Biology — Semester B Practice

Question 1 of 10

TEKS 11A-12F Easy Word Diagram

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

A Nothing changes

B Snake population increases

C All organisms die

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 2 of 10

TEKS 6A-6H Easy Word

DNA is made up of repeating units called:

A monosaccharides

B fatty acids

C amino acids

D nucleotides

Explanation

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

Question 3 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 4 of 10

TEKS 11A-12F Easy Word

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

A Eagle

B Grass

C Fox

D Rabbit

Explanation

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

Question 5 of 10

TEKS 11A-12F Easy Word Diagram

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

A Nitrogen fixation

B Photosynthesis

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 6 of 10

TEKS 10A-10C Easy Word

Homeostasis is:

A the classification of organisms

B the study of ecosystems

C the process of cell division

D maintaining stable internal conditions

Explanation

📌 Homeostasis = maintaining stable internal conditions (body temp, blood sugar, pH, water balance) despite external changes.

Question 7 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 5,000 kcal

B 1,000 kcal

C 10 kcal

D 100 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 8 of 10

TEKS 6A-6H Medium Word Diagram

The diagram shows the central dogma of molecular biology. What process occurs at step 2?

A Transcription

B Replication

C Mutation

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 9 of 10

TEKS 11A-12F Easy Word

Which of the following is a biotic factor?

A Bacteria

B Water

C Temperature

D Sunlight

Explanation

📌 Biotic = living things (plants, animals, bacteria).
Abiotic = non-living (temperature, water, sunlight, soil).

Question 10 of 10

TEKS 6A-6H Easy Word

In DNA, adenine (A) always pairs with:

A cytosine

B thymine

C guanine

D uracil

Explanation

📌 Base pairing rules: A-T (2 hydrogen bonds), G-C (3 hydrogen bonds).
In RNA: A-U instead of A-T.

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