AP Biology Free Response Questions

a. The nervous system plays a role in coordinating the observed activity pattern of the mice in response to light-dark stimuli. Describe ONE role of each of the following anatomical structures in responding to light-dark stimuli.

Photoreceptors detect light/dark stimulus and initiates/transmits signal. The brain integrates/processes/coordinates information. The motor neutron transmits signals from brain to an effector, which is basically a muscle, gland, or organ capable of responding to a stimulus, especially a nerve impulse.

c. The researchers claim that the genetically controlled circadian rhythm in the mice does not follow a 24-hour cycle. Describe ONE difference between the daily pattern of activity under L12:D12 conditions and under DD conditions, and use the data to support the researchers' claim.

As compared to the actogram that logs an active period only during L12:D12, it seems that with this actogram that records activity during DD conditions, the active period of the mice begins a little earlier this day. Now if it were a 24 hour circadian rhythm (basically a sleep/wake cycle), the pattern of activity in DD would be the same as the pattern of activity in L12:D12.

Variables in SP = -iCRT (continued)

Concentration - An increased concentration decreases water potential / increases water movement, OR a decreased concentration increases water potential / decreases water movement.

e. In nature, mice are potential prey for some predatory birds that hunt during the day. Describe TWO features of a model that represents how the predator-prey relationship between the birds and the mice may have resulted in the evolution of the observed activity pattern of the mice.

If birds hunted during the day, the mouse will be more susceptible to predation if it is active during the day. If the mouse is eaten by being active during the day, then it will less likely produce offspring. Therefore, mice that are active at night are selected to have a lesser chance of being hunted, and a higher chance of reproduction.

c. Identify the symbiotic relationship that exists between the cuckoo and the warbler in the presence of predators.

If predation starts to become a problem in the cuckoo and warbler birds' environment, then the two birds both share a mutualistic relationship (both organisms benefit).

Variables in SP = -iCRT

Ionization constant - An increased ionization constant decreases water potential / increases water movement, OR a decreased ionization constant increases water potential / decreases water movement.

d. To investigate the claim that exposure to light overrides the genetically controlled circadian rhythm, the researchers plan to repeat the experiment with mutant mice lacking a gene that controls the circadian rhythm. Predict the observed activity pattern of the mutant mice under L12:D12 conditions and under DD conditions that would support the claim that light overrides the genetically controlled circadian rhythm.

Mutant under L12:D12 conditions: Normal rhythm/rhythm similar to wild-type mouse under L12:D12. Mutant under DD: Random activity throughout the 24 hour period could likely be anticipated. It is also likely probable that an unpredictable pattern/rhythm could occur, as well as intermittent periods of activity/inactivity.

Identify and explain THREE different structural or physiological adaptations that could account for the different transpiration rates of species A and B.

Possible adaptation: Cuticle - Having a thicker cuticle decreases transpiration. Possible adaptation: Root size or structure - Root size or structure affects rates of water absorption, amount of water loss. Possible adaptation: Stomata size - Having an increased number of stomata results in increased transpiration.

Variables in SP = -iCRT (continued)

Pressure - No change in water potential / movement.

c. Water potential is described by the following formulas: WP = SP + PP SP = -iCRT Discuss the variables in both formulas and explain how they affect water potential. Variables in WP = SP + PP

Pressure potential - Water will move from the area of high pressure to low pressure. Solute potential - Water will move from the area of high solute potential (low solute concentration) to the area of lower solute potential (higher solute concentration).

Summarize the difference between the rates.

Species A is losing water or transpiring faster than species B.

a. Under controlled conditions, a transpiration experiment was conducted using two plant species. The data collected are shown in the figure below. Using the data from the experiment, calculate the rate of transpiration for species A and species B between the times of 5 and 15 minutes (show work). Summarize the difference between the two transpiration rates.

Species A: 3.6 mL H20 - 1.2 mL H20 / 15 min - 5 min = 0.24 mL H20 / 100g /min OR 3.6-12 / 15-5 = 0.24 mL H20 / 100g / min OR equivalent

a. (continued)

Species B: 1.8 mL H20 - 0.4 mL H20 / 15 min - 5 min = 0.14 mL H20 / 100g / min OR 1.8-0.4 / 15 - 5 = 0.14 mL H20 / 100g / min OR equivalent

Variables in SP = iCRT (continued)

Temperature - An increased temperature decreases water potential / increases water movement, OR decrease in temperature increases water potential / decreases water movement. Finding solute potential, also known as osmotic potential, allows the movement of water to be predicted or calculated.

a. Describe the symbiotic relationship that exists between the cuckoo and warbler in an environment without predators.

The cuckoo birds and the warbler birds share a parasitic relationship if there is an absence of predation in their environment (the cuckoos are parasitic of the warblers). This is because the offspring of the cuckoos reap the benefits of parental care of warbler birds, where as offspring of the warblers, on the other hand, are negatively affected by the relationship. Offspring of the warblers suffer a small extent of neglection from its own parents, as well as receiving less food.

b. Based on an analysis of the data in Figure 2, describe the activity pattern of the mice during the light and dark periods of the L12:D12 cycle.

The mice are active during the dark phase AND inactive during the light phase. The mice are active ONLY during the dark period. The mice are inactive ONLY during the light period.