26) You have a cube of modeling clay in your hands. Which of the following changes to the
shape of this cube of clay will decrease its surface area relative to its volume?
A) Pinch the edges of the cube into small folds.
B) Flatten the cube into a pancake shape.
C) Round the clay up into a sphere.
D) Stretch the cube into a long, shoebox shape.
27) If an organism was discovered that had no epithelial tissues, it would require adaptations to
maintain homeostasis in which of the following areas? The organism would require adaptations
_____.
A) in its skeleton for structure
B) in its nervous system for sensing external stimuli
C) that would prevent water loss from the body in a terrestrial environment
D) in its muscular system for movement
The crucian carp (Carassius carassius) is a Northern European freshwater fish often inhabiting
ponds that become hypoxic (have reduced oxygen levels) and even anoxic (have no oxygen)
when the surface freezes during the winter. Surprisingly, when oxygen levels are normal, these
fish lack the lamellae that provide a large surface area for gas exchange between water and
blood: their gills are smooth. Yet when the level of oxygen in the water falls, the gill morphology
undergoes a change: packing cells stop dividing and programmed cell death is induced, exposing
gill lamellae that were buried in other tissue. With lamellae exposed, the gills have increased
surface area for gas exchange. These changes in gill lamellar profile are reversible: investigators
observed that the gills return to their normal structure within seven days after returning the fish
to well-oxygenated water. (Jørund Sollid, Paula De Angelis, Kristian Gundersen, and Göran E.
Nilsson. 2003. Hypoxia induces adaptive and reversible gross morphological changes in crucian
carp gills. Journal of Experimental Biology 206:3667-73.)
28) Refer to the paragraph on crucian carp. Gills serve multiple functions in fish in addition to
gas exchange. Given the large surface area of gills with lamellae, what is the most likely
explanation for why crucian carp cover protruding lamellae in their gills when levels of oxygen
are normal?
A) to prevent loss of heat to the surrounding water
B) to prevent loss of ions to the surrounding water
C) to prevent protein loss to the surrounding water
D) to prevent loss of oxygen to the surrounding water