Biology — Semester B Practice

Question 1 of 10

TEKS 6A-6H Easy Word

DNA is made up of repeating units called:

A amino acids

B monosaccharides

C fatty acids

D nucleotides

Explanation

📌 DNA is a polymer of nucleotides. Each nucleotide = phosphate group + deoxyribose sugar + nitrogenous base (A, T, G, C).

Question 2 of 10

TEKS 11A-12F Easy Word

In a food chain, which organism is the primary consumer?

A Eagle

B Fox

C Grass

D Rabbit

Explanation

📌 Primary consumer = herbivore = eats producers (plants).
Producers → Primary consumers → Secondary consumers → Tertiary consumers

Question 3 of 10

TEKS 11A-12F Easy Word Diagram

In the food web below, what would happen if all the frogs were removed?

A All organisms die

B Nothing changes

C Insect population increases and snake population decreases

D Snake population increases

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 4 of 10

TEKS 11A-12F Easy Word Diagram

The diagram shows a carbon cycle. Which process RELEASES carbon dioxide into the atmosphere?

A Photosynthesis

B Nitrogen fixation

C Cellular respiration

D Condensation

Explanation

📌 Processes that RELEASE CO₂:
• Cellular respiration (animals AND plants)
• Combustion (burning fossil fuels)
• Decomposition

Process that ABSORBS CO₂:
• Photosynthesis

Question 5 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 6 of 10

TEKS 6A-6H Medium Word Diagram

Based on the Punnett square below, what is the probability of the offspring being heterozygous?

A 100%

B 50%

C 75%

D 25%

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 7 of 10

TEKS 11A-12F Easy Word

Which of the following is a biotic factor?

A Bacteria

B Temperature

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 uracil

B cytosine

C thymine

D guanine

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 6A-6H Medium Word Diagram

The diagram shows the process of DNA replication. What does the enzyme helicase do?

A Unwinds and separates the DNA strands

B Joins DNA fragments

C Proofreads the new DNA

D Adds new nucleotides

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 10 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?

A 100 kcal

B 10 kcal

C 5,000 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.

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