SC 139 - Second Exam 2006
 Answer Key

Links on Numbers go to relevant passages in the online textbook.

 

MULTIPLE CHOICE.

On the line to the left, place the letter of the choice that best answers the question.
Three Points Each.
NOTE: "e" answers are never the correct answer.

 

1.  The bottleneck of bottleneck effect happens when

___C___           a. Genes shift from chromosome to chromosome
                        b. A subgroup migrates away from a main group
                        c. A group almost goes extinct
                        d. Staging areas are used for a shift in habitat
                        e. Um, bottles get necks put on them-?

                    ...a big population gets small, then grows again - kind of like a
                            traffic bottleneck.

 

2.  When a gene-level DNA mutation happens, the results are usually

___B___           a. Some improvement                             b. Bad or neutral
                        c. A new type of cell                              d. A change in a trait
                                        e. Kept secret by family members

                    ...most mutations don't produce any real change, but if a change
                           happens, it's more likely to screw up the coded protein than to improve it

 

3.  Animals and plants were a long time on land before they "solved" the last problem,
                    the one associated with

___C___           a. Support                 b. Ice Ages                 c. Reproduction
                        d. Lack of nutrients                     e. Ugliness

                    ...both land plant and animal groups were around for a while before
                        they evolved ways to not need open water for sperm transfer.

 

4.  A layer of rusty sediments in the fossil record is an indication that what had just evolved
                    and "caught on" in a big way?

___D___           a. Aerobic respiration                 b. Cells                 c. Fungi
                        d. Photosynthesis                             e. Junk sales

                    ...the rust came from oxygen (rust is iron + oxygen), and the oxygen came
                        from photosynthesis.

 

5.  Which are all autotrophs?

___B___           a. Fungi             b. Plants             c. Animals            d. Bacteria
                                            e. NASCAR champions

                    ...they can take energy from the environment and build fuel molecules.
                            Some, but not all, bacteria can do this;  animals & fungi can't at all.

 

6.  The Gaia hypothesis suggests that

                        a. Earth’s life helps to stabilize the planet’s temperature
                        b. Some cell parts were once independent organisms
___A___           c. Only through mass extinction can true progress be made
                        d. Supernatural forces are involved in the history of Life
                        e. It’s a bad idea to put too many vowels together

                    ...it sees the planet as a big self-regulating organism, sort of.

 

7.  The organic molecules in primordial soup came from

___D___           a. Plants             b. Fungi             c. Volcanoes            d. Space dust             e. Catalogs

                    ...it was all material that the Earth first formed from.

 

8.  Stromatolites are fossils of

___A___           a. Bacterial clumps                     b. Bones                     c. Teeth
                        d. Tree trunks                                 e. What illuminates stroma

                    ...they are some of the very oldest recognizable fossils.

 

9.  In genetics, linkage is between

___C___           a. A gene & a trait                              b. A gene & a protein
                        c. A gene & a chromosome                 d. A protein & a trait
                        e. What I don’t know & what the questions are asking

                    ...genes that are linked share placement on a particular chromosome.

 

10.  Many causes of mass extinction work by

___A___           a. Blocking sunlight in the atmosphere
                        b. Spreading disease from species to species
                        c. Causing very high temperatures
                        d. Changing the orbit of the Earth
                        e. Killing lots of stuff off

                    ...asteroid impacts and giant volcanoes both produce dust and smoke to do this.

 

11.  Plants would not have been able to move onto land without

___C___           a. Rich soil                                 b. Animals already there
                        c. Fungus symbionts                   d. Resistance to land-borne diseases
                                                e. A good real estate broker

                    ...the fungi were able to make the nitrogen-based molecules needed to build proteins,
                        which the plants couldn't do from the atmosphere.

 

12.  The "ticks" of the most-used  molecular clock are

___B___           a. Chromosome changes                     b. Mitochondrial DNA mutations
                        c. Nuclear DNA mutations                  d. Recombination shifts
                                    e. Almost all with the digital read-out now

                    ...mutations in non-gene DNA stretches are supposed to accumulate at a more-or-less
                        regular rate, and mitochondrial DNA doesn't go through the sexual-mixing changes
                        that happen in the nucleus.

 

SHORT ANSWER.

Answer any eight of the following questions for 4 Points Each.
Note: if you answer more than eight, only the first eight will be corrected.
You can get partial credit on these answers.

1.  What are two particular types of Early-Earth energy that might have helped primordial molecules to merge together?
Heat energy (from lava / hydrothermal vents).

"Regular" sunlight (not a likely type).

 Lightning.

Ultraviolet energy from the sun.
2.  What is the Cambrian Explosion?

      ...it's a short period (a few million years) found in the fossil record where the major animal groups sort of "appear."

 
3.  In evolution, what is the definition of sexual selection?

      ...it's the evolution of traits based on the reproductive success they produce (as opposed to natural selection, which is more about survival-to-reproductive-age success).

 
4.  What is the hypothesis of panspermia?

      ...the idea that the first Life on Earth was carried in on meteors from someplace else, rather than evolving here "from scratch."

 
5.  In order to be evolutionarily effective, asexual organisms must produce lots of offspring. Give two reasons why this greatly raises their survival odds.
The larger numbers increase the odds that the effects of bad changes will miss some.  Variation depends mostly on rare mutations - but with big numbers, the odds on those mutations appearing are better.
6.  Photosynthesis may have begun as a combination of two abilities already in place. What were those two abilities?
 Chemosynthesis (fuel production using hot chemicals as an energy source) Light detection (to enable bacteria to get back to their glowing heat sources)
7.  For a high chromosome number -
An                      Greater variety in offspring
advantage              (Good for evolution)		 A                         More errors during new cell
disadvantage               production.
8.  Define alternation of generations, without using those words (or verb forms of them).

      ...a complete life cycle always involves both a sexual reproduction stage and an asexual reproduction stage.

 
9.  What are two things that a water organism does not require protection from, but a land organism must be able to deal with?

Drying.

Direct sunlight.

Temperature fluctuations.

 No support.

High oxygen levels.
10.  Briefly explain the "plant problem."

      ...since it was thought that all Life depends on plants as the base of the food chain, when scientists began to consider how Life arose, it was thought that photosynthesis - a very complex system - had to pretty much appear before anything else.  The heterotroph hypothesis solved that problem.

11.  The hypothetical "Nemesis" -
What is                  A small, dim star that orbits
it supposed     the Sun like a comet, only coming
to be?              close every 26 million years.		 Why do people       There is sort of a 26-million-
think it might         year "period" on the Earth's
exist?                     mass extinction events.
12.  Give two fundamentally different examples of epigenetic traits.
Culture (including language).

Non-genetic cell parts. 

 Territory / location.

Some behaviors, such as food-finding.
13. What is meant by the terms type species or ecospecies? They mean the same thing.

      ...they are different species, in different places, that are in the same niches.
            (such as lions in one place, tigers in another)

 
14.  Briefly explain the genetic concept of hybrid vigor.

      ...having two different alleles together is more of an advantage than having a matched set of either.

 
15.  What are hydrothermal vents, and where are they found?

      ...spots where new ocean floor forms, mostly deep in the ocean middles, where hot lava and buried chemicals mix with water.

 

 

LONG ANSWER.

Answer any four of the following questions for Eight Points Each.
Note: if you answer more than four, only the first four will be corrected.
You can get partial credit on these answers.

1.  Give four examples of things from different general classes that can result in reproductive isolation of one group from another. So not terms or definitions, but specific types of examples of things that can happen to lead to isolation.   Notice that you're being asked for examples, so you'd give...
 An example of something that would produce geographic isolation, like a shifting river or the growth of a desert. An example of something that would produce niche isolation, like a group of day-hunting birds adapting to darker and darker periods until they are night hunters.
An example of something that would produce temporal isolation, like a plant flowering out of synch with the others, but surviving and setting up a population reproducing only within itself. An example of something that would produce behavioral isolation, like a group of birds where females have a liking for shiny courtship baubles or a certain dance type, or that nest in a different type of location.
An example of something that would produce mechanical isolation, like a physical change in a subgroup of beetles that makes them able to only physically have intercourse within their group. An example of something that would produce gamete or zygote isolation, like variant flower that can't be pollinated by all of its species pollen, but only by pollen with certain chemical make-up.
2.  What are four different conditions that a "Hardy-Weinberg population" must have?
 No natural selection. No migration of members in or out.
  Random mating / no sexual selection. No mutations.
Extremely large population size.  
3.  For the earliest "living" systems, give two basic requirements that have to be met for each of the two stages down below.
The first molecular "life" Able to self-organize

Able to reproduce

Able to evolve
   
Eventual, more "modern" life Cells

 Protein-based chemistry 

DNA-based coding system
4.  For the two likely "staging areas" from which organisms moved up onto the land, name each one and give one aspect of it that forced adaptations that would also be useful out of the water.
 Tidal pools - Temperatures fluctuate.
- Dilution levels can fluctuate.
- Often requires movement from one to another.
- Exposure to strong sunlight.
 Fresh Water - Movement in shallows requires support.
- High dilution requires waterproofing.
- Exposure to strong sunlight.
- Temperatures can fluctuate.
- Available nutrients can be very depleted.

5.  For asexual reproduction, in general -
Definition - Advantage over
sexual reproduction -		 Advantage sexual
has over asexual -

Offspring are genetic copies of the original.

 Makes actual copies of the original. Produces more variation - greater evolutionary potential.

6.  For each step in the theoretical development of Life on Earth, put them in chronological order, from earliest to latest, 1 - 8 in the boxes to the left.

4

Photosynthesis
In early prokaryotes, taking advantage of a more widely-available energy source.

3

Prokaryote Cells
First actual cells, after "living molecules"

2

Molecular Evolution
1st step in primordial soup.

8

Movement onto Land
The very last major step, long after complex Life appeared in the oceans.

6

Cellular Colonialism
Only after eukaryotes evolved

1

Primordial Soup
There at beginning!

5

Aerobic Respiration
Needed oxygen from photosynthesis

7

Multicelled Systems
Stage after colonialism

7. Give four major groups of organisms that are considered land / terrestrial groups.
Plants Mammals

Insects

 Reptiles
Spiders / Arachnids Dinosaurs
  Amphibians

No Key for BONUS QUESTIONS.

Answer as many as you are able. Wrong answers will not result in points being lost from the main exam. You can get partial credit on these answers.

Gregor Mendel worked out the rules of genetics using pea plants. Why did he use pea plants? Three Points.

 

There are three different types of genetic redundancy. Describe them, for Three Points each.

 

 

Since Hardy-Weinberg conditions often do not exist in nature, what is the value of the Hardy-Weinberg rule? Three Points.

 

What scientist is considered the originator of biogeography? Three Points.

 

What term from epigenetics is a popular term on the internet? Three Points.

 

What is the major problem that scientists have with Special Creation theories? Three Points.

 

 

Silicate clays may have been involved in the first Life’s beginnings. What about clays makes this a possibility? Three Points for each feature.

 

 

Where, locally, are some truly ancient fossils of early Earth life? Three Points.


 
     

Michael McDarby.

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