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Philosophy Exam 1 ⸻ Sigmund Freud (Psychoanalysis) 1. Id – Ego – Superego Freud explains personality as a system of three interacting structures that are in constant conflict. * Id The id is entirely unconscious and represents instinctual drives such as aggression, hunger, and sexual desire. It operates on the pleasure principle, meaning it demands immediate satisfaction without considering reality, morality, or consequences. It is irrational and purely driven by biological impulses. * Ego The ego develops to mediate between the id and external reality. It operates on the reality principle, meaning it tries to satisfy instinctual desires in realistic and socially acceptable ways. It uses reasoning, planning, and delayed gratification. It is partly conscious and responsible for decision-making. * Superego The superego represents internalized moral values and social rules learned from parents and society. It judges behaviour and produces feelings of guilt or pride depending on whether actions align with moral standards. It often conflicts with the id by imposing strict moral constraints. Key idea: personality results from the continuous tension between instinct (id), reality (ego), and morality (superego). ⸻ 2. Defence Mechanisms Defence mechanisms are unconscious psychological strategies used by the ego to reduce anxiety caused by conflict between the id, superego, and reality. They distort perception in order to protect the individual from psychological discomfort. * Repression Unacceptable thoughts or memories are pushed into the unconscious and become inaccessible, although they may still influence behaviour indirectly. * Denial The individual refuses to accept a painful or threatening reality. * Projection The person attributes their own unacceptable feelings or impulses to others. * Displacement Emotional impulses are redirected from the original source to a safer target. * Rationalization The individual creates false but logical explanations for behaviour in order to avoid guilt or anxiety. * Reaction Formation An unacceptable impulse is transformed into its opposite behaviour. * Regression Under stress, the individual returns to earlier, more childish patterns of behaviour. * Sublimation Unacceptable impulses are transformed into socially acceptable or productive activities. * Intellectualization Emotional situations are dealt with through abstract or logical thinking to avoid confronting feelings. * Compensation The individual develops strengths in one area to make up for weaknesses in another. * Identification The person adopts the traits or behaviours of another individual to reduce anxiety or increase self-esteem. * Undoing The person attempts to symbolically cancel out unacceptable thoughts or actions through corrective behaviour. Key idea: defence mechanisms are automatic, unconscious, and protect the ego by distorting reality. ⸻ 3. Psychosexual Stages Freud argues that personality develops through stages where psychic energy (libido) is focused on different parts of the body. Fixation at a stage can influence adult personality. * Oral stage (0–1): pleasure through feeding; fixation may lead to dependence or oral habits. * Anal stage (1–3): focus on control and toilet training; fixation may lead to orderliness or messiness. * Phallic stage (3–6): development of gender identity and early moral awareness; family dynamics are central. * Latency stage (6–puberty): sexual energy is dormant; focus on learning and social development. * Genital stage (puberty onward): mature sexuality and adult relationships. Key idea: early childhood experiences strongly shape adult personality. ⸻ René Descartes 1. Dualism Descartes argues that reality is composed of two fundamentally different substances: * Mind (res cogitans): non-physical substance responsible for thinking, consciousness, reasoning, and doubt. * Body (res extensa): physical substance that occupies space and follows mechanical laws. Although distinct, mind and body interact, creating the mind–body problem of how two different substances can influence each other. Key idea: humans are composed of both mental and physical substances that are fundamentally different. ⸻ 2. Rationalism Rationalism is the view that reason is the primary source of knowledge, more reliable than sensory experience. Descartes argues that the senses can deceive us through illusions and dreams, so knowledge must be based on clear and distinct ideas produced by reason. He uses methodic doubt, systematically doubting all uncertain beliefs until reaching something absolutely certain. Key idea: reliable knowledge must come from reason rather than the senses. ⸻ 3. Cogito: “I think therefore I am” Descartes establishes that even radical doubt proves existence. If he is doubting, he must be thinking; if he is thinking, he must exist as a thinking being. Key idea: the act of thinking guarantees the existence of the self. ⸻ Plato 1. Ideal Society Plato’s political philosophy divides society into three classes corresponding to parts of the human soul: * Rulers (philosopher-kings): guided by reason and wisdom; they govern society. * Guardians: guided by courage; they protect and defend the state. * Producers: guided by desire; they provide material goods and services. Justice occurs when each class performs its proper function without interfering in the roles of others. Key idea: social justice is harmony through specialization and proper role distribution. ⸻ 2. Theory of Forms Plato distinguishes between two levels of reality: * The physical world: constantly changing, imperfect, and perceived through the senses. * The world of Forms: eternal, perfect, and unchanging essences such as Beauty, Justice, and Equality. Physical objects are imperfect copies of these perfect Forms. Key idea: true knowledge is knowledge of eternal Forms, not sensory appearances. ⸻ 3. Allegory of the Cave Plato describes prisoners chained in a cave who see only shadows and believe them to be reality. One prisoner escapes and discovers the real world illuminated by the sun, which represents truth. When he returns, the others reject him. Key idea: education is the process of moving from illusion to truth, which is difficult and often resisted. ⸻ Francis Bacon 1. Four Idols of the Mind Bacon identifies four sources of systematic error in human thinking: * Idols of the Tribe: universal human biases in perception and reasoning. * Idols of the Cave: individual biases shaped by personal experience and education. * Idols of the Marketplace: errors caused by language and communication. * Idols of the Theatre: blind acceptance of philosophical systems and traditions. Key idea: human reasoning is naturally flawed and must be corrected through scientific method. ⸻ 2. Empiricism Empiricism is the theory that knowledge comes from sensory experience and observation. Bacon argues that scientific knowledge must be based on experimentation, data collection, and systematic observation rather than pure reasoning. Key idea: knowledge is grounded in experience, not abstract speculation. ⸻ 3. Induction vs Deduction Induction is reasoning from specific observations to general laws. Deduction is reasoning from general principles to specific conclusions. Bacon emphasizes induction as the foundation of scientific knowledge because it is based on empirical evidence. Key idea: science progresses by building general laws from observed facts. ⸻ Friedrich Nietzsche 1. “God is Dead” Nietzsche argues that modern science and secular thinking have undermined the authority of traditional religion as a source of meaning and morality. This leads to a cultural crisis in which old values collapse without being replaced. Key idea: the loss of religious authority creates a crisis of meaning. ⸻ 2. Nihilism Passive nihilism refers to despair and the belief that life has no meaning. Active nihilism refers to the rejection of old values in order to create new ones. Key idea: nihilism represents both the breakdown of meaning and the possibility of creating new values. ⸻ 3. Übermensch The Übermensch is the ideal individual who creates their own values, rejects conformity, embraces life fully, and overcomes traditional moral systems. Key idea: humans must move beyond inherited values and become creators of meaning. ⸻ Charles Darwin 1. Natural Selection Evolution occurs through natural selection. Individuals within a species vary, and those with advantageous traits are more likely to survive and reproduce. Over time, these traits become more common in the population. Key idea: evolution is driven by survival advantage rather than purposeful design. ⸻ 2. Morality (Evolutionary view) Darwin argues that morality is not divine but evolved through natural processes. Humans developed social instincts such as empathy and cooperation because these traits improved survival within groups. Key idea: morality is a product of biological and social evolution

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ENV 226: Essential Ecology Final Exam Study Guide — om single-species thinking to the dynamics of many interacting ecies. A community is more even when all species have similar abundances. Diversity: A combined measure of richness and evenness. More diverse = more likely to pull multiple different species out of a 'hat'. Shannon Diversity Index (H′): The most common diversity index. Higher H′ = more diverse (high richness AND high evenness). Formula: H′ = –Σ(pᵢ · ln pᵢ), where pᵢ is the proportion of individuals in species i. Worked example If a community has 4 species, each at 25% (p = 0.25), then H′ = –[4 × (0.25 × ln 0.25)] = 1.39. If one species dominates (e.g., 70/10/10/10), evenness drops and H′ falls even though richness is the same. Why diversity matters — ecosystem function & services Ecosystem function: Biological, geochemical, and physical processes that take place within an ecosystem (e.g., productivity, nutrient cycling, decomposition, pollination). Ecosystem services: The benefits humans derive from ecosystems. Four major categories: Provisioning: food, water, timber, fiber Regulating: climate regulation, flood control, water purification Cultural: recreation, spiritual, aesthetic, educational values Supporting: soil formation, nutrient cycling, primary production How diversity affects function — mechanism Complementary resource use (niche complementarity): Different species use slightly different resources (e.g., water at different soil depths, nutrients at different times). A diverse community captures more of the available resources than any single species could, raising total productivity. Diversity–stability theory Compensation: Species respond differently to environmental fluctuations. When one species declines, another can increase and 'compensate,' keeping overall ecosystem function steady. Insurance hypothesis: A diverse community is more likely to contain at least one species with traits that help the ecosystem cope with change. Diversity acts as ecological 'insurance' against disturbance. Rules of community assembly — what determines diversity at a site Three filters act in sequence on the regional species pool to determine which species actually end up in a local community: Term Definition Dispersal Who can physically get there. Controlled by distance from source populations and by dispersal ability. Connects to the 'mass effect' / rescue effect — regional diversity (gamma) can rescue local diversity (alpha). Environmental filtering What species can tolerate the abiotic conditions (climate, soil, water, salinity). Example: Ponderosa pine will not survive in the Sonoran Desert — environmental filtering excludes it. Biotic filtering What species can coexist given interactions with other species (competition, predation, facilitation). Strongest where abiotic conditions are benign, because more species can be there to interact. Intertidal zonation paradigm — how the filters stack In rocky intertidal communities, abiotic stress (desiccation, wave action) sets the UPPER limit of a species' distribution — an environmental filter. Competition and predation set the LOWER limit — biotic filters. Take-home: environmental filtering dominates in stressful zones; biotic filtering dominates in benign zones. What maintains diversity Intermediate Disturbance Hypothesis (IDH): Diversity is highest at intermediate frequencies or intensities of disturbance. Low disturbance lets competitive dominants exclude others; high disturbance eliminates all but the most disturbance-tolerant species. The middle keeps both groups in the community. Positive species interactions (facilitation): When one species makes conditions better for another (e.g., a nurse shrub providing shade and moisture for seedlings underneath). Facilitation tends to INCREASE biodiversity, especially in stressful environments. 1.2 Succession Primary succession: Colonization of a substrate that has NEVER supported life (e.g., bare bedrock, new volcanic rock, glacial retreat). Soil must be built from scratch, typically by pioneers like lichens and mosses. Secondary succession: Recovery after a disturbance that left soil and some biological legacy behind (e.g., a cleared field, most wildfires). Much faster than primary succession because soil and seed bank persist. Pioneer species: The first species to colonize a disturbed or bare area. Typically fast-growing, high-dispersal, stress-tolerant organisms that modify the site so later-successional species can establish. Quiz-style example The Woodbury Fire burned so intensely on the Tonto NF that only bedrock remained. Recolonization of this area is PRIMARY succession — there is no soil or seed bank left to start from. 1.3 Ecological Energetics Energy: The currency of ecosystems. Most ecological energy originates from the sun as electromagnetic radiation and is stored in tissues (biomass). Trophic level: Organisms that share the same function in the food chain and the same nutritional relationship to primary sources of energy. Level 1 = producers; 2 = primary consumers (herbivores); 3 = secondary consumers (carnivores); 4+ = tertiary / apex predators. Autotroph (primary producer): An organism that produces its own food from inorganic sources — typically plants, algae, and some bacteria via photosynthesis. Consumer (heterotroph): An organism that obtains energy by consuming other organisms. Primary consumers eat producers; secondary consumers eat primary consumers; etc. Production: The rate at which new biomass is created by organisms in an ecosystem (units of mass or energy per area per time). Net primary production (NPP): Gross primary production (total photosynthesis) MINUS the energy plants use for their own respiration. NPP is what is actually available to herbivores. Assimilation and production efficiency Energy is lost at every step of the grazing food chain. Two key efficiencies describe where energy goes: Term Definition Assimilation efficiency (Energy assimilated / energy consumed) × 100%. Assimilated = consumed – egested (waste). Herbivores ≈ 20–50% (tough plant material); carnivores ≈ 80% (similar tissue chemistry). Production efficiency (Energy in new biomass / energy assimilated) × 100%. Endotherms (birds, mammals) are LOW (~1–3%) because most energy is burned as heat; ectotherms (insects, reptiles, fish) are HIGH (~10–50%). Worked example (assimilation efficiency) Eats 400 J, excretes 200 J as waste, puts 50 J into growth. Assimilated = 400 – 200 = 200 J. Assimilation efficiency = 200 / 400 = 50%. The 10% rule Roughly 10% of the energy at one trophic level is transferred to the next. The rest is lost to respiration, heat, and waste. This is WHY food chains are short (usually 4–5 links): there simply isn't enough energy left to support another level. 1.4 Food Webs A food web is many, connected food chains — a map of who eats whom across an entire community. In simple diagrams, arrows point from prey to consumer. Complex diagrams use plus/minus signs to show the direction of effect, and dashed lines to show indirect effects. Top-down control: Higher trophic levels (predators) limit the abundance of lower levels. Removing a top predator releases herbivores, which suppress plants. Bottom-up control: Lower trophic levels (nutrients, producers) limit higher levels. Adding nutrients increases plants, which increases herbivores, which increases predators. Trophic cascade: Indirect effects of a predator propagate down the food web. Classic example: wolves reintroduced to Yellowstone → elk browsing decreases → riparian willow and aspen recover → beavers return → stream ecosystems recover. 2. Ecosystems Ecosystem: A community of organisms PLUS their shared environment. Includes biotic components (plants, herbivores, carnivores, detritivores) and abiotic components (climate, soils, nutrients). 2.1 Ecological building blocks Ecological building block: An atom that (1) makes up organisms and (2) is relatively abundant. Key building blocks: C, H, O, N, P (and sometimes S) — collectively CHONP. Not building blocks: Silicon, aluminum, arsenic, tungsten — they may be abundant in the crust or used by some organisms, but are not core structural elements of life. Potassium is important biologically but is NOT a core 'ecological building block' in this course's sense. 2.2 Liebig's Law of the Minimum Growth is dictated not by the total resources available, but by the SCARCEST resource. The 'limiting nutrient' sets the ceiling on production; adding more of a non-limiting nutrient has no effect until the limit is raised. Application — nutrient pollution A coastal system receives 10 g N, 200 g P, 50 g C, and 20 g O per year as pollutants, and you know the system is N-limited. By Liebig's Law, adding MORE nitrogen is what will most change structure and function — even though phosphorus is arriving in larger quantities, it is not the limiting nutrient. 2.3 Eutrophication Eutrophication is the enrichment of an aquatic system with nutrients (especially N and P) from fertilizer runoff, wastewater, or atmospheric deposition. Process: Excess N fuels algal blooms → algae die and sink → microbial decomposition consumes oxygen → a hypoxic 'dead zone' forms → fish and invertebrates die. Once N is drawn down, the system can become P-limited; phosphorus mined for fertilizer keeps the cycle going. The Gulf of Mexico hypoxic zone is the classic example. 2.4 Nutrient cycles (N, C, P) Term Definition Nitrogen cycle N₂ in atmosphere is biologically inert. Nitrogen-fixing bacteria (free-living and in legume root nodules) convert N₂ → ammonium (NH₄⁺). Nitrification converts NH₄⁺ → nitrite → nitrate (NO₃⁻), the form most plants take up. Denitrification returns N₂ to the atmosphere. Humans roughly DOUBLED global N fixation via the Haber-Bosch process → fertilizer → eutrophication. Phosphorus cycle Largely a SEDIMENTARY cycle — no gaseous phase. P weathers from rock → soil → plants → consumers → back to soil → eventually to ocean sediments. Slow turnover at global scales; a critical component of DNA/RNA, phospholipids, bones, and ATP. Carbon cycle See dedicated section below. C moves among atmospheric, terrestrial, oceanic, and fossil pools. Photosynthesis pulls CO₂ out; respiration and combustion return it. 2.5 Ecotones and cross-ecosystem flows Ecotone: A transition zone between two ecosystems, exhibiting gradients in environmental conditions and a related shift in the composition of plant and/or animal communities (e.g., forest–grassland edge, estuary). Two factors determine how a flow of material/energy from one ecosystem affects another: Relative size of the systems — when the amount of something varies across ecosystems, the LARGER system has a bigger impact on the small system (e.g., a stream flowing into a small pond vs. into the ocean). Quality of the resource — rich subsidies (like salmon carcasses bringing ocean nutrients to streams) matter more than dilute ones. 2.6 Ecological state change & resilience Key components of ecosystems: STRUCTURE (what organisms are there and how they interact), FUNCTION (processes of energy and nutrient movement), and REGIME (which of several possible stable states the system is in). Alternative stable states: An ecosystem can exist in two or more contrasting conditions under the same environmental conditions (e.g., clear lake vs. turbid lake; forest vs. shrubland). Ecological state change (regime shift): A large, persistent, often abrupt shift in the structure and function of an ecosystem, triggered by crossing a critical threshold. Threshold / tipping point: The level of a driver (stressor) at which a system flips to a new state. Hysteresis: Once a system flips, simply reversing the driver does NOT restore the original state — the return path is different from the 'forward' path. Slow vs. fast drivers: Slow drivers (e.g., gradual warming, soil nutrient accumulation) build up until a fast driver (e.g., fire, storm) tips the system across the threshold. Perturbation: Any event (abiotic or biotic) that disturbs the ecosystem. Perturbations that cause regime change can be abiotic (fire, flood, drought) or biotic (pest outbreak, invasion). Resilience: The capacity of a system to absorb disturbance, adapt to change, and recover from adversity while maintaining its essential functions, structure, and identity. The ball-and-cup diagram Picture a ball sitting in a valley (cup) on a hilly landscape. The ball is the current state of the ecosystem; the cup is the 'basin of attraction' for that state. A disturbance pushes the ball; stabilizing (negative) feedback loops pull it back. Strong disturbance or a shrinking cup (loss of resilience) can push the ball over a hill into a NEW cup — that's state change. Negative (stabilizing) feedback loop: A change triggers a response that DAMPENS the change, keeping the system near its current state. Deepens the cup. Positive (amplifying) feedback loop: A change triggers a response that AMPLIFIES the change, pushing the system further from its current state. Flattens the cup and makes state change more likely. Applying resilience to conservation & restoration Manage for resistance — remove stressors that push the ball (exclude high-intensity grazing, reduce pollution). Manage for resilience — rebuild the 'cup' by re-establishing key species, nutrient cycling, and stabilizing feedbacks (planting perennial grasses, restoring hydrology). Passive restoration works when the seed bank, soil, and key species are still intact; active restoration is needed when the system has already crossed the threshold. 3. Landscape Ecology and Biogeography 3.1 Landscape ecology Landscape ecology: The study of spatial patterns of ecosystems and their ecological consequences — explicitly considers the arrangement of habitats across space and how organisms and materials move through them. Spatial elements Term Definition Patch A relatively homogeneous area that differs from its surroundings (e.g., a forest stand in a grassland). Generally the highest-quality habitat. Matrix The background land-cover type that surrounds patches (e.g., desert in Saguaro NP, or agricultural land around forest fragments). Corridor A linear feature connecting patches — allows movement of organisms, genes, and energy. Examples: riparian strips, hedgerows, engineered wildlife crossings (Oracle Road, Tucson). Ecotone See above — the transition zone between landscape elements. Spatial heterogeneity Variability in environmental conditions and habitat types across a landscape. Drives diversity at landscape scales. Scale dependence Ecological patterns and processes depend on the spatial/temporal scale at which they are observed (e.g., a species may look stable regionally but be declining locally). Fragmentation Fragmentation breaks a large continuous habitat into smaller, more isolated patches. Effects include: Loss of total habitat area More edge relative to interior — edge effects (different microclimate, invasives, more predators) penetrate into remaining patches Reduced connectivity — animals cannot move between patches Smaller populations in each patch → inbreeding depression, loss of genetic variability, higher extinction risk Saguaro NP example Mid-sized carnivores in Saguaro NP West crashed after a disease outbreak and never recovered. Why? The city of Tucson grew between Saguaro NP East and West, severing connectivity. No recolonization could occur from the eastern population. Solution: re-establish connectivity — the Oracle Road wildlife crossings documented over 4,400 crossings by 16 species in their first two years. Patch dynamics Patch size, shape, and connectivity change over time because of ecological processes — succession, disturbance (fire, flood, windthrow), and fragmentation — not random chance and not just geology. 3.2 Biomes and realms Biome: A large biological community defined by climate and dominant vegetation type (e.g., tropical rainforest, boreal forest, tundra, desert, savanna, temperate grassland). Biogeographic realm: A large area of the Earth's surface with a distinctive assemblage of taxa, reflecting shared evolutionary history (e.g., Nearctic, Neotropical, Palearctic, Afrotropical, Indomalayan, Australasian, Oceanic, Antarctic). Factors shaping where biomes are found: temperature and precipitation (the primary controls), seasonality, latitude, elevation, continental geography, and evolutionary history. Realms reflect plate tectonics — Pangaea split into Laurasia and Gondwana, then into the continents we have today, producing unique evolutionary trajectories in each realm (e.g., Australia's marsupials, Madagascar's lemurs). 3.3 Island Biogeography and the SLOSS debate MacArthur & Wilson's Theory of Island Biogeography: species richness on an island is set by the balance between the colonization rate (immigration) and the extinction rate. Size effect — larger islands have LOWER extinction rates (bigger populations). Distance effect — islands closer to the mainland have HIGHER colonization rates. Equilibrium species number occurs where colonization and extinction curves INTERSECT. SLOSS debate — Single Large Or Several Small? Originally framed: is a single large reserve or several small reserves of equal total area better for biodiversity? Large favors: lower extinction, room for interior species, bigger populations, full food webs. Several small favors: replication (insurance against one disaster), sampling more habitat types, potentially higher total diversity. Modern answer: it depends — on species' dispersal, the matrix, and whether you value diversity vs. viability. Connectivity (corridors) often matters more than the large/small question alone. Source population: Produces more offspring than can be supported locally — exports individuals to other patches. Population growth rate > 0. Sink population: Organisms arrive but do not reproduce enough to sustain the local population; persists only via immigration from sources. Population growth rate < 0. 4. Extinction and Climate 4.1 The 'Big Five' mass extinctions Term Definition Ordovician–Silurian (~439 Mya) ~85% marine species lost. Cause: rapid glaciation and sea-level drop, then warming. Late Devonian (~364 Mya) Prolonged event; major loss of marine invertebrates, especially reef builders. Probable causes include ocean anoxia and climate change. Permian–Triassic (~251 Mya) 'The Great Dying' — ~96% marine species and ~70% terrestrial vertebrates. THE most severe. Cause: Siberian Traps volcanism → CO₂ spike → warming, ocean acidification, and anoxia. Recovery took 5–10 million years. End Triassic (~199–214 Mya) ~50% of species lost; cleared the way for dinosaurs to dominate. Likely cause: CAMP volcanism and climate change. Cretaceous–Tertiary (K-Pg, ~65 Mya) ~76% of species, including non-avian dinosaurs. Cause: Chicxulub asteroid impact (plus Deccan Traps volcanism) → darkened skies, cooling, then warming. Why scientists are concerned now Current extinction rates are 100–1000× background rates — comparable to mass-extinction levels. Rate of change: current climate change is occurring more rapidly than almost any past episode — faster than many species can adapt or track. Humans have built roads, cities, and agricultural landscapes that BLOCK the range shifts species would otherwise use to follow their climate. Human societies are themselves adapted to current climate (agriculture, supply chains, coastlines) — disruption drives conflict. 4.2 Why climate change affects ecological systems Temperature, precipitation, seasonality, and extreme events all drive the distribution and performance of every species. Shifting climate disrupts energy balance, water balance, food availability, and reproduction; changes the timing of seasonal events; and alters disturbance regimes (fire, floods, storms). All of these cascade through communities and ecosystems. 5. Climate Change — Ecology, Climate, and the Carbon Cycle 5.1 The carbon cycle Term Definition Pool (reservoir) A place where carbon is stored and from which it can be released. Measured as a quantity (e.g., gigatons). Flux The amount of carbon exchanged between pools per unit time (gigatons/year). Measures MOVEMENT. Sink A pool that accumulates more carbon than it releases — net REMOVER of carbon from the active cycle. Source A pool that releases more carbon than it accumulates — net ADDER of carbon to the active cycle. Biggest/smallest pools & fluxes Major carbon pools (approximate, gigatons): Deep ocean: ~37,000 GtC — BY FAR the largest pool Fossil pool (oil, gas, coal): ~10,000 GtC — second largest Reactive ocean sediments: ~6,000 GtC Soils: ~2,300 GtC Surface ocean: ~1,000 GtC Atmosphere: ~800 GtC — this is the pool that drives climate Plant biomass: ~550 GtC (the largest LIVING pool) Major fluxes are photosynthesis and respiration (~120 GtC/yr terrestrial; ~90 GtC/yr ocean), which are normally nearly balanced. Fossil-fuel combustion and deforestation are the (smaller but crucial) fluxes currently unbalancing the system. Why atmospheric CO₂ is increasing Humans are burning fossil fuels — moving carbon from a long-term sink (the fossil pool) into the active atmospheric pool faster than natural sinks can remove it. Deforestation and land-use change also shift carbon from plant biomass and soils to the atmosphere. The balanced photosynthesis/respiration fluxes cannot keep up with the ~10 GtC/yr added by human activity. 5.2 Ocean acidification As atmospheric CO₂ rises, more CO₂ dissolves into the ocean. The chemistry: Step 1: The ocean is slightly alkaline; CO₂ is slightly acidic, so CO₂ dissolves into seawater. Step 2: CO₂ + H₂O → H₂CO₃ (carbonic acid). Step 3: H₂CO₃ dissociates → HCO₃⁻ (bicarbonate) + H⁺. Step 4: Some HCO₃⁻ dissociates → CO₃²⁻ (carbonate) + H⁺. Step 5: Bicarbonate and carbonate exist in equilibrium. Net result: more H⁺ ions → lower pH = acidification. Acidification also reduces carbonate availability, making it harder for corals, shellfish, and plankton to build calcium-carbonate skeletons. Warming and the ocean's ability to sequester carbon Warmer water holds LESS dissolved CO₂ (inverse solubility). As oceans warm, their ability to absorb atmospheric CO₂ decreases — a positive feedback loop that further increases atmospheric CO₂ and warming. 5.3 Important climate feedback loops Term Definition Ice-albedo feedback (POSITIVE) Warming melts polar ice → darker ocean/land replaces reflective white ice → lower albedo, more solar energy absorbed → more warming → more melting. Water vapor feedback (POSITIVE) Warming increases evaporation; water vapor is a greenhouse gas → more warming → more evaporation. Permafrost/methane feedback (POSITIVE) Thawing permafrost releases CO₂ and CH₄ long locked in frozen soils → more warming → more thawing. CO₂ fertilization (NEGATIVE, partially) Higher CO₂ can boost plant photosynthesis, pulling more C out of the atmosphere. Partially counteracts warming but is limited by water, nutrients, and heat stress. Ocean solubility feedback (POSITIVE) Warmer oceans hold less CO₂ → more stays in the atmosphere → more warming. Quiz-style example Melting polar ice caps → decreased albedo → further warming = POSITIVE feedback loop (amplifies the original change). 5.4 Factors affecting Earth's surface temperature Three major controls: Energy arriving from the sun (solar radiation) Earth's albedo — how much of that energy is reflected back to space Greenhouse gases in the atmosphere — how much outgoing infrared is trapped Carbon dioxide is the LARGEST driver of current human-caused climate change (sheer volume, long atmospheric lifetime). Methane is more potent per molecule but far less abundant; water vapor amplifies change via feedback but is not itself a primary driver. 6. Climate Change — Ecological and Human Response 6.1 How climate change affects plants and animals Climate change disrupts performance in three main ways: Term Definition Energy balance Plants: respiration rates rise faster than photosynthesis with warming — net carbon gain (and growth) drops. Animals: thermoregulation costs rise; outside the thermal neutral zone, organisms burn more energy just to stay alive. Water balance Warmer temperatures and higher vapor-pressure deficit mean plants LOSE more water per unit of photosynthesis. Animals face greater dehydration risk; aquatic species face altered hydrology. Food acquisition & reproduction Changed phenology, drought, and heat reduce the resources available for growth and reproduction. Fewer seeds, fewer offspring, lower survival. Examples of species already affected Term Definition Pika Small alpine mammal restricted to cold, rocky talus. Warming pushes them to higher elevations — eventually they 'run out of mountain.' Already extirpated from lower-elevation sites in the Great Basin. Tuatara Reptile with temperature-dependent sex determination. Warming skews sex ratios toward males, threatening population persistence. Wolverine Depends on persistent spring snowpack for denning. Declining snowpack reduces suitable reproductive habitat. 6.2 Responses of species: MOVE, ADAPT, or DIE Move: shift range poleward or upslope to track suitable climate (classic response). Range shifts are highly variable across species — depends on dispersal ability, habitat specificity, and whether barriers (cities, roads, water bodies) intervene. Adapt: through plasticity (phenotypic change within a lifetime) or evolutionary change (genetic change across generations). Long-lived species with small populations adapt slowly. Die: local extirpation or global extinction if neither option is available fast enough. 6.3 Phenology Phenology: The timing of recurring biological events — bud burst, flowering, migration, breeding, hibernation. Climate change is advancing many spring phenological events (earlier bloom, earlier migration). Phenological mismatch occurs when interacting species shift their timing differently — e.g., a migratory bird arrives after its caterpillar prey has already peaked. Mismatches cascade through food webs. 6.4 Characteristics of climate-vulnerable species Narrow thermal tolerance (specialists) Poor dispersal ability (can't move to new climate) Long generation time, low reproductive rate (slow to adapt) Small, fragmented populations (low genetic variation, high stochastic risk) Dependence on climate-sensitive habitats (snowpack, sea ice, coral reefs, alpine tundra) Narrow geographic range, especially on islands or mountain tops (nowhere to go) Tightly tied to a specific phenological window or species interaction 6.5 Why current climate change is especially damaging Rate — change is occurring faster than most species can adapt or move Barriers — human land use has fragmented habitat, blocking the range shifts species used during past climate changes Cumulative stressors — climate change interacts with pollution, invasive species, overharvest, and habitat loss Interconnected systems — ecosystems, human agriculture, and global supply chains are all calibrated to current conditions 6.6 Mitigation vs. Adaptation Term Definition Climate MITIGATION Actions that reduce the magnitude of climate change itself — typically by lowering atmospheric greenhouse gases. Examples: switching to renewables, reforestation (sequestering carbon), reducing fossil-fuel use, more efficient buildings and transport. Climate ADAPTATION Actions that help humans and ecosystems COPE with the climate change that is already happening / unavoidable. Examples: creating migration corridors, building climate-resilient ecosystems through forest thinning, adjusting USDA seed zones, changing crop choices, updating hunting/fishing regulations, designing for sea-level rise. Quick quiz check Planting trees to sequester carbon = MITIGATION (reduces atmospheric CO₂). Thinning Southwest forests to make them more fire-resilient = ADAPTATION (copes with changing fire regime). Geoengineering proposals like stratospheric aerosol injection = a controversial form of mitigation (reduces incoming solar energy). Special cases of adaptation Managed (assisted) relocation: Actively moving species to areas outside their current range that are projected to become climatically suitable. Benefits: may be the only option for species that cannot disperse fast enough; can save species from extinction. Risks: recipient communities may experience novel interactions; potential to create invasive species; ethical questions about intervention. Assisted evolution: Human intervention to increase the rate of evolutionary adaptation — e.g., selective breeding for heat tolerance, or hybridization with warm-adapted populations. Benefits: keeps species in place; works for species that cannot move. Risks: may reduce genetic diversity; unintended consequences; can go wrong (outbreeding depression). 6.7 Corridors, climate refugia, and conservation design Climate refugium: A location whose physical or biological features allow species to persist despite regional climate change — e.g., high-elevation cool pockets, deep canyons, shaded slopes, coastal fog zones. Incorporating corridors (to enable range shifts) and refugia (places species can hold on) into reserve design is essential for climate-integrated conservation. A high-elevation forest that remains cool despite regional warming can serve as a seed source for recolonization — that's the textbook example of a refugium supporting resilience. Final thoughts: making an argument about climate-integrated conservation You should be able to give your own opinion on climate-integrated conservation and defend it. A solid answer acknowledges trade-offs: traditional 'protect what is there' approaches may fail under rapid change, but aggressive interventions (managed relocation, assisted evolution) carry real risks. Most conservation scientists argue for a portfolio approach — protect refugia, build corridors, and use active interventions only where the alternative is extinctionl

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