General Biology II: Study Guide for Exam #3 – Bacteria, Archaea, Protists, Fungi, and Plant Biology

Chapter 26: Bacteria and Archaea

Defining Features of the Three Domains

• Bacteria: Prokaryotic cells lacking a nucleus, peptidoglycan in cell walls, unique ribosomal RNA sequences.

• Archaea: Prokaryotic, no peptidoglycan, unique membrane lipids, extremophiles, distinct rRNA.

• Eukarya: Eukaryotic cells with a nucleus and membrane-bound organelles.

Horizontal Gene Transfer and the Phylogenetic Tree

• Horizontal gene transfer (HGT) is the movement of genetic material between organisms other than by descent.

• HGT causes the phylogenetic tree to appear as a network (web) rather than a simple branching tree, especially among prokaryotes.

Archaea: Environments and Adaptations

• Archaea are often found in extreme environments: high temperature (thermophiles), high salinity (halophiles), acidic or alkaline conditions.

• Adaptations include unique membrane lipids, enzymes stable at extreme conditions, and specialized metabolic pathways.

Koch’s Postulates and Germ Theory

• Koch’s postulates are criteria to establish a causative relationship between a microbe and a disease:

  1. Microbe must be present in diseased individuals, absent in healthy ones.

  2. Microbe must be isolated and grown in pure culture.

  3. Pure culture must cause disease in a healthy host.

  4. Microbe must be re-isolated from the experimentally infected host.

• These postulates were foundational for the germ theory of disease.

Coevolution of Bacteria and Eukaryotes

• Bacteria and eukaryotes have coevolved through symbiotic relationships (e.g., mitochondria and chloroplasts originated from bacteria).

• Microbiomes influence host health, development, and evolution.

Energy and Carbon Acquisition Strategies

• Organisms are classified by energy and carbon sources:

  • Phototrophs: Use light for energy.

  • Chemotrophs: Use chemical compounds for energy.

  • Autotrophs: Use CO2 as a carbon source.

  • Heterotrophs: Use organic compounds as a carbon source.

• Examples: Cyanobacteria (photoautotrophs), E. coli (chemoheterotroph).

Bacteria and Global Climate Change

• Bacteria influence climate via metabolic processes (e.g., methane production by methanogens, nitrogen cycling).

• Cyanobacteria have played a major role in oxygenating Earth’s atmosphere.

• Adaptations: Ability to fix nitrogen, photosynthesize, or metabolize unusual substrates.

Ecological Roles of Bacteria

• Decomposition, nutrient cycling (nitrogen, sulfur, carbon), symbiosis (e.g., gut flora), and disease causation.

Chapter 27: Eukaryotic Origins and Protista

Identifying Features of Eukaryotes

• Membrane-bound nucleus, organelles (mitochondria, ER, Golgi), linear chromosomes, cytoskeleton.

Protists: Monophyly and Classification

• Protists are not a monophyletic group; they are paraphyletic because they include some but not all descendants of their common ancestor.

• Classified by morphology, mode of locomotion, nutrition, and reproduction.

Main Functional Groups of Protists

• Four main types (functional, not phylogenetic):

  • Protozoa (animal-like, heterotrophic)

  • Algae (plant-like, photosynthetic)

  • Slime molds (fungus-like, decomposers)

  • Water molds (oomycetes, decomposers/parasites)

Endosymbiotic Theory

• Explains the origin of mitochondria and chloroplasts from engulfed prokaryotes.

• Primary endosymbiosis: Eukaryote engulfs a prokaryote (e.g., origin of mitochondria).

• Secondary endosymbiosis: Eukaryote engulfs another eukaryote that already has an endosymbiont (e.g., some algae).

• Evidence: Double membranes, own DNA, ribosomes similar to bacteria.

Medical and Ecological Roles of Protists

• Pathogens (e.g., Plasmodium causes malaria), primary producers in aquatic systems, decomposers, symbionts.

Chapter 29: Fungi

Medical and Ecological Roles of Fungi

• Decomposers, nutrient cycling, symbiosis (mycorrhizae, lichens), pathogens (e.g., athlete’s foot, yeast infections), antibiotics (e.g., penicillin).

Fungal Body Structure and Adaptations

• Composed of hyphae (filamentous cells) forming a mycelium.

• Cell walls made of chitin; high surface area for absorption.

• Adapted for growth in moist, nutrient-rich environments.

Fungal Life Cycle

• Generalized life cycle includes haploid, dikaryotic, and diploid stages.

• Reproduce via spores (asexual and sexual reproduction).

Classification and Main Fungal Taxa

• Classified by reproductive structures and life cycles.

• Four main taxa:

  • Chytridiomycota: Flagellated spores.

  • Zygomycota: Zygosporangia.

  • Ascomycota: Asci (sac fungi).

  • Basidiomycota: Basidia (club fungi, mushrooms).

Chapter 28: Plant Diversity

Ecological Roles and Defining Features of Plants

• Primary producers, oxygen production, habitat formation, soil stabilization.

• Defining features: Multicellularity, photosynthesis (chlorophyll a and b), cell walls with cellulose, alternation of generations.

Land Plant Adaptations

• Advantages: More sunlight, less competition, more CO2.

• Challenges: Desiccation, support, reproduction without water.

• Adaptations: Cuticle, stomata, vascular tissue, seeds, pollen.

Classification and Synapomorphies

• Major groups:

  • Bryophytes (mosses): Nonvascular, dominant gametophyte.

  • Pterophytes (ferns): Vascular, no seeds, dominant sporophyte.

  • Gymnosperms: Vascular, seeds, no flowers.

  • Angiosperms: Vascular, seeds, flowers, fruits.

Plant Life Cycle

• Alternation of generations: Multicellular haploid (gametophyte) and diploid (sporophyte) stages.

• Key features: Spore production, gamete production, fertilization, zygote development.

Evolutionary Trends and Coal Formation

• Trend: Green algae → nonvascular plants → seedless vascular plants → seed plants.

• Coal in West Virginia: Formed from ancient plant material (mainly seedless vascular plants) in swampy environments.

Monocots vs. Eudicots

Feature	Monocots	Eudicots
Number of cotyledons	1	2
Leaf venation	Parallel	Net-like
Flower parts	Multiples of 3	Multiples of 4 or 5
Vascular bundles	Scattered	Ring

Chapter 28: Water and Sugar Transport in Plants

Photosynthesis vs. Water Loss Trade-off

• Plants must open stomata for CO2 uptake (photosynthesis), but this leads to water loss via transpiration.

• Trade-off caused by the need for gas exchange and water conservation.

Adaptations to Limit Water Loss

• Thick cuticle, sunken stomata, CAM and C4 photosynthesis, leaf modifications.

Water Potential and Movement

• Water moves from high to low water potential ($\Psi$).

• Water potential ($\Psi$) is determined by solute potential ($\Psi_s$) and pressure potential ($\Psi_p$):

$\Psi = \Psi_s + \Psi_p$

• Solute potential: Effect of dissolved solutes (always negative).

• Pressure potential: Physical pressure on water (can be positive or negative).

Water Flow in Different Conditions

• Wet conditions: Higher water potential in soil, water moves into roots.

• Dry conditions: Lower water potential in soil, water movement is reduced or reversed.

Stomatal Opening and Closing

• Guard cells take up K+ ions, water follows by osmosis, cells swell and open stomata.

• Loss of K+ causes water to leave, guard cells shrink, stomata close.

Water Movement: Soil to Shoots

• Three main hypotheses:

  1. Root pressure: Osmotic pressure pushes water up.

  2. Capillary action: Water moves up narrow tubes by adhesion/cohesion.

  3. Cohesion-tension: Transpiration pulls water up via negative pressure (most supported).

Phloem Sap and Transport

• Phloem sap: Water, sugars (mainly sucrose), amino acids, hormones.

• Flows through sieve tube elements and companion cells.

• Sugar source: Site of sugar production (e.g., leaves).

• Sugar sink: Site of sugar use/storage (e.g., roots, fruits).

• Loading at source: Active transport of sucrose into phloem.

• Bulk flow driven by pressure differences (pressure-flow hypothesis).

• Direction of flow can change depending on source/sink locations.

• Unloading at sink: Sucrose removed by active or passive transport.

Chapter 37: Plant Signaling

Signal Transduction in Plants

• External stimuli (light, gravity, touch, pathogens) are perceived by receptors.

• Generalized pathway: Signal reception → transduction (via second messengers) → cellular response.

Phototropism and Light Sensing

• Plants grow toward light (phototropism) to maximize photosynthesis.

• Light sensed at shoot tip; auxin hormone redistributed to shaded side, causing cell elongation.

• Signal transmission involves movement of auxin and changes in gene expression.

Light and Germination/Flowering

• Phytochromes detect red/far-red light, influencing germination and flowering.

• Different wavelengths signal favorable or unfavorable conditions.

Gravity Sensing

• Statoliths (starch-filled plastids) in root cap cells detect gravity.

Hormones and Growth Regulation

• Auxin: Promotes cell elongation in shoots, inhibits in roots; movement is polar (unidirectional).

• Polarity established by auxin transport proteins; important for apical dominance.

• Cytokinins: Stimulate cell division.

• Gibberellic acid: Promotes stem elongation, seed germination.

• Abscisic acid (ABA): Inhibits growth, promotes dormancy, closes stomata.

• Ethylene: Promotes fruit ripening, leaf abscission.

Leaf Abscission and Hormone Interactions

• Auxin and ethylene levels interact to control leaf drop; high ethylene and low auxin promote abscission.

Stomatal Regulation by Light

• Blue light triggers opening via activation of proton pumps and K+ uptake.

Plant Defense Mechanisms

• Mechanical: Thorns, trichomes.

• Mutualistic: Relationships with ants or predatory insects.

• Chemical: Toxins, secondary metabolites.

• Hypersensitive response: Localized cell death to contain infection.

• Systemic acquired resistance: Whole-plant resistance after initial infection.

Chapter 34: Plant Growth & Development

Sources of Plant Mass and Surface-to-Volume Ratio

• Most dry mass comes from CO2 (photosynthesis).

• High surface area maximizes resource uptake but increases water loss.

Plant Organs and Specialization

• Three main organs: Roots (absorption, anchorage), stems (support, transport), leaves (photosynthesis).

• Specializations: Storage roots, tendrils, spines, tubers.

Growth Patterns

• Indeterminate growth: Continuous growth throughout life, allows access to diffuse resources.

• Primary growth: Lengthening via apical meristems (tips of roots and shoots).

• Secondary growth: Thickening via lateral meristems (vascular cambium, cork cambium).

• Wood = secondary xylem; bark = secondary phloem + cork.

• Growth rings record environmental conditions (e.g., drought, fire).

Chapter 36: Plant Nutrition

Plant Composition and Nutrient Acquisition

• Plants are mostly water, carbon (from CO2), and minerals (from soil).

• Essential nutrients: Required for normal growth and reproduction.

• Macronutrients: Needed in large amounts (N, P, K, Ca, Mg, S).

• Micronutrients: Needed in trace amounts (Fe, Mn, Zn, Cu, etc.).

Mobile vs. Non-Mobile Nutrients

• Mobile: Can be moved to new tissues (e.g., N, P, K).

• Non-mobile: Remain in older tissues (e.g., Ca, Fe).

• Deficiency symptoms appear in different parts depending on mobility.

Fertilizer Composition

• Most fertilizers are high in N, P, K because these are most limiting in soils.

Selective Nutrient Uptake

• Endodermis and Casparian strip regulate entry of substances into vascular tissue, preventing toxins from entering the plant.

Root Uptake Mechanisms

• Cations (e.g., K+, Ca2+): Enter via ion channels, often exchanged for H+.

• Anions (e.g., NO3-, PO43-): Enter via cotransport with H+.

Symbiotic Relationships and Adaptations

• Mycorrhizal fungi: Enhance nutrient uptake (especially P).

• Rhizobia bacteria: Nitrogen fixation in legumes.

• Specialized roots: Root nodules, cluster roots, parasitic roots.