Remote Ready Biology Learning Activities has 50 remote-ready activities, which work for either your classroom or remote teaching.
A digital ecosystem, fueled by serendipity.
Serendip is an independent site partnering with faculty at multiple colleges and universities around the world. Happy exploring!
This examination is designed to take you about an hour to complete, but you may, if you wish, use a period of up to three hours from first looking at the questions to completing the writing of your answers. The additional time is provided to give you time to think about the questions, and to assure that you are not pressed for time in writing your answers. Please do not consult books, notes, or other related material, or discuss the exam questions with others, during the period between first looking at the questions and completing the writing of your answers. This examination consists of twenty questions. The first ten are multiple choice (two points each). The next nine (three points each) require brief answers, which might consist of a phrase or a sentence and should in no case consist of more than three sentences. The last question (twenty points) requires a short essay (less than a page, in the space provided). If you are uncertain about your answer to any questions, leave them while you think and answer other questions, but be sure to return to unanswered questions and do the best job you can within the available time. Please do not exceed the space provided for the short answer and essay questions, and write legibly, putting your name at the top of each page.
Multiple choice questions (2 points each). Put the letter corresponding to the best answer in the space provided to the left (answers in boldface).
1. Characterizing a living organism as a "highly improbable assembly of physical elements (atoms)" means that: A) repeated random mixing of the atoms of which an organism is made would rarely yield a living organism; B) there must be something in a living organism other than atoms; C) a blueprint, plan, or set of instructions for that particular assembly must have existed before it did; D) it is very unlikely that life exists elsewhere in the universe.
2. Assuming the length of a "typical" multicellular organism is 1 meter, roughly how many "typical" cells does one need to go from one end of the organism to the other, and how many "typical" atoms does one need to go from one end of the typical cell to another? A) one hundred cells; 1 billion atoms; B) ten billion cells; ten billion atoms; C) one hundred thousand cells; one hundred thousand atoms; D) ten billion cells; one hundred atoms.
3. If one equates the history of the earth with a twenty-four hour day, the appearance of life, of eukaryotic cells, of multicellular organisms, and of a diversity of mammals: A) occur at roughly equal intervals of time beginning early in the morning; B) occur at roughly equal intervals beginning late in the afternoon; C) occur at progressively shorter intervals of time with a diversity of mammals appearing around noon; D) occur at progressively shorter intervals of time with a diversity of mammals appearing late in the evening.
4. The basic distinction between autotrophs and heterotrophs is that: A) autotrophs can create the energy they need while heterotrophs cannot; B) autotrophs require an external energy source while heterotrophs do not; C) autotrophs require sunlight while heterotrophs do not; D) autotrophs can acquire needed energy from non-living things while heterotrophs depend for their energy on other living things.
5. The cells of multicellular organisms are: A) prokaryotic; B) eukaryotic; C) both prokaryotic and eukaryotic; D) neither prokaryotic nor eukaryotic.
6. Which of the following elements are found exclusively in living organisms? A) carbon; B) silicon; C) iron; D) none of the above.
7. Which of the following elements are much more prevalent in non-living matter than in living organisms? A) helium; B) carbon; C) oxygen; D) none of the above.
8. In relation to the numbers of kinds of subunits which make them up, the number of kinds of atoms (elements) is: A) more than ten times larger; B) a little larger; C) the same; D) smaller
9. In relation to the number of kinds of organisms, the number of kinds of atoms (elements) is: A) much much larger; B) larger; C) the same; D) smaller.
10. Which of the following is NOT a polar bond? A) one between oxygen and hydrogen; B) one between hydrogen and hydrogen; C) one between carbon and hydrogen; D) all three are polar bonds.
Short Answer (3 points each). Three sentences or less. Write legibly in the space provided (sample answers in boldface).
11. Briefly explain what is meant by "life consists of improbable assemblies at several different levels of organization," by specifying parts which make up wholes at two different levels.
Atoms make up molecules; cells make up multicellular organisms. If one were to dissociate molecules into their atomic constituents, or multicellular organisms into their cellular constituents, put the constituents into a bag, mix them up, and pour them out, one would not in general expect to see the assembly with which one started.
12. Give an example of an observation which would indicate that some highly improbable assembly is semi-autonomous.
A dog which wakes up and goes hunting in the absence of any change in its surroundings.
13. "Primitive" versus "advanced" might be understood to mean "less well versus better adapted to the environment," "less complicated versus more complicated," or "earlier versus later appearance in the history of life." Briefly compare bacteria and humans in terms of each of these three characteristics.
Bacteria and humans are both currently living organisms, so must be regarded as comparably well-adapted to the environment. Bacteria are, however, simpler, in the sense that they consist of single bounded cells without membrane bounded internal compartments, whereas humans consist of multiple cells each with bounded internal compartments. Bacteria also appeared earlier in evolution
14. The existing diversity of living organisms is "clumpy," in the sense that there are groups of organisms which are similar to one another as well as an absence of other imaginable kinds of organisms. Give an example of "clumpiness", and provide two different possible reasons for the absence of imaginable organisms.
Vertebrates have in common an endoskeleton and a dorsally located nervous system. Arthropods have in common an exoskeleton and a ventrally located nervous system. There are no known animals with an endoskeleton and a ventrally located nervous system. This may be because such animals existed but are now extinct, or maybe because such organisms have not yet been tried during the evolutionary process.
15. Give two reasons for suggesting that life, as we currently see it on earth, is partly the result of chance events, i.e., that it would likely be different, at least in detail, if it exists elsewhere in the universe
An important component of the history of life is the random change of genetic material on which natural selection acts. Evolutionary change also appears to depend on such unpredictable events as the collision of a meteor with the earth.
16. Many things which appear to be unchanging at the time and space scales most familiar to humans are in fact in continuous motion when observed at other scales of space and time. Give an example of this, illustrating how the recognition of previously unsuspected motion contributes to better understanding some aspect of biological systems.
Water molecules are in constant motion, though undisturbed water may appear unchanging. This constant motion contributes to bringing into contact with one another other molecules whose interactions and resulting changes are a central part of the life process.
17. The assembly rules for making molecules from atoms characterize not only how many covalent bonds a given atom can participate in but also the resulting three-dimensional arrangement of atoms in molecules. Giving an example, briefly discuss an implication of the three-dimensionality of molecules which is significant for understanding biological systems.
Water is a polar molecule because of a combination of the polar character of O-H bonds and the fact that they are oriented at an angle to one another. If they were oriented in other ways, water would not have its typical solubilizing, adhesive, and cohesive properties, which play a major role in terrestrial life.
18. Briefly describe lipids as assemblies of atoms, specifying two characteristics of lipids which distinguish them from other macromolecules, and the significance of these characteristics for understanding biological systems.
Lipids are largely hydrocarbons, long chains of carbon atoms with associated hydrogens. In consequence they tend to be non-polar and hence to be an important component of the boundary layers which separate differing adqueous solutions. They also are a rich store of energy, which can be released by oxidation, the transfer of electrons to oxygen.
19. Biological macromolecules are in general polymers. Name one general class of biological macromolecule and the kind of monomer from which it is constructed, and explain how it can be that there are so many more macromolecules of that class than there monomers from which they are constructed.
Proteins consist of long chains of amino acids, of which there are only about twenty kinds. However, since each position in the chain can be filled by any of the twenty amino acids, the number of proteins.
Short Essay (20 points). One page or less, written legibly in the space provided. (Sample answer in boldface).
20. Briefly describe what is meant by "life", in the context of discussing what aspects of life currently seem to you most understandable in terms of atoms and molecules, what aspects seem least understandable in these terms, and why.
The "summary of observations" suggesting that there is nothing to "life" other than an improbable and complex assembly of atoms and molecules both helps to sharpen inquiry into what exactly "life" is, and provides at least a rudimentary basis for better understanding some of its properties. Clearly, the fact that the "assembly rules" for atoms permit enormous numbers of possible molecules (and that their assembly rules permit enormous numbers of assemblies and so forth) provides a way to begin understanding the diversity which characterizes living systems. It also helps to sharpen the question of why particular assemblies, rather than others, are seen. An appreciation of the continual, in part undirected, motion of atoms and molecules is useful in understanding particular aspects of living systems (such as osmosis and chemical changes), and suggests as well that evolution may be a somewhat undirected exploration of possible forms of improbable systems. The structure of DNA molecules provides a potential understanding of how living systemes sustain an expanding record of such explorations
Among the things which are difficult as yet to understand in terms of atoms and molecules are things like how complex improbable assemblies come into existence, how they remain cohesive in the face of the continuing change inherent in their components, and whether they can in fact give rise to the kinds of properties which are implied by the human experience of living organisms, and of oneself. While one might, in principal, entertain the possibility that successive elaborations of improbable assemblies repeated over and over again might give rise to some of these properties, it remains to be shown that such concepts as "purpose", "meaning", "creativity", and "self" can actually be accounted for without the introduction of some new entity into the assemblies. And, if this can be done, it will very much blur the border between "life" and non-life.
I guess what I'm trying to figure out is the difference between life and non-life. It seems to me that there is a very fine line between the two and that it is difficult to pinpoint exaclty what life is and how life can exist.
Yet, it seems that there must be some "force" guiding these crazy little atoms and molecules. What is the smaller scale within them (if we continue the scale theory). Of course, there must be the theory that the atoms is the smallest possibility in life, but then there must be the counterpart that suggests there's an end (if there's a beginning to the scale level). Life seems hard to define when using atoms and molecules since they cannot be explicitly proven to be like other living organisms that eat, rest, produce, die, etc.
The evolutionary process seems to me the most distant from the level of atoms and molecules. Molecular and evolutionary procees occur at oppoiste ends of the time scale, the one too fast and the other too slow to be perceived by humans. Homeostasis, energy dependnece, and improbability of assembly all are molecular processes on a larger scale, while autonomy, boudnedness and reporduction all have clear links to molecular function. But evolutionary motion, like molecular motion, eludes my imagination and thus my comprehension.
Different things/organisms evolve at different rates but why is this? I wonder if it is possible for evolution to go farther than the currently known type of human.
I guess I'm concused about the little things. How can you look at a glucose molecule in a human and say "that's part of a living thing", and then look at glucose in a grain of wheat and say its not alive? At what scale do things take on properties of life?
It is understandable that the breaking and joining of these bonds releases/stabilizes energy, but how is this energy life? How a much larger scale of "LIFE" results from these minute interactions is incomprehensible.
Molecules on their own are not living; but when they are arranged in such a way that forms a cell, suddenly life appears. Nothing else was added; there were no special bonds formed. So where did this force come from? Does it merely come from particular arrangements of molecules that are exclusive to living organisms, as opposed to other arrangements that are only found in non-living matter?
The randomness and chance associated with evolution and how atoms and molecules fit in are for me right now the least understandable aspects of life. Every living organism is made up of the same atomic subunits resulting in the most improbable assemblies. But then look at bacteria and primates. Are Chance and variation the only things that separate them? My problem is that I can't imagine it but I have no other explanation ... mind-boggling.
Why is it that I get larger as I get older (as all other living organisms do) but a rock, or the dirt on the ground, does not? As we discussed in class, all the elements found in my body or anything else having "life" can also be found in nonliving things all over the universe. So it is not the kinds of atoms and moelcules that are resulting in living things' abilities to walk around, and grow, and maintain a constant body temperature. At times I feel like there must be something else there that has not yet been discovered.
If the first protozoan did just appear, why did it have an inherent desire to continue surviving and striving toward complexity? Why do living things have a tendency towards self-preservation and adaptation that non-living things do not? Biology does a wonderful job of explaining how everything grows, forms, reproducces, and stays alive, but doesn't yet have an explanation as to why living things feel the desire to continue existing. What animates life?
| Forum | Biology | Serendip Home |
