Biology — Semester B
Free Practice · 10 Questions · 180 min
180:00 Exit
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Question 1 of 10
TEKS 6A-6H Medium Word Diagram
The diagram shows the process of DNA replication. What does the enzyme helicase do? Helicase Double-stranded DNA Replication fork → Direction
A Unwinds and separates the DNA strands
B Joins DNA fragments
C Adds new nucleotides
D Proofreads the new DNA
Explanation
📌 Helicase UNWINDS and SEPARATES the two DNA strands by breaking hydrogen bonds between base pairs.
This creates the replication fork where new nucleotides can be added.
DNA polymerase then adds complementary nucleotides to each strand.
Question 2 of 10
TEKS 6A-6H Medium Word Diagram
The diagram shows the central dogma of molecular biology. What process occurs at step 2? DNA Step 1 mRNA Step 2 Protein Transcription Translation
A Replication
B Mutation
C Transcription
D Translation
Explanation
📌 Central Dogma: DNA → mRNA → Protein
Step 1 = Transcription (DNA → mRNA, in nucleus)
Step 2 = Translation (mRNA → Protein, at ribosomes)

mRNA carries the genetic code from DNA to the ribosome where proteins are assembled.
Question 3 of 10
TEKS 9A-9D Easy Word
Which biomolecule is the primary source of quick energy?
A Proteins
B Nucleic acids
C Lipids
D Carbohydrates
Explanation
📌 Carbohydrates = quick energy (glucose, starch).
Lipids = long-term energy storage. Proteins = building/repair. Nucleic acids = genetic info.
Question 4 of 10
TEKS 11A-12F Easy Word
Which of the following is a biotic factor?
A Sunlight
B Bacteria
C Temperature
D Water
Explanation
📌 Biotic = living things (plants, animals, bacteria).
Abiotic = non-living (temperature, water, sunlight, soil).
Question 5 of 10
TEKS 11A-12F Medium Word Diagram
The energy pyramid below shows energy transfer between trophic levels. Approximately how much energy is available to secondary consumers if producers have 10,000 kcal? Tertiary Secondary ? kcal Primary — 1,000 kcal Producers — 10,000 kcal 10% rule
A 5,000 kcal
B 100 kcal
C 10 kcal
D 1,000 kcal
Explanation
📌 The 10% Rule: Only ~10% of energy transfers to the next trophic level.
Producers: 10,000 → Primary: 1,000 → Secondary: 100 → Tertiary: 10
Secondary consumers get approximately 100 kcal.
Question 6 of 10
TEKS 6A-6H Easy Word
DNA is made up of repeating units called:
A fatty acids
B amino acids
C monosaccharides
D nucleotides
Explanation
📌 DNA is a polymer of nucleotides. Each nucleotide = phosphate group + deoxyribose sugar + nitrogenous base (A, T, G, C).
Question 7 of 10
TEKS 6A-6H Medium Word Diagram
Based on the Punnett square below, what is the probability of the offspring being heterozygous? B b B b BB Bb Bb bb Cross: Bb × Bb
A 25%
B 50%
C 75%
D 100%
Explanation
📌 From Bb × Bb cross:
BB = 1/4 (homozygous dominant)
Bb = 2/4 = 1/2 (heterozygous) ← THIS
bb = 1/4 (homozygous recessive)
Probability of heterozygous = 50%
Question 8 of 10
TEKS 10A-10C Easy Word
Homeostasis is:
A the classification of organisms
B the process of cell division
C maintaining stable internal conditions
D the study of ecosystems
Explanation
📌 Homeostasis = maintaining stable internal conditions (body temp, blood sugar, pH, water balance) despite external changes.
Question 9 of 10
TEKS 11A-12F Easy Word Diagram
In the food web below, what would happen if all the frogs were removed? Grass Algae Grasshopper Frog 🚫 Snail Snake
A All organisms die
B Nothing changes
C Snake population increases
D Insect population increases and snake population decreases
Explanation
📌 If frogs are removed:
• Insects (grasshoppers) they ate would INCREASE (no predator)
• Snakes that ate frogs would DECREASE (less food)
• This demonstrates how removing one species affects the entire food web.
Question 10 of 10
TEKS 11A-12F Easy Word
In a food chain, which organism is the primary consumer?
A Grass
B Rabbit
C Eagle
D Fox
Explanation
📌 Primary consumer = herbivore = eats producers (plants).
Producers → Primary consumers → Secondary consumers → Tertiary consumers

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