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Clemson Biology Merit Exam
March 28, 2003



Clemson University Biology Merit Exam
28 March 2003

Please choose the best answer for each of the following questions. Questions marked with an "*" are worth 4 points each; questions marked with a "#" are worth 2 points each; the unmarked questions are worth 1 point each.

CAUTION: Incomplete erasures and smudges can be read as marks. To avoid having a choice read incorrectly, make your marks lightly at first. After you have made all your changes, blacken in your marks just before you turn in your answer sheet.

The theme of this exam is that spreading and noxious pest, the red imported fire ant.


# 1. Which of the following animals is most closely related to a fire ant?
a) a crab b) an earthworm c) a clam d) a sponge

2. Which of the following insects is most closely related to a fire ant?
a) a beetle b) a housefly c) a moth d) a wasp

3. A correct way to write the species name of the red imported fire ant is
a) SOLENOPSIS Invicta. b) Solenopsis invicta.
c) Solenopsis Invicta. d) Solenopsis (invicta).

By the way, "invicta" means "invincible."

# 4. Red imported fire ants originally come from Brazil and Argentina. It is thought that they were introduced into the US at Mobile, Alabama, around 1930. Which of the following bits of biological knowledge was not generally known among biologists in 1930?
a) The cell is the basic unit of biological organization.
b) DNA is the genetic material.
c) Photosynthesizing plants produce oxygen.
d) Blood leaves the heart through arteries and returns to it through veins.

# 5. The first thing we notice about a fire ant is its exoskeleton, which is made mostly of
a) cellulose. b) prothrombin. c) chitin. d) triglycerides.

6. The fire ant body consists of three main sections, shown below.


Body section 3 above is called the
a) abdomen. b) thorax. c) mesosternum. d) sacrum.

* 7. Ants are renowned for their ability to carry burdens that are several times their own weight. This ability comes from the strength of their exoskeleton and their muscles. If fire ant muscles are like human muscles, they contract because of the following events:
1. Binding sites on actin are uncovered.
2. Myosin heads bend.
3. Calcium ions spill from the sarcoplasmic reticulum.
4. Myosin binds to actin.
5. Z lines move closer to the center of the sarcomere.
Starting with the action potential arriving at the muscle, the correct order of these steps, is
a) 4 5 2 1 3 b) 3 2 1 4 5 c) 2 4 3 1 5 d) 3 1 4 2 5

8. ATP is necessary for muscle contraction. In fire ant muscles, as in human muscles, most of the ATP is provided by organelle ... below.

a) b)
c) d)


# 9. The "Endosymbiont" Theory makes assertions about the origins of organelles ... pictured above.
a) a and d b) a and b c) c and d d) b and c

# 10. Aerobic respiration that provides the ATP for muscle contraction consists of three main steps. The correct order for those steps is
a) glycolysis, the Krebs Cycle, and electron transport.
b) fermentation, proton pumping, and electron transport.
c) the Hill Reaction, glycolysis, and the Krebs Cycle.
d) oxidation, reduction, and dialysis.

* 11. Aerobic respiration can be written as the basic equation

C6H12O6 + O2 --> CO2 + H2O


Here, the ... is oxidized by the reaction and the ... is reduced by the reaction.
a) CO2... H2O b) H2O ... O2
c) C6H12O6 ... O2 d) C6H12O6 ... CO2

* 12. One of the stages of the process in the equation above starts with glucose and ends with pyruvate. It also uses ATP. If this first stage is allowed to proceed in a reaction mixture with 1 mM glucose and several different concentrations of ATP, the following concentrations of glucose and pyruvate are observed over time. In each case, the dark line is glucose and the lighter line is pyruvate:



First, what is the best explanation for the fact that the end concentration of pyruvate is twice as high as the starting concentration of glucose?
a) Pyruvate is more oxidized than glucose.
b) Glucose has more energy than pyruvate.
c) During the reaction, glucose takes on atoms and as a result pyruvate is heavier than glucose on a per-molecule basis.
d) Each glucose splits into two pyruvates.

* 13. Now, what is the best explanation for the graphs above? Pay special attention to the data on the middle graph, where a 1 mM concentration of ATP is provided for a 1 mM concentration of glucose.
a) Glucose cannot be made into pyruvate when too much ATP is present.
b) The reaction series requires ATP for activation energy, but later makes more ATP than it requires.
c) ATP is necessary for activation energy, but too much ATP causes the reaction to partially reverse, and slows its net rate.
d) Glucose is made into pyruvate on the right graph, pyruvate is made into glucose on the left graph, and the two processes balance on the middle graph.

14. Fire ants need oxygen just as humans do. Humans absorb oxygen through their ... and fire ants absorb oxygen through their
a) lungs ... spiracles. b) lungs ... gills.
c) trachea ... lungs. d) tracheal tubes ... pneumostomes,

# 15. Fire ants eat a bewildering varity of foods, including seeds, plant parts, invertebrates (especially other insects), and the young of vertebrates such as birds and rodents. Sometimes the fire ants pass nutrients on to other ants in the form of the molecule below.


The molecule above is
a) ribose. b) sucrose. c) acetylcholine. d) NADH.

16. When fire ants pass food to their young, they use a solution that is rich in amino acids. Amino acids are the basic units of ..., and the molecule below


... an example of an amino acid.
a) proteins ... is b) DNA ... is not
c) DNA ... is d) proteins ... is not

# 17. Fire ant cells are much like other animal cells. In an isolated fire ant cell, the outermost layer would be a
a) chitin cell wall. b) tangle of cellulose microfibrils.
c) nucleic acid helix. d) phospholipid bilayer.

# 18. While many people have not looked closely at a fire ant, it is almost impossible to miss fire ant mounds. These are mounds of fresh soil about a foot in diameter and a foot high. Therefore, the diameter of a fire ant mound would be about ... cm.
a) 10 b) 20 c) 30 d) 40

The mound is only a tiny portion of the fire ant nest. Beneath the mound, a maze of galleries and tunnels may extend to 5 feet below the surface. In addition, tunnels several inches below the soil surface radiate out from the mound for up to 75 feet, allowing the ants to exit from the colony far from the mound. A mature colony might contain 300,000 ants!

# 19. Say we want to estimate the number of ants in a colony. We capture several hundred ants and put a dot of paint on the exoskeleton of each one. Then we release these marked ants into the colony. We hope these marked ants mix randomly with the rest of the colony. Later we capture some more ants, and some of them are marked. The ... the proportion of marked ants in our second recapture, the ... the size of the ant population.
a) larger ... larger b) larger ... smaller c) smaller ... smaller

20. When the mound is disturbed, the ants boil out and attack. So many ants respond at once because the first few to detect the disturbance secrete a chemical called a ... that alerts other ants.
a) pheromone b) hormone c) tropin d) local regulator

* 21. When an ant attacks a human, it grasps the skin of its victim with its mandibles and stabs the victim with the stinger on its rear end seven or eight times in a circular pattern around its point of attachment. Each sting injects a small amount of venom. This venom causes a burning sensation, and after that a fluid-filled blister forms. The accumulation of fluid in areas that are inflammed is caused by a release of ..., and has the beneficial effect (for the human) that it
a) leukotriene ... makes damaged cells more resistant to viral attack.
b) interleukin-1 ... hastens blood clotting.
c) histamine ... allows phagocytic cells to reach the damaged area more easily.
d) acetylcholine ... dulls the pain caused by tissue injury.

* 22. The blister is not the end of the story, however. Often, scratching of the blisters breaks them and leads to bacterial infection. If bacterial infection occurs, the body will probably respond with a(n) ...-mediated immune response caused by
a) cell ... release of interferon from damaged cells.
b) antibody ... activation of a clone of B cells.
c) cell ... phagocytosis of the bacteria by lymphocytes.
d) antibody ... release of complement from damaged cells.

# 23. It is ironic that fire ant venom leads to infection, because the venom kills bacteria, and fire ants spray a fine mist of their venom over their eggs to prevent the eggs from being attacked by bacteria. Bacterial cells are different from eukaryotic cells because bacterial cells, but not eukaryotic cells,
a) lack a membrane-bound nucleus. b) lack ribosomes.
c) lack a true cell membrane. d) All of these.

* 24. On the basis of characteristics like ribosomal RNA and membrane lipids, taxonomists have decided that there are two great groups of bacteria that separated long ago in evolutionary time. These groups are the
a) Gram-positives and Gram-negatives.
b) Eubacteria and Archaebacteria.
c) Actinomycetes and Paleomycetes.
d) Paleobacteria and Neobacteria.

25. Fire ants cause agricultural damage. For example, just seeing mounds keeps cattle away from an infested area in a pasture. When light reflecting off a fire ant mound enters a cow's eye, the last structure the ray of light contacts will be the
a) iris. b) cornea. c) retina. d) lens.

* 26. The sight of the mound will begin an action potential in the cow's optic nerve when
a) calcium ions are released from the sarcoplasmic reticulum.
b) potassium ions rush out of the neuron.
c) sodium ions rush into the neuron.
d) the sodium-potassium pump reverses.

* 27. Fire ant mounds also keep light from reaching the grass that the mounds bury. Grass kept in darkness turns yellow and eventually dies. The green color of healthy grass is caused by ... , which has the function in photosynthesis of
a) xanthophyll ... splitting water.
b) chlorophyll ... supplying the light-dependent reactions with excited electrons.
c) chlorophyll ... shading carotenoids and preventing their photooxidation.
d) carotenoids ... using ATP and NADH to reduce CO2 to sugar.

# 28. Also, fire ants are serious seed predators, mostly on minor crops like sunflowers, okra, and cucumbers. A flowering plant seed results when a sperm from a ... unites with an egg from a(n)
a) pollen tube ... female gametophyte. b) sporangium ... endosperm cell.
c) generative nucleus ... pollen grain. d) sporophyte ... female gametophyte.

* 29. Consider the cucumbers above. The flesh, juicy part of the cucumber results when
a) a second sperm unites with the two polar nuclei.
b) the zygote undergoes many divsions, but many of its cells are excluded from the embryo.
c) endosperm gathers around the embryo.
d) the ovary wall expands and ripens.

# 30. Fire ants also damage plants in more indirect ways. Because of their feeding on insects, a fall in other insect populations may mean that some pollinators (such as solitary bees) are driven extinct in an infested area. Pollinators carry pollen from the ... of one flower to the ... of another.
a) anther ... stigma b) style ... carpel c) style ... ovary d) anther ... sepal.

* 31. A fire ant colony starts when winged males and winged females from an existing colony mate in flight. A female mates with just one male. Often, one fire ant colony will produce mostly females and another will produce mostly males. This characteristic is probably ... for the fire ants because it
a) advantageous ... propagates only superior alleles.
b) disadvantageous ... reduces the genetic diversity of the offspring.
c) disadvantageous ... it prevents alleles from reaching an allelic frequency of 1.0.
d) advantageous ... it avoids inbreeding and the expression of deleterious, recessive mutations.

Soon after mating, the males die. A mated female looks for a site for a new colony, lands, loses her wings, and digs out a "brood cell" a few inches beneath the surface of the soil. The loss of wings is a critical step because the female will be unable to dig the brood cell with wings. Say that the ability to lose wings depends on the W locus, and the following phenotypes result from different genotypes:

WW female loses wings before mating flight--never mates
Ww female loses wings after mating flight--starts new colony
ww female can't lose wings--mates, but can't start a new colony

In fire ants, males are haploid. This means that the two choices for males are:

W male loses wings before mating flight--never mates
w male has wings for mating flight--can mate

# 32. Under these conditions, which of the following crosses would be possible and could start a new colony? The male genotype is listed first and the female one second. Answer this question without considering the information on the D allele below.
a) w x Ww b) w x WW c) W ... ww d) All of these.

* 33. If W and w are the only alleles at this locus, what will happen to the allelic frequences of W and w over time in females? Answer this question without considering the information on the D allele below.
a) W will reach a frequency of 1.0.
b) w will reach a frequency of 1.0.
c) W and w will remain at allelic frequencies of about 0.5.
d) Genetic drift will drive this situation, and any of the situations above are equally likely.

Now consider the D allele. Say another allele, D, allows the loss of wings after mating in ww females. It does this as long as at least one D is present. D has no effect on WW or Ww ants because they already lose their wings. The D locus is on a different chromosome from the W locus.

* 34. In a dw x DdWw mating, ... of the female offspring will be able to make a mating flight and then lose their wings and excavate a brood chamber.
a) 3/4 b) 11/16 c) 1/2 d) 5/16

35. The D allele codes for a protein called deciduin. The first few nucleotides in the D allele are GCTATC. The mRNA transcribed from these DNA nucleotides would be
a) GCUTAC. b) CGATAG. c) CTATCG. d) CGAUAG.

* 36. The d allele makes an ineffective form of deciduin. A researcher takes a large number of fire ant females that lost their wings either after or before the mating flight and a large number that could not drop their wings after the mating flight. Protein electrophoresis shows the following bands. The white rectangles are the wells, and assume that only the deciduin is seen:



From this gel, we can conclude that the ineffective form of deciduin is ... than the effective form.
a) lighter b) heavier
c) No conclusion is possible because the researcher has no idea of the genotypes of these ants at the W locus.

# 37. If the fire ant female gets past all these genetic barriers and does mate and excavate a brood chamber, she lays 10-15 eggs. She produces the eggs and uses stored sperm to fertilize them. Fire ants have complete metamorphosis, so the young that hatch from these eggs will be called
a) larvae. b) nymphs. c) pupae. d) imagoes.

The adults that eventually come out of these eggs are very small workers called minims. They open the brood chamber to the outside and start to forage and bring food back to the female, who is now their queen. Within 30 days, several sizes of larger workers begin to be produced, and the colony really takes hold. The queen can live up to 7 years, and produce up to 5,000 eggs/day! And all these eggs draw on the queen's sperm supply, secured during the mating flight, perhaps years before.

# 38. All the worker ants have the same mother and the same father. Yet these workers are not genetically identical because of
a) the fact that complementary strands of DNA do not produce the same proteins.
b) mitosis, which produces genetically variable daughter cells.
c) random assortment of the queen's maternal and paternal alleles during Anaphase I.
d) degeneracy of the genetic code.


Fire ants are not pests in their "home territories" of Brazil and Argentina, and this has prompted entomologists to search there for possible biological control agents. One of these is a related ant (which we will call the invader ant). The invader queen enters the fire ant colony, attaches itself to the fire ant queen, reduces her egg production, and somehow directs the fire ant workers to feed the invader queen's offspring. The invader ant has no workers, just queens and males, and so depends on the fire ant for survival.

39. The relationship between the invader ant and the fire ant is called
a) asocialism. b) mutualism. c) commensalism. d) parasitism.


* 40. Consider the ratio of the invader ant queens to fire ant queens in the general environment. The ability of the average invader ant queen to reproduce will have the following relationship to this ratio:
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