Question
Coyotes are a predator of skunks. Coyote urine has a strong scent and is marketed as a skunk repellant. Which type of signal is coyote urine?
(A) audible
(B) chemical
(C) tactile
(D) visual
▶️Answer/Explanation
Ans:
(B) Scent is a chemical signal. Choices (A), (C), and (D) are incorrect
because audible, tactile, and visual signals depend on sound, touch, and
sight, respectively.
Question
Which of the following is an example of a physiological response to a stimulus?
(A) A female bird moves toward a male bird that is singing an appropriate mating song.
(B) A predator avoids a brightly colored frog in the rain forest.
(C) A bear slows its metabolism in response to shortened day lengths and cooler temperatures.
(D) A primate grooms its offspring.
▶️Answer/Explanation
Ans:
(C) Adjusting metabolism in response to changing environmental
conditions is a physiological response to a stimulus. Choices (A), (B),
and (D) are examples of behaviors or behavioral responses.
Question
Which of the following is true regarding the body temperature regulation in most endotherms (birds and mammals)?
(A) Body temperature is very tightly regulated at 37°C (98.6°F).
(B) Body temperature is constant over the entire body of organism throughout the day.
(C) Body temperature is regulated by the absorption of heat by the skin, sweat glands, respiratory surfaces, and muscles.
(D) The core of the body maintains the highest temperature, while losses of body heat at the surface are adjusted to maintain temperature.
▶️Answer/Explanation
Ans: D
The core temperature is the temperature of the central nervous
system and vital organs of the organism. The temperature of the core is
kept fairly constant, but body temperature is maintained within a range. In humans, for example, the lowest body temperatures are observed during sleep and upon waking and the highest after a meal or exercise. In
endotherms, metabolism is the source of heat that continuously
radiates from the highest to lowest temperatures, typically from the
core to the surface and then lost at the surface.
Body temperature is regulated by the hypothalamus, but the effectors (the
skin, sweat glands, respiratory surfaces, and muscles) can be used to
regulate heat losses and heat production. Humans, primates, and horses (to
a limited extent) can sweat to dissipate (not absorb!) heat. Respiratory
surfaces are used by most mammals to dissipate heat through panting
(increases the rate of evaporative cooling from the lungs). Muscles increase
body temperature through shivering (or just contracting).
Question
A mouse and a frog of equal mass are transferred from a container kept at room temperature and placed at 5°C for 30 minutes. Which of
the following outcomes is expected?
(A) Both organisms would have increased respiratory rates.
(B) The frog but not the mouse would have a significantly increased respiratory rate.
(C) The frog but not the mouse would have a significantly decreased respiratory rate.
(D) Both organisms would have a decreased respiratory rate.
▶️Answer/Explanation
Ans: C
Mice are endotherms (mammals), while frogs are ectotherms
(amphibians). Endotherms maintain their body temperature within a narrow
range despite environmental temperatures (within limits, of course) using
the heat generated by metabolism. Ectotherms maintain their body
temperature, too, but within a much wider range. Importantly, they
don’t use metabolism to generate heat. Instead, they absorb heat from
the environment (and lose it to the environment) to regulate their
temperature.
The metabolic rate of an ectotherm is a function of its body
temperature. A frog with a higher body temperature will have a higher
metabolic rate. It will use more energy and therefore require more oxygen.
A frog with a lower body temperature will have a slower metabolic rate, use
less energy, and require less oxygen. Endotherm metabolic rate is not
dependent on temperature. If anything, lower temperatures would slightly
increase metabolic rate due to shivering (which uses energy). (Question 198
is similar.)
Question
Which of the following correctly compares the energy requirements of a rat and a snake of equal body mass living at room temperature?
(A) The rat and the snake have the same energy (caloric) requirements because they are the same mass and at the same temperature.
(B) The snake would require more energy because it is a carnivore.
(C) The snake would require more energy because it has no fur and little to no subcutaneous (under the skin) fat.
(D) The rat would require more energy because it is a mammal.
▶️Answer/Explanation
Ans: D
The rat is a mammal and therefore an endotherm. Endotherms
require more energy per kilogram of body mass because they use
metabolic energy to maintain their body temperature.
Question
Refer to the following graph of flower temperature versus environmental temperature for three different plants.
Which of the following statements most accurately explains the data above?
(A) Nelumbo regulates its flower temperature to equal the environmental temperature.
(B) In all plants studied, flower temperature is higher than environmental temperature for all temperatures measured.
(C) Philodendron maintains a temperature above the environmental temperature for all temperatures measured.
(D) Symplocarpus maintains a temperature slightly below environmental temperatures for all temperatures measured.
▶️Answer/Explanation
Ans: C
Lines that lie to the upper left of the line of equal temperature
represent flowers that maintain a higher flower temperature than the
environment. Nelumbo maintains a temperature above, at (the points that
intersect the line of equal temperature) or below (the points on the line that
lie to the right of the line of equal temperature). Both Symplocarpus and
Philodendron maintain elevated floral temperatures at all temperatures
measured. See the following figure.
Question
Which of the following is the most convincing evidence that a particular plant regulates its flower temperature?
(A) The number of mitochondria increase in response to lower temperatures.
(B) The rate of photosynthesis decreases in response to lower temperatures.
(C) The flower temperature directly correlates to the environmental temperature.
(D) The plant maintains a relatively constant flower temperature despite fluctuations in ambient temperature.
▶️Answer/Explanation
Ans: D
One of the characteristics of a regulated physiological variable
is that it remains fairly constant despite external perturbations. The
most convincing evidence that a plant regulates its temperature is that it can
maintain a temperature different from the environment in which it lives.
Choice A suggests that temperature regulation may occur as the
mitochondria are capable of generating metabolic heat, but it is not
convincing evidence. Choice C is incorrect because it indicates the exact
opposite of regulation: If a plant’s temperature directly correlates to the
environmental temperature, the plant is conforming to the environment.