Ap bio chapter 40 concept checks

What properties do all types of epithelia share?

All types of epithelia consist of cells that line a surface, are tightly packed, are situated on top of a basal lamina, and form an active and protective interface with the external environment.

At which sites must oxygen cross a plasma membrane in traveling from the external environment to the cytoplasm of a body cell?

An oxygen molecule must cross and plasma membrane when entering the body at an exchange surface in the respiratory system, in both entering and exiting the circulatory system.

Like animals, cyanobacteria have a circadian rhythm. By analyzing the genes that maintain biological clocks, scientists concluded that the 24 hour rhythms of humans and cyanobacteria reflect convergent evolution. What evidence would have supported this conclusion? Explain.

In convergent evolution, the same biological trait arises independently in two or more species. Gene analysis can provide evidence for an independent origin. If the genes for the trait in one species lack significant sequence similarity to the corresponding genes in another species, scientists conclude that there is a separate genetic basis for the trait in the two species and thus an independent origin. In the case of circadian rhythms, the clock genes in cyanobacteria appear unrelated to those in humans.

Suppose the animals at a zoo were resting comfortably an remained at rest while the nighttime air temperature dropped. If the temperature change were sufficient to cause a change in metabolic rate, what changes would you expect for an alligator and a lion?

The alligator's body temperature would decrease along with the air temperature. Its metabolic rate would therefore also decrease as chemical reactions slowed. In contrast, the lion's body temperature would not change. Its metabolic rate would increase as it shivered and produced heat to keep its body temperature constant.

Which animal must eat a larger proportion of its weight in food each day: a house cat or an African lion caged in a zoo? Explain.

The house cat; smaller animals have a higher metabolic rate per unit if body mass and a greater demand for food per unit body mass.

Flowers differ in how much sunlight they absorb. Why might this matter to a hummingbird seeking nectar on a cool morning?

The hummingbird, being a very small endotherm, has a very high metabolic rate. If by absorbing sunlight certain flowers warm their nectar, a hummingbird feeding on these flowers is saved the metabolic expense of warming the nectar to its body temperature.

If a mouse and a small lizard of the same mass (both at rest) were placed in experimental chambers under identical environmental conditions, which animal would consume oxygen at a higher rate? Explain.

The mouse would consume oxygen at a higher rate because it is an endotherm, so its basal metabolic rate is higher than the ectothermkc lizard's standard metabolic rate.

Why might you expect that a fight or flight response requires both the nervous and endocrine system?

The nervous system perceives the danger and provokes a split second muscular response to keep from falling. The nervous system then triggers the release of a hormone (adrenaline) by the endocrine system.

How does negative feedback in thermoregulation differ from feedback inhibition in an enzyme-catalyzed biosynthetic process?

The product of the pathway (a change in temperature) decreases pathway activity by reducing the stimulus. In an enzyme catalyzed biosynthetic process, the product of the pathway inhibits the pathway that generated it.

Why is shivering likely during the onset of a fever?

To raise body temperature to the higher range of fever, the hypothalamus triggers heat generation by muscular contractions, or shivering. The person with the fever may in fact say that they feel cold, even though their body temperature is above normal.

What mode of heat exchange is involved in "wind chill," when moving air feels colder than still air at the same temperature? Explain.

Wind chill involved heat loss through convection, as the moving air contributes to heat loss from the skin surface.

If you were deciding where to put the thermostat in a house, what factors would govern your decision? How do these factors relate to the fact that many homeostatic control sensors in humans are located in the brain?

You would put it close to where you would spend the most time, where it would be protected from environmental perturbations, such as direct sunshine, and not right in the path of the output of the heating system. The sensors for homeostasis in the brain are separated from environmental influences and can monitor conditions in a vital and sensitive tissue.