~ Thermoregulation ~

This week’s blog is on the subject of thermoregulation and how different organisms retain their body temperature in different environments. However, different organisms thermoregulate in various ways, and that is a concept that was tested in our lab this week.

In order to understand what we tested in our experiment and the results we concluded, one must know a background on thermoregulation first. An organisms body temperature is crucial to their overall performance. There is a range of temperatures that an organism can live in that optimize their performance. There are different metabolic states that an organism can be categorized in, and in lab we studied both endothermic and exothermic systems. An endothermic organism maintains a relatively constant body temperature relative to the external temperature. They have higher metabolic rates because of this, and are generally larger animals with greater insulation. For example, endotherms are usually have some type of fur or hair and a large percent of bodyfat. They are able to give off excess heat mainly through their extremeties. Mammals are an example of endotherms.

In contrast, ectotherms rely on the external environment for their body temperatures. They are usually smaller in body size in order to cool down or heat up faster than mammals with greater surface area. They have a much higher heat exchange with the environment than endotherms, or regulators. They can conduct heat more rapidly because they have very little to no insulation on their bodies. Their skin can be very thin and lacking fur as an insulator so heat exchange is high. Their metabolic rates are lower as they do not have to work as hard to regulate their body temperatures. A lizard in the desert is an example of an ectotherm and may bask in the sun in order to raise its body temperature.

Now, for our experiment we wanted to see endothermic and ectothermic processes occur in a lab setting in order to see temperature curves for thermoregulatory processes. We tested how environmental factors effected an animal’s heating and cooling rates. My partner and I chose coat color as our testable variable. We wanted to know how an organism’s body color, such as light or dark effected body temperature heating and cooling curves. We made our animals out of tin foil and cotton balls and used a heat lamp as our heat source. The purpose of the experiment was to be able to see visually what our organisms heating and cooling curve would look like when graphed. So, we began at room temperature and measured how long it took for our animal’s temperature to become constant. Then, we turned off our heat lamps and measured how long it took for our animal to return to room temperature. Our results were what we expected, which I will explain in much greater detail below…

  Graph based off results of lab experiment

Before we tested our animas first we practiced our technique with a foil cube. The thermometer was inserted into the cube, the heat lamb turned on, and then we recorded the temperature of the cube in 30 second intervals. It took around 5 minutes for the temperature to flatline, and that was when we turned off the heat lamp and the cube, over the next several minutes returned to room temperature. Our results from Part A can be seen on the scatter plot above.

Cube being heated in Part A of experiment

Then in Part B of the experiment came the fun part: testing our animals we made our of tin foil.

1. We selected to study color because we wanted to see how an organism’s coat color helps it survive or hinders it in certain environments. It is important to scientists because it shows that there is a “cost” to thermoregulation.  We created one animal out of just tin foil and the other with the addition of cotton balls on its external surface. However, the design of our animals could also be used to hypothesize the heating and cooling rates of endotherms vs ectotherms, but we already know how their graphs are supposed to look like so we thought that that would be too easy.

I gained knowledge of color factors from a scientific article titled “Color Change for Thermoregulation versus Camouflage in Free-Ranging Lizards”. The lizards in question were changing color and the scientists wanted to know why. Their body color was changing, however, their results still correlated to our experiment as the lizards were changing color to be able to be more efficient in thermoregulating as well as camouflage. From this article and the data from our experiment we found that color of a ectothermic organism can alter their thermoregulatory rates while basking in the sun.

2. My partner and I designed the study to answer the question by creating one animal made just from tin foil and the other with an external layer of cotton balls. The cotton balls act as an insulator as well as a heat reflector. We thought that the lighter color would have a smaller temperature curve as it would take much longer to heat up and cool down and the temperature from starting point to where it became constant would be smaller than that of the darker individual. A challenge we found was positioning of the thermometer as it was important to have it placed as similarly as possible for both animals in order to get the most conclusive results. We placed each animal about an inch from the heat source, which is a mimic of the suns rays. We started at room temperature and then took temperature reading (in Celsius) every 30 seconds. Once the temperature became constant we turned off the heat lamp and took the reading in the same intervals until the temperature was back to room temperature.

 

 

 

 

 

 

 

 

 

3. In our experiment the animal that most closely represents ours in terms of thermoregulation could be a turtle, which is an ectothermic organism. Turtles have thin leathery skin and bask in the sun for warmth. They have relatively small body size which is one characteristic of an ectotherm. The plain tin foil animal could represent a dark colored turtle basking in the sun. In contrast, the lighter color animal with the cotton balls covering it could represent a very light colored turtle, perhaps an albino. We expected the tin foil turtle to heat up faster and with a greater temperature range because dark color attracts the sun’s rays. Also, the plain tin foil turtle could also be seen as an ectothermic organism, and this variable also works for our temperature curves.

Hypothesis: Color of an ectothermic animal is a variable that alters how fast or slow their  body temperature will warm up and cool down while basking in the sun.

Graph based off data from lab experiment

Graph based on data from lab experiment

For the experiment, we took measurements on temperature over time. A scatterplot is best used to analyze the data because it will show us if we were correct that we thought there was a correlation between color and heating and cooling rates. A scatterplot shows the temperature curve between our two animals and how the size of the curves varies.

4. Color variation, even in the same species of organism, can alter their thermoregulatory rates. The experiment also revealed that an animal’s temperature variation can be investigated further when looking at metabolic rates. We can see how our variable of color, in dark vs light colored ectothermic turtles, the white turtles took longer to heat up and cool down and had a smaller curve than the darker colored turtles. The darker turtles heated and cooled much faster and has a greater variation in starting temperature and where their temperatures became constant. As one can see from the graphs above, the darker model has a temperature variation from 25 to 37 and the lighter model was from 25 to 35.

Data from lab experiment. Graph compares the heating curve of the different turtle models. As one can see the darker colored turtle had a large heating curve and reached a greater temperature variation than the lighter colored turtle.

From learning about thermoregulation, I know that endotherms have adaptations that aid in keeping their body temperatures constant. One characteristic that most endotherms have is the existence of body hair and a higher fat content. Evidence of this is seen in the article “Huddling for survival: monkeys with more social partners can winter better”. The monkeys being studied huddle together during colder weather in order to stay warm. If I were to explain this scientific explanation to a child or retirees I would make an analogy. For example, The the monkeys huddled together act as an insulator and they are sharing body heat similar to what survivalist say to do when humans are in a dangerous colder environment: get close together. They are creating a greater surface area which takes temperature a greater time to fluctuate.

Maintaining a constant body temperature takes a lot of energy. In warmer conditions it does not take as much energy to maintain body temperature because the difference between the external temperature and internal does not have a very large difference. It is true endotherms do not truly rely on their external environment for body temperature, but their performance is heightened only under certain temperatures. So, if the temperature becomes too cold the animal has to expend more energy in order to thrive. For the monkeys in the article titles “Monkeys eat fats and carbs to keep warm”, the scientists conclude that the monkeys are eating more fats and carbs in the winter compared to different parts of the year. They must consume more in colder temperatures to maintain a healthy metabolism. An analogy to use when explaining this concept to students and older people is to compare the monkey’s body temperature to a car’s air conditioner. In winter, you must have the heat very high in order to stay warm. When you have the heat running on full blast for long periods it will cost a lot more gas to fuel the car and keep the heat running constantly all the time. Having others be able to understand such an important concept is a goal for the scientific community to communicate, and hopefully my blog will be able to convey a greater understanding.

References

Graphs based off classroom lab data

Smith, Kathleen R., et al. “Color Change for Thermoregulation Versus Camouflage in Free-Ranging Lizards.” American Naturalist, vol. 188, no. 6, 2016, pp. 668. ProQuest,

University of Lincoln. “Huddling for survival: monkeys with more social partners can winter better.” ScienceDaily. ScienceDaily, 30 May 2018.

University of Sydney. “Monkeys eat fats and carbs to keep warm: Golden snub-nosed monkeys adjust nutrient intake in winter.” ScienceDaily. ScienceDaily, 8 June 2018.