ESSAY # 11 EVOLUTION QUESTION 1994: AP BIOLOGY

1. ESSAY # 11 • EVOLUTION QUESTION 1994: 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. • Green Algae...Vascular Plants • b. Prokaryotes....Eukaryotes • c. Amphibians.....Reptiles

2. 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

3. 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

4. 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

5. 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)

6. 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

7. 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

8. 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