3 Boardworks AP Biology Controlling Body Temperature
Heat transfer Boardworks AP Biology Controlling Body Temperature

4 How is heat gained and lost?
Boardworks AP Biology Controlling Body Temperature Teacher notes Students could be asked which source of heat is most important to the iguana in the picture. How do they think this would change if the lizard were replaced with a bird?

5 Ectotherms and endotherms
Boardworks AP Biology Controlling Body Temperature There are two major strategies for thermoregulation in the animal kingdom: endothermy and ectothermy. Ectotherms do not exert physiological control over their internal body temperature. They instead rely on external sources of heat to warm their bodies. Despite this, many ectotherms maintain a near-constant body temperature during their hours of activity. Reptiles and amphibians are ectotherms. Photo credit (tree frog): © 2009 Jupiterimages Corporation Endotherms generate their heat metabolically. Most also maintain a constant internal body temperature, higher than the external environment. Mammals and birds are endotherms.

6 Thermoregulation in ectotherms
Boardworks AP Biology Controlling Body Temperature Photo credit (all): © 2009 Jupiterimages Corporation

7 Thermoregulation in endotherms
Boardworks AP Biology Controlling Body Temperature Endotherms generate most of their heat metabolically. As they are warmer than their environment they tend to lose body heat to their surroundings. Adaptations for heat conservation include: Insulation – insulating layers of fat, fur or feathers to prevent heat loss. Metabolism – metabolic rate can be varied to generate more or less heat. Teacher notes Endotherms use similar behavioral thermoregulation to ectotherms. The main difference between the groups is that ectotherms rely on these behavioral mechanisms to maintain their constant body temperature, whereas endotherms have a much wider range of physiological mechanisms to adjust their temperature. Photo credit: © 2009 T-Service / Science Photo Library Thermogram of a wallaby: A thermogram shows variation in temperature on the surface of an object, measured by the long-wave infrared radiation it emits. The temperature scale is color-coded and runs from purple (6 degrees Celsius, coldest) through blue, green, and yellow to red (warmest, 23 degrees Celsius). The wallaby's fur insulates it from the cold. The covering of fur is thinner on its feet and hands which is why heat loss is greater from these parts. Endotherms also use their skin to vary their rate of heat loss and maintain a constant core body temperature.

8 The importance of the skin
Boardworks AP Biology Controlling Body Temperature

9 Thermoregulation in humans
Boardworks AP Biology Controlling Body Temperature Teacher notes This animation demonstrates how body temperature is controlled in humans, highlighting the role of negative feedback in the process. It is important to note that humans also maintain their internal body temperature by varying their metabolic rate like other endotherms. Similarly, not all of the mechanisms used by humans are seen in all endotherms. Sweating is a prime example of this. Many mammals do not sweat to cool down, as the loss of water is far too costly to their metabolism.

10 Hyperthermia and hypothermia
Boardworks AP Biology Controlling Body Temperature Prolonged exposure to high temperatures can lead to hyperthermia. The body’s core temperature rises above 41°C, causing its thermoregulatory mechanisms to break down. When this happens, positive feedback occurs and the person’s body temperature can spiral out of control. A core body temperature of 43°C and higher usually causes death. If the body’s core temperature falls below 35°C a person may suffer from hypothermia. Again, the body’s thermoregulatory mechanisms fail and positive feedback occurs, leading to a further decrease in temperature.

11 Physiological thermoregulation
Boardworks AP Biology Controlling Body Temperature

12 Thermoregulatory control system
Boardworks AP Biology Controlling Body Temperature


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