CSET Subtest II Life Sciences Flashcards

Which mechanism drives natural selection according to Darwin's theory of evolution?

Answer: Differential reproductive success based on heritable traits

Natural selection acts when individuals with heritable advantageous traits survive and reproduce more than others.

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?

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.

Which type of ecological succession occurs on bare rock with no prior soil?

Answer: Primary succession

Primary succession begins on lifeless substrate like bare rock, starting with pioneer species such as lichens.

The Hardy-Weinberg principle states that allele frequencies in a population remain constant if which condition is met?

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.

Which molecule acts as the final electron acceptor in aerobic cellular respiration?

Answer: Oxygen

Oxygen accepts electrons at the end of the electron transport chain, combining with hydrogen ions to form water.

A parent plant with genotype Aa is self-pollinated. What fraction of offspring will be homozygous?

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).

Which structure in the human digestive system is responsible for most chemical digestion and nutrient absorption?

Answer: Small intestine

The small intestine, with its villi and microvilli, is the primary site of enzymatic digestion and nutrient absorption.