ACT science practice test 8

Directions: Each passage is followed by several questions. After reading a passage, choose the best answer to each question and fill in the corresponding oval on your answer document. You may refer to the passages as often as necessary.

You are NOT permitted to use a calculator on this test.


A study was conducted regarding the fossil shells of a particular species of turtle that lives off the coast of the Opulasian Peninsula. Scientists discovered a continuous record of fossilized shells in the seabed off the coast dating back 120,000 years. In addition to examining the fossilized turtle shells, the scientists also examined the shells of living turtles.

From each layer of seabed, the scientists randomly selected five complete, unbroken fossilized shells. Each shell was carefully prepared, measured, and photographed. A bit of each shell was then clipped off and sent to a laboratory for radiocarbon dating to determine the precise age of each shell.

Study 1

All of the living turtles had a distinct band of hexagonal scutes (bony plates) running the length of their shells, from head to tail. The fossilized shells' scutes were not visible to the naked eye; however upon application of a particular dye, a similar band of scutes from head to tail was observed in every shell.

Scutes extending greater than of the length of the shell were labeled major (M), where scutes extending less than or equal to of the length of the shell were labeled minor (m). The pattern of scutes was recorded for each fossil. For each time period, the percent of fossils exhibiting each pattern is given in Table 1.

Study 2

For each shell, the surface area of the shell, the height of the shell's bridge (the part of the shell linking the upper and lower plates), and the total number of scutes were recorded (see Figure 1).

For the shells of each age, the average of each measurement was calculated. The results are presented in Figure 2.

1. In a layer of seabed determined to be 250,000 years old, the scientists found fragments of twelve turtle shells, but no complete, intact shells. Which of the following is the most likely reason this layer of seabed was not included in the studies?

A. 250,000 years is too old to obtain an accurate radiocarbon date.
B. Shells that were 250,000 years old would have been irrelevant to the studies.
C. Accurate measurements of the dimensions of the shells could have been impossible to obtain.
D. The scientists would not have been able to accurately determine the color of the shells.

2. With regard to the descriptions given in Study 1, the shells with the M-M-m-m-M band of scutes probably most closely resembled which of the following?

F.
G.
H.
J.

3. According to the results of Study 2, how do the average number of scutes and the average bridge height of living turtles of the Opulasian Peninsula compare to those of the turtles of the Opulasian Peninsula from 120,000 years ago? For the living turtles:

A. both the average number of scutes and the average bridge height are larger.
B. both the average number of scutes and the average bridge height are smaller.
C. the average number of scutes is larger, and the average bridge height is smaller.
D. the average number of scutes is smaller, and the average bridge height is larger.

4. Suppose, in Study 1, the scientists had found another seabed layer with fossilized shells that were radiocarbon dated and found to be 86,000 years old. Based on the results of Study 1, the scute pattern percents for the group of shells would most likely have been closest to which of the following?

M-m-M-M-m

F. 100%
G. 50%
H. 36%
J. 26%

5. In Study 2, the average shell surface area of fossilized turtle shells that were 80,000 years old was closest to:

A. 670 cm2
B. 680 cm2
C. 690 cm2
D. 700 cm2

6. Which of the following statements best describes how Study 1 differed from Study 2?

F. In Study 1, the scientists examined 3 characteristics regarding the shape and size of turtle shells; but in Study 2, the scientists examined the frequency of occurrence of different patterns of scutes on turtle shells.
G. In Study 1, the scientists examined the frequency of occurrence of different patterns of scutes on turtle shells; but in Study 2, the scientists examined the environment in which turtles live.
H. In Study 1, the scientists examined the frequency of occurrence of different patterns of scutes on turtle shells; but in Study 2, the scientists examined 3 characteristics regarding the shape and size of turtle shells.
J. In Study 1, the scientists examined 3 characteristics regarding the shape and size of turtle shells; but in Study 2, the scientists examined the environment in which turtles live.

The 4 different blood types in sheep are A, B, AB, and O. The blood type of an offspring is determined by the blood types of its parents. Each parent contributes a single gene to its offspring, forming a pair of genes. The genotype of an offspring refers to the arrangement of the offspring's new gene formed by the combination of the parents' genes.

There are three possible alleles (forms) of this gene: the type-A blood allele (IA), the type-B blood allele (IB), and the type-O blood allele (IO). Both IA and IB are dominant to IO, and IO is recessive to IA and IB. This means that an individual with 1 IA and 1 IO will have type-A blood, and an individual with one IB and one IO will have type-B blood. When an individual has one IA and one IB allele, this individual will have type-AB blood, due to the codominance of the IA and IB alleles.

Table 1
Blood TypePossible Genotypes
AIAIA or IAIO
BIBIB or IBIO
ABIAIB
OIOIO

To explore the inheritance patterns of blood types in sheep, researchers conducted 4 analyses. In each analysis, male and female sheep of differing blood types were mated and the resultant blood types of their offspring recorded.

Analysis 1

One thousand males with type-O blood were mated with 1,000 females with type-AB blood. The following blood types were observed in the offspring:

Type A: 50%

Type B: 50%

Analysis 2

Two hundred of the type-A offspring from Analysis 1 were mated with 200 type-O mates from no previous experiment. The following blood types were observed in the offspring:

Type A: 50%

Type O: 50%

Analysis 3

One hundred of the type-A offspring from Analysis 1 parented children with 100 type-B offspring from Analysis 1. The following blood types were observed in the offspring:

Type A: 25%

Type B: 25%

Type AB: 25%

Type O: 25%

Analysis 4

Twenty-five of the type-A offspring from Analysis 3 were mated with type-B mates with Genotype IBIB who were not from any previous analysis. The following blood types were observed in the offspring:

Type AB: 50%

Type B: 50%

7. The ratio of blood types containing at least one IA allele to the blood types containing at least one IB allele produced in Analysis 3 was:

A. 1:00
B. 1:01
C. 2:01
D. 3:01

8. An offspring whose blood type exhibits codominance has which of the following genotypes?

F. IBIB
G. IBIO
H. IAIB
J. IAIO

9. To produce only offspring with AB blood, one would mate two sheep with which of the following sets of genotypes?

A. IAIB × IAIB
B. IAIB × IOIO
C. IAIA × IBIB
D. IBIB × IAIO

10. In Analysis 3, the offspring used from Analysis 1 most likely had which of the following genotypes?

F. IAIO and IBIB
G. IAIO and IBIO
H. IAIA and IBIB
J. IAIA and IBIO

11. Some or all of the offspring had 1 allele for type-O blood in Analyses:

A. 1 and 2 only.
B. 2 and 3 only.
C. 1, 2, and 4 only.
D. 1, 2, 3, and 4.

12. Suppose that 300 offspring were produced in Analysis 3. Based on the results, the number of offspring with type-B blood produced in Analysis 3 would most likely have been closest to:

F. 25
G. 50
H. 75
J. 100