Free STAAR Biology Practice Test Questions

1. In plants and animals, genetic variation is introduced during

a. Crossing over in mitosis
b. Chromosome segregation in mitosis
c. Cytokinesis of meiosis
d. Anaphase I of meiosis

2. Which of the following processes is an example of positive feedback?

a. High CO2 blood levels stimulate respiration which decreases blood CO2 levels
b. High blood glucose levels stimulate insulin release, which makes muscle and liver cells take in glucose
c. Increased nursing stimulates increased milk production in mammary glands
d. Low blood oxygen levels stimulate erythropoietin production which increases red blood cell production by bone marrow

3. Prokaryotic and eukaryotic cells are similar in having which of the following?

a. Membrane-bound organelles
b. Protein-studded DNA
c. Presence of a nucleus
d. Integral membrane proteins in the plasma membrane

4. In a dihybrid cross between bean plants with red (R) wrinkled (w) seeds and white (r) smooth (W) seeds, the F1 progeny is all red and smooth. If the F1 plants are selfed, what proportion of the F2 will also be red and smooth if the genes are linked?

a. All of them
b. 1/4
c. 1/2
d. 9/16

5. All of the following are examples ways of controlling eukaryotic gene expression EXCEPT

a. Regulatory proteins
b. Nucleosome packing
c. Methylation of DNA
d. Operons

6. Which of the following metabolic compounds is composed of only carbon, oxygen, and hydrogen?

a. Phospholipids
b. Glycogen
c. Peptides
d. RNA

7. Two species of finches are able to utilize the same food supply, but their beaks are different. They are able to coexist on an island because of

a. Niche overlap
b. Character displacement
c. Resource partitioning
d. Competitive exclusion

8. Most of the CO2 in blood is converted to carbonic acid in red blood cells. When a body is active, CO2 production increases. Which of the following changes in pH would stimulate increased respiratory rate?

a. A drop in pH
b. A return to normal pH after a drop in pH
c. A rise in pH
d. A return to normal pH after a rise in pH

9. Which of the following is NOT true of homologous pairs of chromosomes in meiosis I?

a. They contain four DNA strands
b. They are held together by centromeres
c. They are composed of two genetically identical chromatids
d. They exchange DNA through forming chiasmata

10. Which of the following is a characteristic of enzymes?

a. They often catalyze more than one kind of reaction
b. They are sensitive to denaturation by heat
c. They catalyze reactions in only one direction
d. They are primarily regulated by gene transcription

Biology Answer Key

1.Answer: D
In anaphase I, homologous chromosome pairs segregate randomly into daughter cells. This means that each daughter cell contains a unique combination of chromosomes that is different from the mother cell and different from its cognate daughter cell.

2. Answer: C
In a positive feedback loop, an action intensifies a chain of events that, in turn, intensify the conditions that caused the action beyond normal limits. Nursing stimulates lactation, which promotes nursing. Contractions during childbirth, psychological hysteria, and sexual orgasm are all examples of positive feedback.

3. Answer: D
Both prokaryotes and eukaryotes interact with the extracellular environment and use membrane-bound or membrane-associated proteins to achieve this. They both use diffusion and active transport to move materials in and out of their cells. Prokaryotes have very few proteins associated with their DNA, whereas eukaryotes' DNA is richly studded with proteins. Both types of living things can have flagella, although with different structural characteristics in the two groups. The most important differences between prokaryotes and eukaryotes are the lack of a nucleus and membrane-bound organelles in prokaryotes.

4. Answer: C
If the genes are linked, there would be only two kinds of alleles produced by the F1 plants: Rw and rW. A Punnet square with these alleles reveals that half the progeny will have both an R and a W allele.

5. Answer: D
Operons are common to prokaryotes. They are units of DNA that control the transcription of DNA and code for their own regulatory proteins as well as structural proteins.

6.Answer: B
Glycogen is a polysaccharide, a molecule composed of many bonded glucose molecules. Glucose is a carbohydrate, and all carbohydrates are composed of only carbon, oxygen, and hydrogen. Most other metabolic compounds contain other atoms, particularly nitrogen, phosphorous, and sulfur.

7. Answer: B
Character displacement means that, although similar, species in the same habitat have evolved characteristics that reduce competition between them. It occurs as a result of resource partitioning.

8. Answer: A
When the CO2 concentration is high, more carbonic acid is formed, and the body needs to increase respiration to remove it from the blood. Thus, a drop in pH causes an increase in the respiratory rate.

9. Answer: B
Tetrads are held together at the crossover points, referred to as synaptonemal complexes. Each homologous pair is linked by centromeres, but during prophase I crossing over between homologs creates a physical connection called a synaptonemal complex. When homologs separate in anaphase I, the synaptonemal complexes are broken.

10. Answer: B
The three-dimensional structure of an enzyme is critical for its ability to bind substrates and catalyze reactions effectively. The three-dimensional structure is held in place by hydrogen bonds between amino acids, and these hydrogen bonds are easily disrupted, denaturing the protein (enzyme), by changes in temperature and pH.

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Last Updated: 07/05/2018