Free Scientific Reasoning MCQs with Answers

111. DNA molecules are composed of two nucleotide strands coiled together in a double helix. The two strands consist of sugar phosphate backbones which are connected by pairs of bases. The DNA molecules may be illustrated as follows. The two most common sugars found in the nucleic acids are

• A. Sucrose and ribose
• B. Deoxyribose and glucose
• C. Ribose and deoxyribose
• D. Glucose and fructose

Explanation: The sugar in the DNA molecule is deoxyribose and the one in RNA is ribose sugar. Example of pentose sugar are ribose and deoxyribose sugar.

112. DNA molecules are composed of two nucleotide strands coiled together in a double helix. The two strands consist of sugar phosphate backbones which are connected by pairs of bases. The DNA molecules may be illustrated as follows. Which of the following is the correct matching of base pairs in DNA?

• A. Adenine - Thymine and Guanine - Cytosine
• B. Guanine - Thymine and Adenine - Cytosine
• C. Adenine - Guanine and Thymine - Uracil
• D. Guanine - Cytosine and Thymine - Uracil

Explanation: DNA (deoxyribonucleic acid) is consists of adenine, thymine, cytosine, and Guanine. Adenine bonded by two hydrogen bonds with thymine and guanine is bonded by three hydrogen bonds with cytosine. Thus, the correct answer is A.

113. DNA molecules are composed of two nucleotide strands coiled together in a double helix. The two strands consist of sugar phosphate backbones which are connected by pairs of bases. The DNA molecules may be illustrated as follows. DNA replication involves the breaking of bonds between

• A. Two bases
• B. Sugars and a base
• C. Phosphate and a base
• D. Sugars and phosphates

Explanation: The enzyme that cleaves the unwound DNA helix structure into two different parental strands, by breaking the hydrogen bonds between the two strands of nucleotides. It literally acts as a pair of scissors that divides the DNA nucleotide into two parental strands.DNA replication occurs through the help of several enzymes. These enzymes "unzip" DNA molecules by breaking the hydrogen bonds that hold the two strands together.Each strand then serves as a template for a new complementary strand to be created. Complementary bases attach to one another (A-T and C-G).

114. DNA molecules are composed of two nucleotide strands coiled together in a double helix. The two strands consist of sugar phosphate backbones which are connected by pairs of bases. The DNA molecules may be illustrated as follows. Recombinant DNA is defined as a DNA produced from

• A. RNA and protein
• B. DNA and haemoglobin
• C. Viral DNA and glucose
• D. DNA of two different organisms

Explanation: What is recombinant DNA technology? Recombinant DNA technology is the joining together of DNA molecules from two different species. The recombined DNA molecule is inserted into a host organism to produce new genetic combinations that are of value to science, medicine, agriculture, and industry.

115. Based on perturbations in Neptune's orbit, the search for a ninth planet was conducted and Pluto was discovered in 1930. Pluto orbits the sun just like the other eight planets, and it has a moon. Charon, and a stable orbit. Based on its distance from the sun, Pluto should be grouped with the planets known as gas giants. In addition, Pluto, like the planet Mercury, has little or no atmosphere. Pluto is definitely not a comet because it does not have a tail like a comet when it is near the sun. Pluto is also not an asteroid, although its density is closer to an asteroid than to any of the other planets. Pluto is a planet because it has been classified as one for more than sixty years since its discovery.Which argument supporting the classification of Pluto as a planet is the weakest?

• A. Pluto orbits the sun just like the other eight planets
• B. Pluto has a moon
• C. Pluto has a stable orbit
• D. Pluto, like the planet Mercury, has little or no atmosphere
• E. Pluto has been classified as a planet for more than sixty years since discovery

Explanation: This is the weakest argument because it is justified with authority, tradition, and past belief, rather than scientific facts.

116. Based on perturbations in Neptune's orbit, the search for a ninth planet was conducted and Pluto was discovered in 1930. Pluto orbits the sun just like the other eight planets, and it has a moon. Charon, and a stable orbit. Based on its distance from the sun, Pluto should be grouped with the planets known as gas giants. In addition, Pluto, like the planet Mercury, has little or no atmosphere. Pluto is definitely not a comet because it does not have a tail like a comet when it is near the sun. Pluto is also not an asteroid, although its density is closer to an asteroid than to any of the other planets. Pluto is a planet because it has been classified as one for more than sixty years since its discovery.Which of the following statements is not backed with an explanation?

• A. Pluto is like a planet
• B. Pluto should be grouped with planets known as gas giants
• C. Pluto is like Mercury
• D. Pluto is not an asteroid
• E. Pluto is not a comet

Explanation: The passage states that Pluto's density is closer to an asteroid's than to any of the planets'. This would lead the reader to think that Pluto, based on its density, may be an asteroid. But the passage states that this is not the case and does not give arguments to support the statement. The statements in all other choices are supported with facts.

117. Predation is an interaction between individuals of 2 species in which one is harmed (the prey), and the other is helped (the predator). Predation can occur among plants and animals as well as between plants and animals. Some biologists contend that herbivores, or plant eaters, are predators. Table 1 indicates some characteristics and examples of certain predators. Predation is very important in maintaining a natural balance in any given ecosystem. For example, without predators, prey populations tend to grow exponentially. Without prey, predator populations tend to decline exponentially. Predators consume individual members of the prey population, thereby controlling the overall numbers in the ecosystem. The number of prey consumed depends on the number of prey present as well as the number of predators present. The rate of change in the number of prey is a function of the birth of new prey minus the death of other prey, due either to predation or other causes. The death rate is assumed to depend on the number of prey available and the number of predators. The rate of change in the number of predators is a function of the births of new predators-which depends on the number of prey-minus the death of some predators. Over long periods of time, predator and prey tend to balance each other out. This is called the predator-prey cycle. Prey numbers will increase when predator numbers decrease. When the number of prey reaches a certain point, predators will start to increase until they eat enough prey to cause a decline in prey numbers. When this happens, the number of predators will begin to decrease because they can't find enough prey to eat, and the cycle will begin again. Figure 1 represents an example of a predator-prey cycle.Based on information in the passage and in Table 1, an herbivore is:

• A. A predator only
• B. Both a parasite and a predator
• C. Prey only
• D. Both a predator and prey

Explanation: The best answer is d. Table 1 lists characteristics of certain predators. Since "herbivore" is listed in the table, a herbivore is a predator. The passage also indicates that some scientists contend that herbivores are predators. According to Table 1, carnivores eat herbivores, which means that a herbivore is also a prey animal.

118. Predation is an interaction between individuals of 2 species in which one is harmed (the prey), and the other is helped (the predator). Predation can occur among plants and animals as well as between plants and animals. Some biologists contend that herbivores, or plant eaters, are predators. Table 1 indicates some characteristics and examples of certain predators. Predation is very important in maintaining a natural balance in any given ecosystem. For example, without predators, prey populations tend to grow exponentially. Without prey, predator populations tend to decline exponentially. Predators consume individual members of the prey population, thereby controlling the overall numbers in the ecosystem. The number of prey consumed depends on the number of prey present as well as the number of predators present. The rate of change in the number of prey is a function of the birth of new prey minus the death of other prey, due either to predation or other causes. The death rate is assumed to depend on the number of prey available and the number of predators. The rate of change in the number of predators is a function of the births of new predators-which depends on the number of prey-minus the death of some predators. Over long periods of time, predator and prey tend to balance each other out. This is called the predator-prey cycle. Prey numbers will increase when predator numbers decrease. When the number of prey reaches a certain point, predators will start to increase until they eat enough prey to cause a decline in prey numbers. When this happens, the number of predators will begin to decrease because they can't find enough prey to eat, and the cycle will begin again. Figure 1 represents an example of a predator-prey cycle.Based on Figure 1, during the first year, predator numbers were mostly:

• A. Higher than prey numbers.
• B. Lower than prey numbers.
• C. Equal to prey numbers.
• D. Unable to be determined.

Explanation: The best answer is a. According to Figure 1, predators are indicated by a series of x's. During the first year, the number of predators was higher than was the number of prey.

119. Predation is an interaction between individuals of 2 species in which one is harmed (the prey), and the other is helped (the predator). Predation can occur among plants and animals as well as between plants and animals. Some biologists contend that herbivores, or plant eaters, are predators. Table 1 indicates some characteristics and examples of certain predators. Studies have shown that a certain species of deer will only eat a specific type of plant found in the deer's nat- ural habitat, and nothing else. Is this finding supported by the information in the passage?

• A. No, because a deer is an herbivore, which means it eats all plants
• B. No, because a deer is a carnivore and does not eat plants
• C. Yes, because a deer is an herbivore, and herbivores can be selective eaters
• D. Yes, because a deer is a prey animal, so it must use caution when eating

Explanation: The best answer is C. According to Table 1, a deer is a herbivore, so eliminate answer choice B. Table 1 also indicates that herbivores can be selective eaters, which means that they may choose to eat a certain type of plant over other types of plants. This best supports answer choice C.

120. Predation is an interaction between individuals of 2 species in which one is harmed (the prey), and the other is helped (the predator). Predation can occur among plants and animals as well as between plants and animals. Some biologists contend that herbivores, or plant eaters, are predators. Table 1 indicates some characteristics and examples of certain predators. Based on Figure 1, during which year were the greatest number of prey animals available?

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: The correct answer is Option B: 2. The graph in Figure 1 shows the line representing the prey population reaching its highest point in the second year, indicating that this was the year with the greatest number of prey animals available. Option A is incorrect because the peak does not occur in the first year. Option C is incorrect because the prey population decreases from its peak by the third year. Option D is also incorrect as the population is lower in the fourth year compared to the peak in the second year.