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Tropical Rainforest Emergent layer Canopy Understory Forest floor Division of Layers • Emergent Layer: Contains the tallest trees in the rainforest(150~200 feet). Windy, relatively dry, lots of sun. • Canopy: The primary layer of the rainforest(15~150 feet). Sun, humidity, water, shelter, leaves, flowers, fruit. • Understory: Seldom grow to more than 12 feet.Difficulty with pollinization because of the lack of air movement. Filtered sun, high humidity, lack of air movement. • Forest Floor: Almost no plants (because 0-2% light & 100% humidity). Few flowering plants, mosses, herbs, and fungi. Species Diversity A mature tropical rainforest has incredible diversity. Why? There are a variety of specialized niches in distinct layers (based mostly on their need for sunlight). Biodiversity Scales of organization • genetic -- diversity of genetic information found within species and populations • species -- diversity of species • community -- diversity of community composition • ecosystem -- diversity of assemblages of communities (Fox River watershed) • landscape -- diversity of assemblages of ecosystems (Western Great Lakes) Definitions: • Sustainability or stability: Maintained by a constant dynamic change in response to changing environmental conditions. Usually comes with high biodiversity. • Persistence or inertia: The ability of a living system to resist being disturbed or altered. • Constancy: Ability of a system (population) to keep its numbers within the limits imposed by available resources. • Resilience: Ability of a living system to bounce back after an external disturbance that is not too drastic. Natural Extinctions • Habitat Disruption – Volcanic Eruptions – Asteroid Impact • Habitat Modification – Climate Change – Mountain-Building – Sea Level Change • “Exotic” Species – Continental Drift Things that Probably Don’t Cause Natural Extinctions • Epidemics – Rapid co-evolution of disease and host • Evolution of New Competitors in Place – Existing organisms already well-adapted Human-Caused Extinction • Excessive Predation (Food, fur, collecting, pest eradication, etc.) • Habitat Destruction • Destruction of keystone species • Introduction of Exotic Species – Competitors – Predators – Diseases • Pollution and Contamination
