USABO OPEN EXAM CERTIFICATION
EVALUATION 2026 QUESTIONS WITH
SOLUTIONS GRADED A+
⩥ Which of the following statements is an acceptable statement about
growth in plants? Answer: Some plants lack secondary growth
⩥ ATP is an important molecule in metabolism because it: Answer: has
high-energy phosphate bonds.
⩥ Crossing over contributes to the genetic variation of a species by
exchanging chromosomal segments between nonsister chromatids of
homologous chromosomes. In the production of which type of cell does
the crossing over occur? Answer: Gametes
⩥ In a population of 15 AA, 25 Aa, and 10 aa individuals, the frequency
of the a allele is: Answer: 0.45
⩥ Use the cladogram below to answer the following question. Which
group(s) represent(s) a monophyletic taxon? (number 47 on 2004 exam)
Answer: A, B, C, D, E, F, and G
⩥ A ribozyme is a(an): Answer: RNA molecule that functions as a
enzyme.
,⩥ When an ant in a colony dies, the live ants will throw the dead ant out
of the anthill. If a live ant from the colony, Ant X, is sprayed with a
chemical characteristic of dead ants, the live ants will repeatedly throw
Ant X out of the anthill, until the chemical on Ant X wears off. What is
the best behavioral explanation of ant colony? Answer: The chemical
acts as a sign stimulus for a fixed action pattern
⩥ Vascular plants share all of the following characteristics EXCEPT:
Answer: development of seeds.
⩥ The production of the genetically engineered "golden rice" could be
important to the people of developing nations, especially in South-East
Asia, because: Answer: golden rice contains higher concentrations of β-
carotene than white rice
⩥ A large population of laboratory rats was allowed to breed randomly
for a number of generations. In this population, a dominant allele at the
A locus codes for agouti fur (A), and a recessive allele codes for black
fur (a). At the beginning of the breeding cycles, 49% of the rats had
black fur. At the end of the breeding cycles, this percentage was the
same. The rest of the animals had agouti fur with heterozygotes
indistinguishable from homozygous dominants. What percentage of this
population is probably heterozygous for the fur color trait assuming the
rats are following Hardy-Weinberg population genetics? Answer: 42%
, ⩥ In Pompe's disease, the liver is damaged due to the accumulation of
glycogen. What organelle is most likely malfunctioning? Answer:
lysosome
⩥ Transport of which nutrient across the intestinal epithelium is by
passive diffusion? Answer: fructose
⩥ Which two brain centers control mammalian respiration? Answer:
medulla oblongata and pons
⩥ The presence of a vertebral column is with respect to all vertebrates
[first term], but is with respect to all chordates [second term]. Answer:
primitive; derived
⩥ The main explanation for the lack of a continuing abiotic origin of life
on Earth today is that: Answer: our oxidizing atmosphere is not
conducive to spontaneous formation of complex molecules
⩥ Scientists have determined that three classes of genes (named A, B,
and C) control development of the four flower parts: Sepals, Petals,
Stamen, and Carpels. Genes A and C mutually repress each other. Gene
B is not regulated by either Genes A or C. The expression pattern of
these genes in wild-type flowers is shown below, where +++ indicates
gene activity.
EVALUATION 2026 QUESTIONS WITH
SOLUTIONS GRADED A+
⩥ Which of the following statements is an acceptable statement about
growth in plants? Answer: Some plants lack secondary growth
⩥ ATP is an important molecule in metabolism because it: Answer: has
high-energy phosphate bonds.
⩥ Crossing over contributes to the genetic variation of a species by
exchanging chromosomal segments between nonsister chromatids of
homologous chromosomes. In the production of which type of cell does
the crossing over occur? Answer: Gametes
⩥ In a population of 15 AA, 25 Aa, and 10 aa individuals, the frequency
of the a allele is: Answer: 0.45
⩥ Use the cladogram below to answer the following question. Which
group(s) represent(s) a monophyletic taxon? (number 47 on 2004 exam)
Answer: A, B, C, D, E, F, and G
⩥ A ribozyme is a(an): Answer: RNA molecule that functions as a
enzyme.
,⩥ When an ant in a colony dies, the live ants will throw the dead ant out
of the anthill. If a live ant from the colony, Ant X, is sprayed with a
chemical characteristic of dead ants, the live ants will repeatedly throw
Ant X out of the anthill, until the chemical on Ant X wears off. What is
the best behavioral explanation of ant colony? Answer: The chemical
acts as a sign stimulus for a fixed action pattern
⩥ Vascular plants share all of the following characteristics EXCEPT:
Answer: development of seeds.
⩥ The production of the genetically engineered "golden rice" could be
important to the people of developing nations, especially in South-East
Asia, because: Answer: golden rice contains higher concentrations of β-
carotene than white rice
⩥ A large population of laboratory rats was allowed to breed randomly
for a number of generations. In this population, a dominant allele at the
A locus codes for agouti fur (A), and a recessive allele codes for black
fur (a). At the beginning of the breeding cycles, 49% of the rats had
black fur. At the end of the breeding cycles, this percentage was the
same. The rest of the animals had agouti fur with heterozygotes
indistinguishable from homozygous dominants. What percentage of this
population is probably heterozygous for the fur color trait assuming the
rats are following Hardy-Weinberg population genetics? Answer: 42%
, ⩥ In Pompe's disease, the liver is damaged due to the accumulation of
glycogen. What organelle is most likely malfunctioning? Answer:
lysosome
⩥ Transport of which nutrient across the intestinal epithelium is by
passive diffusion? Answer: fructose
⩥ Which two brain centers control mammalian respiration? Answer:
medulla oblongata and pons
⩥ The presence of a vertebral column is with respect to all vertebrates
[first term], but is with respect to all chordates [second term]. Answer:
primitive; derived
⩥ The main explanation for the lack of a continuing abiotic origin of life
on Earth today is that: Answer: our oxidizing atmosphere is not
conducive to spontaneous formation of complex molecules
⩥ Scientists have determined that three classes of genes (named A, B,
and C) control development of the four flower parts: Sepals, Petals,
Stamen, and Carpels. Genes A and C mutually repress each other. Gene
B is not regulated by either Genes A or C. The expression pattern of
these genes in wild-type flowers is shown below, where +++ indicates
gene activity.
