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, often extremophiles, distinct rRNA.

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

Horizontal Gene Transfer and Phylogenetic Trees

• Horizontal gene transfer (HGT): Movement of genetic material between organisms other than by descent.

• HGT causes blending in phylogenetic trees, making evolutionary relationships more network-like than strictly tree-like.

Archaea: Environments and Adaptations

• Found in extreme environments: high temperature (thermophiles), high salinity (halophiles), acidic or alkaline conditions.

• Adaptations: Unique membrane lipids, enzymes stable at extreme conditions.

Koch’s Postulates and Germ Theory

• Koch’s postulates: Criteria to establish a causative relationship between a microbe and a disease.

• Foundation for the germ theory of disease, which states that specific diseases are caused by specific microorganisms.

Coevolution of Bacteria and Eukaryotes

• Mutualistic relationships (e.g., gut microbiota), endosymbiosis (origin of mitochondria and chloroplasts).

Energy and Carbon Acquisition Strategies

• Phototrophs: Use light for energy.

• Chemotrophs: Use chemical compounds for energy.

• Autotrophs: Use CO2 as carbon source.

• Heterotrophs: Use organic compounds as carbon source.

Bacteria and Global Climate Change

• Certain bacteria (e.g., methanogens) produce greenhouse gases.

• Cyanobacteria contributed to oxygenation of Earth’s atmosphere.

• Adaptations: Metabolic pathways for methane or oxygen production.

Ecological Roles of Bacteria

• Nutrient cycling (nitrogen fixation, decomposition).

• Symbiosis with plants and animals.

• Pathogenesis (disease-causing).

Chapter 27: Eukaryotic Origins and Protista

Identifying Features of Eukaryotes

• Membrane-bound nucleus, organelles, linear chromosomes, larger cell size.

Protists: Monophyly and Classification

• Protists are not a monophyletic group; they are paraphyletic.

• Classified by mode of nutrition, movement, and life cycle.

Main Functional Groups of Protists

• Grouped by ecological role: Protozoa (animal-like), Algae (plant-like), Slime molds (fungus-like), Water molds.

Endosymbiotic Theory

• Origin of mitochondria and chloroplasts from engulfed prokaryotes.

• Primary endosymbiosis: Eukaryote engulfs prokaryote.

• Secondary endosymbiosis: Eukaryote engulfs another eukaryote with organelles.

• 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 ecosystems.

Chapter 29: Fungi

Medical and Ecological Roles of Fungi

• Decomposers, nutrient cycling, symbiosis (mycorrhizae, lichens).

• Pathogens (e.g., athlete’s foot, yeast infections).

• Antibiotic production (e.g., penicillin).

Fungal Body Structure and Adaptations

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

• Cell walls made of chitin.

• Adapted for absorption and growth in diverse environments.

Fungal Life Cycle

• Alternation between haploid and diploid stages.

• Key features: Plasmogamy (fusion of cytoplasm), karyogamy (fusion of nuclei), spore production.

Classification and Main Fungal Taxa

• Classified by reproductive structures.

• Four main taxa: Chytrids (flagellated spores), Zygomycetes (zygospores), Ascomycetes (sac fungi), Basidiomycetes (club fungi).

Chapter 28: Plant Diversity

Ecological Roles and Defining Features of Plants

• Primary producers, oxygen production, habitat formation.

• Defining features: Multicellularity, photosynthesis, cell walls with cellulose, alternation of generations.

Land Plant Adaptations

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

• Challenges: Desiccation, support, reproduction without water.

Classification and Synapomorphies

• Bryophytes (mosses): Nonvascular, dominant gametophyte.

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

• Gymnosperms: Vascular, seeds, no flowers.

• Angiosperms: Vascular, seeds, flowers, fruits.

Generalized Plant Life Cycle

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

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

Evolutionary Trends and Coal Formation

• Trend: From aquatic green algae to nonvascular to vascular to seeded plants.

• Coal in West Virginia: Formed from ancient plant material (mainly ferns and lycophytes) in swampy environments.

Monocots vs. Eudicots

Feature	Monocots	Eudicots
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 and Water Loss Trade-off

• Stomata must open for CO2 uptake, leading to water loss via transpiration.

• Adaptations: Waxy cuticle, CAM/C4 photosynthesis, reduced leaf area.

Water Potential and Movement

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

• Water potential ($\Psi$) is the sum of 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).

Stomatal Regulation

• Stomata open when guard cells take up K+ ions, water follows osmotically.

• Close in response to water stress, abscisic acid, or darkness.

Water Movement Hypotheses

• Root pressure: Osmotic pressure pushes water up (limited height).

• Capillary action: Water rises in narrow tubes (limited effect).

• Cohesion-tension theory: Transpiration pulls water up via cohesion and adhesion (main mechanism).

Phloem Transport

• Phloem sap: Sucrose, amino acids, hormones.

• Flows through sieve tube elements.

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

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

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

• Direction can change depending on source-sink dynamics.

Chapter 37: Plant Signaling

Signal Transduction in Plants

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

• Signal transduction pathway: Reception → Transduction → Response.

Phototropism and Light Sensing

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

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

• Blue light receptors (phototropins) mediate response.

Light and Germination/Flowering

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

Gravitropism

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

Hormones and Growth Regulation

• Auxin: Promotes cell elongation in shoots, inhibits in roots; polar transport.

• Cytokinins: Stimulate cell division.

• Gibberellic acid: Stimulates stem elongation, seed germination.

• Abscisic acid (ABA): Promotes dormancy, closes stomata.

• Ethylene: Promotes fruit ripening, leaf abscission.

Defense Mechanisms

• Mechanical (thorns), mutualistic (ant-plant), 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

Plant Mass and Surface-to-Volume Ratio

• Most dry mass from CO2 (photosynthesis).

• High surface area maximizes light and CO2 uptake but increases water loss.

Plant Organs and Specialization

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

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

Growth Patterns

• Indeterminate growth: Continuous growth from meristems.

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

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

• Wood: Secondary xylem; bark: Secondary phloem + cork.

• Growth rings record environmental conditions.

Chapter 36: Plant Nutrition

Plant Composition and Nutrient Acquisition

• Composed mainly of C, H, O (from CO2 and H2O), plus minerals from soil.

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

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

• Essential nutrients: Required for normal growth and reproduction.

Mobile vs. Non-mobile Nutrients

• Mobile: Deficiency symptoms appear in older leaves (e.g., N, P, K).

• Non-mobile: Symptoms in new leaves (e.g., Ca, Fe).

Fertilizer Composition

• Most fertilizers supply N, P, K because they are most limiting in soils.

Nutrient Uptake and Selectivity

• Endodermis and Casparian strip regulate entry of substances into vascular tissue.

• Prevents entry of toxins, controls water and nutrient flow.

Root Uptake Mechanisms

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

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

Symbiotic Relationships and Adaptations

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

• Rhizobia bacteria: Nitrogen fixation in legumes.

• Specialized roots (e.g., root nodules, cluster roots) for nutrient acquisition.