Energy Physiology Flashcards
Endo vs Ectotherm
Endotherm: Animals who regulates its heat through internal processes (humans / dogs). Requires more energy but are able to maintain constant body temperature regardless of environment
Ectotherm Animal who regulates its heat through external sources (lizards / frogs / bugs). They cannot keep their body temp separate from the environment, but require less energy
Second Law of Thermodynamics in action (2)
Picture water flowing through a copper pipe. At the start, most of the waters energy is directional, but as that energy degrades it is converted into random motion energy, raising the systems temperature.
In other words, due to the second law of thermodynamics, as temperature changes, so does kinetic energy. More kinetic energy = higher temperatures and vice versa.
Energy use by an animal (4)
- Energy enters and animals body as chemical energy and is absorbed (ingested chemical energy -> absorbed chemical energy)
- Absorbed chemical energy is used to perform physiological work inside the body (biosynthesis, maintenance, generation of external work ex movement)
- The energy is then used to do work, excreted as fecal chemical energy, or because these processes are not 100% efficient - released as heat.
- When the animal dies, the chemical energy in the animals body tissue is ingested by other organisms and the cycle continues.
Potential energy and external work
In some types of external work, some energy driving locomotion is converted into potential energy. Think of someone riding their bike uphill. Most of the mechanical energy used for external work is transformed into heat, but a small amount is stored as potential energy because he is moving his body higher up. When he starts going downhill, this potential energy is converted into kinetic energy.
Endo vs ectotherm metabolic rate
Endothermic animals require more energy to maintain their body temperature, and therefore have a much higher metabolic rate than ectotherms. In a study of two 7g animals living in the same environment, a pigmy mouse had a rate of nearly 300 J/h where a lizard had a metabolic rate of only 40 J/h
Lavoisier’s direct calorimeter
To measure an animals heat production, Lavoisier surrounded the animal’s container with and Ice-filled “jacket”. He then surrounded the whole apparatus in another ice filled “jacket” to protect the internal layer from environmental heat. The internal ice melted by the animals heat created liquid water, which was then collected and measured.
Fats and energy
Fats can hold much more energy than proteins or carbohydrates
SDA
Energy needed to process the food you eat. If a resting animal has not eaten for a while then consumes a meal but remains at rest, its metabolic rate rises. This is SDA. The larger the meal is, the larger the SDA and the less steep falloff it has. In other words a large meal will have a larger spike in SDA, as well as a more gradual return to the normal rate.
Body size effect on weekly food requirements
A vole eats about 6x its body weight per week, while a Rhino eats only 1/3 of its body weight per week. Because the vole is smaller, its oxygen consumption needs are higher and therefore it has a higher metabolic rate. Because of the higher metabolic rate, it needs more food to support it. Think about how hummingbirds, who are very small and require INSANE amounts of energy bc they are so fast and have such high heart rates.
BMR (6)
-Body metabolic rate.
-In mammals, smaller mammals have higher WEIGHT-SPECIFIC BMRs than larger ones
-Birds have the highest WS-BMR because they fly! Its cold up there so to keep warm they need a very high metabolic rate
-Mammals have the second highest, followed lizards then amphibians
-lizards and amphibians have a much lower rate because they are able to get energy from their environment (ectothermic)
-even when correcting for body weight, BMR will decreases with body size
Hearts and BMR
Higher 02 demands do not equal to pumping more blood per heartbeat. Instead it is heartrate that increases
Energy use with age
When an animal is young, they channel a significant amount of their energy into growth, however as they get older this decreases greatly. In sardines 18% of their energy is channeled into growth in their first year of life, however by the 6th year, its only 1%
