MD

8/27 Lecture BIO

Course Logistics and Participation

  • Instructor notes on course participation for financial aid and advisor checks; participation is logged via Canvas activity (login time counts as participation).
  • Last night, the instructor approved all students who had logged into the Canvas course page (even if only for a few seconds or hours). If you missed logging in, you may still be approved after periodic checks over the next 1–2 weeks.
  • There are multiple sections; if emailing, include the section number (e.g., section 1 / 001) or the meeting time to avoid confusion.
  • Correction on lab vs. lecture: the instructor previously stated you could skip concurrent lab, which was incorrect. Now, lab and lecture are separate courses with separate grades. A key note: if you take both concurrently, an edge case exists where passing the lecture but failing the lab may not require re-signing up for both in some situations, but this is unlikely for most students.
  • If you are new to the class, you should be enrolled in lab; the lecture grade does not depend on lab and vice versa.
  • Slides are posted as PowerPoints (not PDFs) because they include animations and an "Notes" section on slides where tiny tidbits or links may be added. Links to YouTube videos or websites will appear on the slide itself or in the notes section.
  • Office hours and supplemental instructor (SI/LA) information:
    • Supplemental Instructor (SI) for this lecture attends the 4:00 PM session; official office hours yet to be determined (post next week, due to Memorial Day holiday logistics).
    • Learning Assistants (LAs) can be re-designated to "peer mentors" to enable posting announcements on Canvas; this re designation does not change job responsibilities, only posting permissions.
  • EO 360 recordings (audio + slides) were processed and posted online within a couple hours after class; watch recordings for clarification if you miss class.
  • First slide each lecture lists contact details and office hours: email, office hours (2:30–3:30 PM, Monday and Wednesday), and SIS office hours (to be determined).
  • If you have trouble hearing or access issues (captioning, volume), inform the instructor so adjustments can be made.
  • Important logistical notes:
    • No class next Monday due to a holiday; plan accordingly.
    • When in doubt, check Canvas for updates and posted announcements.

Taxonomy and Classification: Review and Applications

  • Taxonomic hierarchy mnemonic (as commonly memorized): Domain, Kingdom, Phylum (Division for plants), Class, Order, Family, Genus, Species.
  • Example: Humans
    • Domain: Eukarya
    • Kingdom: Animalia
    • Phylum: Chordata
    • Class: Mammalia
    • Order: Primates
    • Family: Hominidae
    • Genus: Homo
    • Species: sapiens
  • Example: Red fox
    • Domain: Eukarya
    • Kingdom: Animalia
    • Phylum: Chordata
    • Class: Mammalia
    • Order: Carnivora
    • Family: Canidae
    • Genus: Vulpes
    • Species: vulpes
  • Plants diverge from animals in classification terminology: plants are in the Kingdom Plantae; in plants, the term used instead of “phylum” is “divisions” (not a strict phyla usage as with animals).
  • The Tree of Life concept: as you descend the classification triangle, organisms become more closely related genetically, ecologically, and morphologically. Those in the same genus are more closely related than those only sharing a higher taxonomic rank (e.g., order or family).
  • Domains overview: three domains of life—Eukaryotes, Archaea, and Bacteria. For Bio 1500 (the first half of the course), the focus is on Eukaryotes (multicellular organisms) and related groups; Archaea and Bacteria cover single-celled processes and are less central to this course.
  • Plants in this course: primary focus on plants; fungi will also be discussed; expectation is to be comfortable with the plant half of the taxonomy alongside animal comparisons.

Preliminary Discussion Questions and Student Engagement

  • Group work prompts are used to simulate exam-style questions and stimulate interest in plants. Topics include: why study plants and their importance, and what makes plants distinct from animals.
  • Example prompts discussed include: the role of photosynthesis, oxygen production, and plant-derived products.

Why Plants Matter: Functional Roles and Significance

  • Early student responses mentioned the following roles (collected from discussion):
    • Medicine and pharmacology
    • Food and nutrition
    • Oxygen production and air quality improvement
    • Pollution mitigation and environmental cleanup
    • Energy sources and fuel (biofuels)
    • Structural materials (furniture, building materials)
    • Clothing (cotton, hemp)
    • Ecosystem support and biodiversity
  • The instructor emphasizes photosynthesis as a central, transformative process and uses it to illustrate the significance of plants in life on Earth.

Photosynthesis: Process, Energy, and Ecological Significance

  • Core inputs: carbon dioxide, water, sunlight (photons)
  • Core outputs: complex carbohydrates (sugars, starches) and oxygen (O₂) as a byproduct; water is also released as a byproduct in some steps.
  • Energy flow highlight: Plants capture light energy from the Sun, located about 93 million miles away, and convert it into chemical energy that supports all life on Earth.
  • The overall simplified photosynthesis equation (conceptual):
    6 ext{CO}2 + 6 ext{H}2 ext{O} + ext{light energy}
    ightarrow C6H{12}O6 + 6 ext{O}2
  • The significance of stomata and leaf tissues in gas exchange: CO₂ intake and O₂ release occur via stomata and other plant tissues.
  • Priestley’s classic experiment (historical context): plants uptake CO₂ and release O₂, enabling sustained combustion and animal respiration, demonstrating the essential role of plants in air composition.
  • Practical implications: photosynthesis influences climate (via CO₂ uptake and O₂ release) and is foundational for crop production and food security.
  • Extended topics mentioned for future study: energy balance, global warming implications, and plant responses to light, water, and nutrients.

Major Plant-Derived Crops and Global Significance

  • Six major crops that account for a large share of plant-derived energy intake: ext{rice}, ext{wheat}, ext{maize (corn)}, ext{soybean}, ext{potatoes}, ext{sugar cane}
  • These crops together account for about 75% of the world’s plant-derived dietary energy intake.
  • Plants as a source of complex carbohydrates (sugars, starches) feed both humans and animals; plant-derived carbohydrates also serve as feedstock for amino acids and proteins.

Proteins, Amino Acids, and Plant-Based Nutrition

  • Plants synthesize all amino acids; animals typically cannot synthesize all essential amino acids and thus require diets that provide them.
  • Seeds are particularly high in protein; plant tissues collectively contain substantial protein, supporting nutrition and growth.
  • Essential amino acids (in humans): a set of amino acids that must be obtained from the diet; plants provide these through diverse tissues and seeds.
  • The concept of non-essential amino acids (in diet planning) and how plants contribute to complete protein intake when combined with other foods.
  • The relationship between carbohydrates derived from photosynthesis and the amino acid/protein needs of animals.

Plant-Derived Spices, Flavors, and Culinary Uses

  • Vanilla orchid yields vanilla extract; ginger, cumin, mustard, turmeric, and cinnamon are used in various culinary applications.
  • Cinnamon is derived from the bark of trees; other spices can come from roots (ginger, turmeric), seeds, or flowers.
  • Parsley, mint, basil, rosemary, and chives are common culinary herbs used to flavor foods.
  • Pepper and capsaicin: spicy peppers contain capsaicin, which triggers heat receptors and produces a burning sensation; Scoville scale is used to measure heat units; examples include the Carolina Reaper (~1.6–2.2 million SHU) and possibly Dragon’s Breath (~2.5 million SHU per some reports).
  • Effects of capsaicin on digestion and physiology: triggers heat response (sweating, tearing, nasal discharge); may increase intestinal motility; can inhibit gastric acid production and stimulate protective mucus; excessive consumption can cause diarrhea and abdominal pain; lethal dose estimates suggest around 6 g of capsaicin for a 60 kg person, though peppers in practice would require high consumption.
  • Edible uses include common beverages and distillates derived from plants (beer from barley and hops; whiskey from grains; tequila and mezcal from agave).
  • Distinctions between tequila and mezcal (legal and production differences):
    • Tequila: produced in 5 Mexican regions; main region is Jalisco; can only be made from blue agave.
    • Mezcal: produced in 8 regions; main region cited as Guajana in lecture notes (note: this is the instructor’s phrasing from the transcript and may reflect a shorthand or a non-standard naming in this context); can be produced from 30 varieties of agave (not just blue agave).
    • Processing differences: mezcal uses earth-pit roasting of agave with volcanic rock, imparting a smoky flavor; tequila uses large stainless steel ovens (autoclaves).
    • Worms in mezcal: some mezcals include a butterfly caterpillar in the bottle; note that the presence of a worm is not a quality indicator per se; legal/regulatory distinctions are nuanced.
  • Botanically, agave and mezcal/tequila rely on different species and processing methods to produce traditional spirits.

Plants as Medicines and Pharmacognosy

  • The vast majority of medicines have plant origins; estimates suggest that more than 50% of known medicines come from plant sources, potentially higher (80–90% cited in some discussions).
  • Classic plant-derived medicines and examples:
    • Willow bark: source of aspirin (aspirin’s chemist’s origin); basic analgesic/anti-inflammatory use historically.
    • Foxglove: digitalis, used historically for heart-related conditions.
    • Pacific yew tree: Taxol (paclitaxel), used to treat breast cancer (historical context).
    • Coca plant: source of cocaine (historical context in medicine and stimulant use).
    • Coffee and chocolate: stimulants and widely used plant-derived compounds.
    • Datura: highly psychoactive and dangerous; used historically as a cautionary note about plant toxicity.
  • The session includes discussion of both beneficial drugs and potential hazards of plant compounds (ethnobotanical relevance and safety concerns).
  • Hemp vs marijuana (plant varieties):
    • Hemp is typically non-psychoactive, used for textiles, biofuels, and wellness products; grown taller as a fiber crop.
    • Marijuana is psychoactive and falls under different regulatory regimes; the same species (Cannabis sativa) can be bred into different varieties with different properties.
  • The Medicine Man (1994) film is referenced to illustrate plant-based drug discovery and rainforest conservation; a key scene discusses discovery and the challenge of reproducing a pharmacological discovery in another setting.
  • The session briefly notes that plant-based compounds have historically driven major pharmaceutical discoveries and modern drug development.

Plants, Ecology, and the Food Web

  • Food webs and trophic levels: plants form the base level (primary producers) of energy flow in ecosystems.
  • Energy transfer efficiency is typically described by the Rule of 10:
    • Each trophic transfer loses about 90% of energy; only about 10% is passed to the next level.
    • If the base producers start with energy E0, the energy at level n is: En = E0 imes (0.1)^n, where n is the number of steps away from the producers.
    • Example energy cascade: from 100 calories in plants to about 10 calories in herbivores, 1 calorie in small carnivores, and 0.1 calories in top predators.
  • Implications for sustainability and agriculture:
    • With a growing human population, the system relies more on plant production and less on animal-based food sources to meet energy needs.
    • If meat consumption per person rises (as in developing regions approximating US per-capita meat consumption), water and land resources used for feed crops increase; some regions (e.g., parts of China) face water stress that can be exacerbated by high meat demand.
    • The discussion notes that future water supply pressures are real (e.g., potential shifts in freshwater sources to the Great Lakes), particularly for agricultural needs in western regions and the Great Plains.
  • Plant productivity as a building material and economic resource:
    • Lumber, paper, clothing (cotton, hemp), and other plant-derived materials are central to human economies and ecosystems.
    • Plants support ecological networks and are foundational to many ecosystems’ structures (habitat, shelter, food for other organisms).
  • The discussion highlights the concept of food webs as a tool to understand energy flow, sustainability, and the dependence of human systems on plant productivity.

Phytoremediation and Bio-based Plastics

  • Phytoremediation: plants can be used to screen for and remediate environmental contaminants.
    • Plants uptake water and dissolved contaminants, moving them from soil into roots and shoots; they can metabolize contaminants into less toxic forms and release byproducts to the atmosphere or environment.
  • Plant-based or bio-based plastics:
    • Plants can be engineered or utilized to produce plastics via naturally occurring polymers such as starch and cellulose.
    • Early plastics were plant-based (celluloid from cellulose); modern alternatives aim to reduce reliance on non-renewable resources.
    • Bio-based plastics often rely on weaker bonds (C–O, C–N) in plant polymers, allowing microbial degradation and compostability under appropriate conditions.
    • Starch and cellulose serve as major feedstocks for bioplastics; the first true plastic (celluloid) used cellulose derived from plants.
    • The life-cycle perspective contrasts bio-based plastics with conventional petroleum-based plastics, noting potential environmental benefits in production, use, and end-of-life.
  • The video discussion in the lecture highlights real-world applications such as turning potato starch into plastic materials and broader implications for sustainability and circular economy.

Human Use of Plants: Alcohol, Food, and Culture

  • Plant-derived beverages and distillation:
    • Beer (barley and hops), whiskey (grains), tequila/mezcal (agave).
    • Juniper berries used for gin flavoring; other flavorings from plant sources.
  • The role of plants in traditional and modern beverages emphasizes the deep interconnection between botany and culture/economy.
  • The instructor’s humorous asides and anecdotes illustrate the course's emphasis on making plant biology engaging and relevant to daily life.

Important Ethical, Practical, and Real-World Implications

  • Ethical considerations surrounding the use of forests for drug discovery and the importance of rainforest conservation (as discussed via Medicine Man and broader plant-based drug discovery).
  • Environmental implications of shifting agriculture toward plant-based diets to improve sustainability (reducing animal-based agricultural demands, conserving water and land).
  • The potential of phytoremediation and bio-plastics to address pollution and waste, while acknowledging the need for proper deployment, lifecycle assessment, and regulatory oversight.
  • The need to critically assess plant-based claims (e.g., the worm in mezcal as a marketing ploy) and rely on evidence-based information.

Summary of Key Concepts in Mathematical and Factual Form

  • Photosynthesis equation (conceptual):
    6 ext{CO}2 + 6 ext{H}2 ext{O} + ext{light energy}
    ightarrow C6H{12}O6 + 6 ext{O}2.
  • Energy transfer across trophic levels (Rule of 10):
    • If base energy is E0, then energy at level n is En = E_0 imes (0.1)^n.
    • Typical example: from plants (E0) to herbivores (0.1 E0) to primary carnivores (0.01 E0) to top predators (0.001 E0), etc.
  • Lethal-dose note for capsaicin: approximately
    ext{LD}_{50}
    ightarrow 100 ext{ mg/kg (for a 60 kg person)}
    ightarrow 6 ext{ g of capsaicin}.
  • Scoville heat units (SHU) for capsaicin concentration; Carolina Reaper around 1.6 imes 10^6 ext{ SHU} to 2.2 imes 10^6 ext{ SHU}; Dragon's Breath possibly up to 2.5 imes 10^6 ext{ SHU}.
  • Six major global crops contributing to plant-derived energy intake: ext{rice, wheat, maize (corn), soybean, potatoes, sugar cane}; collectively ~75% of plant-derived energy.

Notes on Classroom Practice and Next Steps

  • Watch EO 360 recordings if you miss class or need clarification.
  • Check notes on slides for added resources (links to YouTube videos and relevant websites).
  • Prepare questions for next class and engage in group discussions to reinforce understanding of plant biology, ecology, and applications.
  • Be mindful of classroom etiquette (minimize disruption during videos and discussions; keep conversations focused when videos are playing).
  • Stay aware of schedule changes due to holidays and follow Canvas announcements for updates on office hours and section-specific information.