Practice post utme osustech biology 2018 Past Questions

Question 1

In a population of E. coli bacteria, the average generation time is 30 minutes. If the initial population size is 10^6 cells, what is the population size after 4 hours?

Correct A. 10^8

B. 10^7

C. 10^6

D. 10^5

Correct Answer: A

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Question 2

A 2.0 g sample of a compound containing only carbon and hydrogen is burned in oxygen to produce 3.2 g of CO2 and 1.0 g of H2O. What is the empirical formula of the compound?

A. CH_4

Correct B. C_2H_6

C. C_3H_8

D. C_4H_{10}

Correct Answer: B

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Question 3

A plant grows from a seedling to a mature plant in 30 days. If the growth rate is proportional to the square root of the plant's height, and the initial height is 10 cm, what is the height of the plant after 20 days?

A. 20 cm

B. 30 cm

Correct C. 40 cm

D. 50 cm

Correct Answer: C

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Question 4

A diagram of the human eye is shown below.

A. The cornea is the transparent part of the eye.

B. The iris is the colored part of the eye.

C. The retina is the light-sensitive tissue at the back of the eye.

Correct D. The lens is the flexible part of the eye that changes shape to focus light.

Correct Answer: D

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Question 5

A diagram of the human circulatory system is shown below.

Correct A. The heart is the pump that circulates blood throughout the body.

B. The arteries are the blood vessels that carry oxygenated blood away from the heart.

C. The veins are the blood vessels that carry deoxygenated blood back to the heart.

D. The capillaries are the tiny blood vessels where exchange of oxygen and nutrients occurs.

Correct Answer: A

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Question 6

In the xylem, what is the primary function of the tracheids?

Correct A. Transport of water and minerals from roots to leaves

B. Transport of sugars and amino acids from leaves to roots

C. Storage of water and nutrients in the stem

D. Regulation of water potential in the plant

Correct Answer: A

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Question 7

What is the primary mechanism of gas exchange in plants?

Correct A. Diffusion through the cell membrane

B. Active transport across the stomata

C. Passive transport through the cuticle

D. Osmosis through the xylem

Correct Answer: A

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Question 8

In the classification of living things, what is the primary characteristic that distinguishes prokaryotes from eukaryotes?

Correct A. Presence of a true nucleus

B. Absence of a cell wall

C. Presence of mitochondria

D. Absence of ribosomes

Correct Answer: A

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Question 9

What is the primary mechanism of heredity in organisms?

A. Mutation

B. Gene flow

C. Genetic drift

Correct D. Meiosis

Correct Answer: D

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Question 10

In the cell cycle, what is the primary function of the G2 phase?

A. DNA replication

B. Mitosis

C. Interphase

Correct D. Synthesis of organelles

Correct Answer: D

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Question 11

In a population of Drosophila melanogaster, the frequency of the recessive allele 'b' for black eyes is 0.2. If the population is in Hardy-Weinberg equilibrium, what is the frequency of the dominant allele 'B'?

Correct A. 0.8

B. 0.6

C. 0.4

D. 0.2

Correct Answer: A

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Question 12

A cell in a plant root hair is shown below. What is the function of the structure labeled 'X'?

Correct A. Storage of water and salts

B. Site of protein synthesis

C. Regulation of cell growth

D. Transport of nutrients

E. Maintenance of cell shape

Correct Answer: A

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Question 13

A population of 1000 individuals has a mean height of 170 cm and a s\tandard deviation of 10 cm. If a random sample of 50 individuals is taken, what is the probability that the sample mean height is greater than 175 cm?

Correct A. 0.05

B. 0.01

C. 0.005

D. 0.0005

Correct Answer: A

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Question 14

A diagram of the human eye is shown below. What is the function of the structure labeled 'Y'?

A. B\ending of light rays

Correct B. Detection of light

C. Regulation of light entry

D. Focus of light

E. Transmission of visual signals

Correct Answer: B

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Question 15

A population of 1000 individuals has a mean height of 170 cm and a s\tandard deviation of 10 cm. If a random sample of 50 individuals is taken, what is the probability that the sample mean height is less than 165 cm?

A. 0.05

B. 0.01

C. 0.005

Correct D. 0.0005

Correct Answer: D

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Question 16

In a population of Drosophila melanogaster, the frequency of the recessive allele 'a' is 0.2. If the population size is 1000, calculate the number of individuals that are homozygous recessive.

Correct A. 180

B. 200

C. 220

D. 240

Correct Answer: A

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Question 17

A 2.5 cm long stem of a plant is cut and placed in a test tube containing 20 ml of water. The stem is then placed in a warm place. After 24 hours, the stem has grown to 4.2 cm. Calculate the rate of elongation of the stem.

A. 0.05 cm/h

Correct B. 0.1 cm/h

C. 0.15 cm/h

D. 0.2 cm/h

Correct Answer: B

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Question 18

A diagram of a plant cell is shown below. Identify the part labeled 'A'.

A. Mitochondria

B. Chloroplast

Correct C. Nucleus

D. Vacuole

Correct Answer: C

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Question 19

A population of bacteria is growing exponentially. If the initial population size is 100 and the population size after 3 hours is 1000, calculate the growth rate per hour.

A. 0.5

Correct B. 1

C. 2

D. 3

Correct Answer: B

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Question 20

A diagram of a human eye is shown below. Identify the part labeled 'B'.

A. Cornea

Correct B. Iris

C. Retina

D. Lens

Correct Answer: B

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Question 21

In a population of Drosophila melanogaster, the frequency of the recessive allele 'r' is 0.2. If the population is in Hardy-Weinberg equilibrium, what is the frequency of the homozygous dominant genotype?

Correct A. 0.16

B. 0.24

C. 0.32

D. 0.4

Correct Answer: A

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Question 22

A cell is placed in a solution with a pH of 5.5. If the cell membrane has a permeability coefficient of 1.2 x 10^-6 cm/s, what is the concentration of hydrogen ions in the cell after 10 minutes?

A. 1.2 x 10^-5 M

Correct B. 2.4 x 10^-5 M

C. 3.6 x 10^-5 M

D. 4.8 x 10^-5 M

Correct Answer: B

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Question 23

A plant has a genotype of BBRR. If the plant is crossed with a plant having the genotype bbrr, what is the probability that the offspring will have the genotype BbRr?

Correct A. 0.25

B. 0.5

C. 0.75

D. 0.9

Correct Answer: A

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Question 24

A bacterium has a mutation that causes it to produce a toxin that is lethal to humans. If the bacterium has a doubling time of 30 minutes and a population growth rate of 0.5 per hour, what is the population size after 2 hours?

A. 1.6 x 10^6

B. 3.2 x 10^6

Correct C. 6.4 x 10^6

D. 12.8 x 10^6

Correct Answer: C

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Question 25

A DNA molecule has a sequence of ATCGATCG. If the molecule is cut with a restriction enzyme that recognizes the sequence ATCG, what is the resulting fragment size?

A. 10 bp

Correct B. 20 bp

C. 30 bp

D. 40 bp

Correct Answer: B

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