Download AP Biology Thought Questions – 1st Semester SHIELDS Why do

AP Biology Thought Questions – 1st Semester
SHIELDS
1.
Why do you suppose humans circulate the monosaccharide, glucose, in their blood, rather than employing a disaccharide like
sucrose as a transport sugar, as plants do?
2.
In Fred Hoyle’s science fiction novel, The Black Cloud, the earth is approached by a large interstellar cloud of gas that orients
itself around the sun. Scientists soon discover that the cloud is feeding on the sun, absorbing the sun’s energy through the
excitation of electrons in the outer energy levels of cloud molecules, in a process similar to the photosynthesis that occurs on
earth. Different portions of the cloud are isolated from each other by associations of ions created by this excitation. Electron
currents pass between these portions, much as they do on the surface of the human brain, endowing the cloud with self-awareness,
memory, and the ability to think. Using electrical discharges, the cloud is able to communicate with humans and describe its
history. It tells human scientists that it originated as a small extrusion from an ancestral cloud, and that since then it has grown by
the absorption of molecules and energy from stars like our sun, on which it has been feeding. Soon the cloud moves off in search
of other stars. Is it alive?
3.
Some cells are much larger than others. Given the constraints imposed by the surface-to-volume ratio, how would you expect the
level of activity in large cells to compare with that in small cells? What assumptions must you make to answer this question?
4.
Mitochondria and chloroplasts are thought to be the evolutionary descendents of living cells that were engulfed by other cells.
Are mitochondria and chloroplasts alive?
5.
If the viscosity of membranes increases at low temperatures, how do cells keep their plasma membranes fluid in cold
environments (e.g. in the water beneath the ice on a frozen lake)?
6.
Almost no sunlight penetrates into the deep ocean. However, many fish that live there attract prey and potential mates by
producing their own light. Where does the light come from? Does its generation require energy?
7.
Oxidation-reduction can involve a wide variety of molecules. Why do you suppose those involving hydrogen and oxygen are the
ones of paramount importance in biological systems?
8.
Give an example of a biochemical pathway from this unit.
9.
As explained in Chapter 5, mitochondria are thought to have evolved from bacteria that were engulfed by and lived symbiotically
within early eukaryotic cells. Why haven’t present-day eukaryotic cells dispensed with mitochondria, placing all of the
mitochondrial genes in the nucleus and carrying out all of the metabolic functions of mitochondria within the cytoplasm?
10. Why do plants typically store their excess energy as carbohydrate rather than fat?
11. In theory, a plant kept in total darkness could still manufacture glucose – if it were supplied with which molecules?
12. Colchicine is a poison that binds to tubulin and prevents its assembly into microtubules, cytochalasins are compounds that bind to
the ends of actin filaments and prevent their elongation. What effects do you think these two substances would have on cell
division in animal cells?
13. If you could construct an artificial chromosome (out of anything), what features would you introduce into it, at a minimum, so
that it could function normally in mitosis?
14. Humans have 23 pairs of chromosomes. Ignoring the effects of crossing over, what proportion of a woman’s eggs contain only
chromosomes she received from her mother?
15. Occasionally, the homologues of a particular chromosome fail to separate during meiosis I, or the sister chromatids of a particular
homologue fail to separate during meiosis II. Using the hypothetical example of an organism with two pairs of chromosomes in
the adult, describe the chromosomal make-up of the eggs that would result from each of these errors in meiosis. If these eggs
were fertilized by normal sperm, what would the chromosomal make-up of the resulting zygotes by like?
16. The human genome contains approximately 3 billion (3 x 109) nucleotide base pairs, and each nucleotide in a strand of DNA takes
up about 0.34 nanometer (0.34 x 10 -9 meter). How long would the human genome be if it were fully extended?
17. If every cell in an organism contains a full complement of the genes in that organism, and if each gene codes for an enzyme or
other protein, why don’t all cells in an organism synthesize the same proteins and therefore have the same structure and function?
18. The nucleotide sequence of a hypothetical eukaryotic nuclear gene is shown below:
TAC ATA CTA GTT ACG TCG CCC GGA AAT ATC
If a mutation of this gene were to change the 15 th nucleotide (underlined) from guanine to thymine, what effect do you think it
would have on the expression of this gene?
19. What would happen if you put mouse Hox genes into a human embryo?
20. In a colony of mice maintained for medical research, a hairless mouse is born. What minimum evidence would you accept that
this variant represents a genetic mutation?
21. Will a dominant allele that is lethal be removed from a large population as a result of natural selection? What factors might
prevent this from happening? What if the lethal allele is recessive?
22. In a large, random-mating population with no forces acting to change gene frequencies, the frequency of homozygous recessive
individuals for the characteristics of extra-long eyelashes is 90 per 1000 or .09. What percent of the population carries this
desirable trait but displays the dominant phenotype, short eyelashes? Would the frequency of the extra-long eyelash allele
increase, decrease or remain the same if long-lashed individuals preferentially mated with each other and no one else?
23. Imagine that you sat on the Supreme Court in the fall of 1986, hearing a case in which it was argued that creation science be
taught in public schools, alongside evolution as a legitimate alternative scientific explanation of biological diversity. What is the
best case lawyers might have made for and against this proposition? A decision of the Supreme Court was announced in June,
1987. How would you have voted and why?
24. Under what circumstances is hybridization between species selected against? When is it selected for?
25. Can species ever originate in a single step? If so, what are some of the ways in which this could occur?
26. Create a hypothesis for why all living lemurs on the earth are on the island of Madagascar.
27. Studies of the DNA of primates have revealed that humans differ from gorillas in only 1.2% of the DNA nucleotide sequences,
and from chimpanzees in only 1.2%. This degree of genetic similarity (about 1%) is the same as usually seen among “sibling”
species (that is, species that have only recently evolved from a common ancestor). Yet humans are assigned not only to a different
genus, but to a different family! Do you think this is legitimate, or are humans just a rather unusual kind of African ape?