KO: Tropical Rainforests
Subject: Geography | Year: 7
Name: _________________________ Class/Set: ____________ Date: ____________
1. Climate and Location
- Latitude: Found along the Equator (0°) between the Tropics of Cancer and Capricorn.
- Temperature: Consistently high, averaging between 27°C and 28°C year-round.
- Rainfall: Very high, exceeding 2,000mm annually with no distinct dry season.
- Convectional Rainfall: Daily cycle; morning sun heats ground, moisture rises, cools, and falls as heavy afternoon storms.
- Humidity: High levels (80%+) due to constant heat and evapotranspiration from dense vegetation.
- Global Distribution: Major forests include the Amazon (South America), Congo (Africa), and Southeast Asia.
2. Key Vocabulary
- Biodiversity: The vast variety of different plant and animal species in a specific habitat.
- Buttress Roots: Massive, wide roots that provide stability for tall trees in thin, shallow soils.
- Drip-tips: Waxy leaves with pointed ends allowing heavy rain to run off quickly to prevent rot.
- Epiphytes: Plants that grow on branches of trees to reach sunlight high in the canopy.
- Lianas: Woody climbing vines that use tree trunks to reach the sunlight in the upper layers.
- Leaching: Process where heavy rainfall washes nutrients out of the soil, leaving it infertile.
- Latosol: The red, iron-rich, but nutrient-poor soil typical of the tropical rainforest.
3. Rainforest Structure
- Emergent Layer: Highest layer (up to 50m); contains tallest trees spaced apart, receiving maximum sunlight.
- Canopy Layer: Thick, continuous 'umbrella' layer (20-30m) housing 80% of rainforest life.
- Understorey: Low-light layer; contains smaller trees and saplings adapted to shade.
- Shrub Layer: Dark, humid area near the ground with ferns and soft-stemmed plants.
- Forest Floor: Very dark (2% sunlight); covered in leaf litter that decomposes rapidly.
- Stratification: The distinct vertical layers of the forest created by competition for light.
4. Nutrient Cycling (Gersmehl Diagram)
- Biomass Store: The largest nutrient store; trees and plants hold most of the forest's minerals.
- Litter Store: Small store; dead leaves/twigs fall to the floor but decompose extremely quickly.
- Soil Store: Smallest store; nutrients are absorbed by trees almost instantly or washed away by rain.
- Rapid Decomposition: Heat and moisture allow bacteria to break down organic matter in days.
- Nutrient Transfer: Fast movement from soil to biomass ensures the forest stays lush despite poor soil.
- The Cycle: Nutrients move from Litter → Soil → Biomass → back to Litter.
5. Deforestation: Causes and Impacts
- Cattle Ranching: Largest cause (e.g., Amazon); clearing vast areas for commercial beef farming.
- Logging: Felling high-value hardwoods like Mahogany and Teak for furniture and construction.
- Subsistence Farming: Small-scale clearing by local farmers to grow crops for their families.
- Mineral Extraction: Open-cast mining for gold, copper, and bauxite (aluminium ore).
- Soil Erosion: Without tree roots to bind soil, heavy rain washes away the fertile topsoil.
- Climate Change: Burning trees releases stored Carbon Dioxide (CO₂), contributing to global warming.
- Loss of Biodiversity: Destruction of habitats leads to the extinction of plant and animal species.
6. Adaptations and Biodiversity
- Sloths: Move slowly and have green algae in fur for camouflage against predators.
- Toucans: Long, strong beaks allow them to reach fruit on branches too thin to support their weight.
- Spider Monkeys: Prehensile tails act as a 'fifth limb' for swinging through the canopy.
- Pitcher Plants: Carnivorous plants that trap insects to gain nutrients missing from the soil.
- Medicinal Value: 25% of modern medicines originate from rainforest plants (e.g., Quinine for Malaria).
- Indigenous Tribes: Groups like the Yanomami live sustainably, using only what they need from the forest.
✍️ Knowledge Check: Student Task
Task A: Identify the four main layers of the rainforest and describe one characteristic of each.
Task B: Define 'Leaching' and explain why it happens in the rainforest.
Task C: List three major causes of deforestation in the Amazon.
⚠ TEACHER’S GUIDANCE
💡 Pedagogical Pulse
- Delivery: Use this Knowledge Organiser as a "placemat" during the Rainforest unit. For Year 7, focus on the "Daily Weather Cycle" and the "Layers" first, as these are the most concrete concepts.
- Misconception Alert: Students often think rainforest soil is very fertile because the trees are so big. Explicitly teach the Nutrient Cycle to show that nutrients are held in the Biomass, not the Soil.
- Oracy Tip: Use the "Key Vocabulary" for a 'Taboo' style starter game to build Tier 3 lexical confidence.
✅ Answer Key & Solutions
- Task A Answer: 1. Emergent: Tallest trees/high light. 2. Canopy: Dense 'roof' of leaves. 3. Understorey: Dark/humid. 4. Forest Floor: Leaf litter/decomposition.
- Task B Answer: Leaching is the removal of nutrients from the soil. It happens because heavy, frequent rainfall washes the minerals down through the soil profile, away from the roots.
- Task C Answer: Any three from: Cattle Ranching, Logging, Mining, Road Building, or Subsistence Farming.
