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Unit 2 · The Living World: Biodiversity Unit Hub Flashcards Cheat Sheet Essentials Visual Review MC Practice FRQ Practice

AP Environmental Science Unit 2 Visual Review

A 7-slide visual walkthrough of every Topic 2.1-2.7 concept — the three levels of biodiversity, ecosystem services, island biogeography, ecological tolerance, natural disturbance, adaptation, and succession — built right into the page.

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TOPIC 2.1 Three Levels of Biodiversity Genetic Species diversity Ecosystem diversity Genetic diversity Variation in genes WITHIN a species. It's the raw material for natural selection — more genetic diversity means a population is more likely to have traits that survive new stress. Species & ecosystem diversity Species diversity is the variety AND relative abundance of species in an area. Ecosystem diversity is the variety of habitats, communities, and ecological processes across a landscape. All three levels feed into resilience — losing any one makes an ecosystem more fragile. The Review Hub · AP Environmental Science Unit 2 TOPIC 2.2 Ecosystem Services Provisioning food, timber, fresh water, fiber, medicine Regulating climate control, flood & disease control, pollination Supporting nutrient cycling, soil formation, primary production Cultural recreation, spiritual value, education, aesthetic value Why "services"? Framing nature's benefits as services helps economists and policymakers assign them real value, since markets otherwise treat them as free — a Unit 6 connection to market failure. A quick way to sort any example Ask: does it directly GIVE us something (provisioning), PROTECT us from something (regulating), keep the SYSTEM running (supporting), or ENRICH our experience (cultural)? Wetlands are the textbook multi-service example — flood control, water filtration, and fish nurseries all at once. The Review Hub · AP Environmental Science Unit 2 TOPIC 2.3 Island Biogeography rate number of species present → colonization extinction equilibrium S Two curves, one equilibrium As more species colonize, fewer NEW species remain to arrive, so colonization rate falls. As more species compete for the same space, extinction rate rises. They cross at a stable equilibrium number of species. Size and distance shift the curves Large islands → lower extinction (more room, more resources) → higher equilibrium S. Near islands → higher colonization (easier to reach) → higher equilibrium S. Largest, closest islands have the MOST species. Species richness is predictable from just two variables: how big the island is, and how far it is from the mainland. The Review Hub · AP Environmental Science Unit 2 TOPIC 2.4 Ecological Tolerance population size environmental variable (e.g. temperature) → optimal range stress stress lower limit upper limit Three zones on the curve Optimal range — conditions where the species thrives; population is largest. Zone of physiological stress — survivable but taxing; reproduction & growth suffer. Limits of tolerance Beyond the upper and lower limits, the species cannot survive at all. A generalist has a wide tolerance range (crows, raccoons); a specialist has a narrow one (koalas) — specialists are more vulnerable to change. The same bell-curve logic applies to any variable — temperature, salinity, pH — that limits where a species can live. The Review Hub · AP Environmental Science Unit 2 TOPIC 2.5 Natural Disruptions to Ecosystems Fire Clears dead growth, recycles nutrients to soil, opens sunlight for new growth. Flood Deposits nutrient-rich sediment, resets river channels & wetlands. Volcanic activity Buries land in ash/lava — the classic starting point for primary succession. Storms & drought Hurricanes topple canopy trees, opening gaps. Drought stresses whole communities at once, favoring the most drought-tolerant species. Not all bad Disturbance can increase diversity by preventing one species from dominating. Every natural disturbance is followed by ecological succession (Topic 2.7) — the community rebuilding itself. The Review Hub · AP Environmental Science Unit 2 TOPIC 2.6 Adaptations Genetic variation already exists in the population Selection pressure predators, climate, competition Differential survival & reproduction better-suited traits persist trait frequency shifts across generations Classic examples Structural: camouflage, thick fur · Behavioral: migration, hibernation · Physiological: antifreeze proteins, venom resistance Adaptations aren't chosen by the organism — natural selection filters existing variation over generations. The Review Hub · AP Environmental Science Unit 2 TOPIC 2.7 Ecological Succession PRIMARY SUCCESSION — starts with no soil Bare rock Lichens & moss (pioneer species) Grasses, weeds Shrubs Forest (climax community) SECONDARY SUCCESSION — starts with existing soil Disturbed soil after fire, farming, storm Grasses & fast growers Shrubs & young trees Mature forest (climax) MUCH faster than primary — soil is already there Key vocabulary Pioneer species — first to colonize; break down rock, add organic matter, build soil. Climax community — the relatively stable end-stage community suited to the local climate. Primary succession builds soil from nothing; secondary succession rebuilds on soil that already survived the disturbance. The Review Hub · AP Environmental Science Unit 2
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How to use the visual review

Spend 30 seconds per slide before clicking next. Look at the diagram, then ask yourself: "Could I draw this from memory and explain it?"

Use the fullscreen button () on desktop for the best experience. Use arrow keys to navigate. Tap "Show all slides" to jump around.

This covers every one of Unit 2's 7 CED topics, from the levels of biodiversity through ecological succession.