Race to the Slopes #7

Certain reef-building corals contain photosynthetic, symbiotic algae that have the ability to make dimethylsulphoniopropionate (DMSP), a chemical involved in the marine sulfur cycle. DMSP is released into the surrounding water, where it is converted to the gas dimethyl sulfide (DMS) by microorganisms and enters the atmosphere. Once in the atmosphere, it triggers the formation of sulfate aerosols, which induce cloud formation and block sunlight from heating up the water. The symbiotic algae produce DMSP when they are stressed by a high water temperature. If water temperature is too high, corals will expel the symbiotic algae that produce DMSP. Researchers measured the amount of DMSP produced by juvenile and adult coral and their symbionts under normal and thermally stressed conditions. The data are shown in the graphs in Figure 1.

 

The researchers also measured the density of the symbiont as well as the photosynthetic yield in adult corals at the two temperatures. Photosynthetic yield is an index measure of energy output compared to sunlight energy input in which larger photosynthetic yield values represent photosynthetic organisms producing more energy.

Which of the following best describes the scientists’ findings concerning the density of symbionts presented in Figure 2 ?

• The symbiont density at 32 C° on day 5 was less than the density on day 0 of the experiment.

• The symbiont density at 27 C° on day 0 was less than the density on day 5 of the experiment.

• The symbiont density at 32 C° was different from the density at 27 C° on days 5 and 10 of the experiment.

• The symbiont density at 27 C° was higher than the density at 32 C° for the entire length of the experiment.

Answer explanation

The error bars for days 5 and 10 do not overlap between temperature treatments, indicating that they are statistically different.

Certain reef-building corals contain photosynthetic, symbiotic algae that have the ability to make dimethylsulphoniopropionate (DMSP), a chemical involved in the marine sulfur cycle. DMSP is released into the surrounding water, where it is converted to the gas dimethyl sulfide (DMS) by microorganisms and enters the atmosphere. Once in the atmosphere, it triggers the formation of sulfate aerosols, which induce cloud formation and block sunlight from heating up the water. The symbiotic algae produce DMSP when they are stressed by a high water temperature. If water temperature is too high, corals will expel the symbiotic algae that produce DMSP. Researchers measured the amount of DMSP produced by juvenile and adult coral and their symbionts under normal and thermally stressed conditions.

 

The researchers also measured the density of the symbiont as well as the photosynthetic yield in adult corals at the two temperatures. Photosynthetic yield is an index measure of energy output compared to sunlight energy input in which larger photosynthetic yield values represent photosynthetic organisms producing more energy.

Which of the following best describes the production of DMSP by coral and coral symbionts?

• A negative feedback mechanism that increases the environmental change

• A negative feedback mechanism that reverses the environmental change

• A positive feedback mechanism that increases the environmental change

• A positive feedback mechanism that reverses the environmental change

Answer explanation

This is a negative feedback mechanism in which DMSP is produced to prevent, not encourage, further environmental change as a result of increasing water temperatures.

Certain reef-building corals contain photosynthetic, symbiotic algae that have the ability to make dimethylsulphoniopropionate (DMSP), a chemical involved in the marine sulfur cycle. DMSP is released into the surrounding water, where it is converted to the gas dimethyl sulfide (DMS) by microorganisms and enters the atmosphere. Once in the atmosphere, it triggers the formation of sulfate aerosols, which induce cloud formation and block sunlight from heating up the water. The symbiotic algae produce DMSP when they are stressed by a high water temperature. If water temperature is too high, corals will expel the symbiotic algae that produce DMSP. Researchers measured the amount of DMSP produced by juvenile and adult coral and their symbionts under normal and thermally stressed conditions. The data are shown in the graphs in Figure 1.

 

The researchers also measured the density of the symbiont as well as the photosynthetic yield in adult corals at the two temperatures. Photosynthetic yield is an index measure of energy output compared to sunlight energy input in which larger photosynthetic yield values represent photosynthetic organisms producing more energy.

Which of the following best describes the difference between the total amount of DMSP produced by adults compared to juveniles at the start of the 32 C° trial?

• Adult corals produced 3 times more DMSP than juveniles produced.

• Adult corals produced 3 times less DMSP than juveniles produced

• Adult corals produced 5 times more DMSP than juveniles produced.

• Adult corals produced 5 times less DMSP than juveniles produced.

Answer explanation

The DMSP produced by adult corals at 32°C was approximately 14 nmol/mm2 , and the DMSP produced by juveniles was approximately 3 nmol/mm2 .

Certain reef-building corals contain photosynthetic, symbiotic algae that have the ability to make dimethylsulphoniopropionate (DMSP), a chemical involved in the marine sulfur cycle. DMSP is released into the surrounding water, where it is converted to the gas dimethyl sulfide (DMS) by microorganisms and enters the atmosphere. Once in the atmosphere, it triggers the formation of sulfate aerosols, which induce cloud formation and block sunlight from heating up the water. The symbiotic algae produce DMSP when they are stressed by a high water temperature. If water temperature is too high, corals will expel the symbiotic algae that produce DMSP. Researchers measured the amount of DMSP produced by juvenile and adult coral and their symbionts under normal and thermally stressed conditions. The data are shown in the graphs in Figure 1.

 

The researchers also measured the density of the symbiont as well as the photosynthetic yield in adult corals at the two temperatures. Photosynthetic yield is an index measure of energy output compared to sunlight energy input in which larger photosynthetic yield values represent photosynthetic organisms producing more energy.

Which of the following best describes the effect of temperature on corals’ ability to produce DMSP as shown in Figure 1 ?

• Both juvenile and adult corals produce less DMSP at 27 C° than at 32 C° .

• Both juvenile and adult corals produce less DMSP at 32 C° than at 27 C°

• The amount of DMSP produced over time increases at 32 C° in juveniles only.

• The amount of DMSP produced over time increases at 32 C° in adults only.

Answer explanation

The graphs show that both age groups of corals produce less DMSP at 27°C than they do at 32°C.

Certain reef-building corals contain photosynthetic, symbiotic algae that have the ability to make dimethylsulphoniopropionate (DMSP), a chemical involved in the marine sulfur cycle. DMSP is released into the surrounding water, where it is converted to the gas dimethyl sulfide (DMS) by microorganisms and enters the atmosphere. Once in the atmosphere, it triggers the formation of sulfate aerosols, which induce cloud formation and block sunlight from heating up the water. The symbiotic algae produce DMSP when they are stressed by a high water temperature. If water temperature is too high, corals will expel the symbiotic algae that produce DMSP. Researchers measured the amount of DMSP produced by juvenile and adult coral and their symbionts under normal and thermally stressed conditions.

The researchers also measured the density of the symbiont as well as the photosynthetic yield in adult corals at the two temperatures. Photosynthetic yield is an index measure of energy output compared to sunlight energy input in which larger photosynthetic yield values represent photosynthetic organisms producing more energy.

In addition to the effect of temperature on DMSP produced by corals and their symbionts, which of the following relationships is also being considered in this experiment?

• Effect of varying light levels and coral species

• Effect of additional DMSP produced by symbionts and the corals’ age

• Effect of age and varying light levels

• Effect of coral species and additional DMSP produced by symbionts

Answer explanation

This experiment is also measuring the difference between the amount of DMSP produced by corals versus algae and corals together. It is also looking at the difference in DMSP produced by different-aged corals

Certain reef-building corals contain photosynthetic, symbiotic algae that have the ability to make dimethylsulphoniopropionate (DMSP), a chemical involved in the marine sulfur cycle. DMSP is released into the surrounding water, where it is converted to the gas dimethyl sulfide (DMS) by microorganisms and enters the atmosphere. Once in the atmosphere, it triggers the formation of sulfate aerosols, which induce cloud formation and block sunlight from heating up the water. The symbiotic algae produce DMSP when they are stressed by a high water temperature. If water temperature is too high, corals will expel the symbiotic algae that produce DMSP. Researchers measured the amount of DMSP produced by juvenile and adult coral and their symbionts under normal and thermally stressed conditions. The data are shown in the graphs in Figure 1.

 

The researchers also measured the density of the symbiont as well as the photosynthetic yield in adult corals at the two temperatures. Photosynthetic yield is an index measure of energy output compared to sunlight energy input in which larger photosynthetic yield values represent photosynthetic organisms producing more energy.

Which of the following best explains the result of adult corals being exposed to elevated temperatures for extended periods?

• They are able to obtain more energy from their symbionts because the algae are receiving more light.

• They are able to obtain more energy from their symbionts because the efficiency increases slightly over time.

• They are able to obtain less energy from their symbionts because the algae have been expelled.

• They are able to obtain less energy from their symbionts because more DMSP is being produced at lower temperatures.

Answer explanation

The corals and algae have less photosynthetic ability at higher temperatures because the algae density has been reduced.

A researcher measured the temperature at which two different samples of double-stranded DNA denature (separate into single strands). Sample 1 denatured at a significantly lower temperature than sample 2 did. Based on the data, the researcher claims that the DNA in sample 2 is composed of a higher percentage of guanine and cytosine than the DNA in sample 1 is. Which of the following best supports the researcher’s claim?

• The bonds between guanine and cytosine are covalent bonds, which require more energy to disrupt than those between adenine and thymine.

• Guanine-cytosine pairs denature at a higher temperature because they have more hydrogen bonds between them than adenine-thymine pairs do.

• Adenine-thymine pairs require less energy to separate because adenine and thymine are both single-ring bases.

• Guanine-cytosine pairs require more energy to separate because one is a purine and one is a pyrimidine.

Answer explanation

Three hydrogen bonds form between guanine and cytosine, while only two hydrogen bonds form between adenine and thymine.

Which of the following best estimates the population size of the sea lions in 2000 based on the data shown in Figure 1 ?

• 100,000

• 125,000

• 175,000

• 285,000

Answer explanation

The data indicate that the population in 2000 was almost 175,000.

The amino acid in Figure 1 is found in a region of a polypeptide that folds away from water. Which part of the amino acid most likely contributes to the hydrophobic behavior of this region of the polypeptide?

• Amine (NH2) group

• Carboxyl (COOH) group

• Methyl (CH3) group

• Hydrogen (H) atom

Answer explanation

The methyl group is one of the functional groups that differentiate the twenty amino acids found in proteins. Since the methyl group is nonpolar, it is likely to make this region of the polypeptide more hydrophobic.