EVOLUTION QUESTION 1994: L.PETERSON/AP BIOLOGY
Select two of the following three pairs and discuss the evolutionary relationships
between the two members of each pair you have chosen. In your discussion
include structural adaptations and their functional significance.
a. Green Algae...Vascular Plants
b. Prokaryotes....Eukaryotes
c. Amphibians.....Reptiles
The question was designed to elicit a wide knowledge of organismal structure and
function considered specifically in an evolutionary framework. The question required that
structural adaptations, tied to their functional significance, be included, but did not restrict the
student's response to such discussion. Points, therefore, were also provided for discussion of:
structural adaptation not linked to functional significance; differences in functional ability not tied to
structural difference base; and, appropriately, a discussion of evidence which exists to support the
relationship stated.
Maximum: 6 points total for each pair discussed
3 points maximum for unlinked items
2 points / each linked item
PAIR A: GREEN ALGAE > VASCULAR PLANTS (Maximum: 6 points)
I. Evolutionary Overview: Aquatic > Terrestrial
II. Evolutionary Relationships / Evidence:
A.) similar pigments (similar chlorophylls, chlorophyll b)
B.) similar food storage compounds, carbohydrates (starch)
C.) similar flagellated cells (whiplash type)
D.) Other: cell wall composition, chloroplast anatomy, cytokinesis, cell plate
III. Evolutionary Adaptations Functional Significance
1.) cuticle 1.) prevents desiccation
2.) xylem and phloem 2.) water and mineral /
organic transport
3.) stomata 3.) gas exchange / transpiration
4.) lignified tissues / xylem 4.) support
5.) undifferentiated –> differentiated 5.) functional specialization
tissues (roots, stems, leaves) (division of labor)
6.) sterile jacket 6.) prevents desiccation
7.) flagellated –> nonflagellated cells 7.) terrestrial fertilization
8.) spores –> seeds 8.) protection / dormancy / food
9.) haploid –> diploid 9.) variation
10.) no embryo –> embryo 10.) protection / nourishment
11.) homospory –> heterospory 11.) variation
1994 STANDARDS QUESTION #4 page 2 of 2
PAIR B. PROKARYOTES > EUKARYOTES (Maximum: 6 points)
I. Evolutionary Overview: Endosymbiotic &/or Autogenous Theory
(explanation of)
II. Evolutionary Relationships / Evidence:
A. ribosomes (in prokaryotes and in organelles)
B. nucleic acids (in prokaryotes and in organelles
C. other; see addenda
III. Evolutionary Adaptations* Functional Significance
1.) nuclear membrane 1.) compartmentalization
2.) histones/nucleosomes 2.) packaging of DNA
3.) cytoskeleton 3.) movement/support/etc.
4.) membranous organelles 4.) specialization
5.) multicellularity 5.) complexity
6.) spindle apparatus 6.) necessary for sexual
7.) membrane steroids reproduction (meiosis)
8.) other; see addenda 7.) membrane stability
PAIR C. AMPHIBIANS > REPTILES (Maximum: 6 points)
I. Evolutionary Overview: Aquatic > Terrestrial
II. Evolutionary Relationships / Evidence:
A.) anatomical (homologous structures, 3 chambered heart, appendicular structures)
B.) fossil record: common amphibian ancestor, Labyrinthodon, Devonian period
III. Evolutionary Adaptations* Functional Significance
1.) moist –> keratinized (scales) skin 1.) prevents desiccation
2.) 3 chambers –> septated ventricle 2.) less mixing of oxy,deoxy blood
better O2 delivery
3.) urea ÷> uric acid 3.) water conservation
4.) absence/presence, apparatus 4.) temperature regulation /
for response to environmental poikilothermy –> ectothermy
temperature (cold-blooded
5.) other: 5.) see addenda
skeletal system excretory system
nervous systme respiratory system
6.) jelly coat –> amniotic egg 6.) prevents desiccation
7.) lack of –> copulatory organs 7.) internal fertilization
8.) metamorphosis –> no larval stage 8.) adaptation to terrestrial environment
* citation of more advanced character alone was allowed;
citation of more primitive character alone received no credit;
1994 STANDARDS QUESTION #4 Addenda page #1
PAIR A: GREEN ALGAE > VASCULAR PLANTS
Part II. Evidence for Evolutionary Relationships
øSimilar pigments (similar chlorophylls, chlorophyll b)
øSimilar food storage compounds, carbohydrates (starch)
øSimilar flagellated cells (whiplash type)
øSimilar cell wall composition (cellulose)
øSimilar cytokinesis (cell plate, phragmoplast)
øSimilar chloroplast design
Part III. Structural Adaptations
øno cuticle > cuticle
øno vascular tissue > xylem and phloem
øabsence of stomata > presence of stomata
øabsence of lignin > presence of lignin
ølack of specialization/little differentiation > organs (roots, stems, leaves)
øabsence of sterile jacket > presence of sterile jacket
øflagellated reproductive cells > reproductive cells not flagellated
øspore > seed
ø"N" dominance (gametophyte) > "2N" dominance (sporphyte)
øno embryo > embryo with protection
øhomospory > heterospory
Part III. Functional Significance
ødesiccation
øtransport of water/minerals and organic molecules
øgas exchange / transpiration
øsupport in the absence of water
ødivision of labor (increase in efficiency, adaptation to a terrestrial environment
(less CO2, less H2O, more radiant energy)
ømechanical protection and to prevent desiccaiton (gametangia)
ødispersal of reproductory materials in a terrestrial environment
øfood for developing embryo, protection, dormancy
øincreases v ariation and diversity
øfeeding and protecting the next generation
øincreases variation and diversity
1994 STANDARDS QUESTION #4 Addenda page #2
PAIR B: PROKARYOTES > EUKARYOTES
Part II. Evidence that supports Endosymbiotic Theory:
("organelles" denotes mitochondria &/or chloroplasts)
øribosomes are found in organelles/organelles contain own synthetic machinery
øorganelle ribosomes are of a prokaryotic type (30S, 50S, 70S polysomes)
øantibiotic effects similar on prokaryotic and organelle ribosomes
ør-RNA sequences similar in prokaryotes and organelles
øDNA is found in organelles
øDNA is circular; supercoiled; not associated with histones;
øDNA not arranged in nucleosome packages
øorganelles = size of prokaryotic cells
øorganelles arise only from pre-existing organelles
øorganelle reproduction similar to binary fission
øoxygenic photosynthesis present in certain prokaryotes
øchlorophyll a present in certain prokaryotes
øchlorphyll be (as well as chlorophyll a) present in certain prokaryotes
øinner organelle membranes and prokaryotic cell membranes have some similar transport
and enzyme systems
øfossil evidence: prokaryotes: 3.5 x 109 years, eukaryotes: 1.5 x 109 B.P.
evidence of atomspheric oxygen: 2.5 x 109 year B.P.
Part II. Evidence that supports Autogenous Theory:
øassociation of the nuclear membrane, ER and plasma membrane
øfossil evidence as above
Part III. Structural Adaptations
("prokaryotes" defined as eubacteria)
ønucleoid / nucleus
ølack of histones (divalent cations instead) / histones
øDNA packaging by supercoiling / DNA wrapping around histones
ølack of cytoskeleton / cytoskeleton
ømembranous organelles
øunicellular, plates, filament clusters / true multicellularity
øspindle apparatus
øabsence / presence of membrane steroids (i.e. cholesterol)
øpeptidoglycan cell wall / cell walls of other composition
øcircular DNA / linear DNA
øone chromosome per cell / more than one chromosome per cell
ø30S, 50S, 70S ribosomes / 40S, 60S, 80S ribosomes
(30S, 50S, 70S ribosomes found in organelles)
øpolycistronic m-RNA / monocistronic m-RNA
øabsence / presence of cap and tail on m-RNA
øtypically 1-5 microns / 10-100 microns diameter
øflagellar design for rotary motion vs. "9 + 2" design for whipping motion /
flagellum not surrounded by cell membrane / surrounded by cell membrane /
diameter of prokaryotic flagellum / diameter of eukaryotic flagellum (diameter
of prokaryotic flagellum approximately equals the diameter of eukaryotic
microtubule)
1994 STANDARDS QUESTION #4 Addenda page #3
Part III. Functional Significance
ønucleus provides a microenvironment for RNA and DNA polymerases,
allows separation of transcription and translation
østability / packaging of larger amounts of DNA / finer control of
transcriptional regulation vs. rapidity of transcription
ømovement, orientation of organelles; cytoplasmic streaming,
amoeboid movement, phagocytosis
øspecialization of function (within a cell)
øspecialization of function (between cells)
ødistribution of large amounts of DNA to daughter cells
ømembrane strength in eukaryotic groups without cell walls
øsize of cell that can be protected by a single molecular wrap / construction of cellulosic
and other eukaryotic cell walls places no demand on cell supplies of nitrogen
øonly small amounts of DNA can be packaged in supercoiled circles
øallows transcription and replication of large amounts of DNA
øcoincidence of the original endosymbiotic event
øfiner control of translation vs. rapidity of response to rapidly changing environment
øprotection of m-RNA / transport of m-RNA out of the nucleus
ølarger size permits greater complexity of cellular structure
øeukaryotic design permits more variability in movement, is necessary for movement
of larger cells
PAIR C: AMPHIBIANS > REPTILES
Part I. Evidence for Evolutionary Relationships
øanatomical similarities of recent derviation only (structural similarities at branch point
only)
øthree-chambered heart
øtetrapod character
ølungs
øfossil record (common amphibian ancestor, Labyrinthodon, Devonian Period)
Part II. Structural Adaptations
økeratinized (scales) skin
øseptated ventricle / four chambers
øuric acid
øapparatus for response to environmental temperature (parietal gland)
øskeletal system modifications
øarticulated vertebrae
øreposition of appendages from lateral to ventral side
ømuscular system modifications: muscular tissue in dermis
ørespiratory system modifications
ødevelopment of thoracic / abdominal septum
ødevelopment of nasal cavity
øincreased surface area of the lungs (alveoli)
øexcretory system modifications
øuric acid vs. urea
ømetanephric vs. mesonephric kidneys
øureter, separation of excretory / reproductive componenets
øcollecting tubules, increased length of loop of Henle
ønervous system modifications
øincreased sophistication of the limbic system
øpresence of the parietal glands / temperature control site
øcopulatory organs
øamniotic (cleidoic/shelled) egg
øno larval stage
1994 STANDARDS QUESTION #4 Addenda page #4
PAIR C: AMPHIBIANS > REPTILES continued
Part III. Functional Significance
øprevents desiccation
øless mixing of oxy/deoxygenated blood, better oxygen delivery
øwater conservation
øtemperature regulation / poikilothermy to ectothermy
øskeletal system modifications
øagility / flexibility
øweight support / locomotive speed
ømuscular system modificaitons
øincreased insulation / protection / motility (snakes)
ørespiratory system modifications
øability to generate negative pressure breathing
øability to breathe with food in mouth / ability to warm and humidify respired air
øincreased gas exchange
øexcretory system modifications
ødecrease water loss in terrestrial environment
øincreased ability to reabsorb water
ønervous system modifications
øincreased ability to respond / adapt to environmental conditions
øability for behavioral modification of body temperature
øinternal fertilizaiton
øadaptations to terrestrial environment
øembryo: mechanical protection, food source, water conservation, waste elimination