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TROPICAL RAINFOREST PAGE 37-43 OBJECTIVES • Describe and explain distribution of tropical rainforest. • Describe the features of tropical rainforests. • Describe how tropical rainforest adapt to the environment. OVERVIEW DISTRIBUTION ADAPTATIONS TROPICAL RAINFOREST PLANTS STRUCTURE RAINFOREST DISTRIBUTION Location of tropical rainforests Location of tropical rainforests DISTRIBUTION • Found in places between 10°N and 10°S of the Equator • Mainly located in Amazon Basin, Congo Basin, and parts of Southeast Asia such as Malaysia and Indonesia. DISTRIBUTION DISTRIBUTION • Why?: high temperatures (27°C) and high rainfall (above 1500mm) throughout the year. • This promotes abundant plant growth which is typical of tropical rainforests. RAINFOREST STRUCTURE PAGE 38 STRUCTURE • 5 distinct layers: Emergent, Canopy, Understorey, Shrub, Undergrowth • [You are expected to label/ describe every layer in detail] STRUCTURE • Emergent: – 30-50m – Tall trees (Emergent trees) – Tall, thick, straight trunks • Canopy – 15-30m – Wide, umbrella shaped crowns – Continuous leaf cover called canopy STRUCTURE • Understorey – 6-15m – Narrower, oval-shaped crowns (?) – Young trees of canopy, emergent • Shrub – 5m – Tree saplings, woody plants STRUCTURE • Undergrowth – 0-5m – Grasses, ferns, mosses, fungi – Sparse growth (?) RAINFOREST CHARACTERISTICS PAGE 40-43 C#1 • The undersgrowth in a tropical rainforest is sparse. • This is because, little sunlight RAINFOREST FEATURES #1: Sparse Undergrowth • There is sparse undergrowth in the forest floor of the tropical rainforest. • This is because very little sunlight (about one percent) passes through the canopy and reaches the forest floor. #2: Large Variety • There is a large variety of plants in the tropical rainforest. It is estimated that rainforests may contain more than 750 species of trees and 1500 species of other plants. • This is because of consistent high temperature and rainfall throughout the year that promotes plant growth. #3: Extreme density • Tropical rainforests are extremely dense due to the presence of a large variety of plant species which can grow in the tropical rainforest. #4: Evergreen Leaves • Tropical rainforests have evergreen leaves due to the consistently high rainfall throughout the year. #5: Large & broad leaves • Tropical rainforests have large and broad leaves to maximise the surface area for photosynthesis. #6: Thin & smooth barks • Tropical rainforests have developed thin and smooth barks because there is no need for protection against cold or dry conditions. #7: Buttress Roots • Some trees in the tropical rainforest have buttress roots, which are thick and spread out widely to support the great weight of trees. RAINFOREST ADAPTATIONS #1: Low Light • The canopy layer prevents sunlight from reaching the lower layers of the tropical rainforests. • Some plants such as the epiphytes and lianas have adapted to this low light condition by growing on tree branches. • Furthermore, these trees have branches only on the top one-third portion of the trunks to get maximum sunlight. #2: Bacteria Growth • High temperature and high rainfall in the tropical regions promote rapid growth of bacteria. • Hence, tropical rainforest have waxy leaves with drip tips to allow rainwater to drain off easily. • This prevents harmful bacteria from growing and protects the plants from diseases. #3: Still air below canopy • The presence of the continuous canopy results in still air in the layers below it and this does not allow pollination to be carried out by wind. • Hence, flowers and fruits in the tropical rainforest are colourful and sweet-smelling. • This attracts insects for pollination and animals for seed dispersal. #4: Rapid humus formation • High temperatures and rainfall all year round causes the leaf litter to decompose and form humus rapidly. • This supplies nutrients to the topsoil, which is the uppermost layer of the soil. • Hence, the roots of trees in the tropical rainforest are shallow and spread widely to absorb the nutrients present in the topsoil. RAINFOREST PLANTS EPIPHYTES • This refers to plants that grown on and use trees for physical support. • Rainwater and decaying leaves provide the epiphytes with water and nutrients. • Example: Bird’s Nest Fern, Orchids LIANAS • Refers to thick, woody vines that wind around tree trunks to reach for sunlight PARASITIC PLANTS • This refers to plants that compete with the host tree for space, sunlight and nutrients. • These plants are common in the canopy and understorey layer of the rainforest. • Example: Strangling Fig SUMMARY DISTRIBUTION ADAPTATIONS TROPICAL RAINFOREST STRUCTURE PLANTS Complete Review Worksheet #2