Exploring Biomed Lecture Notes PDF

Module 1 - Exploring Diversity 3: Feeding All individuals require food - Maintains normal cellular function and replication - Required for reproduction Food is either consumed directly or synthesised by individual Autotrophs: Bacteria, Archaea, Protista, Plantae - Synthesises food the...

Module 1 - Exploring Diversity 3: Feeding All individuals require food - Maintains normal cellular function and replication - Required for reproduction Food is either consumed directly or synthesised by individual Autotrophs: Bacteria, Archaea, Protista, Plantae - Synthesises food they require for life - May need to source other nutrients from the environment Chemoautotrophs: - Bacteria that synthesis own organic molecules using oxidation of inorganic compounds as source of energy Photoautotrophs: - Using sunlight as energy source; green plants, bacteria and algae - Earliest form was likely photosynthetic bacteria - anoxygenic – occurs without oxygen - Oxygenic – occurs with presence of oxygen - Cyanobacterium - Early eukaryotic cells engulfed photosynthetic bacteria (via endocytosis) resulting in first plant cells → endosymbiotic theory - Phylogenetically related - Genome reduced Heterotrophs: Found in all domains; exclusively in fungi and animalia - Unable to synthesise own food; must consume other sources of organic carbon and nutrients; consumes other forms of life - Carnivores - eat animals - Insectivores - eat insects - Herbivores - eat plants - Omnivores - variety of organisms, meat plant fungi - Scavengers – eat remains of food left by other animals - Detritivores - eat soil, leaf litter and other decaying organic matter Can be primary, secondary or tertiary consumers The ancestral state – heterotrophs: - Earliest life forms likely to be single-celled primitive heterotrophs - Absorbed acid and base molecules - Chemical breakdown was a form of fermentation Challenges of moving onto land - Water and other nutrients are limited and in the soil - Plants have evolved; adaptations to allow them to obtain resources - Roots to extract water + dissolved nutrients from soil - Vascular tissue transports water + nutrients - Water resistance coagting (cuticle) to minimise water loss - Tissue for structural support - Diversity of leaf types and size for photosynthesis - Roots: - Underground organs of vascular plants - Supports nutrient uptake (N, P, K, Ca, Mg S) and water uptake - Provides anchorage and support - Synthesis of plant hormones and storage of nutritional reserves - Can be modified → mangroves have aerial roots to allow O2 uptake, prop roots, clasping roots in climbing plants - Vascular system: - Tube that transports sugar: Phloem - Tube that transports water: xylem - Xylem reinforced by lignin - Trees have long stems and produce large amounts of wood through secondary growth → Conducting system allows transport of sugars and water to larger areas → lignin prevents xylem cells from collapsing under hydrostatic pressure - Importance of leaves: - Land plants originally had photosynthetic apparatus on stems - Leaves evolved multiple times → increased surface area for photosynthesis and gas exchange - Leaves thought to evolved from overlapping branches - Structure and diversity of leaves vary greatly; depends on ecological niche Autotrophs: some examples: - Parasitic plants: mistletoe - Derives all nutrients from other plants - Modified roots which penetrates host plant walls connecting it to vascular system - Carnivorous plants: venus flytraps - Derives nutrients by capturing prey → then digesting  - Has a trapping structure triggered by trigger hair on inner surfaces - Symbiotic legumes: pea plants - Houses other symbiotic nitrogen-fixing bacteria like Rhizobium in root structures called rood nodules - These bacteria are beneficial when soils have poor nutrients - Symbiotic autotrophic algae - Eg zooxanthellae live in symbiosis with coral - Provides nutrients to coral; gains CO2, phosphates and nitrogen compounds in return Feeding adaptations in heterotrophs: - Diffusion: movement of nutrients through cell membrane - Phagocytosis: engulfing items of food → uses evolved specialised structures - E.g amoeba - Absorbs bacteria by putting out pseudopods, engulfing it into a vacuole, then digesting it, then exocytosis of waste products - E.g sponge - Absorbs small nutrients but can also absorb larger prey - Similar to amoeba → through phagocytosis - Disadvantage of diffusion / phagocytosis: - Prey / species needs to be relatively small to consume so can not support larger or complex species - Filter feeders: - Strains organic matter and food particles from water by passwing water over specialised filtering structure - Diversity of organisms with this feeding - Eg: krill - Small marine crustaceans - Frontmost appendages have fine comb like structures that act as filters - Staple food for many marine vertebrates – therefore essential to the ecosystem - Eg: Blue whale - Largest animal and filter feeder on the planet - Main food source is krill - Have fringed plates of fingernail-like material (baleen) attached to upper jaw  - Likely to have evolved from teeth - Parasitism: - Do not source food themselves, feeds from other species often without killing them but not providing any benefit either - Benefit: do not need to exert energy - Cost: depends on host - Eg: tape worm - Vertebrate gut parasites - Attaches to intestinal lining via head structure -> scolex - Feed by absorption through epidermis (which is very thin and flat) - Eg: jawless fish - Blood-sucking parasites of fish - Early forms had exoskeleten of bone in the skin - Basically they just hang off their vertebrate fish hosts Invertebrates: DIversity of mouth parts: Accumulate most resources during juvenile; preparation for producing offspring as adults - Chewing: huge, strong mandibles - Piercing / sucking: blood is high proteinaceous source to develop eggs - Carving: - Syphoning: like a drinking straw curled up - Sponging Vertebrates: evolution of jaws - earliest fish were jawless; derived from gill arches  - Gill arches move forward, then forms basis of hardened structure – the jaws - Jaws evolved, then teeth Heterotrophs: adaptations - Dragon fish can eat prey as big as themselves - Space between brain case and vertebrate → allows the head to tip back during feeding - Dragonfly larvae can also eat big prey - Has hinged mouthparts folded away → during feeding, will extend then retract 4: Excretion and elimination Excretion: removal of waste products - Regulates internal environment - Controls cell or body water content - Maintenance of solute composition - Excretion of metabolic waste products and unwanted substances Secretion: the movement of material that has a specific task after leaving the cell or organism Elimination: - Removal of unabsorbed food that is not part of the body - Usually faeces Respiration: process of gas exchange Why important? - Can lead to disruption of cell membranes - Inefficient metabolism - May lead to death Species have evolved means by which to effectively excrete and eliminate Passive transport - Solutes pass through the membrane without a transport protein - Osmosis and diffusion due to chemical gradient Active transport - Most species have specialised cells evolved for excretion and elimination - Active transport of waste products allow for organisms to be larger in size; does not depend on diffusion to transport solutes Specialised cells: animals and excretion - Flame cells - Excretory cells found in freshwater invertebrates - Removes waste cells - Bundle = protonephridia - Early animals: protonephridia - Later animals: evolved more complex nephridia - Vertebrates have kidneys and liver - Coelom  - This species has three layers – acoelomate - Relies on diffusion; simple structures - Animals after the flatworm have a coelom - Fluid-filled so can be used as internal support - Separates internal processes from gut - Allows transport of fluids; circulatory / excretory - Provides space for development of internal organs - Enables increase in body size Excretion and elimination in bacteria, fungi and plants Protists and early eukaryotes - Single celled organisms; no specialised organisms - Majority expelled by diffusion - Active transport would occur through specialised membrane channels - Eg amoeba - Endocytosis then amoeba digests food - Post digestion: waste is released via exocytosis Fungi: - No specialised organs - Some waste eliminated by passive diffusion - Active transport would occur through specialised membranes OR expelled directly (exocytosis) - Penicillin discovery - Left bacteria on culture plates; came back to find fungus on the plates - Colonies near the fungus were destroyed - Mould was penicillin; now can be an antibiotic Plants: - Transpiration - Gaseous waste and water excreted through stomata, lenticels of stem and outer surface of stem and fruit - Storing: - Some organic waste is stored as bark and leaves - Diffusion: - Aquatic plants excrete metabolic waste through diffusion - Terrestrial plants through the soil - Transpiration: occurs during the day when stomata are open - Guttation: drops of xylem sap gather on the tip or edge of leaves - Usually happens at night when stomata are closed and water builds up due to root pressure - Storing: waste materials accumulated in vacuoles of ageing cells - Stems, leaves, bark - These cells eventually dies and fall off - Elimination of waste is important; can build up toxic substances Animals: - Nitrogenous waste; high concentrations produced by metabolism of protein - Can convert into one of four products - Ammonia → by aquatic species - Single nitrogen molecule; requires lots of water / extremely soluble - Very toxic - Urea → terrestrial species - Less toxic and requires less water for excretion - Synthesis is complex and has metabolic cost of four ATP molecules - Uric acid → terrestrial species - Highly insoluble and non-toxic; its excretion conserves water - Synthesis is very complex; requires 24 ATP molecules per uric acid - Guanine → spiders - Nearly insoluble - Excreted with very little water loss - Energy cost is very high - Depends on their environment Invertebrates: - Excretory organs transport waste from coelom to exterior - Excretory organs increase in complexity - Protonephridia → nephridia → Malphigian tubules - Hindgut involved in excretion and elimination  - End product mix of nitrogenous matter and faecal waste Vertebrates: - Kidneys: - Primary excretory organ - Other excretory organs; skin, gills and gut - Liver: - Breaks down substances in the blood, including toxins - Birds and reptiles: - Excretion of waste occurs from the hindgut - Mammals: - Two different openings for excretion and elimination Dangers of accumulating waste: - Leaf rolling caterpillar - Rolls into a leaf - Protected and has constant source of food - Faeces builds up inside the leaf - Particular wasp has specialised senses to detect the smell of the faeces - Lays an egg IN the caterpillar and dies - Adaptation: caterpillar has evolved an anal plate that has a small trigger when waste builds up - Will literally fire the faeces out of the leaf lol Faeces is nutrient rich: - Dung flies - Some flies lay their eggs in animal dung - Dung has decaying material and is a food source of growing offspring - Dung beetle - Feed of faeces Excreted matter can be traded for security: - Ant-aphid mutualism - Ants protects aphids from potential predators - Aphids release honeydew from alimentary canal = food for ants 5: Movement Movement: moving from one place to another - Find food - Find mate - Find suitable habitat to live - Escape predators Movement is essential for survival Passive movement: - Involves little or no energy - Organisms can passively through water and air - Some species attach themselves to hosts that move (parasites, spores on seeds) - Little or no control over where you end up - May end up in environment that is suboptimal Active movement: - Can control where to move to - Organisms actively move through all environments - Energy is required Moving in water: - Advantages - Support - Hydration – will not desiccated - Nutrient rich - Environmentally buffered – less changes in temperature - Disadvantages - May passively move to suboptimal environment - Requires buoyancy that needs energy of specialised structures - Water levels might fluctuate - Evolved structures - Cilia and flagella - Feetlike projections - Fins and flippers Moving on land - Challenges - Oxygen in air; need to have evolved to capture - Lack of water; can dehydrate - UV radiation; can cause damage to cells - No support; species require structures to support - Energy hungry – needs to actively move usually - Terrestrial ecosystems are complex and vary dramatically - Structures to facilitate active movement - Cell walls - Vascular tissue - Lignin and bark  - Seeds or spores - Legs Moving in air: - Challenges - Safe but challenging - Gravity: adaptations needs to lift - Strong wind currents – can end up in suboptimal environments - Extremely energy hungry – flying takes enormous muscles - Adaptations: - Lightweight; taken by wind - Produce lots of seeds - Large surface area for lift - Enlarged muscles for flight Early adaptations that facilitate active movement: - Cilia: tiny projections that cover outside of cell - On unicellular species - Beat in co-ordinated movement across the cell - Pseudopods: move out in specific directions - Unicelllular amoebae alter cell shaped by pushing cytoplasm out to produce pseudopodia - Uses to move in a particular direction - Amoebae can aggregate to form one single travelling colony. - Flagella: longer hair-like structures (like a tail) propels organism around - Prokaryotic and eukarytoic bacteria - For locomotion - Can function as a sensory organelle - Helicobacteri pylori - Suspected of causing gastritis and ulcers - H. Pylori culture was drank by a scientist; he became very ill with gastritis lol Movement in water: Molluscs Moving in water: squid, cuttlefish, octopus - Take in water through their mouths and then contract their body to push water through funnel → forward propulsion - Muscles assist - Tentacles also aid in movement Moving on land: slugs, snails - Variations in similar body plan  - Mantle: dorsal body wall, can be shell - Muscular foot: used for moving, feeding, manipulation - Not all species move as adults - Secrete mucus to assist with movement - Use propulsion - Rhythmic waves of movement by muscle Annelids: Movement: Muscles to assist movement - Has segments: consists of longitudinal and circular muscles that oppose one another - When longitudinal muscle contracts, chaetae in the behind muscle releases and chaetae at the front grips onto soil - Chaetae is structure that grips the soil - Circular muscles contract; chaetae will pull the worm forward - Sort of like peristalsis; longitudinal contract, circular relax and vice versa - Marine worms - Free-swimming and sedentary - Have unjointed leg-like parapodia - Trochophore larvae; free swimming ciliated larva - Earthworms: - Mostly terrestrial; lives in soil - Can grow very long - Reacts to vibrations Vertebrates: subphylum of Chordates Chordates have: - Notochord - Dorsal nerve chord - Myomeres Early chordates have: (like fish) - Gill slits - Post-anal tail Fish: - Move using caudal tail and fins - Movement is active; assisted by muscle - Maintenance of buoyancy – requires energy Cartilaginous fish: earliest fish - Large liver filled with lower density oil – still needs to swim to have buoyancy but can have some - Cartilage; lighter than bone – easier to maintain buoyancy - Pectoral fins aids lifting species Bony skeleton: evolved later; all other fish and vertebrates - Have a swim bladder for buoyancy - Similar to lungs - Have fins made of long rays of bone - Some fishes had developed more substantial bones in the fins; bigger and thicker so can support weight of fish → lobe-finned (precursors to legs) The first tetrapod: four-footed - Fish in shallow lagoons don’t always have water available; evolved bones that allowed them to walk - Amphibians: both gills and lungs - Can walk on land but still require water to reproduce - Juveniles have gills, adult terrestrial form allows lungs to evolve Movement on land, then to the air: Insects are the first colonisers of the sky: - Hard exoskeleton - Needs to moult - Inhabit water, land and air - Has six legs - And wings!!! → evolved wings:  - Stiff membrane of exoskeleton, strengthened by veins - Likely to have evolved from gills - Evidence from stoneflies that early wings aid locomotion across surface of water - Wings evolved from structures that would help ‘gliding’ Archosaurs: Reptiles: evolved from amphibians; evolved to survive without water Birds evolved from dinosaurs - Fossil discovered that was thought to be a dinosaur but had feathers and wings Adaptations for flight - Bones less dense - Enlarged chest muscle for flight - Feathers; increases surface area + maintains lift - System of air sacs in body that connects to lungs; can extract more oxygen per breath Evolution of mammals: Dinosaurs come from same lineage as crocodiles; mammals have also evolved from reptiles but walk upright Erect stance: pressure point is on the pelvis, femur sits Underneath pelvis → dinosaurs, mammals Sprawling stance: femur sits outwards to the side, angled from pelvis → lizards, crocodiles - Fish move bodies side to side, just like sprawling animals Change of stance… mammals move the back of body forward and back (imagine like a dolphin or whale) From quadruped to biped: - Humans walk upright - Changes in skeleta structure - Big toe reduced - Pelvis shortened; more bowl-like to help support base of spine - Femur bends inwards; knee straightened; patella central to joint - Connection with spinal column on underside of skull; allows standing straight - Less robust arms 6: Fossils Preserved remains or any preserved trace of a once-living organism Like to fossilise if: - Have bones or hard structures - Organism is quickly covered after it dies - Remains are in anoxic environment so bacteria do not decompose - Chemistry of environment does not dissolve organism How to date fossils? (You ask them out nicely!) Relative dating: - Stratigraphy: order layers of rock from older to more recent at a particular location - Index fossils: fossils with a known date used to date other unknown fossils if found together Absolute dating: - Radiometric dating methods: based on decay of certain elements (like carbon) - Different elements used depending on timescale What can fossils tell us? - Dates, physiology, diet, reproductive mode, movement, migration patterns, development, thermoregulation, colour, behaviour - Infer from shape, size, structure, colour etc of the fossil Major evolutionary transitions: - Involved changes in the way information is stored and transmitted - New units of reproduction - Division of labour - Development of more complex units - Examples: evolution of genome, of eukaryotes etc - Multicellularity: - Evolved multiple times - Organisms alive today help us understand the evolution - Fossils can help us understand WHEN multicellularity evolved Biofilm: bacteria can send signals to one another; some can perform different functions; not multicellular but different bacteria working together Slime moulds produce spores to reproduce Fossil record: first fossil 2.1 billion years ago; suggests when multicellularity evolved → all evidence for evolution Dawn of animals; an evolutionary event: - Fossil evidence suggests first animal was similar to a sponge - Biomarker: molecule made by an organism; shows that animals evolved around 635 million years ago - More larger and diverse animals appear → 575 million years ago; called Edicauran fauna Historic mass extinction: Origination and extinction: - Rate of origination and extinction helps identify diversity + adaptive radiations - Fossil records determine the rates Adaptive radiation: - When evolutionary lineages undergo exceptionally rapid diversification into a variety of lifestyles or ecological niches - Involves new environmental niche in absence of competition What is mass extinction? - staistically significnat departure from background extinction rates that results in substantial loss of diversity - Can occur from many causes: change in climate, habitat loss, predation, competition  - Can be… - local or global - taxonomically specific - taxonomically broad - over different time scales Big five Mass Extinctions: - End-Ordovician mass extinction: - Increase in extinction rates - 50-60% of marine genera and nearly 85% of marine species loss - Cause by climate change – global cooling and glaciation → sea levels dropped = loss of shallow water habitat + change in ocean chemistry (ie more toxins brought up) - Then global warming; → sea levels rose and change in ocean chemistry - End-Triassic mass extinction - Cause by increase in extinction rate AND decrease in orgination rates - Caused by increase in volcanic activity → increase CO2 levels in atmosphere - Increased temperatures and calcification in ocean - Less diversity afterwards; but left lots of new niches to be occupied The Anthroporcene: humans impact - Many organisms gone extinct due to humans - The dodo: hunted by explorers - Introduced rats which ate dodo birds  - The tasmanian tiger - Settlers hunted the tigers Are we heading towards mass extinction? - Extinction rates seem to be elevated to background extinction rates Human causes of extinction: - Habitat loss: deforestation, agriculture, urban development - Case study: hawaii: ⅓ of birds are endangered - 113 birds are found ONLY in Hawaii; 71 have become extinct and 31 are threatened - Species introduction: introduction of predators or competitors; introduction of diseases/ parasites - Pollution: eg runoff - Overexploitation: too much hunting / fishing - Climate change - Atmospheric carbon dioxide is increasing - Greenhouse gas → absorbs and radiates heat - Rising global temperatures - Glaciers shrunk, ice is breaking earlier in the season, trees flowering sooner than previous - Loss of sea ice, accelerated sea level rise, longer more intense heat waves - Oceans becoming more acidic: - Carbon dioxide dissolves in ocean → carbonic acid - Affects calcifying life - If coral affected, could affect the entire ecosystem Extinction of one or a few species can have cascading effects Module 2 - Evolution 7.1: What is evolution? Evolution - cumulative change in a population over time - Different to natural selection Adaptation - biological mechanism which organisms adjust to new environments or to changes in their current environment Natural selection: - Competition (mates, food resources) - Selection (disease, predation)  - Environment (climate, ecology) - So.. not all elephants will survive… The Galapagos Islands: - Diverse ecosystems - Can study adaptation of different species - Eg: natural selection - Santa Cruz island: short-necked tortoises, round-shaped shell can reach food grown on the ground - Isabela island: longer-necked → can elevate its neck to reach food in higher plants → tortoises with longer necks were selected for as they had higher advantage in obtaining food Adaptation: - Environments change - Genetic variation - Species need to survive long enough to adapt - DNA variant needs to be passed down ; parent -> offspring - Eg: adaptation  - Flightless Cormorant: evolved to swim for fish; to the point where they have lost ability to fly - Prickly cactus: developed bark to protect itself from being eaten - Marine Iguana: blunt snout, powerful tails for swimming, special glands for being underwater, can reduce body size when resources are scarce to adapt Adaptations on the Galapagos: - Finch species have radiated into many different species - Galapagos finches all evolved from a common ancestor - Natural selection favours individuals suited to particular environments - Different islands + different habitats = different adaptations / characteristics that get selected for Natural selection vs evolution? - Natural selection: individuals with phenotypes best suited to their environments are more likely to produce offspring with the same phenotypes - Driver of evolution - Acts on heritable variation - Evolution: cumulative change of a species over time 7.2: Macro/micro- evolution: Macroevolution: changes that occur among large taxonomic groups Microevolution: studies the evolutionary ‘agents of change’ that shape the genome of a species Macro:  - Major evolutionary change - Over long period of time - Above the species level Species? - ‘Fundamental unit of evolution’ - Group of potentially interbreeding natural populations that are reproductively isolated from other groups or - Group of living organism consisting of similar individuals capable of exchanging genes - Difficult to define – difficult to determine if a populations can or can not reproduce Micro: - Evolution in a single species / population – caused by what? - Changes in the frequency of alleles within a species - Alleles, genotype, phenotype - Subtle changes - Can occur in shorter periods of time - May not be visible - Agents of change: what causes change in genomes? - Natural selection: survival + reproduction of the fittest - Mutation: random change to heritable DNA - Sexual reproduction: recombination of genes OR mate choice - Genetic drift: changes to allele frequencies based on chance (cyclones, volcanoes, land clearances; random) - Gene flow: migration, movement, hybridisation 7.3: Population Group of organisms that interact and share genetic information Gene pool: genetic information carried by a population; dynamic Population? - Depends on what is being asked but.. - Organisms that interact with one another - Share genetic information - Population can be identical (organisms asexually reproduce) Gene pool: - Genetic information carried by a population; it is dynamic - Differences can exist between individuals: genetic variation - Combination of all the differences = gene pool (thank you variation!) - Larger gene pool → larger genetic diversity - Small gene pool → less genetic diversity Population: size, distribution, structure Agents of change affecting gene pool: - natural selection: predation - Genetic drift: - Sexual reproduction: - Mutation: larger population = higher chance of mutation - Gene flow: one species dominantly in one area compared to other species Population size: - Effective population size: number of individuals contributing offspring to the next generation - Smaller populations fix alleles that are under selection faster 8.1 The Hardy-Weinberg Theorem Most traits are complex; involves cumulative action of many genes: polygenic Some traits are produced by a single gene: monogenic -> haemoglobin, skin pigment, eye colour Remember: Selection acts on the population -> can be identified through allele frequencies How to determine if selection is happening? - Observe allele frequencies of a population Carry out Hardy-Weinberg - See if the number of phenotypes is what we would expect in a population - Genotypes:  - Use Punnett square: find expected genotypic and phenotypic outcomes will be - Phenotypic ratio – 3:1 - Genotypic ratio – 1:2:1 What is the Hardy-Weinberg theorem? - Why don’t dominant alleles overrun recessive alleles in a population? - Genotype frequencies expected for any possible set of allele frequencies - Under certain conditions, allele frequencies will NOT change from one generation to the next - Therefore, they remain in equilibrium – recessive alleles can not be overrun B allele = p b allele = q p + q = 1.0 8.2 For allele frequencies to remain in equilibrium, five unrealistic conditions are met: - No migration - No introduction of new variants to a population - No mutation - Unrealistic - Equal fitness; no selection - Infinite population size - Small populations are susceptible to genetic drift - Mating is random Calculate allele frequencies: - ALLELE. Count same alleles in a population - E.g how many B alleles and how many b alleles 8.3 - Migration often occurs, DNA mutates, fitness varies, population size not infinite, mating is not random so.. - Genotypes not in Hardy-Weinberg equilibrium can indicate a population is under selection - Compare observed frequencies to expected frequencies - Chi-squared test!!! - Check to see if Chi-squared value is significant - Chi-squared is a test of how different values are.. > than critical value = significantly different - D.f: n-1 where number of alleles is n - If frequencies are significantly different, the characteristic may be under natural selection 9: Natural selection – agents of change Variation, heredity, selection - Galapagos medium ground finch → beak length - Different seeds on the island: hard and soft - Variation: beak size - Heredity: beaks of parents correlate to beaks of offspring - Selection: environmental conditions - After a drought, only large, woody seeds remained - After drought, average beak depth was much larger - Selection differential: difference between population mean and selected mean  - Those with larger beaks survived and were more likely to reproduce → passes down trait - Eg Peppered moth → wing pattern - Black moth vs white moth - Black moth camouflage on bark = more likely to survive - Eg rock pocket mice: - Variation: coat colour - Due to different alleles - Heredity: alleles are heritable - Selection: environmental conditions - Dark volcanic rock and pale sandstone - Darker coloured coats survived better on rock and lighter coats on the sandstone Selection occurs on traits that increase reproductive success Can act in different ways: - Directional selection: positive selection - Favours individuals on one end of the distribution of phenotypes - Stabilising selection: favours individuals in the middle - Disruptive selection: favours individuals at either end of the distribution Eg industrial melanism → directional selection - Pale coloured moth → selective advantage on light colour trees and vice versa - Post-industrial revolution: trees darken, therefore easier for predators to see pale moths Selection acts faster on dominant alleles than recessive alleles  Red Line (Favoured Dominant Allele): ○ Immediate Increase: When a dominant allele is favoured by natural selection, its frequency quickly rises in the population. This is because the allele’s effects are expressed even in heterozygotes (organisms with one copy of the dominant allele and one copy of the recessive allele). ○ Slower Fixation: However, the graph shows that this allele rarely reaches complete fixation (1.0). This is because recessive alleles can "hide" in heterozygous individuals where they are not subject to selection, allowing the recessive allele to persist in the population. Blue Line (Favoured Recessive Allele): ○ Initial Lag: When a recessive allele is favoured, its frequency increases much more slowly at first. This is because recessive alleles must be in a homozygous state (two copies) to express the beneficial trait. Until enough homozygotes appear, selection cannot efficiently favour the recessive allele. ○ Rapid Fixation: Once enough homozygotes (individuals with two copies of the recessive allele) emerge, selection acts strongly, and the allele quickly becomes fixed (reaches 1.0). Eg birth weight of human babies → stabilising selection - Can not grow too large, can not grow too small Eg fish feeding on different species (algae / insects) → disruptive selection Artificial selection - Results from human activity - Breeders NONRANDOMLY choose individuals with economically favourable traits - Eg: corn, dogs Balancing selection: provides advantage for heterozygotes - Selection favours heterozygotes Eg Sickle cells Homozygous wild type, heterozygous, homozygous sickle cell; heterozygous = both traits expressed - Found that members of a tribe near a lake had high levels of sickle cell alleles - Further research shows those who had high sickle cell trait lived in areas of high malaria rates  - Heterozygote had highest survival rate in areas of malaria - Balance between surviving malaria and surviving sickle cell anaemia Fitness and relative fitness: Fitness: success of an organism at surviving and reproducing Relative fitness (w): describes success of genotype at producing new individuals; standardised by success of other genotypes in the population Fittest genotype has w = 1 Calculating relative fitness: Selective advantage = Highest relative fitness / next highest relative fitness 10.1: Mutation – agents of change Mutations alter DNA → introduces variation - Induced DNA mutation ; chemicals / radiation - spontaneous mutation ; replication errors Germ-line mutation: - Affects gametes - Mutation transmitted via sexual reproduction - Mutations in germline create new variation ; heritable Somatic mutation: - Affects all daughter cells of a single cell  - Not heritable Mutations arise in all parts of genome - Occur in genes or regulatory regions - → impact organism phenotype Mutations can occur at different scales - Smaller: eg single nucleotide - Single base substitution - Bases inserted/deleted - Leads to frameshift mutation - Larger: eg entire chromosomes  - Gene duplication: same genes playing different roles - Gene inversion: can affect gene expression - Chromosomes joined or lost - Chromosome fusion - Entire genomes duplicated Mutations impact gene expression and function: - Regulatory regions: - Promoter: increases transcription - = presence or absence of tissues - Coding regions: - May be large or small impact How do mutations impact evolution? - Changes gene pool - With selection, mutations can be significant - Can be small changes - Can be large changes Humans: Approximately one SNP per 30 million base pair 10.2: Sexual reproduction – agents of change Hardy Weinberg → assumes mating is random in a population Is mating really random? Modes of reproduction: - Asexual: - Fission, fragmentation, budding, vegetative reproduction - No change in allele composition - Sexual: - Recombination via meiosis - Sperm and egg - Novel offspring → unique genotype combinations so selection can act - Change in allele composition Twofold cost of sex: - Evolution should favour asexual - Asexual faster - ‘Search’ costs in finding a mate - No risk of transmitted infection - But.. sexual reproduction has benefits  - Combining beneficial alleles - Generation of novel genotypes - ‘Faster’ evolution - Clearance of deleterious mutations → any carriers may not undergo sexual reproduction Sexual mating systems: - Random mating: equal probability - Non-random: probability bias - Assortative: Common - Individuals share alleles - Less genotypic diversity - Increase homozygosity - Eg: humans: - Select for traits like height, skin colour, intelligence - Eg: sea snails: - Size and location → larger animals live further up the shore and smaller ones lower - Eg: sea slug - Size: individuals that differ in size unable to bring reproductive organs - Behavioural: - Promiscuity: multiple males with multiple females (closer to random mating) - Monogamy: one maple pairs with one female - Polyandry: female with multiple males - Polygny: male with multiple females - Disassortative: - Do not share alleles - Can increase genotypic - Increase heterozygous - Maintains variation - Eg: wolves: mating between different coloured coats 10.3: Genetic drift – agents of change Genetic drift involves random changes in allele frequencies - Alleles become more or less common just by chance - Always element of randomness Allele frequency → population size = ‘sampling error’ COnclusion: allele frequencies change with each successive generation One allele can reach frequency of 100%, but can not predict which will be fixed or lost Unlike selection, genetic drift does not favour an allele → can not predict Population: - Effect of population size on allele frequency: - Smaller: probability of larger change - Genetic drift is a strong evolutionary agent of change - Outcomes unpredictable - Larger: - Even larger: distribution of allele frequency similar to starting; frequency of P will remain close to starter values Population size decreases by chance: - allele frequency can be wiped out entirely Random events: genetic bottleneck → reduce size of population + genetic diversity - Events that reduce number of individuals - Events that separate a population Founder event → smaller group from larger population creates a distinct population After bottleneck event; population size may recover, but not genetic diversity - Impacts how species adapt to environment Implications: - Conservation: - Fragmented populations continue to lose genetic diversity - Speciation: - Populations stop exchanging alleles and continue to differentiate, eventually evolving into different species 11.1: Gene flow – agents of change Migration, movement, hybridisation Gene flow: transfer of genetic information from one population to another - Introduce new genetic variation - reintroduce existing genetic variation Gene flow homogenises connected populations / lack of gene flow promotes interpopulation differentiation Migration: gene flow between distinct populations Movement: gene flow between subpopulations Barriers to gene flow: Less connected: less porous barrier Mountains, forests More connected: more porous barrier Lake, river For gene flow to occur, individuals must be able to interbreed and produce viable offspring Impact of gene flow depends on: - Level of migration, movement or hybridisation - Let m be migration rate - Genetic difference between populations - f(A) = allele frequency Calculate rate of change of allele: m(x-p) What is the change of f(A)? (How much does this allele frequency change when migration is occurring?) - Small migration rates and small difference in allele frequencies (0.05)(0.6 - 0.4) = 0.01 - After on generation of migration, frequency of A will change by 0.01 - f(A) = 0.4 + 0.01 = 0.41 - Large migration and small differences in allele frequencies  (0.5)(0.6 - 0.4) = 0.1 - Changes by 0.1 - Large migration event and large difference in allele frequency (0.5)(0.8-0.2) = 0.3 - Changes by 0.3 Gene flow has a large impact when - Allele frequencies between two populations have large differences - Migration rate is very high 11.2: Speciation Agents of change results in speciation Speciation: evolutionary process where new species arise through reproductive isolation  - Causes one evolutionary lineage to split into two or more lineages - There will be a barrier to reproduction Reproductive barriers: prevent gene flow + enables speciation - Pre-mating isolation - Geographical isolation - Prevents reproduction because of environment - Agents of change can work; insects having adaptive traits for their environment causing selection - Causes genetic divergence; - Mutation arises: chromosomal / DNA differences - Selection occurs in each population: change phenotype / behaviour - Genetic drift: lead to reproductive isolation - Behavioural isolation - Eg courtship calling - Selection for different mating signals creates reproductive isolation - Pre-zygotic isolation: Genetic, behavioural, physiological or ecological aspect preventing sperm fertilising egg - Mating time differences - Spawning times of two coral species do not overlap - Therefore, one species will not fertilise another species’ gamete - Ecological: - Pollinators: mimulus species attract different pollinators - One attracts bees, one attracts hummingbirds - → natural selection has enabled plants and pollinators to co-evolve - Post-zygotic isolation: mating can occur, but offspring may not be viable - Hybrid fails to develop or dies soon after birth Allopatric speciation: Speciation occurs in different geographical areas Sympatric speciation: speciation in the same location 11.3: Hybridisation Gene flow via hybridisation: - Interbreeding of individuals from genetically distinct populations produce viable offspring - Offspring display traits and characteristics of both parents but may be sterile Outcomes of hybridisation: - Adaptive introgression: inheritance of beneficial variation from related species that accelerate adaptation and survival in new environments - Eg Tibetans sharing parts of their genome to Denisovan - Denisovan adapted to living at high altitude; limited oxygen - So, if there were pre-adapted species (Denisovan) hybridising with human species, this will allow for selection of the beneficial trait - Eg: coat colour of dogs and wolves - Adaptive advantage: camouflage Introgression describes movement of alleles from one species or population to another - DNA and fossil evidence show humans, Neanderthals and Denisovans represent separate, parallel lineages descended from a common ancestor - Molecular studies indicate that modern humans interbred with Neanderthals and Denisovans Examples: Neanderthal or Denisovan alleles → Humans - HYAL2: cellular response to UV: 49% East Asians - EPAS1: Hypoxia at high altitudes: 80% Tibetans Incomplete lineage sorting: - Genetic signals from DNA does not match what is expected in a species tree 12: Molecular Genetics and Genomics Molecular genetics and genomics involves sequencing and analysis of select genes or entire genomes - Molecular Genetics: study DNA understand function of a specific gene - Genomics: Study of DNA sequences of all the organism’s genes Investigate using different approaches: - Compare specific situations - Controls vs cases - Look across distributions of phenotype - Look at evolutionary relationships - Look at genomes of different species to find when they may have diverged - Whole genome sequencing - Isolate DNA and fragment genome; then sequence it altogether - Genomic analysis of many individuals: - Collect samples, create ‘libraries’ of DNA sequences, investigate on locus and identify SNPs Genomes size can vary - Need good sample size to study a population Genetic databases: genome wide analyses - Sequences your genome + determine your genotype at different polymorphic sites Genome wide association studies: - Associating genotypes with measurable phenotypes - Identify traits for - Medical research - Evolutionary biology - Agriculture; identify beneficial traits of economical value Module 3: Sensing and Responding to Environment 13: Homeostasis What is life? - How energy, matter and information is exchanged - Individuals are special → goal-directed behaviour - Schrodinger’s writing - Negative entropy: - Information passed down  - Paul Davies writing: - ‘information’ : what you know; ‘entropy’ : what you don’t know - ‘Maxwellian demons’: little devices that use information about identity of molecules and control their movement → they do not obey the second law of thermodynamics - Operates more effectively than non-living - Order vs disorder ‘Swimming against the entropy tide’: - Temperature = measure of heat; heat = measure of energy - Individual molecules in motion move randomly; heated up → bump into each other and pass on energy - Entropy: tendency for random movement of molecules to spread energy out evenly - Energy that gets spread out like this lost - Second law of thermodynamics: natural tendency of energy in the universe to spread out more evenly - Why don’t organisms fall apart? - Work goes on in an organism; work is a kind of energy - Energy all goes in the same direction; there is an order to it - Ordered movement can push molecules into specific configurations - Metabolism: release energy to do work on molecules - Helps organism to stay in an ordered state - Do living things violate the second law of thermodynamics? - Not all energy from food goes into work; some do shoot off in random directions - This heat spread releases into the environment; some of the disorder goes into the environment - OVERALL there is disorder → metabolic heat adds disorder to environment - Total amount of disorder from organism + from environment = increased - Therefore = positive entropy - Living things: maintain high level of order - Homeostasis: ‘staying the same’; stay in order; find food, find water, avoid getting too hot and too cold - Means to the greater aim of transferring information → copy its genes into a new individual Ecology of survival: Problem Energy Matter Information Temperature Information and life: Processing and storing information is fundamental to life - Homeostasis: the way organisms keep themselves ordered - Receive information, store it then respond to it - On a molecular scale: cellular activity - On an organism scale: response to their environment - Encoding: code of an organism where information is stored → DNA - ultimate goal: organism passes this information on 14: Metabolism Building bodies Scale in biology: - Molecular: nanometers - DNA; transcription; proton pumps - Molecular: micrometres - Intracellular - Organelles; cholroplasts and mitochondria - Individual: micrometre to metre - Population: mm to km - Groups of individuals - Populations that share genetic materials → species - Community: mm to km - Different species living together - Ecosystem: mm to km - Community interacting with environment Occurs at different scales of time Nanoseconds → billions of years Individual as a thermodynamic system: - System: the individual and its interaction with environment  - Radiation: heat passes through or from - Food: chemical energy coming in - Heat produced from organism’s metabolism → loss of order into environment = entropy increasing - Heat loss from moving into a cooler environment - Heat loss from surface of organism as radiated heat - Heat loss through air in the wind = convection - Heat loss through the ground = conduction - Heat loss through water = evaporation (sweat, tears, saliva) - Matter coming into organism = food, gases, water - Matter leaves organism in form of undigested food + metabolic waste - Matter lost in form of reproduction Summed up into: temperature, breathing, water, feeding → metabolism! Flow of energy going in must equal flow of energy going out → energy + matter can not be destroyed Metabolism: complex chemical reactions - Maintaining homeostasis to allow building and survival of next generation Measuring metabolic rate: - Direct calorimetry: measure heat production - Indirect calorimetry: gas measurement Basal metabolic rate: - Animal not moving, not digesting, in thermoneutral zone, in its inactive phase, an adult, not reproducing Standard metabolic rate: - Same conditions, but body is at a known temperature Resting: - Not moving, not digesting, in thermoneutral zone Field metabolic rate: - Organism behaving naturally in the wild - Using doubly labelled water - Organism injected with heavy water (has an extra neutron); labelled water essentially - Capture animal and take blood - Find how much the labelled water has been diluted Temperature and metabolic rate: Homeothermic: organism needs to stay at constant temperature Endotherm: generates heat to raise body temperature - Increasing temperature = lower metabolic rate - Increased metabolism required to produce heat - Movement of muscle eg Heterothermic: variable temperature Ectotherm: body temperature varies with ambient temperature - As temperature increases, metabolic rate increases - Temperature increases the speed of metabolism Body size and metabolic rate: M = aWb - Because of Surface area to volume ratio Metabolic web: - Feeding  - Assimilation - Growth - Maintenance - Development - Reproduction → ontogeny: growth and development - Egg, juvenile, adult - Metamorphosis - haploid/diploid stages Patterns in individual growth and reproduction → affects population growth - Size at maturity - Clutch size - Longevity - Food through process of feeding; assimilation turns food into new molecules (reserve) - Waste products produced; not 100% efficient - Reserve accessed by body to carry out metabolic processes - Growth → structure of body - Maintenance to prevent degradation - Maturation → Increase level of organisation - Once matured → reproduction Work is done to get through these different processes Basal metabolic rate = just maintenance Growth curves: - Shows amount of growth in time - Due to Different patterns of growth and reproduction - Determined by metabolism of organism  - Gradually decreasing rate of growth; head towards asymptote - Rapid exponential rise of growth then sudden stop - Something in between lol There is a relationship between metabolic rate and growth pattern Metabolic rate: measure by heat production; gas production or consumption Reflects how organism goes through its life cycle These processes lead to reproduction rate 15: Thermoregulation Organisms must live in an environment that allows them to maintain survival up to reproducing enough offspring to allow population growth Metabolic niche: specific set of environmental conditions Important factors: - Abiotic: Temperature, sunlight, water - Biotic: Mates, competitors, prey, predators Temperature: All organisms have a thermal limit; can only survive between a particular range of temperatures Q10: determines rise in temperature (by 10º); ie metabolism at Q10 = 2 will double every 10º rise Response curves: - Limits show extreme temperatures that will cause death upon exposure - Rates rise rapidly according to Q10 function - Animals target for optimum range - More time spent within optimum region, the higher the overall performance, the higher the reproductive rate = more likely to persist as a species - Therefore, animal must find environmental condition to achieve the optimum temperature - Outside optimum range: can survive, but will not be able to effectively carry out metabolic activities Experimental: - Toads heated at different temperatures made to hop in a race lol - Can be used as a predictor of where cane toads may spread - Cane toads are poisonous to some animals - Use thermal response curve to predict a distribution map based on different temperatures of the land 16: Signals and Responses 16.1 Information: signals and cues Six sensory modalities; depending on where it lives Environment of organism constantly changes: - Abiotic: temperature, humidity, sunlight - Biotic: temporal and spatial variation in food, competitors, predators, parasites, pathogens and reproductive partners Eg: food - Patchily distributed in space; needs to be detected - Animals need to use cues to find food - Also may need to respond to a predator arriving Cues for predators: - Eg field experiment with broken shells of a newly-hatched black headed gull - Placed broken eggshell next to intact egg at varying distances away from each other - Counted number of eggs taken by crows - Number of intact eggs that were taken were much higher if broken eggshell was nearby - Therefore, predators use broken eggshells as an indicator there is possible food nearby Signals and cues provide information; no intrinsic meaning but convey information - Must be recognisable - Selection must favour the evolution of sensory mechanisms that allow signal or cue to be detected - Sex pheromones; odours produced by different animals to convey messages, such as indication for reproductive ability 16.2: Sensory modalities: - Chemical - Olfaction - Production and dispersal of pheromones - Odours detected by receptors; pheromones bind to receptors which will then be activated and trigger an action - Electricity - Works well in aquatic environments - Detection of food in an electric field - Eg; shark attracted to electrodes producing electric dipole field - Light - Visual - Varies amongst different species; can depend on eye size - Eg ability to detect a signal varies with distance and species - Magnetic - Magnetoreception - Bacteria and many animals detect and respond to magnetic field - Allows them to orient over long and short distances - Birds kept in a closed funnel scratched at a certain direction, even with varying weather conditions - Mechanical - Web building spiders use vibrations to detect location of prey - Sound - Eg sound emitted by whales - Echolocation by bats: - High frequency sound - Objects located by directing sounds at them and detecting the echoes (when the sound waves bounces back) 16.3: How to respond Signal: Eg: fireflies flashing light → indication for mating Cue: eg: red necked wallabies use odour of faeces as a cue to reveal likely presence of predator → wallaby more vigilant when smelling faeces of an organism that had fed on wallabies Signal vs cue: Signal: any act or structure that influences the behaviour of other organisms; evolved specifically for that effect Cue: an incidental source of information that may influence behaviour of a receiver Ant pheromones: - Signal for other ants - Cue for adult butterflies - Cue for spiders to locate webs where butterflies can be found Signals are only effective when they are detected - May not reach intended receiver; may get ‘attenuated’; signal lost - Background noise: eg how does one flower stand out among diversity of flowers; how can a chick distinguish itself from other chicks Signals are strategic and efficacious - Signalling strategy: eg bright colours = high toxicity - Signalling efficacy: same information, different impact Source of information allows animals to behave: Innate: performed for first time Learned: modified from experience Module 4: 4.1.1: Homeostasis Golden rules of biology: - Cells are big protein factories: designed to synthesise proteins - Proteins do all the work inside the cell - Protein shape = protein function - Changed shape = altered function Homeostasis: maintaining a stable environment in an organism - For optimal protein function Proteins operate at optimal temperatures; moving away would cause it to lose functionality Denaturation: unfolding of protein - Things that disrupt hydrogen bonds between amino acids - Temperature - pH - Ions (including salts) - Solvents (polar molecules) - Therefore we homeostatically regulate… - All the above! (things that affect hydrogen bonds) What is homeostasis? Maintenance of relatively stable internal environment notwithstanding changes in external environment Reflexive - Unconscious Regulatory: - Endocrine system: - Hormones; chemical signalling molecule - Nervous system: autonomic - Specifically intended to regulate homeostasis Feedback loops: - Negative feedback: self-regulatory - Stable relationship between stimulus and response - Oscillates around and equilibrium setpoint - Disease occurs when we move out of our normal range - Positive feedback: amplification - Eg blood clotting Thermoregulation is a negative feedback loop… Essentials of negative feedback: - Stimulus: produces change in variable - Receptor: detects change - Input: sent along afferent pathway to control centre - Output: information sent along efferent pathway to effector - Response: effector acts feeding back to influence magnitude of stimulus In physiology: - Eg stable blood glucose levels - High blood glucose → release insulin - Insulin removes glucose from blood → lowering blood glucose - Low blood glucose → release glucagone - Glucagon converts glygoen to glucose → increasing blood glucose - Blood pressure 4.1.2: somatic vs visceral Sensory: - Somatic: - Sensory information from ‘body wall’ - Skin, skeletal muscle, bones and joints - Are consciously aware of - Visceral: - Sensory information from internal organs - not consciously aware of Motor: - Somatic: skeletal muscle activity - Voluntary movement - Visceral: smooth and cardiac muscle activity - Involuntary movement Autonomic nervous system divided: - sympathetic nervous - Regulates reflexes: fear; fight or flight - Increase heart rates, respiratory rate - Prepare body to run away or engage with threat - Parasympathetic nervous - Occur when we are not under threat - Digestive processes Thermoregulatory activity involves changes in the sympathetic nervous system 4.1.3: Chemical signalling Cells communicate with each other through chemical messages Endocrine system: Chemical signalling molecules travel from cell that releases hormone to target cell via circulatory system Receptors: Chemical singalling molecules detected by receptors Chemical signalling molecule: ‘ligand’ - Neurotransmitters - Hormones - Inflammatory mediators Ligands bind to receptors; → receptor binding initiates events inside cells → produce response So.. presence of receptor determines action Receptor - ligand specificity - Receptor is specific for a particular signalling molecule  - When ligand binds to receptor, it produces a specific response Neurotransmitters vs hormones: Neurotransmitter: - Released in small packets at the synapse - Synapse = connection between two neurons - Action is discreet; restricted to receptors at the synapse Endocrine hormones: - Released into circulatory system - Actions on any cell in the body with a receptor for the ligand Key neurotransmitters and hormones involved in thermoregulation Neurotransmitter: - Noradrenaline - Released by neurons of sympathetic nervous system - Evokes fear, flight or fight - Activates class of receptors: adrenergic receptors Hormones: - Adrenaline - Secreted by adrenal gland (under sympathetic control) - Activates adrenergic receptors - Thyroid - Secreted by thyroid gland, under hypothalamic regulation - Increases energy expenditure = increased heat production 4.1.4: Circadian rhythm Core body temperature oscillates throughout the day Circadian rhythm: 24 hour cycles that are part of body’s internal clock Oscillations in homeostatic regulation Core body temperature: Sleep cycle: decline in core body temp Wake cycle: arousal; increase body temp → oscillates around a setpoint Subjective alertness: Linked to oscillations in core body temp - When core body temp is low, relatively tired - Core body temp → related to hormone level, alertness, performance ability 4.1.5: Thermoregulation Ways we exchange heat with the environment: - Radiation: sun, infrared radiation - Evaporation: heat transfer when water evaporates - Convection: heat exchange with surrounding medium; air / water - Conduction: heat exchange with another object → changes in blood flow help using these systems Physiological thermoregulatory responses: - Metabolism - Nonshivering thermogenesis (heat production) - Sympathetic regulation - Endocrine system involved - Through increased metabolic activity  - Shivering thermogenesis: - Somatic regulation - endocrine system - Through muscular activity - Skin blood flow - Sympathetic; increase or decrease blood flow - Vasoconstriction - Vasodilation - Sweating - Sympathetic - Evaporation of water Elements of reflex pathway Involves both somatic and visceral: respond to stimulus and control body temp Crosstalk between somatic and visceral system: Changes in ambient temperature is sensed → evokes responses to protect core body temperature Note afferent and efferent pathways 4.1.6: Fever Fever: altered temperature regulated ‘set point’ is higher than normal - Infectious agents activate immune response (pyrogens: causes fever) - Releases inflammatory mediators - Stimulates production of prostaglandin - Alters neuronal activity in hypothalamus leading to altered set point - Increase heat production: shivering - Decrease heat loss: vasculature - → rise in core body temperature Physiological benefits of fever: - Proteins do work of cell - Protein shape = protein function - Bacteria:  - operating range is impacted - Viruses: - Human cells operate at 37ºC, shifting away from that reduces efficiency of viral replication rate Certain proteins in immune system actually operate more optimally at higher temperatures - Immune response is low activity during normal temperature - Immune response is selectively activated during infection - Because proteins involved actually operate better at higher temperatures Sepsis: uncontrolled inflammatory response - Excess high temperature can lead to organ damage - Our own cells are not performing optimally due to high temperature 4.2.1: What is asthma Respiratory system: - Transfer oxygen from environment to RBC - Transfer CO2 from blood to air - Regulate acid-base balance Bronchial system: airway conducting system - Transmission of air to alveoli What is asthma? - Variable airflow obstruction - Inflammation and remodelling - Hyperresponsiveness Physiology: Airway obstruction → reduced airflow on expiration Forced vital capacity: accessible volume of lungs FEV1: amount of air that can be blowed out in one second - Healthy lungs: can be expelled in one second - Asthmatic lungs: takes more time to expel all the air - Reduced FEV1 to