Part 2 — Answer key

Compare your answers after you have finished Part 1.

1. You stain a human cheek cell and see a dark, round structure that holds most of the cell’s DNA. What are you looking at?
   Nucleus
2. Arteries always carry oxygen-rich blood.
   False
3. In DNA, which base pairing is correct?
   A pairs with T
4. Which organism is a producer in an ecosystem?
   Algae making sugars from sunlight
5. A microbe has circular DNA in a nucleoid region, divides by binary fission, and has no mitochondria. What is it?
   Bacterial cell
6. Which blood vessel type carries blood toward the heart?
   Vein
7. Energy is recycled in ecosystems in the same way water is.
   False
8. In a Mendelian trait, allele A is dominant to allele a. Which statement must be true?
   Heterozygotes show the dominant phenotype
9. Ribosomes can be free in the cytoplasm or attached to the rough endoplasmic reticulum.
   True
10. A biologist says a population has evolved. What did they most likely measure?
    Allele frequencies changing across generations
11. A rabbit eating grass is a primary consumer.
    True
12. During inhalation, the diaphragm contracts and moves downward.
    True
13. A cell in the ovary is about to produce an egg cell. Which process must occur?
    Meiosis
14. A red blood cell is placed in a very salty solution and shrivels. Which water movement best explains this?
    Water moves out of the cell toward higher solute concentration
15. An enzyme reaction runs well at 37°C, but almost stops after heating the mixture to 95°C. What is the most likely reason?
    The enzyme’s shape changed permanently
16. Which relationship is mutualism, where both species benefit?
    Bee pollinating a flower
17. Which vessel carries deoxygenated blood from the heart to the lungs?
    Pulmonary artery
18. Crossing over occurs during prophase I of meiosis.
    True
19. A few storm-blown lizards colonize a small island. Ten generations later, the island population has very different allele frequencies from the mainland, mostly due to the tiny starting group. What is this called?
    Founder effect
20. Mitochondria are found in all living cells.
    False
21. In many freshwater lakes, which nutrient most often limits algal growth, so adding it can trigger a bloom?
    Phosphorus
22. Right after a sugary drink, which hormone helps bring blood glucose back down?
    Insulin
23. Giraffes evolved long necks because individual giraffes needed to reach higher leaves.
    False
24. In snapdragons, crossing a red-flowered plant with a white-flowered plant produces pink offspring. What inheritance pattern is this?
    Incomplete dominance
25. A cell uses ATP to pump sodium ions out even though sodium is already more concentrated outside. What kind of transport is this?
    Active transport
26. Decomposers return nutrients to ecosystems by breaking down dead organisms and wastes.
    True
27. Why does myelin around an axon typically make nerve impulses travel faster?
    It insulates the axon so impulses jump between nodes
28. Two unaffected parents have an affected child with a rare trait, and the trait appears equally in males and females. Which inheritance pattern fits best?
    Autosomal recessive
29. Sharks (fish) and dolphins (mammals) both have streamlined bodies and fins for fast swimming, but their last common ancestor did not. What evolutionary pattern does this illustrate?
    Convergent evolution
30. In a kelp forest, sea otters eat sea urchins, and urchins eat kelp. If otters are removed, what change is most likely?
    Urchins increase, kelp forests shrink
31. A person can live indefinitely with no kidney function as long as they drink plenty of water.
    False
32. In a testcross, two genes are very close together on the same chromosome. What offspring pattern is most likely?
    Mostly parental combinations, few recombinants
33. A cell that lacks mitochondria can still make a small amount of ATP from glucose. Where does this pathway occur?
    Cytosol
34. Which example best shows negative feedback in the human body?
    Sweating as body temperature rises
35. Two identical twins have the same DNA sequence, but as adults they show different gene expression patterns linked to chemical tags on DNA. What mechanism best explains this?
    DNA methylation changing transcription
36. A toxin that does not break down easily enters a lake food chain. Which organism is most likely to have the highest toxin concentration due to biomagnification?
    Orca