Deck 28: Temperature and Body Fluid Regulation

Question 1

Reptiles are said to be behavioral homeotherms. Explain what this means.

Answer 1

Homeotherms are animals which can maintain a constant body temperature by means of metabolic activity. Their body temperature is mostly more than its environment. Heterotherms on the other hand are animals that can change their body temperature according to the temperature of the surroundings.
Ectotherms are animals that are dependent on external sources or the environment for body heat. Most ectotherms are heterotherms, though there are some exceptions to this.
Reptiles are animals that are ectotherms. Thus they derive their heat from the environment which results in variation of their body temperatures according to the temperature of the external environment.
Though reptiles are ectothermic, most reptiles change position and location during the day to equalize loos and gain of heat. As a result they are able to maintain a homeothermic temperature by various behavioral adaptations. Some of these adaptations are found even in mammals. They include:
• Conserving body heat by routing blood through circulatory shunts to body's center- found in diving reptiles
• Producing more heat in response to hormones like thyroxine and epinephrine
• Salivating and frothing at the mouth to cool the body- found in land turtles
• Other methods of cooling include: urinating at the back legs, moistening the eyes and panting
Since the above mentioned behavioral adaptations help the reptiles to maintain a near constant body temperature (like homeotherms), reptiles are known as behavioral homeotherms.

Question 2

Which of the following represents heat loss from an animal's body due to the movement of air over the animal's body?

A) Conduction
B) Convection
C) Evaporation
D) Radiation
E) None of the above (a-d)

Answer 2

Heat is produced due to metabolism in animals. This heat is either gained from the environment or lost to the environment and thus helps determine the temperature of the body. There are four main ways by which heat is exchanged with the environment. They are: conduction; convection; evaporation and radiation.
Conduction occurs between areas of higher temperature to that of lower temperature. It is a process in which thermal motion (heat) between molecules is directly transferred to the body surface of the animal.
Thus option (a) is incorrect.
Evaporation is a process that leads to loss of heat from a surface as a result of escaping of water molecules in gaseous form. The best example of evaporation in animals is sweating in hot temperatures.
Hence option (c) is incorrect.
In radiation, heat is transferred even when the objects are not in direct contact. This is a process in which electromagnetic waves are emitted either from an object or from an animal's body.
Thus option (d) is incorrect.
When heat is lost or gained by the body due to movement of either air or liquid, then it is known as convection. If cool air passes over the body, then heat is lost and if hot air passes over the body then heat is gained.Thus correct option is (b)

Question 3

Every animal's physiological functions are linked to its body temperature because metabolism and enzyme functioning are temperature dependent. Ectotherms derive most of their body heat from the environment, whereas endotherms obtain heat from cellular processes. The evolutionary significance of the rete mirabile is that it acts as a heat generator and enables those fish that posses it to swim faster and capture more prey.
Based on what you have learned in this section, why are the terms "cold blooded" and "warm blooded" outmoded and inaccurate with respect to describing temperature regulation in animals?

Answer 3

The current distinction should be between the ability to generate metabolic heat in an animal in order to modulate body temperature or the lack of that ability. "Warm-blooded and "cold-blooded" are adjectives that describe the temperature of the blood and not how an animal modulates that temperature. Thus, ectotherms and endotherms are more current and descriptive from a physiological point of view.

Question 4

Why do very small birds and mammals go into a state of torpor at night?

Question 5

Most birds and mammals are called

A) ectotherms.
B) endotherms.
C) homeotherms.
D) heterotherms.
E) both b and c.

Question 6

Osmotic balance must be maintained in an animal so that tissues can carry out metabolic functions in a homeostatic state. Physiological mechanisms help most vertebrates keep blood osmolarity and various ion concentrations relatively constant (homeostasis). Marine invertebrates are osmoconformers in that their body fluids are isosmotic to their environment. Most vertebrates are osmoregulators in that their body fluids are either hyperosmotic or hypoosmotic compared to their environment.
During osmosis, does water move toward regions of higher or lower osmolarity ( see figure 2.10 )
Figure 2.10
Osmosis. ( a ) A selectively permeable membrane separates the beaker into two compartments. Initially, compartment 1 contains sugar and water molecules, and compartment 2 contains only water molecules. Due to molecular motion, water moves down the concentration gradient (from compartment 2 to compartment 1) by osmosis. The sugar molecules remain in compartment 1 because they are too large to pass across the membrane. ( b ) At osmotic equilibrium, the number of sugar molecules in compartment 1 does not increase, but the number of water molecules does.

Question 7

How does the countercurrent mechanism help regulate heat loss?

Question 8

Most amphibians have difficulty controlling body heat because they produce little of it metabolically and rapidly lose most of it from their body surfaces.

Question 9

Contractile vacuoles are found in protozoa; protonephridia are found in some flatworms; metanephridia are found in earthworms; antennal (green) glands are found in crayfish; Malpighian tubules are found in insects; and coxal glands are found in arachnids.
How are the functions of the Malpighian tubules and kidneys similar?

Question 10

In endotherms, what controls the balance between the amount of heat lost and the amount gained?

Question 11

The hormonal triggering of heat production is called

A) shivering thermogenesis.
B) gular flutter.
C) thermogenesis.
D) nonshivering thermogenesis.
E) hibernation.

Question 12

In the vertebrate kidney, the three key physiological processes used in osmoregulation and excretion are filtration, reabsorption, and secretion. Freshwater fishes must keep water out and retain electrolytes. Marine fishes must keep water in and excrete electrolytes. Water and certain solutes move out of the blood and into the tubular systems of the kidney by way of filtration (passive) and secretion (transported). The important solutes, ions, and water are then returned to the blood through reabsorption. The mammalian kidney is divided into a cortex and a medulla. Within each kidney are about a million nephron units-the functional units of the kidney. The parts of the nephron include the glomerulus and glomerular capsule, proximal tubule, loop of the nephron, distal tubule, and collecting duct.
Mammals and birds have nephrons with a loop of the nephron but reptiles do not. How would you explain this from an evolutionary point of view?

Question 13

If marooned on a desert isle, do not drink seawater; it is better to be thirsty. Why is this true?

Question 14

Which of the following is a function of the kidneys?

A) The kidneys remove harmful substances from the body.
B) The kidneys recapture water for use by the body.
C) The kidneys regulate the concentration of ions in the blood.
D) All of these (a-c) are functions of the kidney.

Question 15

Humans excrete their excess nitrogenous waste as

A) uric acid crystals.
B) molecules containing proteins.
C) ammonia.
D) urea.

Question 16

An osmoregulator would maintain its internal fluids at a concentration that is _________ relative to its specific surroundings (environment).

A) isosmotic
B) hyperosmotic
C) hypoosmotic
D) All of these (a-c).