INVESTIGATION FIVEESSENTIAL QUESTION: HOW DO ORGANISMS MAINTAIN STABILITY IN AN EVER-CHANGING ENVIRONMENT?

EXPERIMENTBy Oliver Oglesby and Henry Kamp Due December 1st, 2010

Question:How does change in physical exertion

(sitting compared to jogging) and temperature (approximately 70° F compared to 40° F) effect a person’s heart rate?

Hypothesis:We predict that both increase in physical exertion

and decrease in temperature would increase a person’s heart rate. Nonetheless, we think that sitting compared to jogging would increase a person’s heart rate more than a change in temperature from 70° F compared to 40° F. We also think that the increase in heart rate is an example of homeostasis, which is the act of an organism to alter its internal environment to sustain its proper functioning, regardless of the outside environment.

Experimental Design:Independent Variable: Change in physical exertion

and temperature.Dependent Variable: Heart rate.Constant Variables: External environment

temperature in each trial, amount of heartbeats in each trial.

Control Group: Number of seconds per 50 heartbeats while sitting indoors (70° F).

Number of Repeated Trials: We tested two people’s heart rates three times for each of the physical exertion and temperature specifications.

Materials: A timer Lab notebook (to document results) Two people

Procedure:1. Gather Materials.2. Head to indoor area and begin first part of

experiment.1. Time number of seconds per 50 heartbeats three

times sitting and running for the first person then record results.

2. Time number of second per 50 heartbeats three times sitting and running for the second person then record results.

3. Head to outdoor area and begin second part of experiment.

1. Repeat steps 1 and 2 in the first part of the experiment.

Results:

Changes Oliver HenryTemperature

Physical Exertion

Seconds per 50 heartbeats

Average

Seconds per 50 heartbeats

Average

Indoor(70° F)

Sitting 36.9 42.1 43.2 40.7 38.1 35.2

37.5

36.9

Jogging 25.8 24.2 22.6 24.2 20.6 21.2

21.4

21.0

Outdoor(40° F)

Sitting 34.9 34.6 35.1 34.9 31.6 32.4

31.8

31.9

Jogging 22.8 20.4 21.1 21.4 19.4 19.3

20.2

19.6

Results:

Indoor Sitting

Indoor Jogging

Outdoor Sitting

Outdoor Jogging

0 5 10 15 20 25 30 35 40 45

HenryOliver

Seconds per 50 heartbeats (Averages)

Discussion: Experimental Results:Introduction:Overall our experiment went very well

considering there were a lot of variables that could effect our results. We noticed a lot of trends between temperature, physical exertion, and heart rate, which gave us a much better understanding of homeostasis and how it works in humans.

Discussion: Experimental Results:Initial Observations:As we expected the slowest heart rates

was when a person was inside sitting down and the fastest was when a person was outside jogging. What was surprising is that the heart rate of a person sitting inside was nearly twice as much as a person jogging outside. In this case we found that change in physical exertion had a greater effect on heart rate than temperature. However, this can vary depending on the particular situation.

Discussion: Experimental Results:Further Observations:According to our results a person jogging has

approximately 60% or 65% the seconds per 50 heartbeats of to someone sitting; whereas a person outside has approximately 85% or 90% the second per 50 heartbeats of someone inside. This shows that in our experiment, physical exertion had a greater effect on heart rate than temperature. One finding we found particularly interesting is that Henry’s heart rate was faster than Oliver’s heart rate.

Discussion: Experimental Results:Final Observations:Henry’s heart rate was about three beats

faster than Oliver’s heart rate on average, which demonstrates another variable that can alter the results of our experiment. However, this variable isn’t entirely negative, it illustrates variation in humans and probably gave us more accurate results on the whole. In conclusion, our experiment was very successful and educational and truly exemplified an act of homeostasis in human beings.

Discussion: Scientific Research:Introduction:A living organism requires a relatively

stable environment to function properly and therefore survive. However, organisms must endure the issues of a constantly changing environment. These changes are often deadly and organisms consequently must adapt to or avoid these complications by adjusting their internal environment and continue carrying out a variety of necessary tasks.

Discussion: Scientific Research:Luckily, organisms have a solution:

homeostasis. Homeostasis is vital to all living systems on earth. The term was created in 1959 to describe the necessary parameters for an organism to function. To fully understand this concept and the specifics of how it works, one must thoroughly examine the question, “How do organisms maintain stability in an ever-changing environment?”

Discussion: Scientific Research:Homeostasis in Humans:Some of the best examples of homeostasis

can be seen in ourselves, human beings. Surprisingly, it isn’t rare or unusual at all, actually, it happens frequently in our daily lives. Homeostasis can be seen at work in a number of our organ systems including the nervous and endocrine systems. It can also be seen on a much smaller level with cell membranes. Every cell contributes to maintaining homeostasis.

Discussion: Scientific Research:Nervous System

Homeostasis:The nervous system plays

an important role in maintaining homeostasis. It does this primarily in what is referred to as negative feedback loops. It controls homeostasis for rapid responses such as reflexes.

Discussion: Scientific Research:Nervous System Homeostasis Examples (Reflexes): Pulling hand off of hot stove to avoid being

burned. Taking foot out of icy water to avoid getting cold. Jumping or jolting when you feel something

unexpected or startling.How does this work? Nerves in the skin detect stimuli and transmit a

message up the spinal cord to the brain. There, the message is processed and sent to an effecter system, such as the muscular system, to respond to the stimulus.

Discussion: Scientific Research: Endocrine System

Homeostasis:The endocrine system plays

an important role in maintaining homeostasis as well. It controls homeostasis for longer-term responses. The endocrine system involves more of a chemical component to the reflex.

Discussion: Scientific Research:Endocrine System Homeostasis Example: Managing the body’s calcium levels. Maintaining proper glucose levels.How does this work?Sensors detect a change within the body and

send a message to an effecter in the endocrine system, which makes PTH. PTH is released into the bloodstream when calcium levels are low, which causes bones to release calcium into the bloodstream thus raising blood calcium levels and shutting down further production of PTH.

Discussion: Scientific Research:Cell Membrane

Homeostasis:The cell membrane is

crucial to maintaining the homeostasis of the cell and its organism because it’s what regulates material, including both nutrients and waste, in and out of the cell. The cell membrane is the blue protective exterior lining in the diagram at right.

Discussion: Scientific Research:Other Organ System Homeostasis:The nervous and endocrine systems are not the

only organ systems that perform homeostasis. Many reflexes or other responses of homeostasis involve combinations of organ systems. The nervous and endocrine systems serve as the major, central homeostatic controls while other systems aide in the reflexes and responses. For example, heat control is a major function of homeostatic conditions that involves the skin, muscular, circulatory, and nervous systems.

Discussion: Scientific Research:Negative Feedback:The usual means of maintaining homeostasis

is a mechanism called a negative feedback loop. It turns off the stimulus that caused it in the first place. In other words, negative feedback simply reverses the change. The nervous system often uses negative feedback loops to maintain homeostasis as well as body temperature regulation. In this case neurons sense abnormal body temperature and activate negative feedback loops to return the temperature to normal.

Discussion: Scientific Research:Positive Feedback:There is also what’s called positive feedback

loops, which are essentially the opposite of negative feedback loops. Positive feedback is a process whereby a change is detected and activates mechanisms that accelerate or increase that change. This can aid in homeostasis, but often does the opposite and can be fatal. An example of positive feedback’s beneficial effect can be seen in blood clotting and child birth. However, many diseases involve dangerous results and in other situations it can trigger heart attacks.

Conclusion: Experimental Results:Our hypothesis was correct. We are satisfied

with the way our experiment turned out given the circumstances. However, it would be very interesting to test more homeostatic changes and on more people. We also found it very useful doing a lot of research on homeostasis as well because it increased our understanding of our experiment and homeostasis in general. In conclusion, we found that increase in a person’s physical exertion and decrease in temperature increases a person’s heart rate.

Conclusion: Scientific Research:Organisms maintain stability in an ever-

changing environment through homeostasis. Through this simple answer to my essential question and the details previously stated one greatly comprehends how homeostasis works and how it contributes to our lives. Undoubtedly homeostasis is a fundamental property for life and a necessity for all living things. It enables all living organisms to maintain internal stability in spite of a persistently changing and challenging environment.