Prokaryotic Organisms: Characteristics and Classification

Lecture Notes: Evolution of Prokaryotic Domains Introduction to Prokaryotic Domains * First organisms on Earth are from two prokaryotic domains. * Uncertainty about simultaneous evolution; likely one evolved first. * Domain Bacteria likely evolved first based on DNA analysis. * Domain Archaea and eukaryotes share closer relationships. * Prokaryotes evolved around 3.5 billion years ago. Characteristics of Prokaryotic Domains * Originally categorized together in Kingdom Monera due to common features. * General Characteristics: * Unicellular organisms that can grow in colonies. * No membrane-bound organelles, though some have internal membranes. * Single circular chromosome. * Size ranges from 0.5 to 5 micrometers. * A micrometer is 1 millionth of a meter (smaller than human hair thickness). * Example comparison: A dime's thickness is about a millimeter (1,000 micrometers). Differences Between Bacteria and Archaea * Cell Wall Composition: * Both domains have cell walls, but compositions differ. * Cell walls are semi-rigid and permeable, allowing material exchange. * Domain Bacteria: * All cell walls made of the same material: peptidoglycan. * Peptidoglycan: composed of polysaccharides and short polypeptides. * Polypeptides provide flexibility. * Domain Archaea: * Cell walls have various constructions, distinct from bacteria. Summary * The type of cell wall is a key evolutionary distinction between the two domains. * Peptidoglycan in bacteria is a major identifying feature. * Archaeal cell walls show diversity and are fundamentally different from bacterial ones. Lecture Notes: Prokaryotic Organism Classification Overview of Prokaryotic Species * Identified Species: Over 6 million species identified * Only about 10,000 have been successfully cultured in laboratories * DNA Analysis: Most identifications are based on DNA differences * Estimate: There may be up to 1 trillion prokaryotic species worldwide * Repeated discoveries of new species suggest vast diversity * Long evolution allows occupation of diverse ecological niches Classification Characteristics * Shape: * Cocci: Spherical shape * Bacilli: Rod-shaped * Spirilla: Corkscrew shape * Common across domains bacteria and archaea * Cell Wall: * Domain bacteria have peptidoglycan cell walls * Similar structure thought to exist in domain archaea, but less verified Gram Staining * Development: A diagnostic technique by a Danish physician * Purpose: * Initially for identifying bacterial infections in patients * Stains the peptidoglycan cell wall * Stain Colors: * Gram Positive: Dark purple * Gram Negative: Lighter pink * Gram Variable: Intermediate staining Difference in Gram Staining * Gram Positive Bacteria: * Directly expose peptidoglycan cell wall to the environment * Stain vigorously, resulting in a dark purple color * Gram Negative Bacteria: * Have an additional outer membrane made of lipopolysaccharides * Outer membrane inhibits staining of the peptidoglycan layer * Results in a lighter pink color due to less vigorous staining Conclusion * The gram stain's interaction with peptidoglycan is impacted by the presence of an additional outer membrane in gram-negative bacteria. * Understanding these differences is crucial for bacterial classification and diagnosis of infections. Lecture on Prokaryotic Movement and Taxis Introduction to Prokaryotic Movement * Many prokaryotes rely on environmental movement for locomotion. * Approximately half of the studied prokaryotic species can move using flagella. Mechanism of Flagella Movement * Flagella Functionality: * Moves by spinning, creating propulsion similar to a propeller. * Anchored by an "axle and wheel" arrangement in the plasma membrane. * Electron Micrograph: Shows the rotational mechanism of the flagella. * Movement is chaotic, not linear. Directionality and Environmental Influence * Movement is influenced by environmental heterogeneity. * Net Directional Movement: * Occurs when moving towards/away from something. * In uniform environments, movement is random without clear direction. Taxis: Movement Toward/Away from Stimuli * Definition of Taxis: * Movement or orientation in response to a stimulus. * Examples include a plant orienting towards light. * Types of Taxis: * Positive Taxis: Movement towards a stimulus. * Negative Taxis: Movement away from a stimulus. Morphological and Ecological Characteristics * Morphological: Presence of flagella. * Ecological: Usage of flagella for movement toward or away from a stimulus. * Prokaryotes typically exhibit either positive or negative taxis, not both. Classification of Taxis by Stimulus * Chemotaxis: Movement in response to chemical stimuli. * Phototaxis: Response to light stimuli. * Magnetotaxis: Response to magnetic fields. * Each organism responds to specific stimuli only. Detailed Explanation of Magnetotaxis * Mechanism: * Detected through iron particles in the plasma membrane acting as a compass. * Iron particles align with magnetic fields, detecting strength and orientation. * Magnetic Field Strength and Orientation: * Planet Earth’s magnetic field is used for orientation (up/down direction). * Positive magnetotaxis: movement towards increasing field strength, downwards. * Negative magnetotaxis: movement towards decreasing field strength, upwards. Conclusion * Prokaryotes use various taxis mechanisms to navigate and orient themselves in their environment, utilizing stimuli such as chemical, light, and magnetic cues for movement. Prokaryotic External Characteristics and Classification Importance of Adherence * Prokaryotes may benefit from adhering to surfaces if they can't move independently. * Adherence can provide an evolutionary edge by allowing organisms to stay in favorable environments. Capsules and Slime Layers * Both serve the function of allowing adherence to surfaces and are composed of proteins and polysaccharides. * Capsules: * More organized structure and firmly attached to the cell wall. * Slime Layers: * Less organized, amorphous, and not as firmly attached. Advantages * Provide a protective layer against environmental factors. * Not all prokaryotes have these; they can be constitutive or inducible traits. * Morphological and ecological traits to consider during classification. Practical Example * Bacteria utilize these layers to adhere to surfaces such as teeth, potentially causing cavities by secreting acids. Fimbriae (or Pili) * Short, hair-like appendages made of protein. * Allow adherence to soft surfaces, substrates, or other cells. Evolutionary Advantage * Living in colonies through adherence increases the capacity to manipulate the microenvironment, enhancing survival and reproduction. Conclusion * Adherence mechanisms like capsules, slime layers, and fimbriae offer significant evolutionary advantages by enabling prokaryotes to remain in favorable environments or work together as colonies. Lecture: Characteristics of Prokaryotes Internal Structures of Prokaryotes Internal Membranes * Prokaryotes traditionally lack internal organelles, but some have internal membrane structures. * Aerobic prokaryotes use these membranes similarly to mitochondria: * Utilize respiratory membranes for energy extraction. * Electron transport chains function similarly to those in mitochondria. * Photosynthetic prokaryotes have membrane structures analogous to thylakoid membranes: * Light-harvesting complexes and electron transport chains. * ATP generation occurs in a process similar to that of chloroplasts. Energy Acquisition * Prokaryotes have diverse methods for energy acquisition: * Photosynthesis in photosynthetic prokaryotes. * Aerobic respiration in heterotrophic prokaryotes. Nucleoid Region * Contains the majority of the genetic material, not membrane-bound. * Functions of the nucleoid region: * DNA-related functions, including replication and RNA synthesis. * Some ribosomal functions. Plasmids * Small, circular DNA rings containing additional genes. * Accessory genes: * Not necessary for basic survival but beneficial in certain conditions, e.g., antibiotic resistance. * While common in prokaryotes, they are rare in eukaryotes. Survival Mechanisms Endospores * Definition: Structures formed inside bacteria to survive harsh conditions. * Characteristics of endospores: * Thick, resistant exterior. * Resistant to dehydration, extreme temperatures, and radiation. * Can remain dormant until conditions become favorable. * Allows prokaryotes to survive virtually indefinitely. Evolutionary Adaptations * Prokaryotes adapt to a wide range of environmental conditions. * Micro niches: * Specific environmental conditions for individual species. * Evolutionary adaptation allows different species to occupy various niches. Misconception * Range of conditions: While prokaryotes as a group can exist in many environments, individual species are specialized for specific conditions. Prokaryotic Nutritional Diversity Introduction * Prokaryotes are highly adaptable and can occupy diverse ecological niches. * They can grow under various conditions and utilize different energy and carbon sources. Autotrophic Growth * Autotrophs derive energy and carbon from non-organic sources. * Chemosynthesis: Synthesis of organic compounds using inorganic chemicals for energy and carbon. * Prokaryotes excel at this. * Photosynthesis: Utilization of sunlight for energy to drive chemosynthesis. * Cyanobacteria are an example. * They use pigments to capture light energy and have membrane structures similar to chloroplasts (thylakoid membranes). Heterotrophic Growth * Heterotrophs get carbon and energy from organic food sources. * High-energy organic molecules: sugars, amino acids, lipids. Oxygen Utilization * Anaerobic prokaryotes can live without oxygen. * Considered primitive as early Earth lacked atmospheric oxygen. * Aerobic prokaryotes require oxygen. * Engage in reactions similar to cellular respiration within mitochondria, involving the electron transport chain and chemiosmosis. Nutritional Modes * Four main nutritional modes in prokaryotes: * Autotrophic Modes * Photoautotrophic: Use light energy; carbon from inorganic sources. * Chemoautotrophic: Use inorganic chemicals for energy and carbon. * Heterotrophic Modes * Photoheterotrophic: Use light for energy; rare in prokaryotes. * Chemoheterotrophic: Common in prokaryotes; use organic molecules for energy and carbon. Summary * Prokaryotes display a vast range of nutritional strategies. * Their ability to utilize different energy and carbon sources allows them to thrive in various environments. Lecture Notes on Systematics of Bacteria and Archaea Introduction * Biologists are working on subdividing the domain Bacteria and domain Archaea into kingdom levels. * This is an ongoing process with many complexities and unresolved issues. Challenges in Classification * Polytomies Present: Difficulty in obtaining critical data to discern evolutionary history. * Organisms evolved long ago and diversified into many niches. * Molecular Basis: Many species have been described only based on molecular biology (DNA sequences). * More research needed to understand their growth and ecological impact. Textbook Resource * A two-page spread in the textbook (page numbers may vary) covers initial descriptions of these organisms. * An image will be posted on the course Moodle site. * Proteobacteria: Contains subgroup alpha, beta, gamma, delta. * Potential to become a kingdom, but hierarchy and categorization are still uncertain. Ecological Roles of Prokaryotes * Primary Producers: Form the base of the food web in many ecosystems. * Chemical Recycling: Key role in recycling chemicals between living and non-living environments. * Important decomposers breaking down corpses, vegetation, and waste products. * Chemoheterotrophs play a significant role in nutrient cycling. Prokaryotes in New Eco Niches * First to explore and exploit new ecological niches. * Post-extinction events, they can quickly inhabit new environments. * Reproductive Cycle: Short generational time allows for rapid evolutionary rates. * Some can reproduce every 20 minutes under ideal conditions. Conclusion * There is still much work to be done in understanding and classifying bacteria and archaea. * Their roles in ecosystems highlight their importance in global biodiversity and ecological processes. Symbiotic Relationships for Prokaryotes Definition of Symbiotic Relationships * Symbiotic Relationships: Two organisms living in intimate contact with benefits or consequences. * Types include: * Mutualistic Relationship: Both organisms benefit. * Commensalistic Relationship: One organism benefits, the other is neither helped nor harmed. * Parasitic Relationship: One organism benefits at the expense of the other. Examples of Symbiotic Relationships Mutualistic Relationships * Nitrogen Fixing Prokaryotes and Plants * Nitrogen fixing bacteria convert atmospheric nitrogen to forms usable by plants, such as legumes (peas, beans, soybeans). * Plants provide habitat or resources. * Both species benefit. * Light-Emitting Prokaryotes and Fish * Prokaryotes living in fish tissue emit light, attracting prey for fish. * Fish provide nutrients for the prokaryotes. * Both species benefit from this mutualistic relationship. Commensalistic Relationships * Bacteria and Pine Trees * Bacteria in soil release potassium as they decompose soil matter. * Pine trees benefit from increased potassium for better growth. * Bacteria grow independently of the presence of pine trees. Evolution of Symbiotic Relationships * Evolved after both involved species have individually evolved. * Relationships evolve to enhance survival (mutual aid, competition, etc.). * Example: Parasites and hosts co-evolving resistance and counter-resistance. Pathogenic Prokaryotes * While most bacteria are harmless or beneficial, some can cause diseases. * Examples of Pathogenic Bacteria: * Gonorrhea * Syphilis * Tuberculosis * Lyme Disease Antibiotic Resistance * Misuse of Antibiotics: Leads to resistance. * Overuse in medicine and agriculture (e.g., livestock). * Consequences: * Once effective antibiotics like penicillin become ineffective. * Resistant strains can spread resistance to other bacteria via plasmids. * Current Measures: More judicious use in medicine, but agricultural use remains high. * Antibiotic-free labeling only ensures absence at market time. * Natural Selection in Antibiotics: Evolutionary pressures leading to resistant strains. * Surviving bacteria repopulate and increase resistance. * Long-term loss of effectiveness of antibiotics like penicillin. Conclusion * Understanding symbiotic relationships helps in assessing ecological and evolutionary dynamics. * Antibiotic resistance is a growing societal problem, requiring careful management. Lecture Notes on Protists Introduction to Protists * Originally a catch-all group for eukaryotic, non-multicellular organisms. * Protists do not share a common evolutionary ancestry. * No longer considered a single kingdom; being divided into multiple kingdoms. Characteristics of Protists * Eukaryotic Nature: * Protists are eukaryotic, distinct from prokaryotic organisms such as Bacteria and Archaea. * Single-celled for most of their life; can form colonies or be multicellular. * Differences from Prokaryotes: * Contain membrane-bound organelles. * Have a nucleus with a double membrane. * Other organelles include mitochondria, chloroplasts, endoplasmic reticulum, and Golgi apparatus. * Complex cytoplasmic organization. * DNA: Linear chromosomes (2 or more), compared to a single circular chromosome in prokaryotes. Evolutionary Relationships * Similarities exist between Protists and other eukaryotic kingdoms. * Evolutionary relationships between Protists and other eukaryotes are complex. Diversity in Nutritional Methods * Autotrophic Protists: * Photosynthetic autotrophs. * Heterotrophic Protists: * Decomposers: Break down molecules externally, absorb nutrients. * Similar to fungal nutrition. * Ingestive heterotrophs: Animal-like, consume and digest internally. * Parasitic symbiotes. * Mixotrophic Protists: * Combine photosynthesis with ingestion or absorption. * Can switch between photosynthesis and other nutritional methods. * Indicates a varied evolutionary history. Reproductive Cycles * Significant variation in reproductive cycles among Protists. * Complex and unusual reproductive strategies to be discussed further. ________________ These notes provide an overview of the characteristics and diversity of Protists, highlighting their eukaryotic nature, nutritional strategies, and reproductive cycles as discussed in the lecture. Excavates Lecture Notes Overview of Excavates * Excavates are a supergroup with a more solidified classification in recent years. * Characterized by: * Use of flagella for movement. * Presence of a feeding groove on the cell surface. * Heterotrophic organisms with modified mitochondria. * Includes three main subgroups, with a potential fourth related to Euglenozoans. Subgroups of Excavates Diplomonads * Key Characteristics: * Possess a pair of haploid nuclei (hence the "dye" in Diplomonads). * Multiple flagella (typically 3-5 or more). * Include both free-living and parasitic symbiotes. * Notable Genus: * Giardia: Causes intestinal upset through parasitism, consuming normal gut prokaryotes. Parabasalids * Anaerobic and Symbiotic: * Due to modified mitochondria, they lack normal cellular respiration abilities. * Includes parasitic and commensal symbiotes. * Notable Parasite: * Trichomonas vaginalis: A sexually transmitted disease causing damage, particularly in females, which can lead to sterility if untreated. Euglenozoans * Subdivided into Euglenids and Kinetoplastids. Euglenids * Characteristics: * Freshwater, free-living organisms with 1-3 flagella. * Mixotrophic nutrition (photosynthesis and ingestion). * Lack a rigid cell wall but possess an eye spot as a photoreceptor. * Notable Genus: * Euglena: Widespread in freshwater environments. * Functionality: * Eye spot detects light; controls flagella activity. * Contractile vacuole regulates water balance for maintaining cell size. Kinetoplastids * Characteristics: * Single flagella and very large mitochondria. * Can be free-living or symbiotic, with notorious parasitic species. * Notable Parasite: * Trypanosoma: Causes sleeping sickness through red blood cell consumption, leading to severe anemia and lack of energy. Summary * Excavates showcase diverse evolutionary adaptations, especially in mitochondria. * Their study provides insight into parasitism and symbiosis in microorganisms. * Each subgroup has unique traits significant to their ecological roles and impacts on hosts. Lecture Notes on the SAR Supergroup Overview * SAR Supergroup: Formed by merging three separate groups: * Stramenopiles * Alveolates * Rhizarians * Reason for Merger: DNA analysis and other data showed an evolutionary relationship. * Complexity: Large and diverse groups leading to complexity. Endosymbiosis Events * Stramenopiles and Alveolates: Result of secondary endosymbiosis of a red algae. * Rhizarians: Lineage from a more recent secondary endosymbiosis of a green algae. Group-Specific Details Stramenopiles * Forms live as multi-cell colonies. * Photosynthetic Behavior: All species show some photosynthetic behavior. * Mixotrophic behavior observed, unclear if truly photosynthetic or appear due to genes. Multi-cell Organisms vs Colonies * Multi-cell Colony: Single-cell organisms living together for benefit; can be separated. * Multi-cell Organism: Cells are interdependent; cannot survive when separated. Subgroups of Stramenopiles Diatoms * Habitat: Freshwater or marine. * Characteristics: * Photosynthetic. * Have glass shells (tests) allowing exchange of substances. * Shell morphology species-specific. * Structure: Two-part test (top and bottom). Brown Algaes * Name Origin: Accessory pigment enhancing photosynthesis. * Habitat: Range from deep water to tidal ranges. * Cell Wall: Composed of cellulose and added polysaccharides. * Structure: Resemble plants, form large multicellular colonies (e.g., giant kelp). * Giant Kelp: Has gas bladders, upright posture due to flotation. Oomycetes * Previous Classification: Fungal kingdom (based on lifestyle and appearance). * Characteristics: * DNA links them to Stramenopiles. * Heterotrophic decomposers. * Cell Wall: Composed of cellulose, different from fungi's chitin. Summary * SAR Supergroup consists of highly diverse clades showing significant evolutionary events like secondary endosymbiosis. * The lecture covered details about Stramenopiles, focusing on their characteristics and differences from other groups. * The next lectures will discuss Alveolates and Rhizarians. Lecture Notes: Alveolates in the SAR Supergroup Overview of Alveolates * Part of the SAR supergroup, consisting of: * Apicomplexins * Dinoflagellates * Ciliates * Characteristics: * Mostly single-celled organisms * Variety in nutritional methods, including parasitic forms * Notable for differing modes of motility * Presence of alveoli at their surface, small sacs that stabilize the membrane Dinoflagellates * Habitat: Both freshwater and marine * Structural characteristics: * Two flagella: one at the end, another in an equatorial groove * Cell wall may contain cellulose * Nutritional methods: * Photosynthetic, mixotrophic, and heterotrophic * Can cause red tide events, leading to fish kills due to toxin production * Photosynthesis: * Spinning via equatorial groove flagella enhances light absorption Apicomplexans * Also known as sporozoans, indicating animal-like behavior and spore formation * Nutritional method: heterotrophic, primarily parasitic * Notable genera: * Plasmodium: Causes malaria * Toxoplasma: Vectors through house cats, risks during pregnancy * Malaria life cycle: * Involves dormant merozoite stage * Parasitic symptoms can be sporadic * Eradicated in some regions by eliminating mosquito vectors Ciliates * Solitary freshwater organisms * Nutritional method: heterotrophic, voracious eaters * Locomotion via cilia, which also aid in feeding * Cilia move in an ore-like fashion * Structural features: * Oral groove for feeding * Contractile vacuoles for osmoregulation * Two nuclei: macronucleus and micronucleus Unique Reproductive Cycle * Conjugation: sexual reproduction process * Diploid macronucleus and micronucleus undergo meiosis * Exchange of micronuclei between compatible mates, forming genetic variation * Multiple mitotic divisions of micronuclei * Cytoplasmic division results in population amplification * Complex process for single-celled organisms This concludes the lecture on the various lineages within the alveolate group of the SAR supergroup, highlighting their unique characteristics and biological importance. Lecture on Rhizarians in the SAR Supergroup Overview of Rhizarians * Unique clade with early and recent evolutionary developments * Primarily single-cell organisms * Mostly heterotrophic; some mixotrophic (photosynthetic + heterotrophic) * Motility through pseudopodia (thin, needle-like) Pseudopodia * Extension of the plasma membrane * Uses cytoskeleton to push out the membrane * Functions: * Movement: plasma membrane latches onto environmental objects * Feeding: used for ingesting food by engulfing it Main Groups of Rhizarians Foraminiferins (Forams) * Have external shell-like covering (test) made of calcium carbonate * Found in both marine and freshwater environments * Important for aquatic food webs * Identified based on shell morphology * Pseudopodia extend through holes in the test for movement and feeding Radularians * Test comprised of silica (similar to glass) * Mainly marine organisms * Use pseudopodia for heterotrophic nutrition * Characterized by variation in shell morphology * Test may have spike-like structures for defense Circazoans * The outgroup with unique evolutionary traits * Found in marine, freshwater, and moist terrestrial environments * Mostly heterotrophic but contain mixotrophic species * Known for recent primary endosymbiosis * Engulfment of a prokaryotic photosynthetic organism * Formation of chromatophores (not fully evolved chloroplasts) * Demonstrates ongoing evolutionary potential in endosymbiosis Endosymbiosis in Circazoans * Primary endosymbiosis: Engulfment of a photosynthetic prokaryote * Chromatophores: Intermediate between engulfed prokaryote and organelles * Secondary endosymbiosis events observed: * Involves engulfment of red and green algae * Different evolutionary paths within Circazoans linked to these events Conclusion * Rhizarians showcase a variety of forms and evolutionary adaptations * Pseudopodia play a crucial role in both mobility and feeding * Foraminiferins and Radularians feature distinct test compositions * Circazoans display potential for further evolutionary developments through endosymbiosis Lecture Notes: Archaeoplastids and Eukaryotic Multicellular Kingdom Overview of Archaeoplastids * Archaeoplastids are a supergroup with significant evolutionary evidence. * Closest relatives of land plants and include land plants as part of the supergroup. * Avoid creating paraphyletic clades by excluding land plants. * Among the oldest eukaryotic lineages in terms of evidence. Key Groups within Archaeoplastids * Red Algae * Marine and some freshwater species at freshwater-saltwater boundary. * Named for accessory pigment, phycoerythrin, which aids light absorption. * Appear multicellular but are not truly; can survive as individual cells. * Found in shallow and photic zone deep waters; important in deep-water food webs. * Cell walls contain polysaccharides; some add calcium carbonate for stiffness. * Used in cosmetics, paints, and food (e.g., sushi, ice cream for smoothness/creaminess). * Alginates extracted from red algaes improve stability of frozen dairy products. * Green Algae * Two lineages: Chlorophytes and Charophytes. * Chlorophytes * Outgroup within green algae. * Charophytes * Closely related to land plants. * Found in marine and freshwater environments; ancestral to land plants. * Range from unicellular to colonial forms; colonies appear multicellular. * Example: Chlamydomonas, a flagellated single-cell species. * Typical chloroplasts similar to land plants in morphology and pigment. * Cellulose-only cell walls, unlike red algae. Important Concepts * Primary endosymbiosis in red and green algae development. * Importance of accessory pigments for light absorption in photosynthesis. * Relationship between green algae and land plants in evolutionary context. * Use of algae in commercial products and food industries. Lecture Notes: Unicots, Amoebazoans, and Slime Molds Overview of Unicots * Unicots consist of two large clades: * Epistokonts: includes fungi and animals. * Amoebazoans: a large diverse clade with organisms that have lobe-shaped pseudopodia. Epistokonts * Contains the fungal kingdom and the animal kingdom. * Sister taxa include nuclearids for fungi and choanoflagellates for animals. Amoebazoans * Characteristics: * Lobe-shaped pseudopodia different from thin pseudopodia of rhizarians. * Exhibits cytoplasmic streaming aiding pseudopodia movement. * All are heterotrophic, with both ingestive and absorption methods. * Major Groups: * Slime Molds: Divided into cellular and acellular slime molds. * Tubulinids: Free-living, solitary, using phagocytosis for feeding. * Entamoebas: Internal parasites, not free-living. Slime Molds * Acellular (Plasmodial) Slime Molds: * Forms a large plasmodium (multi-nucleated single cell). * Engages in cytoplasmic streaming for movement and feeding. * Life cycle includes sexual reproduction: alternating haploid and diploid stages. * Spores are produced in sporangia during reproduction. * Environmental stress triggers formation of fruiting bodies. * Cellular Slime Molds: * Composed of individual cells during feeding stage. * Aggregates into a pseudoplasmodium under stress to form fruiting bodies. * Mainly undergoes asexual reproduction, remaining in haploid condition. * Occasionally undergoes sexual reproduction involving fusion and meiosis. Other Amoebazoan Groups * Tubulinids: * Free-living, found in varied environments. * Use pseudopodia for movement and phagocytosis. * Entamoebas: * Internal parasites of vertebrates and invertebrates. * Cause diseases like amoebic dysentery, often related to poor water quality. Conclusion * Amoebazoans play various ecological roles, from decomposers to parasites. * Their adaptation through pseudopodia and cytoplasmic streaming highlights their diverse survival strategies. Land Plants and their Ancestry Common Ancestry with Chirophytes * Origins: Land plants arose from a common ancestry that includes some chirophytes. * Evolutionary Environment: The lineage evolved from a freshwater environment similar to that of chirophytes. Characteristics of Chirophytes * Freshwater Organisms: Primarily single-cell organisms living in freshwater environments conducting photosynthesis. * Shared Characteristics with Land Plants: * Cellulose in Cell Walls: Both have a cellulose synthesizing complex made of enzymes, functioning in a hand-off system during synthesis, indicative of shared ancestry. * Peroxisomes: Both possess peroxisomes with identical enzymes to eliminate peroxides, a byproduct of photosynthesis. * Flagellated Sperm: Share similar structures in sperm, differing from other algae types. * Phragmatoplast Formation: A structure forming prior to cell wall during cytokinesis, crucial for cell division. Differences and Traits of Chirophytes * Life Cycle: Most of the life cycle occurs in water. * Lack of Vascular Tissue: No pipelines to transport material; absence of true leaves, roots, stems, and stomata. * No Cuticle: Unlike land plants that use cuticles to prevent water loss. * Dominant Form Variability: * Dominance: Defined by longevity and size in the life cycle. * Variability: No clear pattern of dominance between sporophyte and gametophyte forms. * Morphology: Can be heteromorphic (different shapes) or isomorphic (identical shapes) in the life cycle stages. Evolutionary Traits in Land Plants * Derived Traits: * Alternation of Generations: Involves multicellular and dependent embryos. * Apical Meristems: Regions of growth through cell division. * Walled Spores: Developed for drought resistance, crucial for terrestrial survival. * Multicellular Gametangia: Structures for producing gametes, differing from the single-cell structures in algae. Summary * Land plants share several ancestral traits with chirophytes, indicating a close evolutionary relationship. * They also exhibit distinct derived traits enabling them to adapt to terrestrial environments, marking a significant evolutionary step from their aquatic ancestors. Alternation of Generation in Plants Overview * Alternation: Switching between conditions or functions. * Generations: Two separate multicellular generations in a single life cycle. * Two types of generations: * Sporophyte Generation: Diploid phase, produces haploid spores via meiosis. * Gametophyte Generation: Haploid phase, produces gametes (sperm and eggs) that fuse during fertilization to form a diploid zygote. Life Cycle Details * Sporophyte: * Diploid phase. * Produces spores via meiosis, transitioning to haploid phase. * Gametophyte: * Haploid phase. * Produces gametes via mitosis (no further chromosomal reduction needed). * Meiosis: Transition from diploid to haploid. * Fertilization: Fusion of gametes to form diploid zygote, beginning the next sporophyte cycle. * Embryo Development: * Zygote develops into a multicellular embryo, growing into an adult sporophyte. Evolutionary Adaptations in Land Plants * Roots: * Function as anchoring and acquisition mechanisms for nutrients and water. * Vascular Tissues (Xylem & Phloem): * Conducting vessels for transporting nutrients, water, and photosynthesis products throughout the plant. * Lignin: * Strengthens cell walls for better support against gravity and to support leaves, flowers, and fruit. * Cuticle: * Waxy layer on plant surfaces, preventing water loss. * Stomata: * Openings for gas exchange, regulating water loss. Key Themes in Plant Evolution * Gradual appearance of traits during land plant evolution. * Not all adaptations appear at once; they develop over evolutionary stages. * Land Plant Adaptations: * Transition from aquatic to terrestrial environments requires new structures (e.g., roots, vascular tissue). Structural Features * Xylem & Phloem: * Transport water, nutrients, and sugars. * Essential for vascular plants. * Lignin: * Adds stiffness to cell walls; present in woody tissues. * Cuticle: * Keeps water from exiting plant surfaces too quickly. * Stomata: * Allow entry of CO2 and exit of O2. * Control water loss while facilitating gas exchange. Evolutionary Insights * Traits emerge progressively in response to environmental pressures. * Emphasis on the gradual adaptation to terrestrial life. Evolution of Land Plants Major Lineages * Two main lineages arose as plants evolved on land: 1. Non-vascular plants (Bryophytes): Do not have vascular tissue. 2. Vascular plants (Tracheophytes): Evolved vascular tissue. Timeline of Evolution * Origin of land plants: 475 million years ago * Bryophytes (non-vascular plants): * Consist of hornworts, mosses, and liverworts. * Liverworts are the outgroup; some controversy exists on branching order between mosses and hornworts. * Vascular plants: 425 million years ago * Evolved 50 million years after non-vascular plants. * Seed plants: 370 million years ago Drivers for Terrestrial Evolution * Light: Stronger on land (10-100 times) compared to water. * CO2 Availability: Higher in the atmosphere than in water. * Nutrient Concentration: Variable on land; potential for higher concentration in soils. * Reduced Competition and Predators: Initially, fewer herbivores and pathogens. * Adaptive Radiation: New eco-niches provide opportunities for diversification. Non-vascular Plants (Bryophytes) * Do not possess vascular tissue (xylem, phloem). * Lack true roots, stems, leaves. * Use rhizoids for anchoring and nutrient/water absorption. * Require moist environments; considered semi-aquatic. * Some have cuticle and stomata, but not widespread. * Utilize diffusion for water and nutrient movement, which restricts size and habitat. Characteristics and Limitations * Must remain in moist environments; vital for reproduction. * Sexual reproduction involves gametangia: * Archegonium: Houses female gametes (eggs). * Antheridium: Houses male gametes (sperm). * Relatively small size due to reliance on diffusion (typically half an inch or less). Competitive and Evolutionary Dynamics * Bryophytes initially flourished but were outcompeted by vascular plants. * Seedless vascular plants then dominated but were surpassed by seed plants. * Evolutionary competition led to reduced diversity in earlier plant lineages. Nonvascular Plants: Liverworts, Hornworts, and Mosses Overview * Nonvascular plants, also known as Bryophytes, include three divisions (or phyla): * Liverworts * Hornworts * Mosses * These plants do not have a vascular system for transporting water and nutrients. * Their life cycle involves two main phases: * Gametophyte: The dominant phase in which gametes (sperm and eggs) are produced. * Sporophyte: Grows out of the gametophyte and produces spores. Life Cycle Characteristics * Sporophyte Structure: * Composed of three parts: * Foot: Anchors sporophyte to the gametophyte. * Seta (plural: setae): The stalk. * Capsule (Sporangium): Produces spores through meiosis. * Orientation varies: * Can grow upright or downward. * Gametophyte Structure: * Produces structures called gametangia: * Archegonia: Produces and houses eggs. * Antheridia: Produces and houses sperm. * Requires water for fertilization as sperm must swim to the egg. Dominance in Life Cycle * Textbook defines gametophyte as dominant because the sporophyte grows out of it. * Instructor suggests dominance should be based on size and longevity, not solely on the physical growth of the sporophyte from the gametophyte. Reproductive Process * Reproduction: * The haploid gametophyte generates gametes: * Sperm from antheridia. * Eggs from archegonia. * Fertilization occurs when sperm swims to the archegonium and reaches the egg. * A zygote is formed and grows into the sporophyte. * Sporophyte Development: * Begins with fertilization. * Zygote develops into an embryo within the archegonium. * Mature sporophyte produces spores via meiosis in the capsule. Characteristics of Bryophytes * Do not have true roots, stems, or leaves but have structures that resemble them: * Rhizoids: Anchor the plant. * Stem-like and leaf-like structures lack vascular tissue. * Different species may have separate male and female gametophytes or both on the same structure. Key Points * Water is essential for reproduction due to the swimming sperm. * Both gametophyte and sporophyte phases are crucial to the life cycle, with the gametophyte often seen as dominant in traditional interpretations. * Understanding of the life cycle and structure helps in grasping the evolutionary adaptations of nonvascular plants. Vascular Plants Lecture Notes Introduction to Vascular Tissue * Vascular tissue in land plants includes xylem and phloem. * Allows for the development of true roots and larger growth. * Vascular tissue supports by providing structural mechanisms such as lignin. Origin of Vascular Plants * Appeared approximately 425 million years ago. * Important groups: Lycophytes and Terophytes (seedless vascular plants). * Future studies will include seed plants: gymnosperms and angiosperms. Xylem and Phloem Functions * Xylem: * Conducts water and minerals upwards in the plant. * Unidirectional flow. * Phloem: * Distributes organic products, such as sugars and hormones. * Multi-directional flow depending on production and storage needs. True Roots and Leaves * Vascular tissue allows for true roots, enhancing anchoring and absorption. * True leaves increase surface area for light capture, aiding growth and reproduction. Seedless Vascular Plants * Include lycophytes and terophytes. * Represent a "grade" (paraphyletic group based on morphological traits). * Produce spores instead of seeds for dispersal. Life Cycle of Seedless Vascular Plants * Sporophyte: * Dominant life cycle form, larger and longer-lived than gametophyte. * Produces spores by meiosis in structures called sporangia. * Sporangia are grouped in structures called sorus. * Gametophyte: * Smaller, short-lived, needs water for reproduction. * Produces sperm in antheridium, eggs in archegonium. Ferns as an Example * Sporophytes can grow to a significant size compared to gametophytes. * Fertilization requires water, albeit minimal, for sperm mobility. * Lifecycle involves transition from haploid spores to diploid sporophyte through fertilization. These notes summarize the key concepts of vascular plants, focusing on their structure, evolution, and reproductive cycles. Lecture Notes: Seedless Vascular Plants - Lycophytes and Monilophytes Overview * Seedless vascular plants are classified into two main groups: * Lycophytes * Monilophytes (also known as Pterophytes) Common Characteristics * Sporophyte: Larger and more long-lasting part of the alternation of generations life cycle. * Gametophyte: Very small, grows at or below soil surface, short-lived. Lycophytes * Examples: Spike mosses, quillworts, club mosses. * Historically could grow very large, forming early forests due to lack of competition. * Growth limited by need for moist environments. * Abundant 300-350 million years ago. * Decline due to climate shift (continental drift leading to drier habitats) and competition from seed plants. Monilophytes * Examples: Ferns, horsetails, whisk ferns. * Modern ferns typically around 3 feet, but can reach up to 20 feet in protected areas. * Ancestors of monilophytes were much larger due to lack of competition, reaching sizes of 30 feet or more. * Ferns: * Over 12,000 species still viable. * Success attributed to well-developed leaves. * Range expanded due to niches created by seed plants. Ecological Impact * Lycophytes and monilophytes formed the first terrestrial forests. * Die-off contributed to the formation of coal deposits. * Fossils commonly found in areas of mining activity. Evolutionary Pressures * Climate changes (shift to drier environments) created pressure on seedless vascular plants. * Competition from seed plants led to further decline. Conclusion * The decline of these seedless vascular plants paved the way for the rise of seed plants. * The next chapter will focus on seed plants. Seed Plants and Their Evolutionary Significance Introduction * Last chapter covered plant kingdom up to seed plants. * Seed plants originated approximately 315-320 million years ago. * Significant evolutionary step as plants moved further away from water dependency. Categories of Seed Plants * Gymnosperms * Older group, fewer in number today. * Angiosperms * Evolved after gymnosperms, more dominant today. * Outcompeted gymnosperms due to evolutionary advantages. Key Characteristics of Seed Plants * Do not require water for reproduction. * Sperm and eggs still present but part of reduced gametophytes. * Female Gametophyte: Ovule * Male Gametophyte: Pollen grain * Evolutionary advantage through seeds over spores: * Seeds provide stored food and a multicellular embryo. Spores vs. Seeds * Spores: Single cell, no nutrients, limited dispersal. * Seeds: Multicellular, nutrient-rich, better dispersal mechanism. * Heterosporous nature (different male and female spores). * Megaspore: Female * Microspore: Male Mechanisms of Seed Plant Reproduction * Pollen dispersal via wind or animals. * Pollen can travel vast distances, unlike sperm. * Gametophytes become dependent on sporophyte. * Develop within the walls of the spore. * Retained within the parent sporophyte. Sporophyte and Gametophyte Relationship * Increased dominance of sporophyte. * Shift from independent to dependent gametophyte. * Integration of gametophyte into sporophyte structure. Reproductive Structures * Ovule: Female gametophyte structure * Contains integument layer * Develops from megasporangium via meiosis. * Pollen Grain: Male gametophyte * Develops from microspore. * Eliminates need for water in fertilization. Fertilization Process * Pollen tube growth allows sperm to reach egg. * Fertilization merges sperm and egg nuclei, forming a diploid zygote. * Zygote grows into an embryo within the seed. * Seed development: * Integument becomes the seed coat. * Stored food nourishes embryo. Conclusion * Seeds provide evolutionary advantage by enhancing survival and dispersal. * Detailed examination of seed structure to follow in subsequent discussions. Lecture Notes: Male and Female Gametophyte Development Overview * The development of male and female gametophytes occur along different lines. * Megaspore and microspore give rise to female and male gametophytes, respectively. * Focus on gymnosperm and angiosperm gametophyte development. Female Gametophyte Development Megaspore Development * Mega Sporangium: Spore-producing structure that produces the megaspore. * Transition from diploid to haploid through meiosis. * Meiosis: Results in four haploid megaspores. * Three megaspores break down. * Remaining megaspore continues development. Gymnosperm Process * Cell division results in a cell within a cell: * Outer cell: Embryosac (female gametophyte/ovule). * Inner cell: Egg cell (female gamete). Angiosperm Process * Single megaspore undergoes three rounds of mitosis producing eight nuclei: * Nuclei distribution: Three at each end, two in the center. * Cytokinesis results in seven cells instead of eight: * Three cells at each end, one becomes the egg. * Middle cell known as central or endosperm cell (diploid with polar nuclei). Male Gametophyte Development Microspores Development * Microsporangium: Spore-producing structure that produces microspores. * Meiosis results in four haploid cells, all continue development. Comparative Philosophy * Female side: Fewer, higher quality gametes due to nutrient concentration. * Male side: Greater quantity, less focus on quality. Gymnosperm Process * Microspores undergo cell division: * Outer cell: Pollen tube cell. * Inner cell: Male gamete (sperm cell). * Pollen grain is effectively two cells within one (cell within a cell). Angiosperm Process * Cell division results in: * Outer cell: Pollen tube cell. * Inner cell: Generative cell (undergoes further division). * Second division yields two sperm cells inside the pollen tube cell. Key Concepts * Female gametophyte: Ovule or embryosac in gymnosperm and angiosperm. * Male gametophyte: Pollen grain in both gymnosperm and angiosperm. * Differences in gamete production strategies between male and female gametophytes reflect broader biological trends. Lecture Notes: Seed Plant Divergence - Gymnosperms vs Angiosperms Introduction to Seed Plant Groups * Seeded Plants Split: Two main groups: Gymnosperms and Angiosperms. * Gymnosperms: * Non-flowering plants. * Evolved earlier, once dominant in ecosystems. * Known as 'naked seeds' due to lack of an outer covering. * Angiosperms: * Flowering plants. * Became more dominant over time, outcompeting gymnosperms. * Seeds have an additional covering known as fruit. Evolutionary Competition * Initial Dominance: * Gymnosperms initially outcompeted seedless vascular and non-vascular plants. * Dominated terrestrial environments until the rise of angiosperms. * Angiosperms' Rise: * Quickly displaced gymnosperms in various ecosystems. * Superior evolutionary adaptations. Differences in Seed Structure * Similarities: * Both have embryos. * Both contain stored food to nourish the embryo. * Both feature a protective seed coat. * Gymnosperm Seeds: * 'Naked seeds' without additional covering. * Angiosperm Seeds: * Fruit acts as an additional covering. Seed Coat Functionality * Protection: * Protects embryo and stored food from elements and predators. * Timing of Germination: * Ensures germination occurs under favorable conditions. * Example: Fire pines require fire to trigger germination, reducing competition. Stored Food Differences * Gymnosperms: * Stored food is haploid, derived directly from the female gametophyte. * Angiosperms: * Stored food is triploid (3N), resulting from a combination of male and female gametophyte material. Corrections and Clarifications * Notes Correction: * Angiosperm stored food arises from both male and female gametophytes, not just female. ________________ These notes summarize the key distinctions and evolutionary aspects of gymnosperms and angiosperms, focusing on seed structure and ecological competition. Characteristics of Gymnosperms Major Groupings * Conifers * Includes evergreens, pines, firs, cypress, cedars * Endemic to regions like Louisiana * Cycads * Now mostly found in botanical gardens * Ginkgos * Ginkgo biloba is the sole survivor of its group * Common in urban landscaping, highly adaptable to city environments * Nidophytes * Thrive in arid environments, have tough leaves to withstand harsh conditions Evolutionary Context * Gymnosperms were more dominant in the past * Many species have gone extinct due to competition with angiosperms * Gymnosperms produce cones; bristlecone pines and redwoods are notable for longevity and size Longevity and Size * Sporophytes: Long-lived (1000-2000 years), larger than gametophytes * Gametophytes: Short-lived, often only a few days or weeks Gymnosperm Groups * Conifers: Largest group, successful historically and still widespread * Cycads: Reduced to botanical specimens * Ginkgos: Found in urban areas * Nidophytes: Adapted to survive in harsh arid conditions Life Cycle of Gymnosperms * Key Characteristics: Pollen and dominant sporophytes * Heterosporous: Produces microspores (male) and megaspores (female) * Sporophyte undergoes meiosis to create spores * Microsporangia: Produces male gametophyte (pollen) * Megasporangia: Produces female gametophyte (ovule) * Fertilization Process: * Pollen tube allows sperm to reach egg * Fusion forms a diploid zygote * Seed Development * Zygote grows into an embryo within the seed * Seed coat forms from parental sporophyte tissues * Reproductive Success * Long-lived sporophytes lead to enhanced reproductive efforts * Allows gymnosperms to outcompete many seedless vascular plants Conclusion * Gymnosperms have distinct characteristics and life cycles making them significant in the plant kingdom * Next topic will be angiosperms Lecture Notes: Characteristics of Angiosperms Introduction * Angiosperms are the dominant group of land plants. * Over 95% of visible plants are angiosperms. * Key features that provide a competitive edge: 1. Flowers 2. Seeds enclosed in a fruit 3. Broad leaves 4. Advanced vascular tissue Competitive Advantages of Angiosperms Reproductive Advantages 1. Flowers * Flowers improve reproductive success. * Gymnosperms rely on wind pollination (low probability). * Angiosperms attract pollinators to transfer pollen efficiently. * Result: Increased likelihood of fertilization and reproduction. 2. Seeds in a Fruit * Fruits aid in seed dispersal. * Seeds move further from the parent plant, reducing competition and increasing survival chances. * Dispersal allows colonization of new areas, ensuring species survival. Physiological Advantages 3. Broad Leaves * Increase light capture, enhancing photosynthesis. * Result: More energy and materials for growth and reproduction. 4. Advanced Vascular Tissue * Efficient transport of materials within the plant. * Provides physiological advantages over gymnosperms. Flower Structure and Function * Flowers are specialized shoot structures with modified leaves. * Essential for sexual reproduction. * Complete flowers have four main parts: 1. Sepals - Protects the flower bud. 2. Petals - Attract pollinators and protect reproductive structures. 3. Stamens - Male reproductive part. 4. Carpels - Female reproductive part. Detailed Flower Structure * Petals * Serve as a corolla to contain reproductive structures. * Act as signals to pollinators. * Offer food (pollen and nectar) to attract pollinators. * Sepals * Protect the flower before blooming. * Green, leaf-like structures around the bud. Reproductive Structures * Stamens (Male) * Comprised of filament (stalk) and anther (pollen production). * Pollen grains (male gametophytes) develop in the anther. * Carpels (Female) * Located centrally in the flower. * Comprised of stigma (pollen reception), style (pollen tube growth), and ovary (egg development). * Ovules within the ovary become seeds after fertilization. * The ovary's outer layer becomes the fruit, aiding seed dispersal. Conclusion * Angiosperms' evolution of flowers and fruits significantly enhanced their reproductive and survival strategies. * Physiological adaptations further strengthened their dominance over other plant species. * Future discussions will explore fruit characteristics and seed dispersal mechanisms. Seed Dispersal in Angiosperms Overview * Purpose of Fruit: The primary role of fruit in angiosperms is seed dispersal. * Origin of Fruit: Fruit develops from the base of the carpal, specifically the ovary. * Example: Tomato — the wall of the tomato is the enlarged ovary. * Non-edible example: Milkweed pod. Types of Seed Dispersal Mechanisms 1. Wind Dispersal * Seeds adapted to be carried by the wind. * Example: Milkweed seeds with parachute-like structures. * Other examples: Seeds with wing-like structures acting as helicopters. 2. Mechanical Dispersal * Seeds attach to passing animals via hooks. * Example: Seeds sticking to clothes or animal fur. * Seeds are carried and eventually fall off or are removed away from the parent plant. 3. Water Dispersal * Seeds encased in a flotation device. * Example: Coconuts floating across oceans. * Seeds can travel long distances to new locations downstream or across oceans. 4. Animal Dispersal (Edible Fruit) * Fruits are consumed by animals, seeds are discarded. * Examples: * Humans eating apples and discarding cores elsewhere. * Seeds requiring digestion by animals to break down seed coat and assist in germination. * Benefits: * Increased dispersal distance. * Seeds are deposited with natural fertilizer from animal waste. Evolutionary Advantage * Fruit provides a significant evolutionary advantage by enabling plant species to disperse broadly within ecosystems. Pollination and Fertilization in Angiosperms Overview * Discusses the process of pollination and fertilization in angiosperms. * Sequence of events leading to double fertilization. Pollination * Definition: Transfer of pollen from an anther to a stigma. * Types: * Self-Pollination: Within a single flower, allowed in some species. * Cross-Pollination: Pollen must move from one plant to another, enforced by some species. * Role of Style: * Acts as a quality control. * Prevents self-fertilization by stopping pollen tube growth if pollen is from the same plant. Pollen Tube Formation * Pollen grain lands on stigma. * Tube cell elongates to form pollen tube. * Function: Conduit for two sperm cells from the generative cell to the ovary. Double Fertilization * Process: * Two sperm cells travel down pollen tube to the ovary. * Fertilization occurs at the carpel's base. * Involvement of Female Gametophyte: * Consists of three cells at each end and a central cell. * Central cell contains two haploid nuclei. Fertilization Details * Diploid Zygote Formation: * Haploid egg fuses with haploid sperm. * Results in diploid zygote. * Triploid Endosperm Formation: * Second sperm fuses with central cell's nuclei. * Central cell becomes triploid, serving as stored food. * Provides nourishment for the developing embryo. Importance of Two Sperm Cells * Purpose: * One sperm fertilizes the egg (forming the diploid zygote). * Other sperm fertilizes the central cell (forming triploid endosperm). Conclusion * Double fertilization results in both a diploid zygote and a triploid endosperm. * Next discussion to address angiosperm phylogeny. Angiosperm Lineages Overview * Angiosperms dominate plant species, over 95% of plants seen. * Dicots/Eudicots make up over 95% of visible angiosperm species. * Four Major Angiosperm Lineages: * Basal Angiosperms: Includes water lilies and possibly two separate lineages. * Magnoliids: Related to magnolia trees. * Monocots: Includes grasses, grains, orchids, and palms. * Eudicots/Dicots: The bulk of visible plant species. Evolutionary Background * Gymnosperms appear in the fossil record around 305 million years ago. * Angiosperms appear around 140 million years ago. * They became the dominant seed plants despite the gymnosperms' head start. * Coincided with the evolution of animal involvement in pollination. Key Differences Between Monocots and Dicots Flower Structure * Monocots: Floral structures in multiples of three. * Dicots: Floral structures in multiples of four, five, or arranged in a ring. Leaf Structure * Monocots: * Long, narrow leaves (e.g., grass). * Parallel veins. * Dicots: * Broader leaves. * Branching or net-like vein patterns. Vascular Tissue * Monocots: Scattered vascular bundles in the stem. * Dicots: Vascular bundles arranged in a ring. Root System * Monocots: Fibrous roots, shallow, good for frequent shallow watering. * Dicots: Tap root system, deeper roots, suitable for infrequent deep watering. Pollen Structure * Monocots: Pollen grains with one opening. * Dicots: Pollen grains with three openings. Seed Leaves (Cotyledons) * Monocots: One cotyledon. * Dicots: Two cotyledons. * Useful for distinguishing seedlings and identifying weeds during early growth stages. Implications for Plant Care * Monocots: Require frequent, shallow watering. * Dicots: Adapted to deeper water and less frequent soaking. * Understanding these differences is crucial for successful cultivation and management of plants.

These notes provide an overview of the characteristics and diversity of Protists, highlighting their eukaryotic nature, nutritional strategies, and reproductive cycles as discussed in the lecture.
Excavates Lecture Notes
Overview of Excavates
* Excavates are a supergroup with a more solidified classification in recent years.
* Characterized by:
   * Use of flagella for movement.
   * Presence of a feeding groove on the cell surface.
   * Heterotrophic organisms with modified mitochondria.
   * Includes three main subgroups, with a potential fourth related to Euglenozoans.
Subgroups of Excavates
Diplomonads
* Key Characteristics:
   * Possess a pair of haploid nuclei (hence the "dye" in Diplomonads).
   * Multiple flagella (typically 3-5 or more).
   * Include both free-living and parasitic symbiotes.
* Notable Genus:
   * Giardia: Causes intestinal upset through parasitism, consuming normal gut prokaryotes.
Parabasalids
* Anaerobic and Symbiotic:
   * Due to modified mitochondria, they lack normal cellular respiration abilities.
   * Includes parasitic and commensal symbiotes.
* Notable Parasite:
   * Trichomonas vaginalis: A sexually transmitted disease causing damage, particularly in females, which can lead to sterility if untreated.
Euglenozoans
* Subdivided into Euglenids and Kinetoplastids.
Euglenids
* Characteristics:
   * Freshwater, free-living organisms with 1-3 flagella.
   * Mixotrophic nutrition (photosynthesis and ingestion).
   * Lack a rigid cell wall but possess an eye spot as a photoreceptor.
* Notable Genus:
   * Euglena: Widespread in freshwater environments.
* Functionality:
   * Eye spot detects light; controls flagella activity.
   * Contractile vacuole regulates water balance for maintaining cell size.
Kinetoplastids
* Characteristics:
   * Single flagella and very large mitochondria.
   * Can be free-living or symbiotic, with notorious parasitic species.
* Notable Parasite:
   * Trypanosoma: Causes sleeping sickness through red blood cell consumption, leading to severe anemia and lack of energy.
Summary
* Excavates showcase diverse evolutionary adaptations, especially in mitochondria.
* Their study provides insight into parasitism and symbiosis in microorganisms.
* Each subgroup has unique traits significant to their ecological roles and impacts on hosts.
Lecture Notes on the SAR Supergroup
Overview
* SAR Supergroup: Formed by merging three separate groups:
   * Stramenopiles
   * Alveolates
   * Rhizarians
* Reason for Merger: DNA analysis and other data showed an evolutionary relationship.
* Complexity: Large and diverse groups leading to complexity.
Endosymbiosis Events
* Stramenopiles and Alveolates: Result of secondary endosymbiosis of a red algae.
* Rhizarians: Lineage from a more recent secondary endosymbiosis of a green algae.
Group-Specific Details
Stramenopiles
* Forms live as multi-cell colonies.
* Photosynthetic Behavior: All species show some photosynthetic behavior.
   * Mixotrophic behavior observed, unclear if truly photosynthetic or appear due to genes.
Multi-cell Organisms vs Colonies
* Multi-cell Colony: Single-cell organisms living together for benefit; can be separated.
* Multi-cell Organism: Cells are interdependent; cannot survive when separated.
Subgroups of Stramenopiles
Diatoms
* Habitat: Freshwater or marine.
* Characteristics:
   * Photosynthetic.
   * Have glass shells (tests) allowing exchange of substances.
   * Shell morphology species-specific.
* Structure: Two-part test (top and bottom).
Brown Algaes
* Name Origin: Accessory pigment enhancing photosynthesis.
* Habitat: Range from deep water to tidal ranges.
* Cell Wall: Composed of cellulose and added polysaccharides.
* Structure: Resemble plants, form large multicellular colonies (e.g., giant kelp).
   * Giant Kelp: Has gas bladders, upright posture due to flotation.
Oomycetes
* Previous Classification: Fungal kingdom (based on lifestyle and appearance).
* Characteristics:
   * DNA links them to Stramenopiles.
   * Heterotrophic decomposers.
* Cell Wall: Composed of cellulose, different from fungi's chitin.
Summary
* SAR Supergroup consists of highly diverse clades showing significant evolutionary events like secondary endosymbiosis.
* The lecture covered details about Stramenopiles, focusing on their characteristics and differences from other groups.
* The next lectures will discuss Alveolates and Rhizarians.
Lecture Notes: Alveolates in the SAR Supergroup
Overview of Alveolates
* Part of the SAR supergroup, consisting of:
   * Apicomplexins
   * Dinoflagellates
   * Ciliates
* Characteristics:
   * Mostly single-celled organisms
   * Variety in nutritional methods, including parasitic forms
   * Notable for differing modes of motility
   * Presence of alveoli at their surface, small sacs that stabilize the membrane
Dinoflagellates
* Habitat: Both freshwater and marine
* Structural characteristics:
   * Two flagella: one at the end, another in an equatorial groove
   * Cell wall may contain cellulose
* Nutritional methods:
   * Photosynthetic, mixotrophic, and heterotrophic
   * Can cause red tide events, leading to fish kills due to toxin production
* Photosynthesis:
   * Spinning via equatorial groove flagella enhances light absorption
Apicomplexans
* Also known as sporozoans, indicating animal-like behavior and spore formation
* Nutritional method: heterotrophic, primarily parasitic
* Notable genera:
   * Plasmodium: Causes malaria
   * Toxoplasma: Vectors through house cats, risks during pregnancy
* Malaria life cycle:
   * Involves dormant merozoite stage
   * Parasitic symptoms can be sporadic
   * Eradicated in some regions by eliminating mosquito vectors
Ciliates
* Solitary freshwater organisms
* Nutritional method: heterotrophic, voracious eaters
* Locomotion via cilia, which also aid in feeding
* Cilia move in an ore-like fashion
* Structural features:
   * Oral groove for feeding
   * Contractile vacuoles for osmoregulation
   * Two nuclei: macronucleus and micronucleus
Unique Reproductive Cycle
* Conjugation: sexual reproduction process
   * Diploid macronucleus and micronucleus undergo meiosis
   * Exchange of micronuclei between compatible mates, forming genetic variation
   * Multiple mitotic divisions of micronuclei
   * Cytoplasmic division results in population amplification
   * Complex process for single-celled organisms
This concludes the lecture on the various lineages within the alveolate group of the SAR supergroup, highlighting their unique characteristics and biological importance.
Lecture on Rhizarians in the SAR Supergroup
Overview of Rhizarians
* Unique clade with early and recent evolutionary developments
* Primarily single-cell organisms
* Mostly heterotrophic; some mixotrophic (photosynthetic + heterotrophic)
* Motility through pseudopodia (thin, needle-like)
Pseudopodia
* Extension of the plasma membrane
* Uses cytoskeleton to push out the membrane
* Functions:
   * Movement: plasma membrane latches onto environmental objects
   * Feeding: used for ingesting food by engulfing it
Main Groups of Rhizarians
Foraminiferins (Forams)
* Have external shell-like covering (test) made of calcium carbonate
* Found in both marine and freshwater environments
* Important for aquatic food webs
* Identified based on shell morphology
* Pseudopodia extend through holes in the test for movement and feeding
Radularians
* Test comprised of silica (similar to glass)
* Mainly marine organisms
* Use pseudopodia for heterotrophic nutrition
* Characterized by variation in shell morphology
* Test may have spike-like structures for defense
Circazoans
* The outgroup with unique evolutionary traits
* Found in marine, freshwater, and moist terrestrial environments
* Mostly heterotrophic but contain mixotrophic species
* Known for recent primary endosymbiosis
   * Engulfment of a prokaryotic photosynthetic organism
   * Formation of chromatophores (not fully evolved chloroplasts)
* Demonstrates ongoing evolutionary potential in endosymbiosis
Endosymbiosis in Circazoans
* Primary endosymbiosis: Engulfment of a photosynthetic prokaryote
* Chromatophores: Intermediate between engulfed prokaryote and organelles
* Secondary endosymbiosis events observed:
   * Involves engulfment of red and green algae
   * Different evolutionary paths within Circazoans linked to these events
Conclusion
* Rhizarians showcase a variety of forms and evolutionary adaptations
* Pseudopodia play a crucial role in both mobility and feeding
* Foraminiferins and Radularians feature distinct test compositions
* Circazoans display potential for further evolutionary developments through endosymbiosis
Lecture Notes: Archaeoplastids and Eukaryotic Multicellular Kingdom
Overview of Archaeoplastids
* Archaeoplastids are a supergroup with significant evolutionary evidence.
* Closest relatives of land plants and include land plants as part of the supergroup.
* Avoid creating paraphyletic clades by excluding land plants.
* Among the oldest eukaryotic lineages in terms of evidence.
Key Groups within Archaeoplastids
* Red Algae
   * Marine and some freshwater species at freshwater-saltwater boundary.
   * Named for accessory pigment, phycoerythrin, which aids light absorption.
   * Appear multicellular but are not truly; can survive as individual cells.
   * Found in shallow and photic zone deep waters; important in deep-water food webs.
   * Cell walls contain polysaccharides; some add calcium carbonate for stiffness.
   * Used in cosmetics, paints, and food (e.g., sushi, ice cream for smoothness/creaminess).
   * Alginates extracted from red algaes improve stability of frozen dairy products.
* Green Algae
   * Two lineages: Chlorophytes and Charophytes.
   * Chlorophytes
      * Outgroup within green algae.
   * Charophytes
      * Closely related to land plants.
   * Found in marine and freshwater environments; ancestral to land plants.
   * Range from unicellular to colonial forms; colonies appear multicellular.
   * Example: Chlamydomonas, a flagellated single-cell species.
   * Typical chloroplasts similar to land plants in morphology and pigment.
   * Cellulose-only cell walls, unlike red algae.
Important Concepts
* Primary endosymbiosis in red and green algae development.
* Importance of accessory pigments for light absorption in photosynthesis.
* Relationship between green algae and land plants in evolutionary context.
* Use of algae in commercial products and food industries.
Lecture Notes: Unicots, Amoebazoans, and Slime Molds
Overview of Unicots
* Unicots consist of two large clades:
   * Epistokonts: includes fungi and animals.
   * Amoebazoans: a large diverse clade with organisms that have lobe-shaped pseudopodia.
Epistokonts
* Contains the fungal kingdom and the animal kingdom.
* Sister taxa include nuclearids for fungi and choanoflagellates for animals.
Amoebazoans
* Characteristics:
   * Lobe-shaped pseudopodia different from thin pseudopodia of rhizarians.
   * Exhibits cytoplasmic streaming aiding pseudopodia movement.
   * All are heterotrophic, with both ingestive and absorption methods.
* Major Groups:
   * Slime Molds: Divided into cellular and acellular slime molds.
   * Tubulinids: Free-living, solitary, using phagocytosis for feeding.
   * Entamoebas: Internal parasites, not free-living.
Slime Molds
* Acellular (Plasmodial) Slime Molds:
   * Forms a large plasmodium (multi-nucleated single cell).
   * Engages in cytoplasmic streaming for movement and feeding.
   * Life cycle includes sexual reproduction: alternating haploid and diploid stages.
   * Spores are produced in sporangia during reproduction.
   * Environmental stress triggers formation of fruiting bodies.
* Cellular Slime Molds:
   * Composed of individual cells during feeding stage.
   * Aggregates into a pseudoplasmodium under stress to form fruiting bodies.
   * Mainly undergoes asexual reproduction, remaining in haploid condition.
   * Occasionally undergoes sexual reproduction involving fusion and meiosis.
Other Amoebazoan Groups
* Tubulinids:
   * Free-living, found in varied environments.
   * Use pseudopodia for movement and phagocytosis.
* Entamoebas:
   * Internal parasites of vertebrates and invertebrates.
   * Cause diseases like amoebic dysentery, often related to poor water quality.
Conclusion
* Amoebazoans play various ecological roles, from decomposers to parasites.
* Their adaptation through pseudopodia and cytoplasmic streaming highlights their diverse survival strategies.
Land Plants and their Ancestry
Common Ancestry with Chirophytes
* Origins: Land plants arose from a common ancestry that includes some chirophytes.
* Evolutionary Environment: The lineage evolved from a freshwater environment similar to that of chirophytes.
Characteristics of Chirophytes
* Freshwater Organisms: Primarily single-cell organisms living in freshwater environments conducting photosynthesis.
* Shared Characteristics with Land Plants:
   * Cellulose in Cell Walls: Both have a cellulose synthesizing complex made of enzymes, functioning in a hand-off system during synthesis, indicative of shared ancestry.
   * Peroxisomes: Both possess peroxisomes with identical enzymes to eliminate peroxides, a byproduct of photosynthesis.
   * Flagellated Sperm: Share similar structures in sperm, differing from other algae types.
   * Phragmatoplast Formation: A structure forming prior to cell wall during cytokinesis, crucial for cell division.
Differences and Traits of Chirophytes
* Life Cycle: Most of the life cycle occurs in water.
* Lack of Vascular Tissue: No pipelines to transport material; absence of true leaves, roots, stems, and stomata.
* No Cuticle: Unlike land plants that use cuticles to prevent water loss.
* Dominant Form Variability:
   * Dominance: Defined by longevity and size in the life cycle.
   * Variability: No clear pattern of dominance between sporophyte and gametophyte forms.
   * Morphology: Can be heteromorphic (different shapes) or isomorphic (identical shapes) in the life cycle stages.
Evolutionary Traits in Land Plants
* Derived Traits:
   * Alternation of Generations: Involves multicellular and dependent embryos.
   * Apical Meristems: Regions of growth through cell division.
   * Walled Spores: Developed for drought resistance, crucial for terrestrial survival.
   * Multicellular Gametangia: Structures for producing gametes, differing from the single-cell structures in algae.
Summary
* Land plants share several ancestral traits with chirophytes, indicating a close evolutionary relationship.
* They also exhibit distinct derived traits enabling them to adapt to terrestrial environments, marking a significant evolutionary step from their aquatic ancestors.
Alternation of Generation in Plants
Overview
* Alternation: Switching between conditions or functions.
* Generations: Two separate multicellular generations in a single life cycle.
* Two types of generations:
   * Sporophyte Generation: Diploid phase, produces haploid spores via meiosis.
   * Gametophyte Generation: Haploid phase, produces gametes (sperm and eggs) that fuse during fertilization to form a diploid zygote.
Life Cycle Details
* Sporophyte:
   * Diploid phase.
   * Produces spores via meiosis, transitioning to haploid phase.
* Gametophyte:
   * Haploid phase.
   * Produces gametes via mitosis (no further chromosomal reduction needed).
* Meiosis: Transition from diploid to haploid.
* Fertilization: Fusion of gametes to form diploid zygote, beginning the next sporophyte cycle.
* Embryo Development:
   * Zygote develops into a multicellular embryo, growing into an adult sporophyte.
Evolutionary Adaptations in Land Plants
* Roots:
   * Function as anchoring and acquisition mechanisms for nutrients and water.
* Vascular Tissues (Xylem & Phloem):
   * Conducting vessels for transporting nutrients, water, and photosynthesis products throughout the plant.
* Lignin:
   * Strengthens cell walls for better support against gravity and to support leaves, flowers, and fruit.
* Cuticle:
   * Waxy layer on plant surfaces, preventing water loss.
* Stomata:
   * Openings for gas exchange, regulating water loss.
Key Themes in Plant Evolution
* Gradual appearance of traits during land plant evolution.
* Not all adaptations appear at once; they develop over evolutionary stages.
* Land Plant Adaptations:
   * Transition from aquatic to terrestrial environments requires new structures (e.g., roots, vascular tissue).
Structural Features
* Xylem & Phloem:
   * Transport water, nutrients, and sugars.
   * Essential for vascular plants.
* Lignin:
   * Adds stiffness to cell walls; present in woody tissues.
* Cuticle:
   * Keeps water from exiting plant surfaces too quickly.
* Stomata:
   * Allow entry of CO2 and exit of O2.
   * Control water loss while facilitating gas exchange.
Evolutionary Insights
* Traits emerge progressively in response to environmental pressures.
* Emphasis on the gradual adaptation to terrestrial life.
Evolution of Land Plants
Major Lineages
* Two main lineages arose as plants evolved on land:
   1. Non-vascular plants (Bryophytes): Do not have vascular tissue.
   2. Vascular plants (Tracheophytes): Evolved vascular tissue.
Timeline of Evolution
* Origin of land plants: 475 million years ago
   * Bryophytes (non-vascular plants):
      * Consist of hornworts, mosses, and liverworts.
      * Liverworts are the outgroup; some controversy exists on branching order between mosses and hornworts.
* Vascular plants: 425 million years ago
   * Evolved 50 million years after non-vascular plants.
* Seed plants: 370 million years ago
Drivers for Terrestrial Evolution
* Light: Stronger on land (10-100 times) compared to water.
* CO2 Availability: Higher in the atmosphere than in water.
* Nutrient Concentration: Variable on land; potential for higher concentration in soils.
* Reduced Competition and Predators: Initially, fewer herbivores and pathogens.
* Adaptive Radiation: New eco-niches provide opportunities for diversification.
Non-vascular Plants (Bryophytes)
* Do not possess vascular tissue (xylem, phloem).
* Lack true roots, stems, leaves.
* Use rhizoids for anchoring and nutrient/water absorption.
* Require moist environments; considered semi-aquatic.
* Some have cuticle and stomata, but not widespread.
* Utilize diffusion for water and nutrient movement, which restricts size and habitat.
Characteristics and Limitations
* Must remain in moist environments; vital for reproduction.
* Sexual reproduction involves gametangia:
   * Archegonium: Houses female gametes (eggs).
   * Antheridium: Houses male gametes (sperm).
* Relatively small size due to reliance on diffusion (typically half an inch or less).
Competitive and Evolutionary Dynamics
* Bryophytes initially flourished but were outcompeted by vascular plants.
* Seedless vascular plants then dominated but were surpassed by seed plants.
* Evolutionary competition led to reduced diversity in earlier plant lineages.

Nonvascular Plants: Liverworts, Hornworts, and Mosses
Overview
* Nonvascular plants, also known as Bryophytes, include three divisions (or phyla):
   * Liverworts
   * Hornworts
   * Mosses
* These plants do not have a vascular system for transporting water and nutrients.
* Their life cycle involves two main phases:
   * Gametophyte: The dominant phase in which gametes (sperm and eggs) are produced.
   * Sporophyte: Grows out of the gametophyte and produces spores.
Life Cycle Characteristics
* Sporophyte Structure:
   * Composed of three parts:
      * Foot: Anchors sporophyte to the gametophyte.
      * Seta (plural: setae): The stalk.
      * Capsule (Sporangium): Produces spores through meiosis.
   * Orientation varies:
      * Can grow upright or downward.
* Gametophyte Structure:
   * Produces structures called gametangia:
      * Archegonia: Produces and houses eggs.
      * Antheridia: Produces and houses sperm.
   * Requires water for fertilization as sperm must swim to the egg.
Dominance in Life Cycle
* Textbook defines gametophyte as dominant because the sporophyte grows out of it.
* Instructor suggests dominance should be based on size and longevity, not solely on the physical growth of the sporophyte from the gametophyte.
Reproductive Process
* Reproduction:
   * The haploid gametophyte generates gametes:
      * Sperm from antheridia.
      * Eggs from archegonia.
   * Fertilization occurs when sperm swims to the archegonium and reaches the egg.
   * A zygote is formed and grows into the sporophyte.
* Sporophyte Development:
   * Begins with fertilization.
   * Zygote develops into an embryo within the archegonium.
   * Mature sporophyte produces spores via meiosis in the capsule.
Characteristics of Bryophytes
* Do not have true roots, stems, or leaves but have structures that resemble them:
   * Rhizoids: Anchor the plant.
   * Stem-like and leaf-like structures lack vascular tissue.
* Different species may have separate male and female gametophytes or both on the same structure.
Key Points
* Water is essential for reproduction due to the swimming sperm.
* Both gametophyte and sporophyte phases are crucial to the life cycle, with the gametophyte often seen as dominant in traditional interpretations.
* Understanding of the life cycle and structure helps in grasping the evolutionary adaptations of nonvascular plants.
Vascular Plants Lecture Notes
Introduction to Vascular Tissue
* Vascular tissue in land plants includes xylem and phloem.
* Allows for the development of true roots and larger growth.
* Vascular tissue supports by providing structural mechanisms such as lignin.
Origin of Vascular Plants
* Appeared approximately 425 million years ago.
* Important groups: Lycophytes and Terophytes (seedless vascular plants).
* Future studies will include seed plants: gymnosperms and angiosperms.
Xylem and Phloem Functions
* Xylem:
   * Conducts water and minerals upwards in the plant.
   * Unidirectional flow.
* Phloem:
   * Distributes organic products, such as sugars and hormones.
   * Multi-directional flow depending on production and storage needs.
True Roots and Leaves
* Vascular tissue allows for true roots, enhancing anchoring and absorption.
* True leaves increase surface area for light capture, aiding growth and reproduction.
Seedless Vascular Plants
* Include lycophytes and terophytes.
* Represent a "grade" (paraphyletic group based on morphological traits).
* Produce spores instead of seeds for dispersal.
Life Cycle of Seedless Vascular Plants
* Sporophyte:
   * Dominant life cycle form, larger and longer-lived than gametophyte.
   * Produces spores by meiosis in structures called sporangia.
   * Sporangia are grouped in structures called sorus.
* Gametophyte:
   * Smaller, short-lived, needs water for reproduction.
   * Produces sperm in antheridium, eggs in archegonium.
Ferns as an Example
* Sporophytes can grow to a significant size compared to gametophytes.
* Fertilization requires water, albeit minimal, for sperm mobility.
* Lifecycle involves transition from haploid spores to diploid sporophyte through fertilization.
These notes summarize the key concepts of vascular plants, focusing on their structure, evolution, and reproductive cycles.
Lecture Notes: Seedless Vascular Plants - Lycophytes and Monilophytes
Overview
* Seedless vascular plants are classified into two main groups:
   * Lycophytes
   * Monilophytes (also known as Pterophytes)
Common Characteristics
* Sporophyte: Larger and more long-lasting part of the alternation of generations life cycle.
* Gametophyte: Very small, grows at or below soil surface, short-lived.
Lycophytes
* Examples: Spike mosses, quillworts, club mosses.
* Historically could grow very large, forming early forests due to lack of competition.
* Growth limited by need for moist environments.
* Abundant 300-350 million years ago.
* Decline due to climate shift (continental drift leading to drier habitats) and competition from seed plants.
Monilophytes
* Examples: Ferns, horsetails, whisk ferns.
* Modern ferns typically around 3 feet, but can reach up to 20 feet in protected areas.
* Ancestors of monilophytes were much larger due to lack of competition, reaching sizes of 30 feet or more.
* Ferns:
   * Over 12,000 species still viable.
   * Success attributed to well-developed leaves.
   * Range expanded due to niches created by seed plants.
Ecological Impact
* Lycophytes and monilophytes formed the first terrestrial forests.
* Die-off contributed to the formation of coal deposits.
* Fossils commonly found in areas of mining activity.
Evolutionary Pressures
* Climate changes (shift to drier environments) created pressure on seedless vascular plants.
* Competition from seed plants led to further decline.
Conclusion
* The decline of these seedless vascular plants paved the way for the rise of seed plants.
* The next chapter will focus on seed plants.
Seed Plants and Their Evolutionary Significance
Introduction
* Last chapter covered plant kingdom up to seed plants.
* Seed plants originated approximately 315-320 million years ago.
* Significant evolutionary step as plants moved further away from water dependency.
Categories of Seed Plants
* Gymnosperms
   * Older group, fewer in number today.
* Angiosperms
   * Evolved after gymnosperms, more dominant today.
   * Outcompeted gymnosperms due to evolutionary advantages.
Key Characteristics of Seed Plants
* Do not require water for reproduction.
* Sperm and eggs still present but part of reduced gametophytes.
* Female Gametophyte: Ovule
* Male Gametophyte: Pollen grain
* Evolutionary advantage through seeds over spores:
   * Seeds provide stored food and a multicellular embryo.
Spores vs. Seeds
* Spores: Single cell, no nutrients, limited dispersal.
* Seeds: Multicellular, nutrient-rich, better dispersal mechanism.
* Heterosporous nature (different male and female spores).
   * Megaspore: Female
   * Microspore: Male
Mechanisms of Seed Plant Reproduction
* Pollen dispersal via wind or animals.
* Pollen can travel vast distances, unlike sperm.
* Gametophytes become dependent on sporophyte.
   * Develop within the walls of the spore.
   * Retained within the parent sporophyte.
Sporophyte and Gametophyte Relationship
* Increased dominance of sporophyte.
* Shift from independent to dependent gametophyte.
* Integration of gametophyte into sporophyte structure.
Reproductive Structures
* Ovule: Female gametophyte structure
   * Contains integument layer
   * Develops from megasporangium via meiosis.
* Pollen Grain: Male gametophyte
   * Develops from microspore.
   * Eliminates need for water in fertilization.
Fertilization Process
* Pollen tube growth allows sperm to reach egg.
* Fertilization merges sperm and egg nuclei, forming a diploid zygote.
* Zygote grows into an embryo within the seed.
* Seed development:
   * Integument becomes the seed coat.
   * Stored food nourishes embryo.
Conclusion
* Seeds provide evolutionary advantage by enhancing survival and dispersal.
* Detailed examination of seed structure to follow in subsequent discussions.
Lecture Notes: Male and Female Gametophyte Development
Overview
* The development of male and female gametophytes occur along different lines.
* Megaspore and microspore give rise to female and male gametophytes, respectively.
* Focus on gymnosperm and angiosperm gametophyte development.
Female Gametophyte Development
Megaspore Development
* Mega Sporangium: Spore-producing structure that produces the megaspore.
* Transition from diploid to haploid through meiosis.
* Meiosis: Results in four haploid megaspores.
   * Three megaspores break down.
   * Remaining megaspore continues development.
Gymnosperm Process
* Cell division results in a cell within a cell:
   * Outer cell: Embryosac (female gametophyte/ovule).
   * Inner cell: Egg cell (female gamete).
Angiosperm Process
* Single megaspore undergoes three rounds of mitosis producing eight nuclei:
   * Nuclei distribution: Three at each end, two in the center.
   * Cytokinesis results in seven cells instead of eight:
      * Three cells at each end, one becomes the egg.
      * Middle cell known as central or endosperm cell (diploid with polar nuclei).
Male Gametophyte Development
Microspores Development
* Microsporangium: Spore-producing structure that produces microspores.
* Meiosis results in four haploid cells, all continue development.
Comparative Philosophy
* Female side: Fewer, higher quality gametes due to nutrient concentration.
* Male side: Greater quantity, less focus on quality.
Gymnosperm Process
* Microspores undergo cell division:
   * Outer cell: Pollen tube cell.
   * Inner cell: Male gamete (sperm cell).
   * Pollen grain is effectively two cells within one (cell within a cell).
Angiosperm Process
* Cell division results in:
   * Outer cell: Pollen tube cell.
   * Inner cell: Generative cell (undergoes further division).
   * Second division yields two sperm cells inside the pollen tube cell.
Key Concepts
* Female gametophyte: Ovule or embryosac in gymnosperm and angiosperm.
* Male gametophyte: Pollen grain in both gymnosperm and angiosperm.
* Differences in gamete production strategies between male and female gametophytes reflect broader biological trends.
Lecture Notes: Seed Plant Divergence - Gymnosperms vs Angiosperms
Introduction to Seed Plant Groups
* Seeded Plants Split: Two main groups: Gymnosperms and Angiosperms.
* Gymnosperms:
   * Non-flowering plants.
   * Evolved earlier, once dominant in ecosystems.
   * Known as 'naked seeds' due to lack of an outer covering.
* Angiosperms:
   * Flowering plants.
   * Became more dominant over time, outcompeting gymnosperms.
   * Seeds have an additional covering known as fruit.
Evolutionary Competition
* Initial Dominance:
   * Gymnosperms initially outcompeted seedless vascular and non-vascular plants.
   * Dominated terrestrial environments until the rise of angiosperms.
* Angiosperms' Rise:
   * Quickly displaced gymnosperms in various ecosystems.
   * Superior evolutionary adaptations.
Differences in Seed Structure
* Similarities:
   * Both have embryos.
   * Both contain stored food to nourish the embryo.
   * Both feature a protective seed coat.
* Gymnosperm Seeds:
   * 'Naked seeds' without additional covering.
* Angiosperm Seeds:
   * Fruit acts as an additional covering.
Seed Coat Functionality
* Protection:
   * Protects embryo and stored food from elements and predators.
* Timing of Germination:
   * Ensures germination occurs under favorable conditions.
   * Example: Fire pines require fire to trigger germination, reducing competition.
Stored Food Differences
* Gymnosperms:
   * Stored food is haploid, derived directly from the female gametophyte.
* Angiosperms:
   * Stored food is triploid (3N), resulting from a combination of male and female gametophyte material.
Corrections and Clarifications
* Notes Correction:
   * Angiosperm stored food arises from both male and female gametophytes, not just female.
________________

These notes summarize the key distinctions and evolutionary aspects of gymnosperms and angiosperms, focusing on seed structure and ecological competition.
Characteristics of Gymnosperms
Major Groupings
* Conifers
   * Includes evergreens, pines, firs, cypress, cedars
   * Endemic to regions like Louisiana
* Cycads
   * Now mostly found in botanical gardens
* Ginkgos
   * Ginkgo biloba is the sole survivor of its group
   * Common in urban landscaping, highly adaptable to city environments
* Nidophytes
   * Thrive in arid environments, have tough leaves to withstand harsh conditions
Evolutionary Context
* Gymnosperms were more dominant in the past
* Many species have gone extinct due to competition with angiosperms
* Gymnosperms produce cones; bristlecone pines and redwoods are notable for longevity and size
Longevity and Size
* Sporophytes: Long-lived (1000-2000 years), larger than gametophytes
* Gametophytes: Short-lived, often only a few days or weeks
Gymnosperm Groups
* Conifers: Largest group, successful historically and still widespread
* Cycads: Reduced to botanical specimens
* Ginkgos: Found in urban areas
* Nidophytes: Adapted to survive in harsh arid conditions
Life Cycle of Gymnosperms
* Key Characteristics: Pollen and dominant sporophytes
* Heterosporous: Produces microspores (male) and megaspores (female)
* Sporophyte undergoes meiosis to create spores
   * Microsporangia: Produces male gametophyte (pollen)
   * Megasporangia: Produces female gametophyte (ovule)
* Fertilization Process:
   * Pollen tube allows sperm to reach egg
   * Fusion forms a diploid zygote
* Seed Development
   * Zygote grows into an embryo within the seed
   * Seed coat forms from parental sporophyte tissues
* Reproductive Success
   * Long-lived sporophytes lead to enhanced reproductive efforts
   * Allows gymnosperms to outcompete many seedless vascular plants
Conclusion
* Gymnosperms have distinct characteristics and life cycles making them significant in the plant kingdom
* Next topic will be angiosperms
Lecture Notes: Characteristics of Angiosperms
Introduction
* Angiosperms are the dominant group of land plants.
* Over 95% of visible plants are angiosperms.
* Key features that provide a competitive edge:
   1. Flowers
   2. Seeds enclosed in a fruit
   3. Broad leaves
   4. Advanced vascular tissue
Competitive Advantages of Angiosperms
Reproductive Advantages
1. Flowers
   * Flowers improve reproductive success.
   * Gymnosperms rely on wind pollination (low probability).
   * Angiosperms attract pollinators to transfer pollen efficiently.
   * Result: Increased likelihood of fertilization and reproduction.
2. Seeds in a Fruit
   * Fruits aid in seed dispersal.
   * Seeds move further from the parent plant, reducing competition and increasing survival chances.
   * Dispersal allows colonization of new areas, ensuring species survival.
Physiological Advantages
3. Broad Leaves
   * Increase light capture, enhancing photosynthesis.
   * Result: More energy and materials for growth and reproduction.
4. Advanced Vascular Tissue
   * Efficient transport of materials within the plant.
   * Provides physiological advantages over gymnosperms.
Flower Structure and Function
* Flowers are specialized shoot structures with modified leaves.
* Essential for sexual reproduction.
* Complete flowers have four main parts:
   1. Sepals - Protects the flower bud.
   2. Petals - Attract pollinators and protect reproductive structures.
   3. Stamens - Male reproductive part.
   4. Carpels - Female reproductive part.
Detailed Flower Structure
* Petals
   * Serve as a corolla to contain reproductive structures.
   * Act as signals to pollinators.
   * Offer food (pollen and nectar) to attract pollinators.
* Sepals
   * Protect the flower before blooming.
   * Green, leaf-like structures around the bud.
Reproductive Structures
* Stamens (Male)
   * Comprised of filament (stalk) and anther (pollen production).
   * Pollen grains (male gametophytes) develop in the anther.
* Carpels (Female)
   * Located centrally in the flower.
   * Comprised of stigma (pollen reception), style (pollen tube growth), and ovary (egg development).
   * Ovules within the ovary become seeds after fertilization.
   * The ovary's outer layer becomes the fruit, aiding seed dispersal.
Conclusion
* Angiosperms' evolution of flowers and fruits significantly enhanced their reproductive and survival strategies.
* Physiological adaptations further strengthened their dominance over other plant species.
* Future discussions will explore fruit characteristics and seed dispersal mechanisms.
Seed Dispersal in Angiosperms
Overview
* Purpose of Fruit: The primary role of fruit in angiosperms is seed dispersal.
* Origin of Fruit: Fruit develops from the base of the carpal, specifically the ovary.
   * Example: Tomato — the wall of the tomato is the enlarged ovary.
   * Non-edible example: Milkweed pod.
Types of Seed Dispersal Mechanisms
1. Wind Dispersal
   * Seeds adapted to be carried by the wind.
   * Example: Milkweed seeds with parachute-like structures.
   * Other examples: Seeds with wing-like structures acting as helicopters.
2. Mechanical Dispersal
   * Seeds attach to passing animals via hooks.
   * Example: Seeds sticking to clothes or animal fur.
   * Seeds are carried and eventually fall off or are removed away from the parent plant.
3. Water Dispersal
   * Seeds encased in a flotation device.
   * Example: Coconuts floating across oceans.
   * Seeds can travel long distances to new locations downstream or across oceans.
4. Animal Dispersal (Edible Fruit)
   * Fruits are consumed by animals, seeds are discarded.
   * Examples:
      * Humans eating apples and discarding cores elsewhere.
      * Seeds requiring digestion by animals to break down seed coat and assist in germination.
   * Benefits:
      * Increased dispersal distance.
      * Seeds are deposited with natural fertilizer from animal waste.
Evolutionary Advantage
* Fruit provides a significant evolutionary advantage by enabling plant species to disperse broadly within ecosystems.
Pollination and Fertilization in Angiosperms
Overview
* Discusses the process of pollination and fertilization in angiosperms.
* Sequence of events leading to double fertilization.
Pollination
* Definition: Transfer of pollen from an anther to a stigma.
* Types:
   * Self-Pollination: Within a single flower, allowed in some species.
   * Cross-Pollination: Pollen must move from one plant to another, enforced by some species.
* Role of Style:
   * Acts as a quality control.
   * Prevents self-fertilization by stopping pollen tube growth if pollen is from the same plant.
Pollen Tube Formation
* Pollen grain lands on stigma.
* Tube cell elongates to form pollen tube.
* Function: Conduit for two sperm cells from the generative cell to the ovary.
Double Fertilization
* Process:
   * Two sperm cells travel down pollen tube to the ovary.
   * Fertilization occurs at the carpel's base.
* Involvement of Female Gametophyte:
   * Consists of three cells at each end and a central cell.
   * Central cell contains two haploid nuclei.
Fertilization Details
* Diploid Zygote Formation:
   * Haploid egg fuses with haploid sperm.
   * Results in diploid zygote.
* Triploid Endosperm Formation:
   * Second sperm fuses with central cell's nuclei.
   * Central cell becomes triploid, serving as stored food.
   * Provides nourishment for the developing embryo.
Importance of Two Sperm Cells
* Purpose:
   * One sperm fertilizes the egg (forming the diploid zygote).
   * Other sperm fertilizes the central cell (forming triploid endosperm).
Conclusion
* Double fertilization results in both a diploid zygote and a triploid endosperm.
* Next discussion to address angiosperm phylogeny.
Angiosperm Lineages Overview
* Angiosperms dominate plant species, over 95% of plants seen.
* Dicots/Eudicots make up over 95% of visible angiosperm species.
* Four Major Angiosperm Lineages:
   * Basal Angiosperms: Includes water lilies and possibly two separate lineages.
   * Magnoliids: Related to magnolia trees.
   * Monocots: Includes grasses, grains, orchids, and palms.
   * Eudicots/Dicots: The bulk of visible plant species.
Evolutionary Background
* Gymnosperms appear in the fossil record around 305 million years ago.
* Angiosperms appear around 140 million years ago.
   * They became the dominant seed plants despite the gymnosperms' head start.
   * Coincided with the evolution of animal involvement in pollination.
Key Differences Between Monocots and Dicots
Flower Structure
* Monocots: Floral structures in multiples of three.
* Dicots: Floral structures in multiples of four, five, or arranged in a ring.
Leaf Structure
* Monocots:
   * Long, narrow leaves (e.g., grass).
   * Parallel veins.
* Dicots:
   * Broader leaves.
   * Branching or net-like vein patterns.
Vascular Tissue
* Monocots: Scattered vascular bundles in the stem.
* Dicots: Vascular bundles arranged in a ring.
Root System
* Monocots: Fibrous roots, shallow, good for frequent shallow watering.
* Dicots: Tap root system, deeper roots, suitable for infrequent deep watering.
Pollen Structure
* Monocots: Pollen grains with one opening.
* Dicots: Pollen grains with three openings.
Seed Leaves (Cotyledons)
* Monocots: One cotyledon.
* Dicots: Two cotyledons.
   * Useful for distinguishing seedlings and identifying weeds during early growth stages.
Implications for Plant Care
* Monocots: Require frequent, shallow watering.
* Dicots: Adapted to deeper water and less frequent soaking.
* Understanding these differences is crucial for successful cultivation and management of plants.

Transcript for:Prokaryotic Organisms: Characteristics and Classification

Transcript for:
Prokaryotic Organisms: Characteristics and Classification