But in each case, the body temperature must remain within the acceptable limits that are inherent to that species. For example, although humans have adapted to survival in a wide range of environmental temperatures, the temperature of the body must remain relatively close to the ideal ICC in order to avoid any impairment of physiological functions. The ideal body temperature may change with each species, but the general principle remains the same: the normal physiological processes of an organism can only be carried out within a relatively narrow range of temperatures.

Fortunately, humans, like most mammals and birds, are endothermic, which meaner that most of the body heat is derived from its own metabolism. In order to maintain a fairly constant body temperature, a combination of behavioral and physiological adaptations is utilized. For example, when endothermic get too cold, they may increase heat production by moving around, shivering, and releasing hormones that increase their metabolic rate. When they get too hot, they may pant or sweat. In addition, endothermic may alter their blood flow, utilize their insulation (fat, feathers, r fur), or simply relocate to a warmer or cooler area.

This type of thermal physiology is especially advantageous for a few reasons. First, it enables marine and terrestrial endothermic to maintain a relatively constant body temperature when faced with severe environmental temperature fluctuations (homeostasis). Second, it allows these animals to endure vigorous activity for fairly long periods of time due to their high levels of aerobic metabolism (cellular respiration). This is especially important to terrestrial animals because moving on land requires a much greater effort than moving in water.

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An alternative type of thermal physiology is referred to as ectoderm. Isotherms rely almost entirely on environmental sources of heat to warm their bodies. Most invertebrates, fishes, reptiles, and amphibians are included in this classification. The term “cold-blooded” is often used to describe isotherms, but this is sometimes misleading. Often times these so-called cold-blooded animals actually have active body temperatures that are higher than those of mammals. An example of this is seen in the desert iguana Spymaster.

Permission granted to make unlimited copies for use in any one school building. For educational use only. Not for commercial use or resale. 2002 WARD’S Natural Science Establishment, Inc. All Rights Reserved Daphnia produce most of their young without mating. This is known as parthenogenesis reproduction. (Duplicitous dorsal), which has one of the highest preferred body temperatures known for any vertebrate – 1000 to 1080 Fahrenheit! The advantage of being an ectoderm is that very little energy is used to maintain body temperature, since this is taken care of by the environment.

For example, when a lizard’s body temperature is cool, it will sit in the sun to raise its temperature back up again. When it gets too warm, the lizard will seek shade to cool off again. In addition, isotherms are able to produce a small amount of heat metabolically at low rates, and use some physiological meaner of triangulation. However, isotherms have a bit of a disadvantage in that they are somewhat limited as to the environments that they can inhabit. Alaska is certainly not an ideal home for a lizard!

We can easily study an isotherm’s rate of metabolism by examining the water flea, Daphnia magna. Daphnia are of great importance in the aquatic food chain and are a principle t staple tort young and adult ties. The body tot a Daphnia is translucent which makes the beating, football-shaped heart readily visible under a microscope. Because the heart rate is variable with water temperature, it is easy to alter the Dauphin’s heart rate and observe the changes. 2 0 2002 WARD’S Natural Science Establishment, Inc.

OBJECTIVES Illustrate and label the main anatomical structures of a Daphnia Alter the temperature of a Dauphin’s environment and quantify the changes in its heart rate Differentiate between endothermic and exothermic animals Understand the advantages and disadvantages of each type of hierological An adult blue whale, with a heart the size of a small car, NAS one tot the slowest heart rates… To 6 beats per minute. Petroleum Jelly Daphnia culture PROCEDURE Obtain each of the following: 50 ml room temperature water 50 ml ice water 250 ml beaker Heat protective gloves are recommended when working with hot plates GLOVES 2. Place 150 ml of tap water in the beaker and allow it to boil on a hot plate. While you wait, proceed to Step 3. . Set the lid of the Petri dish aside and fill the bottom of the dish with 25 ml of room temperature water (approximately ICC). 4. Place a dab of petroleum Jelly in the center of a microscope slide. Obtain a graduated pipette and cut the pipette at the line marked “. 5”. Use this pipette to place one large Daphnia on the dab of petroleum Jelly. Make sure that the Daphnia cannot swim away and then pour off all of the extra water from the slide into the upside-down lid of the Petri dish. 6. Dispense 25 ml of room temperature water into the Petri dish (not the lid). Place the lied with the Daphnia in the dish, and allow it to sit for at least one minute to equilibrate. 7. Place the entire dish on the stage of a stereoscope’s. 8.

Look through the microscope and locate the beating heart of the Daphnia, which sits behind the dark line of the digestive tract. Draw what you see in the space below. Be sure to label the heart as well as any other anatomical structures you may recognize. 9. Practice counting the number of heart beats in a 15 second period: Have one partner keep track of the time while the other observes. Once the observer indicates that hey are ready, the timing should begin. Switch positions and repeat this practice. Do not move on to the next step until both partners feel comfortable measuring the heartbeat.

A hummingbird’s heart beats about 1,000 times per minute. HINT It may be helpful for the observer to count in increments often and keep track of every tenth beat by counting off with their fingers (I. E. , three fingers would equal thirty beats). 10. Take the temperature of the room temperature water in the Petri dish and record this number in Table 1. Count the number of times the heart beats over a period tot 5 seconds and record this data Repeat the count three more times and record your results in Table 1 . 11. Remove the slide and empty the Petri dish of the water. Fill the dish with approximately 30 ml of ice water and place the slide in the dish. Let the preparation acclimate for one minute on the stage of the stereoscope’s. 12. Again locate and focus in on the heart of the Daphnia. Record the temperature of the water and measure the Dauphin’s heart rate as before. Record the data in Table 13. Gradually add the boiling water to the Petri dish while gently stirring and keeping rack of the temperature.

At ICC intervals, take a heart rate measurement and record the temperature and the number of heart beats in Table 1. If the Petri dish gets too full, simply remove some of the water to make room for more. DID YOU KNOW? The average human heart beats 72 times per minute. Within one day, the heart beats over 100,000 times. 14. Stop taking heart rate measurements when the Dauphin’s heart rate stops changing, or when you can no longer measure the heart rate of the specimen. 15. Study Figure 1 below and compare it to your Daphnia drawing.