ACT Science : Biology

Study concepts, example questions & explanations for ACT Science

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Example Questions

Example Question #641 : Biology

     Phylogenetics is a tool utilized by evolutionary and molecular biologists to investigate the similarities that exist in the molecular sequences of proteins in varying organisms. The amino acid sequences that build proteins are often used to construct distance matrices that aid in determining evolutionary ties. The study of these matrices helps to expose evolutionary relationships between species that may not have the same phenotypical and existential characteristics.

Study 1

     A researcher decides to compare several bat species to several bird and mammalian species in order to determine which two groups were more closely related. The study compares a ghost bat and a tomb bat with two birds, the pigeon and eagle, and two mammals, the spider monkey and macaque. The researcher compared the amino-acid sequences of beta hemoglobin molecules in order to determine whether bats were more related to birds or mammals. Percent similarities of the data were calculated for comparison purposes (Figure 1).

Figure 1

 

Bat

 

 

Study 2

     A researcher decides to compare a whale to a fish and to several ungulates (hoofed mammals). One set of ungulates that were studied were artiodactyls, meaning they were “even-toed” (hippopotamus and sheep).  The other set of ungulates belonged to a class of mammals known as perissodactyls meaning that they were “odd-toed” (rhinoceros and zebra). The researcher compared the amino-acid sequences of beta hemoglobin molecules in order to determine which species were more related to the Minke whale. Percent similarities of the data were calculated for comparison purposes (Figure 2).

Figure 2

Whale

Archeological investigators argue that homologous limb structure and physical characteristics are the most important factors in determining evolutionary ties. Homologous limb structure is defined as a structure found in the anatomy of an organism that is similiar to that of another species. Would the scientists of Study 1 and Study 2 agree with this information?

Possible Answers:

No, the researchers state that molecular chemistry is the only way to prove evolutionary ties.

No, these researchers studied the genetic make-up of organisms in order to determine similarities in evolutionary histories.

Yes, the researchers would agree that apparent anatomical similarities are most important to determine evolutionary ties.

Yes, because the researchers' evidence supports the idea that molecular chemistry results in similiar physiological features like the bird and bat species that were studied.

Correct answer:

No, these researchers studied the genetic make-up of organisms in order to determine similarities in evolutionary histories.

Explanation:

No, these researchers studied the genetic make-up of organisms in order to determine similarities in evolutionary histories.

This is the correct answer because the scientists make no statement as to whether or not phylogenetics is the only way to study evolutionary histories. They simply suggest that despite physical similarites some species share a greater similarity on the genetic level. For instance birds and bats are similiar creatures physically but they are very different on the molecular level.

Example Question #642 : Biology

     Phylogenetics is a tool utilized by evolutionary and molecular biologists to investigate the similarities that exist in the molecular sequences of proteins in varying organisms. The amino acid sequences that build proteins are often used to construct distance matrices that aid in determining evolutionary ties. The study of these matrices helps to expose evolutionary relationships between species that may not have the same phenotypical and existential characteristics.

Study 1

     A researcher decides to compare several bat species to several bird and mammalian species in order to determine which two groups were more closely related. The study compares a ghost bat and a tomb bat with two birds, the pigeon and eagle, and two mammals, the spider monkey and macaque. The researcher compared the amino-acid sequences of beta hemoglobin molecules in order to determine whether bats were more related to birds or mammals. Percent similarities of the data were calculated for comparison purposes (Figure 1).

Figure 1

 

Bat

 

 

Study 2

     A researcher decides to compare a whale to a fish and to several ungulates (hoofed mammals). One set of ungulates that were studied were artiodactyls, meaning they were “even-toed” (hippopotamus and sheep).  The other set of ungulates belonged to a class of mammals known as perissodactyls meaning that they were “odd-toed” (rhinoceros and zebra). The researcher compared the amino-acid sequences of beta hemoglobin molecules in order to determine which species were more related to the Minke whale. Percent similarities of the data were calculated for comparison purposes (Figure 2).

Figure 2

Whale

What is the central theme of the two phylogenetic studies?

Possible Answers:

None of these statements are the central theme to the phylogenetic studies.

The central theme of the studies is that physical characteristics do not tell the complete story of evolutionary histories and that investigation on the molecular level may be needed to make valid conclusions.

The central theme of the studies is that no matter how alike species appear to be, they are never related in an evolutionary context.

The central theme of the studies is that molecular investigation of amino-acid composition is the only way to study evolutionary history.

Correct answer:

The central theme of the studies is that physical characteristics do not tell the complete story of evolutionary histories and that investigation on the molecular level may be needed to make valid conclusions.

Explanation:

The central theme of the studies is that physical characteristics do not tell the complete story of evolutionary histories and that investigation on the molecular level may be needed to make valid conclusions.

This is the correct answer because the researchers found that species that seem to share physical characteristics were not the most similarly related when compared with other species. In doing so, the scientists suggest that researchers should move past physical characteristics and take into account the genetic structure of related species before making evolutionary claims or assumptions.

Example Question #643 : Biology

Ecological succession refers to the observable change of the species composition of an ecological community over a period of time. This phenomenon is also known as forest succession. It is a process that begins with the colonization of a habitat by robust pioneer species that can survive inclement and harsh environments. Pioneer species are characterized by small size and rapid reproduction of many offspring. Over successive generations these species are replaced with increasing complexity, until the ecosystem reaches a self-perpetuating climax community that ceases to vary in composition.

Several scientists express their views on the phenomenon of ecological succession.

Scientist 1

Ecological succession can be explained as primary succession. This theory suggests that forest evolution is the product of repeatable sequences of community changes known as seres. Each sere is predictable and deterministic to particular environmental circumstances. Scientists can therefore predict the changes in an environment with accuracy and precision based on observation.

Scientist 2

Ecological succession is not defined by predictable models. Chance plays a large role in creating ecological communities, whose species respond individualistically to environmental cues and pressures. These models are more complex in nature, and less simplified, than deterministic models. In these models, communities are regarded as products of the correlations between species distributions and environmental factors independent to each community.

According to Scientist 1, seres are best described by which of the following statements?

Possible Answers:

They are deterministic and based upon models of chance.

They are deterministic and easily predicted by simple models of succession.

The scientist would not agree with any of these choices.

They are subject to change based upon specific environment-species interactions.

Correct answer:

They are deterministic and easily predicted by simple models of succession.

Explanation:

They are deterministic and easily predicted by simple models of succession.

Scientist 1 has observed that seres occur in predictable patterns that can be easily modeled. In his opinion, these models can help scientists to infer the structures of communities. This is the correct answer, because it is suppoted by the passage; the other answers are incorrect because they involve specific species interactions and the role of chance that may alter species composition.

Example Question #644 : Biology

Ecological succession refers to the observable change of the species composition of an ecological community over a period of time. This phenomenon is also known as forest succession. It is a process that begins with the colonization of a habitat by robust pioneer species that can survive inclement and harsh environments. Pioneer species are characterized by small size and rapid reproduction of many offspring. Over successive generations these species are replaced with increasing complexity, until the ecosystem reaches a self-perpetuating climax community that ceases to vary in composition.

Several scientists express their views on the phenomenon of ecological succession.

Scientist 1

Ecological succession can be explained as primary succession. This theory suggests that forest evolution is the product of repeatable sequences of community changes known as seres. Each sere is predictable and deterministic to particular environmental circumstances. Scientists can therefore predict the changes in an environment with accuracy and precision based on observation.

Scientist 2

Ecological succession is not defined by predictable models. Chance plays a large role in creating ecological communities, whose species respond individualistically to environmental cues and pressures. These models are more complex in nature, and less simplified, than deterministic models. In these models, communities are regarded as products of the correlations between species distributions and environmental factors independent to each community.

What is the main difference between the viewpoints of Scientist 1 and Scientist 2?

Possible Answers:

Scientist 2 disregards the ability of species to respond individualistically to environmental stimuli.

Scientist 2 overcomplicates chance factors involved with ecological succession.

Scientist 1 does not have enough evidence to create predictive models for each sere.

Scientist 1 disregards role of chance and specific species interactions with the environment in the development of ecological communities.

Correct answer:

Scientist 1 disregards role of chance and specific species interactions with the environment in the development of ecological communities.

Explanation:

Scientist 1 disregards role of chance and specific species interactions with the environment in the development of ecological communities. 

The main difference between the views of the scientists is that one creates simple models of prediction, while the other observes the complex relationships of species, the environment, and chance factors. This is the only answer directly supported by information within the passage.

Example Question #645 : Biology

Ecological succession refers to the observable change of the species composition of an ecological community over a period of time. This phenomenon is also known as forest succession. It is a process that begins with the colonization of a habitat by robust pioneer species that can survive inclement and harsh environments. Pioneer species are characterized by small size and rapid reproduction of many offspring. Over successive generations these species are replaced with increasing complexity, until the ecosystem reaches a self-perpetuating climax community that ceases to vary in composition.

Several scientists express their views on the phenomenon of ecological succession.

Scientist 1

Ecological succession can be explained as primary succession. This theory suggests that forest evolution is the product of repeatable sequences of community changes known as seres. Each sere is predictable and deterministic to particular environmental circumstances. Scientists can therefore predict the changes in an environment with accuracy and precision based on observation.

Scientist 2

Ecological succession is not defined by predictable models. Chance plays a large role in creating ecological communities, whose species respond individualistically to environmental cues and pressures. These models are more complex in nature, and less simplified, than deterministic models. In these models, communities are regarded as products of the correlations between species distributions and environmental factors independent to each community.

An ecological study observes plots of land that are allowed to grow for extended periods of time. There are five plots that have grown under seemingly identical conditions; however, each climax community possesses a species composition slightly different from the others. Which scientist would agree with the possibility of accurately obtaining these results?

Possible Answers:

Neither of the scientists

Both of the scientists

Scientist 2

Scientist 1

Correct answer:

Scientist 2

Explanation:

Scientist 2

This is the correct answer, because only Scientist 2 believes that individualistic interactions and chance can play complex parts in the development of climax communities. These views would acknowledge and account for subtle variations in climax communities. Scientist 1 would disagree completely, because his simple predictive models do not account for such variation.

Example Question #646 : Biology

Many motile organisms exhibit “fight or flight” responses in order to survive and reproduce. Aggressive posturing and combative behavior are important for the reproductive success and the formation of pack hierarchies of some species. Submissive actions and retreats permit other species the ability to evade capture or danger and enhance survival capabilities. Scientists have debated about the mechanics and moderation of these behaviors within organisms. Two studies regarding this behavior were performed.

Study 1

Researchers decided to study crayfish, a type of freshwater arthropod, in an aquarium. They placed two crayfish opposing one another in an enclosed space. The crayfish were divided by an opaque screen that inhibited their ability to notice one another. The screen was lifted and the crayfish were permitted to interact with one another. The scientists observed their interactions and noted the crayfish's submissive and aggressive behaviors. The scientists noticed that more dominant and aggressive behaviors correlated with larger sized individuals. Their observations indicate that large size and aggression are traits actively selected for within the crayfish population and are necessary for survivorship and reproductive success.

Study 2

Researchers in this study suggest that aggressive behaviors are linked to chemical messengers. They attempted to alter the crayfish’s lateral giant escape reaction through chemical manipulation. They injected crayfish with serotonin, an aggression stimulant, and octopamine, a natural facilitator of the flight response. They monitored and recorded the crayfish’s response to aggressive stimuli (see Figure 1). The researchers concluded that the crayfish escape response is significantly different in the chemical trials in comparison to the control trial that observed the injection of an inert saline solution into the arthropods.

Arthropod

Figure 1

If the researchers of Study 1 read the work of those involved of Study 2, they would most likely agree with which of the following conclusions?

Possible Answers:

Smaller crayfish contain higher levels of serotonin.

Larger crayfish contain lower levels of serotonin.

Larger crayfish contain higher levels of octopamine.

Larger crayfish contain higher levels of serotonin.

Correct answer:

Larger crayfish contain higher levels of serotonin.

Explanation:

In Study 1, the scientists noted that the larger crayfish exhibited aggressive tendencies. In Study 2, the scientists found that crayfish with high levels of serotonin were least likely to retreat from an aggressive stimuli. From this information, it is safe to conclude that the researchers of the first study would readliy agree with the statement that "larger crayfish contain higher levels of serotonin." None of the other choices are logically supported by the passage.

Example Question #647 : Biology

Bacterial resistance is a common issue encountered in various infections. Scientists have attributed this phenomenon to the overuse of anti-bacterial sanitizers and prescription antibiotics. Two groups of researchers performed studies to test bacterial resistance.

Study 1

Researchers in this study state that bacterial resistance is the result of bacterial plasmid translocation. Bacteria carry their genes on circular rings of bacterial DNA and on small, physically separate molecules known as plasmids. Plasmids are unique because they are replicons that are capable of replication autonomously within a suitable host. Researchers radioactively marked plasmids in bacterial specimens and noted that they could be easily transmitted from one bacterium to another via horizontal gene transfer. They then observed that the genes transferred from the plasmid could be incorporated into the bacteria’s genetic makeup. These genetic alterations enhanced survivorship within the environment and promoted resistance to antibiotics. They concluded that plasmids carry genes important for survival and facilitate bacterial resistance to antibiotics.

Study 2

Researchers in this study state that resistance is the result of the misuse of antibiotics. Researchers administered various antibiotics to a culture of E. coli and studied their effects over time (Figure 1). They concluded that bacterial resistance is the result of natural selection. In other words, the strongest bacteria survive antibiotics and reproduce, which produces anitbiotic-resistant offspring bacteria. 

Bacterial_fixed

Figure 1

A common problem present in the Russian prison system is that of antibiotic resistant tuburculosis. Scientists have traced this epidemic to the misuse of antibiotics. Within the prison system, antibiotics are costly and doctors have attempted to save money by cutting down the doses of antibiotics administered to inmates. The doctors concluded that this process only killed off weak bacteria and produced antibiotic-resistant strains. Which group of researchers would most readily agree with this conclusion?

Possible Answers:

The researchers of both studies

The researchers of Study 2

The researchers of neither study

The researchers of Study 1

Correct answer:

The researchers of Study 2

Explanation:

The researchers of Study 2 would agree with this research because it directly supports their hypothesis. The Russian doctors administered small amounts of antibiotics that only killed off weaker bacteria. Stronger bacteria lived on to reproduce and this eventually produced antibiotic-resistant strains that were harder to eradicate.

Example Question #648 : Biology

In the 19th century, there were two competing views as to how diseases spread.

 

Miasma theory:

Miasma (Greek for pollution) is a poisonous vapor that comes from rotting carcasses or other diseased bodies. It carries particles of the decomposing matter in it and spreads illness. This is why the bubonic plague spread so quickly in Europe: the air itself was foul-smelling and polluted with disease which caused everyone in the locale to become sick and die. It also explains why epidemics tend to originate in a certain area and infect everyone within that area -- they are all breathing in this noxious gas and getting the same disease. In hospitals, we need to ensure that the air is fresh smelling and clean so as to avoid all patients breathing in this miasma and all getting sick.

 

Germ theory:

Disease is spread through small microbial organisms called germs. These germs, which can be bacteria, viruses, or other pathogens, should be able to be isolated from an infected host and then should no longer exist in the host's body when the host becomes healthy. Germs can move from one body to another through direct or indirect contact -- they can move through touching, spreading of fluids (coughing, sneezing, etc.) and potentially air, but not exclusively through the air.

In a certain hospital, a doctor found that by washing his hands, he decreased the spread of infection in pregnant women from 18% to 2%. Which theory does this best support?

Possible Answers:

Neither theory

Both theories

Miasma theory

Germ theory

Correct answer:

Germ theory

Explanation:

This best supports germ theory. If it supported miasma, then the patients would all get sick regardless of whether or not the doctors washed their hands -- they would get sick simply from being in the locale.

Example Question #649 : Biology

In the 19th century, there were two competing views as to how diseases spread.

 

Miasma theory:

Miasma (Greek for pollution) is a poisonous vapor that comes from rotting carcasses or other diseased bodies. It carries particles of the decomposing matter in it and spreads illness. This is why the bubonic plague spread so quickly in Europe: the air itself was foul-smelling and polluted with disease which caused everyone in the locale to become sick and die. It also explains why epidemics tend to originate in a certain area and infect everyone within that area -- they are all breathing in this noxious gas and getting the same disease. In hospitals, we need to ensure that the air is fresh smelling and clean so as to avoid all patients breathing in this miasma and all getting sick.

 

Germ theory:

Disease is spread through small microbial organisms called germs. These germs, which can be bacteria, viruses, or other pathogens, should be able to be isolated from an infected host and then should no longer exist in the host's body when the host becomes healthy. Germs can move from one body to another through direct or indirect contact -- they can move through touching, spreading of fluids (coughing, sneezing, etc.) and potentially air, but not exclusively through the air.

Which of the following observations, if true, would best support miasma theory?

Possible Answers:

Many combatants in World War I died after breathing in mustard gas.

Two people both eat the same bad food and both come down with food poisoning.

Everyone within two square miles became infected with the same illness in spite of not being near each other.

A child goes to class while sick. The next day the teacher is sick.

Correct answer:

Everyone within two square miles became infected with the same illness in spite of not being near each other.

Explanation:

Miasma theory suggests that people can get sick without contact. It's spread in a foul smelling vapor within a small locale -- this would support the idea of everyone in a small area all getting sick at the same time with the same disease.

The student/teacher example is incorrect as the two were in close enough proximity to spread germs.

Mustard gas and food poisoning are irrelevant.

Example Question #650 : Biology

In the 19th century, there were two competing views as to how diseases spread.

 

Miasma theory:

Miasma (Greek for pollution) is a poisonous vapor that comes from rotting carcasses or other diseased bodies. It carries particles of the decomposing matter in it and spreads illness. This is why the bubonic plague spread so quickly in Europe: the air itself was foul-smelling and polluted with disease which caused everyone in the locale to become sick and die. It also explains why epidemics tend to originate in a certain area and infect everyone within that area -- they are all breathing in this noxious gas and getting the same disease. In hospitals, we need to ensure that the air is fresh smelling and clean so as to avoid all patients breathing in this miasma and all getting sick.

 

Germ theory:

Disease is spread through small microbial organisms called germs. These germs, which can be bacteria, viruses, or other pathogens, should be able to be isolated from an infected host and then should no longer exist in the host's body when the host becomes healthy. Germs can move from one body to another through direct or indirect contact -- they can move through touching, spreading of fluids (coughing, sneezing, etc.) and potentially air, but not exclusively through the air.

Which of these solutions would a proponent of miasma theory give to  someone who is sick?

Possible Answers:

Move to an area with fresh air, away from where you currently are.

Stay close to a heating source to keep your temperature consistent.

Wash your hands daily and don't touch people.

Take antibiotics.

Correct answer:

Move to an area with fresh air, away from where you currently are.

Explanation:

People who support miasma theory believe that disease is transmitted through a foul-smelling vapor. The best way to avoid this disease (or to get better) would be to avoid this vapor.

Antibiotics would be a result of germ theory.

Washing your hands and staying away from people also would be a part of germ theory.

A heating source is not mentioned by either theorist, therefore it is irrelevant.

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