Practice Test 28 - High School Biology

20 questions. Answer them in any order, then submit to see your score and every explanation.

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1. In a diagram of DNA, the molecule is shown as a twisted ladder. The sides of the ladder represent the sugar-phosphate backbone, and the rungs represent paired bases. Where are the nitrogenous bases located in the double helix?
2. A diagram of a leaf shows arrows labeled: (1) $CO_2$ entering the leaf, (2) light energy shining onto the leaf, (3) $H_2O$ moving up from the roots into the leaf, (4) $O_2$ leaving the leaf. Which arrow represents a product of photosynthesis leaving the plant?
3. A pond energy pyramid shows producers (algae) with 50,000 energy units. Using the 10% rule, approximately how much energy would be available to the secondary consumers (3rd trophic level)? (Food chain: algae → zooplankton → small fish.)
4. Which statement best explains why DNA is wrapped around histone proteins and further coiled in cells?
5. A student claims: "Natural selection happens when individual animals evolve new traits during their lifetime to survive a challenge." Which response best corrects the claim using the key idea of how natural selection works?
6. A researcher compares two genes and finds that Gene X and Gene Y are the same length but have many bases in different positions. What does this most strongly suggest about the information in these genes?
7. A coastal fish population has declined due to overharvesting. Managers propose creating a no-take marine reserve covering 30% of the fish's breeding habitat. Fishing would still be allowed outside the reserve. Which statement best evaluates this strategy using ecological principles and realistic trade-offs?
8. A bacterial population contains two variants: antibiotic-resistant and antibiotic-susceptible. When an antibiotic is present, about 95% of resistant bacteria survive, but only about 5% of susceptible bacteria survive. Which choice best explains how resistance affects fitness in the antibiotic environment?
9. A stable system uses sensors to monitor an internal condition, compares it to a set point, and activates effectors to correct deviations. An unstable system does not detect changes or does not respond effectively. Which scenario best represents a stable (homeostatic) system?
10. A cut on the skin becomes infected. White blood cells need to reach the wound site quickly. How do the immune and circulatory systems work together to fight the infection?​
11. In a food web, a hawk eats snakes, and snakes eat mice, and mice eat grass seeds. Which reason best explains why there are usually fewer hawks than mice in the same ecosystem?
12. A scientist compares two organisms: (1) a human, where sperm and egg are made by meiosis and then fuse during fertilization; (2) a bacterium, where one cell splits into two identical cells by binary fission. Which statement correctly describes the genetic outcomes of these two reproduction methods?
13. In a meadow ecosystem, carbon atoms can follow this pathway: atmospheric CO2 is taken in by grasses, a rabbit eats the grass, a fox eats the rabbit, and decomposers break down dead organisms and waste. Which statement best describes how carbon matter moves through this ecosystem over time?
14. A bacterial population contains heritable variation: about 1% of the bacteria carry a mutation that makes them resistant to a certain antibiotic. A patient takes that antibiotic repeatedly over many bacterial generations. After treatment, most surviving bacteria are resistant. Which explanation best connects this outcome to natural selection and adaptation?
15. In a rock layer sequence, older layers contain fossils of fish with fins only, middle layers contain fossils with fin bones resembling a wrist, and younger layers contain early tetrapods with digits. What is the best evolutionary interpretation of this pattern?
16. Which example is best classified as sexual reproduction?
17. A tropical rainforest area is cleared and burned to create cattle pasture. In the following years, fewer native bird and insect species are observed, and soil washes away more easily during storms. Which pair of ecosystem impacts is most directly linked to this land-use change?
18. Some textbooks estimate that about 40% of the energy from glucose is captured in ATP during cellular respiration (the rest is released as heat). Which statement best matches this idea?
19. Two mRNA molecules have different base sequences. How will this most likely affect the proteins produced during translation?
20. A simplified example of a real condition: in sickle cell disease, a single base substitution in the hemoglobin gene changes one amino acid in the hemoglobin protein. Which statement best describes the mutation-to-function pathway shown by this example?

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