1. [3 pt] One reason bioluminescence (BL) is so prevalent in the ocean is that it has many uses. Examining some of these, why do you think BL is so much rarer on land?
This answer could have been gotten from your lecture notes from 5/8/00, the lecture outline on line for this lecture (see link above) and/or the article handed out in class that week called, "The Ecology of Bioluminescence".
The vast majority of the ocean is in total darkness, unlike the terrestrial ecosystem, therefore using light as a signaling mode is highly effective because there will be a high signal to noise ratio (there is little or no background light to interfere with the light from a bioluminescent organism, therefore this light is easily detected). This would explain the prevalence of bioluminescence used for communication and defense against predation (used to startle a predator or attract a predator: burglar alarm).
On land, other modes of signaling are more dominant, acoustical and chemical because these modes of signaling will have a better signal to noise ratio on land than they would in the ocean AND they also provide the organism with more signal security.
The midwater depths, where some sunlight penetrates, but only enough to dimly illuminate, is a 3-dimensional environment where an organism's shadow gives away its location. Bioluminescence used to counterilluminate, and thus, eliminate one's shadow is a highly effective mode of hiding in an environment where there is little to hide behind or in. Compare this to the terrestrial world where there is tons of foliage for an organism to hide in and thus be protected from predation, whereas in the open ocean, there is none. Also, because there is so much foliage in the terrestrial ecosystem, if you were bioluminescent, your light signal would not be able to be seen from as far away as it would if you were in the ocean. |
2. [2 pt] Describe 3 pieces of evidence that supports the hypothesis that BL evolved ~30 different times.
This answer could have been gotten from your lecture notes from 5/8/00, the lecture outline on line for this lecture (see link above) and/or the article handed out in class that week called, "The Ecology of Bioluminescence".
Answer: there are at least 5 different luciferin (the bioluminescent reaction substrate) structures known
There are many different biochemical control mechanisms of the bioluminescence reaction (ex. Ca+2 pulses, H+ pulses, O2).
Of all the various bioluminescent organisms found in a variety of phyla, there is no one common ancestor to whic these can all be linked. There is a discontinuity in the phylogenetic distribution of bioluminescent organisms, specifically, there are no bioluminescent sponges or flatworms, yet there are lower forms of organisms that are bioluminescent (protists) and there are many higher forms of organisms that are bioluminescent. |
3. [2 pt] Describe 2 pieces of evidence that supports the hypothesis that BL and vision are evolutionarily linked.
There are several acceptable answers for this question.
You could have described how fireflies have huge eyes relative to the size of their head indicating the importance of vision in seeing the BL communication flashes that occur between males and females.
The deep sea Black Dragonfish have evolved a red-light emitting (BL) photophore AND their eyes have also evolved in concert to see the red light (either by way of a yellow-sensitive antenna pigment or directly having a red-sensitive visual pigment).
Generally the fact that deep sea fish have eyes at all in the total absence of celestial light indicates that seeing BL is evolutionarily worthwhile, otherwise why have eyes?
The fact that most midwater and deep sea fish have only blue-sensitive visual pigments is also indicative of the linkage between BL and visual systems: most BL is blue. |
4. [2 pt] Fireflies are one of the few terrestrial organisms to use bioluminescence. They use bioluminescence as a means of between males and females of the same species for mating. There are many firefly species on the East Coast of the United States that all live mixed together in one area. To ensure same-species mating, the males have evolved a certain
| signaling flash code or flash frequency |
that is characteristic to its species. The female of this species will respond only when she recognizes this. In Malaysia there are fireflies of one species that coordinate their bioluminescence flashes. They are known as. Thousands of individuals can quickly coordinate their flashes so that they are all flashing in unison—without a leader starting the whole process. This phenomenon is known generally as
| anticipatory synchronization |
. The Malaysian fireflies are thought to coordinate their flashing in order to
| attract females from far away. |
.
5. [2 pt] Choose 2 "stories" describing two different uses of BL. Describe the use or function of BL, then discuss the selective pressure(s) that may have been important in the evolution of this use of BL.
| There are many different answers that are acceptable for this question. Please see the article "The Ecology of Bioluminescence" and/or the lecture outline from 5/8 (link above) for the uses of BL. ASK ME IF YOU DON'T UNDERSTAND THESE. |
6. [1 pt] True/False. Bees have a higher resolution spatial map of the area near their hive vs. the area further away from their hive.
Explain why or why not in one sentence.
 True
 False
See Syllabus p. 80.
Bees fly a certain set flight pattern. When they take off from their hive they begin by flying fairly low, as they fly further from the hive, they gain altitude (and they will also speed up because they maintain constant angular velocity). Think about the size of their field of view as they fly this path. When they are flying low, near the hive, their field of view is smaller and because they're lower (and slower), they can see landmarks better. When they gain altitude as they get further from the hive, their field of view is larger, and because they are further from the ground (and flying faster), they cannot see landmarks as well. So, the bee has a higher resolution spatial map of the area near its hive vs. areas that are further from its hive simply because the bee flies lower (and slower) when it is near its hive and higher (and faster) when it is further from its hive. |
7. [2 pt] What is the difference between the way bumble-bees inform other bumble-bees of a good food source and the way honeybees inform their cohorts of a good food source.
See Syllabus p. 109.
Bumble bees are thought to have a less highly evolved communication mode compared to honeybees. Bumble bees do not communicate the location of a food source to other bees, they just perform "excitatory runs" in the nest that allows the other bees to smell the odor that the bee has picked up from the visited flower. It is by this odor that the bees can then choose the same species of flower when they are out foraging, regardless of where it is located. Honeybees, on the other hand, have a much more sophisticated mode of communicating a good food source to other colony mates. Honeybees, by way of the waggle dance, communicate the distance and direction to the food. While they are performing the dance the other bees can get the flower odor information from the dancing bee as well. |
8. [2 pt] What did the Y-maze experiments indicate about honeybee learning?
See Syllabus p. 113.
This experiment indicated 2 things about honeybee learning:
(1) That honeybees exhibit associative learning: they associate seeing a particular color with performing a certain behavior that leads to a sugar reward. In this case they learned whenever they saw a certain color out of one eye, they needed to turn left to get the food.
(2) NOTE: honeybees do not have binocular vision, that is, each eye does see the same visual space at all, as our eyes do. So what one eye sees is totally independent of what the other eye on the other side of the head sees. It was observed that even if the bees were trained to make the association described in (1) in one eye, they would exhibit the same behavior when the other eye was presented with the same information. This indicated that there was a transfer of learned material from one eye to the other occurring at some higher level: aka, interocular transfer. |
9. [2 pt] (a) Describe the relationship that this graph indicates. (b) What does this indicate about a honeybee’s visual odometer.
See Syllabus p. 111.
This graph indicates that bees maintain a constant angular velocity by increasing their flight (and ground) speed as they increase their flying altitude. (= bee height). They do this because as they gain altitude their field of view increases in size, so, in order to keep the # of new fields of view passing through their visual field per unit time constant, they have to speed up as the size of their field of view increases. This ability allows the bees to make graceful, gentle landingson objects even though it has no ability to perceive depth (because its eyes do not have binocular overlap). |
10. [2 pt] Why has evolution selected a mechanism in which a bee only learns to associate a particular odor with sucrose presentation (as indicated by proboscis extension) when the odor is provided before the sucrose and not in the reverse order?
| Think about the way the bee has these things presented to her in nature. The scent of the flower helps her home in on the flower when she is in close range, so she is always presented with the scent of the flower before the reward (= nectar). It never, or very rarely occurs that the bee would be presented with the nectar of the flower, then later the odor of the flower. So, because in nature the order of the presentation is set: first odor, then reward, the bee has evolved to make this association only when these things are presented in this order and to ignore the opposite order. So the bee is hard wired to pay attention to the odor then reward. It would not be very adaptive for her to pay attention to the reverse order when it never occurs in nature and therefore would give her no selective survival advantage. |
11. [3 pt] Briefly describe 5 pieces of information that a honeybee uses to locate a previously visited particular species of flower.
From the waggle dance the following pieces of information are actively communicated by another bee:
(1) distance to a flower -- # of waggles and tempo of dance
(2) direction to the flower -- angle of dance relative to axis of gravity
While the bee is doing the waggle dance the other bees also get
(3) the scent of the flower she had visited from her (passively communicated)
(4) Bees naturally go to vertically symmetrical shapes (flowers have this type of symmetry) , so this helps the bees find flowers
(5) Bees use color info to help them find a flower: Blue and UV are common colors of nectar-rich flowers, bees are attracted to these colors. |
12.[2 pt] Draw the two waggle dances that would result from one forager finding food source A and another forager finding food source B.
Describe the key differences coded within each dance.
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This assumption applies for when you are drawing the waggle dances, not for the alignment of the hive as it is shown in this drawing.
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See Syllabus p. 107.
The ground distance to food source A is greater than the ground distance to food source B. Therefore, A will have a dance that has a slower tempo, but a greater # of waggles per waggle run and the waggle run will be longer (in space and time).
Note arrows of direction of dance, this is important! See how the dance for A is done away from the top of the comb? That is because the bees will need to fly directly away from the sun when they leave the hive to reach food source A. The bees always do their dance with the assumption that the "sun" is at the top of the comb (or the opposite of the force of gravity).
Also, see how the angle of the dance relative to straight up and down on the comb (see dashed lines on comb drawings) matches the angle in horizontal space that the bee will need to take relative to the sun-hive imaginary line it can draw to get to the food? |
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