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0

In most stable freshwater environments, populations of Daphnia are almost entirely female and reproduce asexually. However, males are observed in low oxygen environments or when food is scarce. Based on these observations, a researcher suggests that male Daphnia develop in response to unfavorable environmental conditions. This is an example of a:

A. Result B. Theory C. Procedure D. Hypothesis

D. Hypothesis

1

Two students were testing the amount of fertilizer that would best promote the growth of strawberries in a garden. Which of the following could be an unavoidable source of experimental error?

A. Length of the study
B. Variation in the strawberry plants
C. The cost of watering the plants
D. Fertilization during the study

B. Variation in the strawberry plants

2

For a virus to infect a host cell, the virus must first adhere to the cell's surface. Viruses accomplish this by fitting specific sites on the surfaces of their host cells in a "lock and key" arrangement. The "lock and key" arrangement between a virus and receptor sites on its host cells is most important in determining the:

A. Rate at which the virus normally replicates itself inside the host cell.
B. Length of time the virus normally remains infective outside the cell.
C. Specific type of cell that is normally infected by the virus.
D. Amount of damage the virus normally inflicts upon the host cell.

C. Specific type of cell that is normally infected by the virus.

4

The fundamental difference between materials and energy is that

A. Materials are cycled through ecosystems; energy is not.
B. Energy is cycled through ecosystems; materials are not.
C. Energy can be converted into materials; materials cannot be converted into energy.
D. Materials can be converted into energy; energy cannot be converted into materials.
E. Ecosystems are much mor efficient in their transfer of energy than in their transfer of materials.

A. Materials are cycled through ecosystems; energy is not.

5

Which of the following is primarily responsible for limiting the number of tropic levels in most ecosystems?

A. Many primary and higher order consumers are opportunistic feeders.
B. Most predators require large home ranges.
C. Nutrient cycles involve both abiotic and biotic components of ecosystems.
D. Nutrient cycling rates tend to be limited by decomposition.
E. Each energy transfer is less than 100% efficient.

E. Each energy transfer is less than 100% efficient.

6

A primary function of gap junctions between cell membranes is to:

A. Integrate the metabolic or electrical activity of a group of cells through permeable channels.
B. Allow all surfaces of a functional unit of cells to contact the extra-cellular matrix.
C. Permit the exchange of genetic information between adjacent cells.
D. Reinforce the structural cohesion of cells that form a particular tissue.

A. Integrate the metabolic or electrical activity of a group of cells through permeable channels.

7

Which of the following best explains why the catabolism of fats yields about twice as much energy as the catabolism of the same mass of carbohydrates?

A. More energy is released as unusable heat in the breakdown of carbohydrates than of fats.
B. Fats contain a higher proportion of carbon-hydrogen bonds than carbohydrates do.
C. The breakdown of carbohydrates requires an initial input of ATP, while the breakdown of fats
does not.
D. Energy used to make enzymes that break down carbohydrates reduces the efficiency of its catabolism.

B. Fats contain a higher proportion of carbon-hydrogen bonds than carbohydrates do.

8

An important role of histamine in the humoral response to infection is to:

A. deactivate an antigen through chemical denaturation.
B. speed the immune response to an antigen the body
has previously encountered.
C. signal the presence of an antigen to other components of the immune system.
D. increase cell division among B cells to enhance the immune response.

C. signal the presence of an antigen to other components of the immune system.

9

What is the role of helper T cells in the function of the human immune system?

A. to lyse and destroy infected cells for removal from the body
B. to generate B cells for the production of antibodies
C. to mobilize both the humoral and cell-mediated responses to antigens
D. to distinguish an antigen from a normally occurring substance in the body

C. to mobilize both the humoral and cell-mediated responses to antigens

10

The ability to identify particular loci associated with a given genetic trait has the greatest implications for which of the following areas of medicine?

A. assistive reproductive technologies
B. screening for hereditary diseases
C. diagnosis of cardiopulmonary diseases
D. DNA replication technologies

B. screening for hereditary diseases

11

Variations in phenotypes are sometimes evident in individuals with abnormal chromosome numbers. Which of the following events accounts for a significant portion of the instances of abnormal chromosome numbers?

A. nondisjunction during meiosis
B. deletion of DNA during translation
C. mutations during embryonic cell mitosis
D. transposition of DNA during replication

A. nondisjunction during meiosis

12

Which of the following examples best illustrates the idea that differential gene expression accounts for specialization of cells in multicellular organisms rather than differences among the genes themselves?

A. Epithelial cells in humans and other mammals have strong similarities in form and function.
B. Cells from the mammary gland of a sheep can provide the genetic material needed to clone a sheep.
C. Hormones produced by other mammals can be used to treat disorders in humans.
D. Alterations in pH levels can reverse normal differentiation of the dorsal and ventral sides of a chick embryo.

B. Cells from the mammary gland of a sheep can provide the genetic material needed to clone a sheep.

13

Genetic engineering has the potential to correct some human genetic diseases in individuals. In gene therapy, a defective gene is replaced or supplemented by using a genetically engineered retrovirus to insert a normal gene in the DNA of some of the patient's cells. This treatment will be most successful if the retrovirus is inserted into cells that:

A. are found throughout the body rather than in one specific organ.
B. are recycled after death rather than removed from the body.
C. continue to divide during the life of the patient.
D. carry out one specific function rather than multiple functions.

C. continue to divide during the life of the patient.

14

Which of the following is one consequence of the fact that natural selection acts on the phenotype of an individual rather than on its genotype?

A. Harmful recessive alleles are less easily removed from a population than dominant alleles that are harmful.
B. Genetically similar individuals may have different phenotypes if they grow and develop under different environmental conditions.
C. A trait that is selectively neutral may increase in frequency in a population if it is genetically linked to a second trait that increases the fitness of the individual.
D. Differences in the behavior of individuals in a population are strongly influenced by differences in genotypes in the population.

A. Harmful recessive alleles are less easily removed from a population than dominant alleles that are harmful.

15

Researchers studying northern elephant seals have found a remarkable lack of genetic diversity in the population. In contrast, the southern elephant seal population exhibits a normal amount of genetic variation. Which of the following is the most likely explanation for this difference in the two elephant seal populations?

A. The northern elephant seal population was greatly reduced in the recent past, while the southern elephant seal population was not.
B. Southern elephant seals are exposed to many mutagenic substances from pollution, while northern elephant seals live in less polluted waters.
C. Northern elephant seals compete with many other seal species, while southern elephant seals have no close competitors.
D. Southern elephant seals mate primarily inside their own group, while northern elephant seals mate primarily outside their own group.

A. The northern elephant seal population was greatly reduced in the recent past, while the southern elephant seal population was not.

16

A species of finch on an island is divided into two distinct morphs based on bill size. Finches with large bills eat mostly large, hard-shelled seeds of a particular plant, while finches with small bills eat smaller, softer seeds of a different plant.

A smaller number of finches with bills of intermediate size eat both large and small seeds. Which of the following scenarios would be most favorable for sympatric speciation of this finch species?

A. The reproductive success of finches with intermediate bills increases relative to that of finches with large or small bills.
B. The plant species that produces either the large or small seeds becomes extinct on the island.
C. The population size of the finches on the island is sharply reduced by a natural disaster and then
gradually increases to predisaster numbers.
D. Individual finches begin to choose mates with a bill size similar to their own.

D. Individual finches begin to choose mates with a bill size similar to their own.

17

The effective cycling of nutrients in an ecosystem depends primarily on maintaining:

A. rapid rates of decomposition of organic material.
B. a large standing crop biomass.
C. balanced rates of production, consumption, and decomposition.
D. high levels of species diversity.

C. balanced rates of production, consumption, and decomposition.

18

Use the passage below to answer the question that follows.

Brown-headed cowbirds are members of the blackbird family that lay their eggs in other birds' nests. Usually a single egg is laid in the nest of a smaller species. The
egg hatches sooner than those of the host species, and after it hatches, the baby cowbird often pushes the other eggs out of the nest. The cowbird is then raised by
the foster parents, whom it often dwarfs in size.

The relationship between the brown-headed cowbird and its host species is an example of:

A. competition.
B. predation.
C. commensalism.
D. parasitism.

D. parasitism.