CSET CSET Subtest II Life Sciences 4 — Questions and Answers
Question 1: Which mechanism drives natural selection according to Darwin's theory of evolution?
- Inheritance of acquired characteristics
- Random mutation only
- Differential reproductive success based on heritable traits (Correct answer)
- Geographic isolation alone
Correct answer: Differential reproductive success based on heritable traits
Natural selection acts when individuals with heritable advantageous traits survive and reproduce more than others.
Question 2: A cell in G2 phase of the cell cycle has a DNA content of 8 picograms. What was the DNA content at the start of S phase?
- 2 picograms
- 4 picograms (Correct answer)
- 8 picograms
- 16 picograms
Correct answer: 4 picograms
S phase replicates DNA, so before replication (G1 end/S start) the cell had 4 pg; after S phase it has 8 pg.
Question 3: Which type of ecological succession occurs on bare rock with no prior soil?
- Secondary succession
- Primary succession (Correct answer)
- Retrogressive succession
- Climax succession
Correct answer: Primary succession
Primary succession begins on lifeless substrate like bare rock, starting with pioneer species such as lichens.
Question 4: The Hardy-Weinberg principle states that allele frequencies in a population remain constant if which condition is met?
- The population is small and isolated
- Natural selection, mutation, migration, and genetic drift are absent (Correct answer)
- Mutations occur at a constant rate
- All individuals have the same fitness
Correct answer: Natural selection, mutation, migration, and genetic drift are absent
Hardy-Weinberg equilibrium requires no mutation, random mating, no selection, no gene flow, and large population size.
Question 5: Which molecule acts as the final electron acceptor in aerobic cellular respiration?
- Carbon dioxide
- NAD+
- Oxygen (Correct answer)
- ATP
Correct answer: Oxygen
Oxygen accepts electrons at the end of the electron transport chain, combining with hydrogen ions to form water.
Question 6: A parent plant with genotype Aa is self-pollinated. What fraction of offspring will be homozygous?
- 1/4
- 1/2 (Correct answer)
- 3/4
- All offspring
Correct answer: 1/2
A cross of Aa × Aa yields 1/4 AA, 1/2 Aa, 1/4 aa, so 1/2 of offspring are homozygous (AA or aa).
Question 7: Which structure in the human digestive system is responsible for most chemical digestion and nutrient absorption?
- Stomach
- Large intestine
- Small intestine (Correct answer)
- Esophagus
Correct answer: Small intestine
The small intestine, with its villi and microvilli, is the primary site of enzymatic digestion and nutrient absorption.
CSET CSET Subtest II Life Sciences 4
Which mechanism drives natural selection according to Darwin's theory of evolution?