Case Study • Read and summarize
Community Structure • Biological communities (ecosystems) are described by appearance: • Size, stratification, distribution of populations and species • Edges of ecosystems can vary and create a transition into another ecosystem
Species Diversity and Types of Species • Species diversity: • Coral reefs and rain forests have high species richness but low species evenness.
Types of Species • Native species: • Nonnative, alien, invasive, exotic species: • Some are beneficial (crops) • Most are harmful (reduce native species) • Indicator species:
Types of Species • Keystone species: • Foundation species: • Elephant pushing over larger trees allowing grasses to grow, which benefits smaller herbivores.
Species Interactions • Interspecific competition: • Resource Partitioning: • 5 species of insect eating warblers feed at different levels in the tree.
Species Interactions • Predator-prey relationships • Parasitism: • Mutualism: • Commensalism:
Ecological Succession: Communities in Transition • Ecological succession: • Primary succession: • Secondary succession:
Primary succession • Can take thousands of years to occur: • 1st: soil is formed (many years) by early successional species (lichen and mosses) that attach themselves to rocks and catch windblown soil particles, produce organic matter, secrete acids that break down the rock and add their own waste when dead to the soil. • 2nd: Once soil is formed it can support midsuccessional species (herbs, grasses and low shrubs) and trees that need lots of sunlight. • 3rd: trees bring in shade allowing late successional species (shade loving trees) to establish
Secondary succession • Occurs in areas that have be disturbed, removed or destroyed but soil remains. • Abandoned farmland, burned forest • Because soil is already present secondary succession does not take long.