Comprehensive Lecture Notes on Evolution, Antibiotic Resistance, and Macromolecule Testing

Lab Final Requirements and Deadlines

  • Submission Details: Two students have already submitted their lab final videos. These can be graded early, so they do not have to wait until the official due date.

  • Deadlines: Lab final videos cannot be turned in late. The due date is the same day as the lecture final exam.

  • Quantity: Students are required to upload a total of 44 videos for their lab final grade.

  • Strategy: It is recommended to complete these early to avoid conflicts with other final exams and to secure a grade of 100100.

Evidence for Evolution: Paleontology and Specialized Case Studies

  • Nature of Evolutionary Change: Evolution is characterized by a slow, gradual pace.

  • Fossils as Evidence: Fossils provide tangible, physical evidence that is difficult to deny because they are objects that can be held and studied.

  • Case Study: The Baleen Whale:     * Transition from Land to Water: At least one species, the Baleen whale, originated as a land animal. This transition did not occur quickly; it took approximately 40×106 years40 \times 10^6 \text{ years}.     * Ancestor: Indohyas: The distant ancestor is a rat-sized terrestrial creature called Indohyas. It was non-aquatic and would drown if held underwater. It lived near the ocean and hunted on land.     * Ecological Pressure: A shortage of land-based prey forced the organism to adapt. Natural selection offered a choice: adapt or die. The organism began venturing into shallow water to eat crabs or small fish.     * Caloric Intake and Reproductive Success: Survival is not just about avoiding starvation. In females, extreme malnourishment or obesity can lead to amenorrhea (the cessation of the menstrual cycle). If caloric intake is insufficient, nature "cuts off" the ability to ovulate and reproduce. By bringing back food from the water, the ancestor ensured the female could ovulate and produce offspring, facilitating the "survival of the fittest."

Adaptations and Morphology

  • Webbing:     * Human embryos possess webbing between fingers and toes out to the fingertips, a remnant that disappears before birth as it is not needed.     * Increased webbing provides a swimming advantage. In the Indohyas lineage, those with more webbing were better adapted for aquatic life.

  • Morphological Changes in Water:     * Gigantism: Organisms in water can grow significantly larger because buoyancy counteracts the effects of gravity.     * Limb Modification: Appendages like legs eventually transitioned into flippers. In whales, the hind legs eventually disappeared.

  • Vestigial Structures:     * Definition: Structures that have lost their original functionality through evolution and are slowly being removed.     * Whale Thighs: When a Baleen whale is dissected, two small bones the size of pinkies are found in the pelvic region. These are vestigial thigh bones, remnants of the legs possessed by their terrestrial ancestors.     * Human Vestigial Traits:         * Wisdom Teeth: The third set of molars is no longer necessary for the modern diet.         * Body Hair: Humans no longer rely on body hair (e.g., a "sweater" of chest hair) for warmth due to the use of clothing. Hair is now primarily retained around "portals of entry" (eyebrows, nose, ears, armpits, and genitals).

  • Camouflage: The "stick bug" (named simply by entomologists because it looks like a stick) is an example of an adaptive trait in morphology and coloration. This adaptation is highly effective in a forest but ineffective in an urban environment like New York City.

Common Descent and Biological Relatedness

  • Homologous Structures: Humans, whales, and bats share the exact same number of bones from the shoulder to the fingertips/wingtips.     * Human Hand: Adapted for manipulation.     * Whale Fin: Adapted for swimming.     * Bat Wing: Adapted for flight. The bones in bats are narrow and hollow to remain lightweight.

  • Ancestry: This similarity indicates a common ancestor that existed approximately 70×106 to 80×106 years ago70 \times 10^6 \text{ to } 80 \times 10^6 \text{ years ago}, before the era of dinosaurs ended, which then branched into avian, aquatic, and terrestrial lineages.

  • Common Descent with Modification: While the number of bones is the same, their shape and ability to perform tasks have changed to suit the organism's environment.

  • DNA Sequence Homology: The more closely related two species are, the more similar their genetic code.     * Chimpanzees: Humans' closest evolutionary cousin.     * Mice: Frequently used for medical testing due to genetic similarity and easier ethics, though more distant than chimpanzees.     * Chickens: A much more distant relative.

Biogeography and Earth History

  • Pangaea: Approximately 200×106 years ago200 \times 10^6 \text{ years ago}, the continents were joined in a supercontinent called Pangaea.

  • Evidence from Plate Tectonics:     * Dinosaur fossils of the same species are found in the Southwest United States and Northeast China, as well as the Eastern coast of South America and West Africa.     * The shapes of South America and Africa fit together like puzzle pieces.     * Continental plates continue to move tectonically today.

Embryology and Zoonotic Disease

  • Embryological Similarity: At roughly 14 days14 \text{ days}, embryos of fish, reptiles, birds, and humans look remarkably similar. Humans look most similar to bird embryos at this stage.

  • Zoonosis: Diseases can jump between related species.     * 1918 Influenza: This was originally a bird virus that became zoonotic and jumped to humans. Prior to 19181918, seasonal influenza did not exist in humans; they primarily dealt with coronaviruses or metapneumoviruses.     * Zoo and Aquarium Closures: During the pandemic, zoos closed because primates (orangutans) and birds have lungs and could catch respiratory viruses from humans. Aquariums also host lung-bearing animals like seals, dolphins, and pilot whales that are susceptible.

Mechanisms of Evolution: Antibiotic Resistance

  • Bacterial Evolution: Since bacteria have short lifespans—a generation is approximately 20 to 30 minutes20 \text{ to } 30 \text{ minutes}—evolution can be witnessed in real-time.

  • The Problem of Resistance: Antibiotic resistance is a significant threat found in clinics, hospitals, and nursing homes.

  • Mechanism of Selection: Antibiotics act like a "strainer" or colander. They kill the majority of bacteria (reducing a population from, for example, 100,000,000 to 1,000,000100,000,000 \text{ to } 1,000,000), but the most dangerous, resistant individuals survive. The immune system (white blood cells) is then responsible for cleaning up the survivors.

  • Major Resistant Pathogens:     * MRSA (Methicillin-resistant Staphylococcus aureus): A common skin bacterium that has become pathogenic and resistant. It causes skin breakdown and tissue loss. It is found on the floors of gyms, yoga studios, and pilates studios.     * VRSA (Vancomycin-resistant Staphylococcus aureus): Vancomycin is the "drug of last resort," administered only via IV in hospitals. It is highly toxic and can kill healthy cells. VRSA infections are often fatal because no more powerful drugs exist.

  • Medical Advice: One should only take antibiotics when absolutely necessary to prevent the further evolution of resistant strains.

Lab Demonstration: Identifying Macromolecules in Food

  • Food Labeling History:     * Currently, nutrition labels list calories, protein, sugar, and fat per serving.     * 40 years ago40 \text{ years ago}, nothing was labeled.     * By the year 20302030, a New York City law will require all food service establishments (pizzerias, delis, bodegas) to analyze and label their food's nutritional content.

  • Colorimetric Reagents: Reagents that change color to indicate the presence of a substance.

  • Biuret Reagent (Proteins):     * Initial Color: Blue.     * Positive Result: Changes to Violet/Purple.     * Experiment: Potato juice (Negative/Blue) vs. Egg whites/Albumin (Positive/Purple).

  • Lugol's Iodine (Polysaccharides/Complex Sugars):     * Initial Color: Yellowish-brown.     * Positive Result: Changes to Dark Blue/Black.     * Experiment: Egg whites (Negative), Apple juice (Negative), Potato juice (Positive/Black due to starch).

  • Sudan IV (Lipids/Fats):     * Mechanism: A fat-soluble dye. It does not mix with water (polar) but blends with lipids.     * Experiment:         * Water: Sudan IV floats as a red ribbon on top; it does not blend.         * Corn Oil: The golden oil turns reddish and stays blended because the dye is soluble in the lipid.     * Historical Note: Corn oil was originally an engine lubricant from WWII that was repurposed as food by adding golden dyes to make it look appealing.