Explain the difference between autotrophic organisms and heterotrophic organisms.

Question 1. Explain the difference between autotrophic organisms and heterotrophic organisms.

undefined

Question 2. If there is an “energy advantage” for organisms which use aerobic respiration, do you suppose this could explain why there are more aerobic species than anaerobic species? Explain your answer.

undefined

Question 3. Assuming that an animal loses heat to its environment from its surface, suggest an evolutionary explanation for the following question: why do arctic hares have shorter ears than those of San Diego County jackrabbits?

undefined

Question 4. Which animal taxonomic groups include endotherms?

undefined

Question 5. What is an ectotherm? Give examples of animals which are ectotherms.

undefined

Question 6. As the size of the cubes got smaller and smaller, what happened to the surface area : volume ratio?

undefined

Question 7. Examine Figure 1. For each visible cube in the whole “organism”, count the number of sides exposed to the outside. Write these numbers on the cubes in the diagram. Is there a cube with no sides exposed to the environment in Figure 1?

undefined

undefined

undefined

undefined

undefined

undefined

Question 8. Locate the cube marked “a” in each of the three figures on page 6. Compare cube “a” in the three figures: how many sides of each “a” cube are actually exposed to the outside surface?

undefined

Cube “a”	Number of Sides Exposed
Figure 1. 3 x 3 x 3
Figure 2. 2 x 2 x 2
Figure 3. 1 x 1 x 1

undefined

Question 9. Referring the Question 8, if each cube “a” were an equal amount of living tissue, which one would lose heat to a cooler environment fastest?

undefined

undefined

undefined

Question 10. Referring to Question 8, if each cube “a” were an equal amount of living tissue, which one would need the fastest heat production to maintain homeostasis of its body temperature? (Remember, Cubus quadrangularis is a mammal.)

undefined

Question 11. As an animal grows larger, what do you expect to happen to its rate of heat production per gram of body mass?

undefined

undefined

undefined

Question 12. Based on the reasoning above, you will formulate a hypothesis for the following experiment. Small mice, medium-sized rats and large rats are available in the laboratory. We will measure their rate of oxygen uptake per gram body mass.

undefined

• What is the dependent variable we will measure?

undefined

• What is the independent variable?

undefined

• What are the groups being compared?

undefined

• Now, write the entire formula using the If…, and…, then… format.

undefined

Question 13. Which mammal do you expect to have the fastest oxygen uptake per gram body mass? Explain why.

undefined

undefined

Table 1. Metabolic rate measurements for 3 mammals

undefined

with different surface area to volume ratios.

undefined

Group 1		Mouse	Young Rat	Adult Rat
Body weight (g):		26.4	90.5	126.6
5 measurements of time required (in seconds) for animal to consume 5000 µL of Oxygen (O2):	1.	170	128	149
	2.	128	205	73
	3.	203	104	88
	4.	125	97	87
	5.	104	110	68
Average time (sec) to consume 5000 µL O2 :
Step 1: Divide 5000 µL O2 by the average number of secondsrequired by animal to consume it:
Step 2: Divide your answer, obtained in Step 1, by the animal’s body weight in grams. This will give you the metabolic rate in µL O2 per 1 second per 1 gram of animal.

undefined

undefined

Group 2		Mouse	Young Rat	Adult Rat
Body weight (g):		13.1	52.2	181.2
5 measurements of time required (in seconds) for animal to consume 5000 µL of Oxygen (O2):	1.	330	204	141
	2.	335	114	69
	3.	210	166	66
	4.	208	87	85
	5.	208	89	51
Average time (sec) to consume 5000 µL O2 :
Step 1: Divide 5000 µL O2 by the average number of secondsrequired by animal to consume it:
Step 2: Divide your answer, obtained in Step 1, by the animal’s body weight in grams. This will give you the metabolic rate in µL O2 per 1 second per 1 gram of animal.

undefined

undefined

Group 3		Mouse	Young Rat	Adult Rat
Body weight (g):		30	76.6	211.6
5 measurements of time required (in seconds) for animal to consume 5000 µL of Oxygen (O2):	1.	157	79	79
	2.	158	144	61
	3.	184	43	53
	4.	119	89	50
	5.	135	92	48
Average time (sec) to consume 5000 µL O2 :
Step 1: Divide 5000 µL O2 by the average number of secondsrequired by animal to consume it:
Step 2: Divide your answer, obtained in Step 1, by the animal’s body weight in grams. This will give you the metabolic rate in µL O2 per 1 second per 1 gram of animal.

undefined

undefined

Group 4		Mouse	Young Rat	Adult Rat
Body weight (g):		24.0	76.0	160.3
5 measurements of time required (in seconds) for animal to consume 5000 µL of Oxygen (O2):	1.	208.5	117.1	59.3
	2.	183.6	111.0	17.1
	3.	174.5	96	61.8
	4.	142.1	121.5	52.5
	5.	170.0	105.3	62.7
Average time (sec) to consume 5000 µL O2 :
Step 1: Divide 5000 µL O2 by the average number of secondsrequired by animal to consume it:
Step 2: Divide your answer, obtained in Step 1, by the animal’s body weight in grams. This will give you the metabolic rate in µL O2 per 1 second per 1 gram of animal.

undefined

undefined

undefined

undefined

Table 2. Metabolic rate for all groups.

undefined

undefined

undefined

	Mouse		Young Rat		Adult Rat
Group:	Mass (g)	Average Metabolic Rate	Mass (g)	Average Metabolic Rate	Mass (g)	Average Metabolic Rate
1
2
3
4
5	XXXX	XXXX	XXXX	XXXX	XXXX	XXXX
6	XXXX	XXXX	XXXX	XXXX	XXXX	XXXX
7	XXXX	XXXX	XXXX	XXXX	XXXX	XXXX
8	XXXX	XXXX	XXXX	XXXX	XXXX	XXXX
Average

undefined

undefined

undefined

• Analysis Questions

undefined

Fill in the Table 3 with the class average data:

undefined

undefined

undefined

Mammal type	Average Mass (g)	Average Metabolic Rate (µL O2 per second per gram of animal)
Mouse
Young Rat
Mature Rate

undefined

undefined

Question 14. Based on the class data, describe the relationship which appears to exist between a mammal’s size and its metabolic rate.

undefined

undefined

undefined

Question 15. Has your hypothesis been supported by the class data?

undefined

If not, where did your reasoning go wrong?

undefined

Question 16. Which would you predict to be higher, the metabolic rate of a sparrow or that of a gull? Explain your answer in terms of thermoregulation.

undefined

undefined

Question 17. To what extent do you think it would be valid to apply this “metabolic rate to body size relationship” to animals other than mammals (clams, insects, fish, frogs, reptiles and birds)? Explain.

undefined

Question 18. Is there a thermoregulatory advantage for marine mammals such as whales to be so large? Explain your answer.

undefined

Question 19. Suggest a reason why there are no rat-sized marine mammals.

undefined

Question 20. If an animal is an ectotherm, which is without internal physiological thermoregulation, how does it manage to survive when the weather is very hot or very cold? Give an example.