The enhanced greenhouse effect from Lesson 28 isn't an abstraction — it's already reshaping the planet: melting ice, rising and souring seas, shifting seasons, and species on the move or on the brink. This lesson is the payoff of Unit 9, connecting the physics of trapped heat to the living consequences. We'll follow the heat into the oceans (which absorb most of it and much of our CO₂), watch coral bleach and shells struggle to form, and then widen out to the full roster of what's driving Earth's sixth mass extinction — captured in the acronym HIPPCO. Climate change is the single heaviest topic on the exam; this is where the points are.
The enhanced greenhouse effect (Lesson 28) is warming the planet. Evidence includes the Keeling curve (steadily rising atmospheric CO₂ since 1958), rising global average temperatures, ice cores, and shrinking ice.
[DIAGRAM: Two-line graph over time — atmospheric CO₂ concentration (Keeling curve, rising with a small annual sawtooth) alongside global average temperature (rising). Both trend upward together since the mid-20th century.]
Major impacts: - Melting ice — glaciers, ice sheets, and sea ice shrink; contributes to sea-level rise and ice-albedo feedback (Lesson 28). - Sea-level rise — from melting land ice and thermal expansion (water expands as it warms); threatens coastal cities, low-lying islands, and wetlands with flooding and saltwater intrusion. - Shifting climate zones and species ranges — organisms move poleward/upslope to track tolerable conditions (Lesson 6); mismatches disrupt ecosystems. - More extreme weather — intense storms, heat waves, droughts, and floods. - Disrupted agriculture and water supplies; spread of pests and disease. - Ocean changes (below).
The oceans absorb most of the excess heat and much of the added CO₂: - Ocean warming → coral bleaching (heat-stressed corals expel their symbiotic algae, losing color and food; prolonged bleaching kills reefs), reduced dissolved oxygen, and shifting fish distributions. - Ocean acidification → dissolved CO₂ reacts with seawater to form carbonic acid, lowering ocean pH. This reduces available carbonate ions, making it harder for corals, shellfish, and plankton to build calcium carbonate shells/skeletons — threatening the base of marine food webs.
[DIAGRAM: Ocean acidification — atmospheric CO₂ dissolves into seawater → CO₂ + H₂O → carbonic acid → lowers pH and reduces carbonate ions → shell-building organisms (corals, mollusks, plankton) struggle to form shells.]
The main drivers of biodiversity loss and extinction (introduced in Lesson 4):
Invasive (non-native/exotic) species are introduced (often by humans) to an area where they lack natural predators/controls, letting them spread and harm native ecosystems. Examples: zebra mussels (clog waterways, outcompete natives in the Great Lakes), kudzu (smothers vegetation), cane toads (Australia), Burmese pythons (Florida Everglades), Asian carp. Impacts: outcompete natives, prey on them, spread disease, reduce biodiversity, and cause economic damage. Solutions: prevention (ballast-water rules, inspections), early detection, removal, and biological control (carefully).
Extinction is natural (background rate), but human activity has accelerated it toward a possible sixth mass extinction. Species most vulnerable: specialists (narrow tolerance, Lesson 6), K-selected species (slow reproduction, Lesson 8), endemic species (found nowhere else), top predators, and those with small ranges.
Protection: the Endangered Species Act (ESA) protects listed species and their critical habitat; CITES regulates international trade in endangered species; captive breeding, habitat protection, corridors, and restoration (Lesson 18) all help.
Unit 9 is the single largest exam weight (15–20%), and these impacts — sea-level rise (thermal expansion + melting land ice), coral bleaching, ocean acidification chemistry, HIPPCO, and invasive/endangered species — are its heart. Expect data interpretation (Keeling curve, pH trends) and solution FRQs. This lesson also synthesizes tolerance (L6), populations (L7–8), biodiversity (L4), and conservation (L18).
Name the two main causes of sea-level rise from climate change.
Solution: (1) Melting land ice (glaciers and ice sheets adding water to the ocean) and (2) thermal expansion (seawater expands as it warms). (Note: melting sea ice doesn't raise sea level much, since it's already floating.)
Interpretation: Land-ice melt + thermal expansion. Floating sea ice is a distractor.
Explain how rising atmospheric CO₂ leads to ocean acidification and why it harms coral.
Solution: Excess atmospheric CO₂ dissolves into seawater, forming carbonic acid, which lowers ocean pH and reduces available carbonate ions. Corals need carbonate to build their calcium carbonate skeletons, so acidification makes reef-building harder — weakening or dissolving structures and threatening reef ecosystems.
Interpretation: CO₂ → carbonic acid → lower pH → less carbonate → weaker shells/skeletons.
A frog species is declining due to a drained wetland, a introduced predatory fish, and a warming climate. Identify the HIPPCO factors involved.
Solution: Habitat destruction (drained wetland), Invasive species (introduced predatory fish), and Climate change (warming beyond the frog's tolerance). Multiple HIPPCO drivers often act together.
Interpretation: Name each driver by its HIPPCO letter; real declines usually stack several.
Explain why an introduced species often spreads explosively in a new ecosystem.
Solution: In its new range, an invasive species typically lacks natural predators, parasites, and competitors that controlled it in its native range. With those checks removed and often broad tolerance (generalist traits), its population grows rapidly (near-exponential) and outcompetes or preys on natives, reducing biodiversity.
Interpretation: No natural enemies → unchecked growth → harm to natives.
(B) Listed species and their critical habitat.
Rising CO₂ enhances the greenhouse effect, and the oceans absorb most of the excess heat → ocean warming (harm: coral bleaching as heat-stressed corals expel symbiotic algae). The oceans also absorb much of the CO₂ itself, which forms carbonic acid, lowering pH → ocean acidification (harm: shell/skeleton-building organisms struggle as carbonate ions decline).
(a) Bleaching ← ocean warming (heat stress); shellfish decline ← ocean acidification (harder to build shells). (b) Global: reduce CO₂ emissions (renewables, efficiency). Local: protect the reef from other stressors (reduce runoff/pollution, limit fishing, establish an MPA).
FRQ rubric (10 pts): - (a) 1 pt melting land ice; 1 pt thermal expansion of seawater. (2) - (b) 1 pt oceans absorb excess heat → warming → coral bleaching (expel symbionts); 1 pt oceans absorb CO₂ → carbonic acid → lower pH; 1 pt reduced carbonate impairs shell/skeleton formation in shellfish/coral. (3) - (c) 1 pt spreads fast because it lacks natural predators/competitors in the new range; 1 pt HIPPCO category = Invasive species. (2) - (d) 1 pt climate solution (cut CO₂ via renewables/efficiency, reforestation) + justification; 1 pt invasive-species solution (removal, prevention/ballast rules, biological control, early detection) + justification; 1 pt both plausibly address the named problem. (3)
A coastal region faces rising seas, a bleaching coral reef, declining shellfish, and an invasive predatory fish spreading through its bays.
(a) Explain the two main causes of the sea-level rise. (2 pts) (b) Explain how CO₂ drives both the coral bleaching and the shellfish decline (name the distinct mechanisms). (3 pts) (c) Explain why the invasive fish spreads rapidly and identify its HIPPCO category. (2 pts) (d) Propose two solutions — one addressing climate/CO₂ and one addressing the invasive species — and justify each. (3 pts)
MC: 1. (B) Melting land ice and thermal expansion. 2. (B) CO₂ dissolving to form carbonic acid. 3. (B) Heat stress causing corals to expel symbiotic algae. 4. (B) Habitat destruction. 5. (B) Lack natural predators and competitors. 6. (B) Steadily rising atmospheric CO₂. 7. (B) A specialist endemic with a small range. 8. (A) Shell- and skeleton-building organisms. 9. (C) Overexploitation. 10. (B) Listed species and their critical habitat.
Rising CO₂ enhances the greenhouse effect, and the oceans absorb most of the excess heat → ocean warming (harm: coral bleaching as heat-stressed corals expel symbiotic algae). The oceans also absorb much of the CO₂ itself, which forms carbonic acid, lowering pH → ocean acidification (harm: shell/skeleton-building organisms struggle as carbonate ions decline).
(a) Bleaching ← ocean warming (heat stress); shellfish decline ← ocean acidification (harder to build shells). (b) Global: reduce CO₂ emissions (renewables, efficiency). Local: protect the reef from other stressors (reduce runoff/pollution, limit fishing, establish an MPA).
FRQ rubric (10 pts): - (a) 1 pt melting land ice; 1 pt thermal expansion of seawater. (2) - (b) 1 pt oceans absorb excess heat → warming → coral bleaching (expel symbionts); 1 pt oceans absorb CO₂ → carbonic acid → lower pH; 1 pt reduced carbonate impairs shell/skeleton formation in shellfish/coral. (3) - (c) 1 pt spreads fast because it lacks natural predators/competitors in the new range; 1 pt HIPPCO category = Invasive species. (2) - (d) 1 pt climate solution (cut CO₂ via renewables/efficiency, reforestation) + justification; 1 pt invasive-species solution (removal, prevention/ballast rules, biological control, early detection) + justification; 1 pt both plausibly address the named problem. (3)
⭐ Exam strategy: For Unit 9 — the exam's biggest — keep the two ocean effects separate (warming → bleaching; CO₂/acid → shell trouble), remember sea-level rise = land-ice melt + thermal expansion, and use HIPPCO as your checklist for any biodiversity-loss question.
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