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 11A-12F Easy Word
In a food chain, which organism is the primary consumer?
A Rabbit
B Grass
C Fox
D Eagle
Explanation
📌 Primary consumer = herbivore = eats producers (plants).
Producers → Primary consumers → Secondary consumers → Tertiary consumers
Question 3 of 10
TEKS 10A-10C Easy Word
Homeostasis is:
A the classification of organisms
B maintaining stable internal conditions
C the process of cell division
D the study of ecosystems
Explanation
📌 Homeostasis = maintaining stable internal conditions (body temp, blood sugar, pH, water balance) despite external changes.
Question 4 of 10
TEKS 6A-6H Easy Word
DNA is made up of repeating units called:
A nucleotides
B monosaccharides
C fatty acids
D amino acids
Explanation
📌 DNA is a polymer of nucleotides. Each nucleotide = phosphate group + deoxyribose sugar + nitrogenous base (A, T, G, C).
Question 5 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 Mutation
B Replication
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 6 of 10
TEKS 11A-12F Easy Word Diagram
The diagram shows a carbon cycle. Which process RELEASES carbon dioxide into the atmosphere? CO₂ in Air Plants Animals Decomposers Photosynthesis (absorbs CO₂) Respiration (releases CO₂) eating decomposition
A Photosynthesis
B Condensation
C Cellular respiration
D Nitrogen fixation
Explanation
📌 Processes that RELEASE CO₂:
• Cellular respiration (animals AND plants)
• Combustion (burning fossil fuels)
• Decomposition

Process that ABSORBS CO₂:
• Photosynthesis
Question 7 of 10
TEKS 11A-12F Easy Word
Which of the following is a biotic factor?
A Temperature
B Bacteria
C Water
D Sunlight
Explanation
📌 Biotic = living things (plants, animals, bacteria).
Abiotic = non-living (temperature, water, sunlight, soil).
Question 8 of 10
TEKS 6A-6H Easy Word
In DNA, adenine (A) always pairs with:
A guanine
B uracil
C thymine
D cytosine
Explanation
📌 Base pairing rules: A-T (2 hydrogen bonds), G-C (3 hydrogen bonds).
In RNA: A-U instead of A-T.
Question 9 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 100 kcal
B 10 kcal
C 1,000 kcal
D 5,000 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 10 of 10
TEKS 9A-9D Easy Word
Which biomolecule is the primary source of quick energy?
A Nucleic acids
B Proteins
C Carbohydrates
D Lipids
Explanation
📌 Carbohydrates = quick energy (glucose, starch).
Lipids = long-term energy storage. Proteins = building/repair. Nucleic acids = genetic info.

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