SC 139 - Second Exam 2005

Answer Key

 

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 concept of panspermia is connected to

___C___         a. A type of sexual reproduction                b. A type of asexual reproduction
                      c. The beginnings of Life on Earth            d. A particular type of isolation
                                                e. A fairly dirty Greek myth

                        ...it's the idea that Earth's first Life actually originated somewhere
                            else and was carried in on meteors.

 

2. The vast majority of mutations have

___A___         a. No or almost no effect                             b. A really bad effect
                      c. At least a partly good effect                     d. A really good effect
                                                        e. No nicknames

                        ...because of the way DNA works, most changes miss genes, and many
                            changes in genes don't significantly change the proteins coded for.

 

3. Even after true prokaryotes had evolved here, the Earth would have lacked

___C___         a. Oceans         b. Rain         c. An ozone layer        d. Molecules
                                            e. Insurance salesmen

                        ...there were simple cells, but not yet photosynthesis.  Photosynthesis
                            produced the oxygen which produced the ozone layer.

 

4. Genetic drift would be most obvious in descendent groups that are also

___B___         a. Aerobic respirators                 b. Ecospecies             c. Greatly reduced in number
                      d. Asexual                                              e. On a genetic raft

                        ...although this is a confusing question, only one answer comes even close
                            to making sense if you know what genetic drift is.  Isolated groups in
                            similar environments stay in the same niches even as random changes
                            make them into different species - ecospecies are different species
                            occupying similar niches.

 

5. Alleles are

___D___         a. A primitive organism             b. Epigenetic            c. Colonial organisms
                      d. Variations in gene codes                        e. A very odd word

                        ...match the term with the definition.

 

6. Which was an important clue in understanding the evolution of photosynthesis?

                      a. Fungi can use carbon dioxide
                      b. Hydrothermal vents glow
___B___         c. Primordial soup had chlorophyll in it
                      d. DNA can absorb light
                      e. Finding someone who understood photosynthesis

                        ...the combination of chemosynthesis and light-sensing may have led to
                            photosynthesis.  That, and no other choices are even true.

 

7. Stromatolites are some of the best fossils of early

___D___         a. Plants                 b. Animals                c. Fungi
                      d. Bacteria                    e. Stroma, before they got heavier

                        ...link the term with part of its definition.

 

8. The materials that made up the primordial soup were figured out by analyzing

___D___         a. Fossils                     b. Lava                     c. The Sun
                      d. Space dust                     e. Chickens and noodles

                        ...as part of the early Earth, it would have come from the materials
                            that formed the Earth.

 

9. The disadvantage of having a high chromosome number appears when

___A___         a. Cells divide                 b. Environments change            c. Lethal genes appear
                      d. Oxygen is low                        e. You’re trying to look all humble

                        ...that's when getting all of the duplicates properly distributed to the new
                            cells becomes an issue.

 

10. Which can be autotrophs?

___B___         a. Animals only                 b. Plants only             c. Bacteria and animals
                      d. Bacteria and plants                    e. Is that an award with a car on it?

                        ...autotrophs are fuel-makers, including photosynthesizers, which are
                            found in Monerans, Plants, and also Protistans, and chemosynthesizers,
                            found in Monerans and Archaeans.

 

11. There seems to be a limit on how big peacock tails can get - they can’t be so large that the
        males can’t fly away from predators. This means that

___C___         a. Sexual selection is just as important as natural selection
                      b. Sexual selection is more important than natural selection
                      c. Natural selection is more important than sexual selection
                      d. None of these is indicated
                      e. Peacocks is stupid

                        ...in order to pass on traits that help you get mates, you have to survive
                            long enough to be in the game.

 

12. The endosymbiont theory talks about the beginnings of

___A___         a. Chloroplasts                 b. Multicelled systems                 c. Life on land
                      d. Genetics                                e. My nervous breakdown

                        ...these are cell structures that probably started as little specialized cells
                            taken in and used by larger ones - mitochondria and chloroplasts.

 

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. The rate at which things evolve is closely linked to two other rates. What are they? (Not looking for the two different patterns of evolution rates here!)
How fast the environment changes How quickly the organisms themselves can reproduce
2. Briefly describe the Gaia hypothesis.

     ...it's the idea that the presence of life acts as a kind of thermostat that keeps the planet from overheating or overcooling.
3. What circumstances bring about a bottleneck effect?

     ...a near-extinction event (most of the population dies off and all descendants come from a small starting group).
4. Briefly explain the "plant problem" that faced early theorists for the origins of Life.

     ...since all life today depends upon photosynthesizers as the basis of the food chain, it was thought that life had to start with photosynthesis, which is too complicated to just arise as a first step.
5. There are several widely-accepted explanations for how mass extinctions are caused. What are two?
Asteroid impacts.
Huge volcanic eruptions.
Continental contacts.		 Ice Ages.
Greenhouse effects.
6. Define heterotroph.

     ...an organism that needs its energy-containing molecules / fuel already made.
7. Give two non-human examples of memes in Nature.  This can be any example of a trait that can be "passed" without being coded in DNA.
 LOCATIONS - such as passed from plant parents or though hunting territory LEARNED traits, such as predators learning to hunt.

8. What are two types of energy that could have been easily used by molecules during the very earliest stages in the development of Life on Earth?
 Heat.
Chemical energy in simple molecules.		 Lightning.
Ultraviolet.
9. Briefly explain how molecular clocks are supposed to work.

     ...on different branches from a single ancestor, mutations produce changes in long molecule sequences.  Mutations happen randomly according to chance, averaging one change over a set period of time, like ticks in a clock.  X number of changes on the 2 branches is figured into Y amount of time the two branches have been separate.
10. RNA has two different abilities that make it a good candidate for the first living molecule systems. What are they?
They can code for proteins  They can have complex chemical activities
11. A gene is a stretch of (A) - What molecule? whose specific purpose (modern definition!) is to (B) .
A -   DNA B -  Code for a particular type of protein
12. Briefly explain the circumstances under which the first protocells were supposed to have formed.

     ...floating oils driven into submerged bubbles by turbulence (were captured and stabilized by evolving molecular systems that used them for containment and protection).
13. Explain what is meant if two genes have linkage.

     ...they are both found on the same chromosome.
14. Some living things still today have almost the exact same form that their distant ancestors had. What circumstances typically lead to such a situation?

     ...these organisms are well-adapted to a type of environment (or bit of environment) that itself hasn't changed much since those ancestors fit into it.

 

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. For sexual reproduction, in general -
Definition -  Offspring are a genetic mix from 2 sources.

 

 		Advantage over asexual
reproduction -  More variety / adaptability in offspring.
 		 Advantage asexual has
over sexual -  Successful forms can be exactly reproduced.
 

2. Briefly describe (don’t just give labels!) four basically different types of evolutionary isolation.
 Geographic barriers separate groups. Groups are active / reproductive at different times.
 Groups separate into different jobs / niches. Groups use different behaviors or reproductive choices.
Physical change in one group makes it reproductively incompatible with the other. Rejection arises so one group becomes reproductively incompatible with the other.

3. When organisms moved onto the land, there were many new conditions that they had to adapt to. Briefly explain four different ways that the conditions differed from living in the water.
Very nutrient-poor (not much up there yet). Water evaporates into the air.
No buoyancy support. Temperature fluctuates more sharply.
Sunlight is stronger (no water to absorb it). Oxygen levels much higher
 No support pathway for sperm.

4. 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.
3

Photosynthesis
Once soup fuel started to run out.

5

Eukaryote
Cells
After prokaryotes "worked out" most of what single cells could do.

 2

Molecular
Evolution
Molecules in primordial soup.

 7

Cambrian
Explosion
Complex animals from simple multicellular animals.
8

Movement
onto Land
After all the multicelled phyla appeared.

 1

Primordial
Soup
Part of first-Earth
formation.

 4

Aerobic
Respiration
Needed oxygen from photosynthesis.

 6

Multicelled
Systems
From eukaryote cells.

5. What are four different conditions that a "Hardy-Weinberg population" must have?
No natural selection  No sexual selection
 No mutation No migration of subgroups
Huge size  

6A. Two critical features that early molecular systems had to have to be considered the first steps of "Life" on Earth -  Ability to self-organize is possible.
Ability to reproduce  Ability to evolve
6B. Two critical features that didn’t have to be there right at the beginning, but had to develop early because all modern Life has them -
Cells.
Protein-based chemistry.

DNA-based coding system.

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.

What, according to a hypothesis about Earth’s past, is Nemesis? Three Points.

 

Why were pea plants the organism that Mendel did his experiments on? Three Points.

 

For what adaptive situations has alternation of generations arisen in various groups? Three Points each.

 

What famous scientist is considered the founder of biogeography? Three Points.

 

Breeding of close relatives can be a good thing, evolutionarily. How? Three Points.

 

About how quickly do the continents generally drift? Three Points.

 

The political wing of Creation "Science" has recently been replaced by another approach. What is it? Three Points.

 

What evidence in the fossil record is there for the appearance of photosynthesis (Two Points), and why is that evidence there? (Four Points)

 

 

What was the first fossil clue for the Snowball Earth period? Three Points.


 
     

Michael McDarby.

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