Activity 3: Biology to Go

1. As energy is stored in a human during the dynamics of a food web some of it is dissipated as heat energy. This might be used to maintain normal body temperature or be given off into the environment. During exercise, cellular respiration speeds up to provide extra energy for the activity. A byproduct of this process is thermal energy and the excess may have to be eliminated to maintain normal body temperature. If the heat-regulating mechanisms of the body are unable to eliminate this excess heat produced by the high degree of physical activity because of a hot and humid environment the body temperature rises and could result in heat stroke.

2. Shivering is the same as any muscle activity; it results in an increase in heat energy. Hands in cold water cause the body to lose heat to the environment. Shivering is a protective action that tries to produce heat to replace the heat that is being lost. Violent shivering can increase the body’s heat by as much as 18 times normal.

3. The first law of thermodynamics states that energy can be transformed, but cannot be created or destroyed. Energy from the Sun is transformed by plants into a form that can be used by the consumers in a food chain. The second law of thermodynamics states that in any energy transformation some energy is lost from the system. At each step of the food chain about 10% of the energy is lost.

4. Energy is lost at each step of a pyramid of energy. This puts a limit on the number of trophic or energy levels that can be sustained.

5. A pyramid of numbers is often not a good example of the flow of energy. In some cases a single tree can sustain a large number of first-order consumers.

6. Producers = 10,000 kcals
Primary consumers = 10,000 X 10% = 1000 kcals
Secondary consumers = 1000 X 10% = l00 kcals
Top-level consumers = l00 X 10% = 10 kcals

7. In this pyramid there are only three levels. There is no primary consumer.
The corn, the producer, contains 10 kcals of energy.
The steer, the secondary consumer, gets 10% of that energy, or 1 kcals.
The human, the top consumer, get 10% of that energy, or 0.1 kcals.
This illustrates how humans can obtain far more food energy by eating a given amount of grain than by eating the chicken or beef supported by the same amount of grain.