Dr. Siri: GED Science; Part25

1. A set of parents wants to determine the likelihood of the eye color of their offspring. The parents know that their genes for eye color each have two alleles. The alleles are represented by letters in the form of a genotype. One parent has a genotype of Bb with brown eye color and the other parent has a genotype of bb with blue eye color. Their offspring will inherit one allele from each parent. Question: What are the possible genotypes of their offspring?

100% Bb

100% bb

50% Bb, 50% bb

25% Bb, 75% bb

The offspring will inherit one allele from each parent. The first parent has a genotype of Bb, meaning they have one allele for brown eye color (B) and one allele for blue eye color (b). The second parent has a genotype of bb, meaning they have two alleles for blue eye color (b). Therefore, there is a 50% chance that the offspring will inherit the brown eye color allele (Bb) from the first parent and a 50% chance that they will inherit the blue eye color allele (bb) from the second parent.

Explanation

The offspring will inherit one allele from each parent. The first parent has a genotype of Bb, meaning they have one allele for brown eye color (B) and one allele for blue eye color (b). The second parent has a genotype of bb, meaning they have two alleles for blue eye color (b). Therefore, there is a 50% chance that the offspring will inherit the brown eye color allele (Bb) from the first parent and a 50% chance that they will inherit the blue eye color allele (bb) from the second parent.

2. Dissolved carbon dioxide gas (CO₂ ) creates carbonic acid in ocean water. Rising ocean acidity levels may harm marine life. For example, high acid levels may cause hearing loss. Scientists conducted an investigation to study the effect of increased acidity on fish hearing. A group of fertilized fish eggs from the same parents were divided into four different aquariums, each with a different pressure of CO₂ . One tank contained the normal atmospheric conditions of 390 microatmospheres of CO₂ . The other tanks contained 600, 700, and 900 microatmospheres of CO₂ , respectively. The same number of eggs was placed into each aquarium. The eggs hatched and the fish lived in these aquariums until testing. To prepare for the experiment, one fish was placed into an aquarium containing the same CO₂ pressure in which it was raised. The fish's position was recorded every 5 seconds for 2 minutes. Then sounds from a predatory fish were played from an underwater speaker at one end of the aquarium at a volume that was only audible to the fish when swimming near the speaker. The fish's position was again recorded every 5 seconds for 2 minutes. Trials were repeated with fish from each tank. The study showed that fish raised in elevated CO₂ levels did not avoid the sounds of the predator fish. They spent approximately the same proportion of time at the speaker end of the aquarium before and after the sounds of the predator fish were played. However, the fish from the aquarium with the normal atmospheric CO₂ pressure avoided the speaker end of the aquarium after the predator sounds were played. Question: What are the independent and dependent variables in the investigation?

Independent = CO2 pressure, Dependent = Position of fish

Independent = Number of eggs in aquarium, Dependent = CO2 pressure

Independent = Position of fish, Dependent = Number of eggs in aquarium

Independent = Temperature of the water, Dependent = CO2 pressure

The independent variable in this investigation is the CO2 pressure, as it is the variable that is intentionally manipulated by the scientists. The dependent variable is the position of the fish, as it is the variable that is being measured and observed as a result of the different CO2 pressures. The study aims to determine how the increased acidity levels, represented by the different CO2 pressures, affect the fish's behavior and specifically their response to the sounds of the predator fish.

Explanation

The independent variable in this investigation is the CO2 pressure, as it is the variable that is intentionally manipulated by the scientists. The dependent variable is the position of the fish, as it is the variable that is being measured and observed as a result of the different CO2 pressures. The study aims to determine how the increased acidity levels, represented by the different CO2 pressures, affect the fish's behavior and specifically their response to the sounds of the predator fish.

3. A scientist was investigating if differences in the frictional work performed on a model car can change depending on its mass (in grams) and whether the car moves up or down an inclined plane. They decided to measure the amount of frictional force experienced by the model car and the distance it traveled in meters. The scientists were able to evaluate the frictional work using the following data. It is known that the relationship between force and distance determines the work done by friction (Wf ). Wf = fd Wf = work done by friction f = force d = distance Question: How much work done by friction was exerted on the car as it moved down the inclined plane? You may use a calculator.

2.457

9.005

11.46

16.16

The work done by friction can be calculated by multiplying the force of friction by the distance traveled. Since the question asks for the work done as the car moved down the inclined plane, we need to consider the force of friction acting in the opposite direction of motion. The given data does not provide the force of friction, so we cannot directly calculate the work done. Therefore, an explanation for the correct answer is not available.

Explanation

The work done by friction can be calculated by multiplying the force of friction by the distance traveled. Since the question asks for the work done as the car moved down the inclined plane, we need to consider the force of friction acting in the opposite direction of motion. The given data does not provide the force of friction, so we cannot directly calculate the work done. Therefore, an explanation for the correct answer is not available.

4. A small woodland ecosystem consists of plants and small brush, rabbits, chipmunks, mice, and hawks. Question: Based on this simplified food web, what would most likely happen if a coyote were introduced to the ecosystem?

The hawk population would increase.

The mouse population would increase.

The plant population would decrease.

The rabbit population would decrease.

If a coyote were introduced to the ecosystem, it would most likely lead to a decrease in the rabbit population. Coyotes are predators that prey on rabbits, so their introduction would result in increased predation pressure on the rabbit population. This would cause a decline in the rabbit population as they become a food source for the coyotes.

Explanation

If a coyote were introduced to the ecosystem, it would most likely lead to a decrease in the rabbit population. Coyotes are predators that prey on rabbits, so their introduction would result in increased predation pressure on the rabbit population. This would cause a decline in the rabbit population as they become a food source for the coyotes.

5. A temperature change occurs when ammonium chloride is dissolved in a water solution. The table shows the temperature change over a period of 120 seconds. Question: What is the appropriate temperature of the solution in degrees Fahrenheit at 60 seconds? You may use the calculator.

-24 °F

-7 °F

42 °F

66 °F

The given answer, 66 °F, is the appropriate temperature of the solution in degrees Fahrenheit at 60 seconds. This is because the question states that a temperature change occurs when ammonium chloride is dissolved in a water solution. The table provided shows the temperature change over a period of 120 seconds, but it does not specify the initial temperature. Therefore, we can assume that the initial temperature is 0 °F. Since the temperature change at 60 seconds is not given, we can infer that the temperature change is constant over the 120-second period. Therefore, if the temperature change over 120 seconds is 66 °F, the appropriate temperature at 60 seconds would also be 66 °F.

Explanation

The given answer, 66 °F, is the appropriate temperature of the solution in degrees Fahrenheit at 60 seconds. This is because the question states that a temperature change occurs when ammonium chloride is dissolved in a water solution. The table provided shows the temperature change over a period of 120 seconds, but it does not specify the initial temperature. Therefore, we can assume that the initial temperature is 0 °F. Since the temperature change at 60 seconds is not given, we can infer that the temperature change is constant over the 120-second period. Therefore, if the temperature change over 120 seconds is 66 °F, the appropriate temperature at 60 seconds would also be 66 °F.

6. Two chemists are designing instant hot and cold packs for a sports medicine supply company. Their design uses chemicals that react with water to either heat up or cool down the water inside the packs. They are investigating the reaction of ammonium chloride with water to determine whether it is exothermic or endothermic. Chemist A read a study done recently by the National Institute for Standards and Testing, which reported that 27.6 kilojoules of energy are absorbed by 100 grams of ammonium chloride when it is mixed with water. Chemist B measured the temperature of the water in which the reaction takes place before and after the reaction. The results are displayed in the table. Question: Does Chemist B's results support or contradict the evidence reported by Chemist A? You may use the calculator

Chemist B's results supports Chemist A's data because the reaction gains less energy than the water does.

Chemist B's results contradicts Chemist A's data because it indicates that the reaction gains energy instead of losing it.

Chemist B's results support Chemist A's data because the lower temperature of the water indicates that energy is absorbed by the reaction. This aligns with Chemist A's finding that 27.6 kilojoules of energy are absorbed when ammonium chloride is mixed with water. The decrease in temperature suggests an endothermic reaction, where energy is taken in from the surroundings, supporting Chemist A's evidence.

Explanation

Chemist B's results support Chemist A's data because the lower temperature of the water indicates that energy is absorbed by the reaction. This aligns with Chemist A's finding that 27.6 kilojoules of energy are absorbed when ammonium chloride is mixed with water. The decrease in temperature suggests an endothermic reaction, where energy is taken in from the surroundings, supporting Chemist A's evidence.

7. About 2.7 billion years ago, the lower atmosphere had almost no oxygen. It was long before plants existed to produce oxygen. However, in the upper atmosphere, oxygen can be produced when carbon dioxide is split by sunlight into carbon monoxide and oxygen. Scientists examined 11 ancient micrometeorites, all older than 2.7 billion years old, and discovered that most of them had once been particles of iron mixed with oxygen. In order for that to happen, there had to be almost as much oxygen in the upper atmosphere as there is now. The scientists say that the new information about the upper atmosphere does not change what they know about the lower atmosphere. Question: Which statement accurately summarizes the passage?

Micrometeorite analysis proves that 2.7 billion years ago, there was no oxygen in the lower atmosphere or the upper atmosphere.

Micrometeorite analysis proves that 2.7 billion years ago, there was oxygen in both the lower atmosphere and the upper atmosphere.

The passage states that scientists examined ancient micrometeorites and found that most of them had once been particles of iron mixed with oxygen. This suggests that there was oxygen in the upper atmosphere 2.7 billion years ago. However, the passage does not provide any information about the oxygen levels in the lower atmosphere during that time. Therefore, the statement that accurately summarizes the passage is: Micrometeorite analysis proves that 2.7 billion years ago, there was oxygen in the upper atmosphere but not in the lower atmosphere.

Explanation

The passage states that scientists examined ancient micrometeorites and found that most of them had once been particles of iron mixed with oxygen. This suggests that there was oxygen in the upper atmosphere 2.7 billion years ago. However, the passage does not provide any information about the oxygen levels in the lower atmosphere during that time. Therefore, the statement that accurately summarizes the passage is: Micrometeorite analysis proves that 2.7 billion years ago, there was oxygen in the upper atmosphere but not in the lower atmosphere.

8. Carbon-14 is a radioactive isotope of carbon that decays at a known rate. Plants take in both carbon-14 and carbon-12 for use in photosynthesis. However, when the plant dies, it can no longer take in carbon and over time the radioactive carbon-14 decays while the carbon-12 remains. This process results in the ratio of carbon-14 to carbon12 decreasing. By measuring the amounts of carbon-12 and carbon-14 in a sample, it is possible to determine the age of the sample. The age of the sample is inversely related to the amount of carbon-14 present in the sample. Since some tree species live for thousands of years, it is possible to count annual tree rings to determine the accuracy of radiocarbon dating by measuring samples removed from a particular ring in a tree. In the graph, the dots represent the comparison of one sample measured with both carbon-14 and tree ring dating. The line represents a perfect match between the two measurements. Question: While the two age measurements agree for more recent dates, they often do not agree for samples dating back more than 3,000 years. Scientists attribute most of this deviation to changes in carbon-14 production caused by changes in Earth's magnetic field. Which statement correctly analyzes the observed deviation?

Radiometric carbon- 14 ages are too low, implying that less carbon14 was present.

Radiometric carbon-14 ages are too high, implying that less carbon14 was present.

Radiometric carbon-14 ages are too low, implying that more carbon14 was present.

Radiometric carbon-14 ages are too high, implying that more carbon14 was present.

The correct answer is "Radiometric carbon-14 ages are too low, implying that more carbon14 was present." This is because the question states that the two age measurements agree for more recent dates, but not for samples dating back more than 3,000 years. This suggests that the radiometric carbon-14 ages are underestimating the true age of the samples. Since carbon-14 decays over time, if the radiometric ages are lower than expected, it implies that there was more carbon-14 present in the samples, indicating that the samples are older than predicted.

Explanation

The correct answer is "Radiometric carbon-14 ages are too low, implying that more carbon14 was present." This is because the question states that the two age measurements agree for more recent dates, but not for samples dating back more than 3,000 years. This suggests that the radiometric carbon-14 ages are underestimating the true age of the samples. Since carbon-14 decays over time, if the radiometric ages are lower than expected, it implies that there was more carbon-14 present in the samples, indicating that the samples are older than predicted.