Transcript Slide 1
Ecological Succession – ecological succession - ecosystem change from an early, immature, transient stage to a more mature and final stage (climax community) – examples: clearcuts to mature forest, burned prairies to mature grasslands – seral stages – a temporary, distinct stage in succession – primary succession - on sites previously unoccupied by living organisms; lava flows, volcanic islands – secondary succession - on sites where organisms existed; burned or cut areas – structure and function of ecosystem becomes more complex with each seral stage – disclimax - system held at a stage below climax by some disturbance; longleaf pine forests, some prairie areas – biologists are interested in which stages support different organisms; some depend on early stages (quail) some on old-growth stages (woodpeckers, goshawk); many animals rely on several stages for food or shelter Niche and Environment – niche - role or function of an organism in the biotic community; includes trophic level (feeding level), foraging location (forest, pasture, etc.), where it feeds (canopy, mid-story, ground, etc.), what it eats (insects, seed, etc.), what size food it eats (large or small seeds) – habitat - set of environmental conditions under which an individual, species, or community exists; can have seasonal habitats – environment - habitat of an organism plus all surrounding conditions (flooding regimes, regular weather patterns, etc.) – microhabitat - small area of intensive use within the habitat of an organism; dead logs for salamanders, nest sites for birds – guild - group of organisms that use resources in similar patterns and often have much niche overlap (bottom feeder fish, insectivorous birds, grazers on the African plains) Competition – occurs when 2 or more organisms living in the same area try to use the same resource that is in limited supply – 2 types 1. interspecific - between 2 or more species; density dependent 2. intraspecific - within a species; highly density dependent For interspecific (between 2 or more species): – niche segregation - species can overlap on several niche dimensions and still not have competition; hawk and owl (same area and food but different time of day) – competitive exclusion principle (Gause’s principle) - no 2 species can completely occupy the same niche indefinitely; one species will win (outcompete) and the other perish Examples: sunfish partition food in a pond, they’ll feed in different levels of the water column; yellow and red-winged blackbirds will partition nesting sites when using the same area of a marsh – in natural, undisturbed systems, interspecific competition (niche partitioning) has been worked out by co-evolution; problems usually arise when we introduce exotic species into a system (giant marine toad, fish from SE U.S. moved to west coast U.S., many plant problems) Gause’s paramecium experiment Niche partitioning by warblers in a New England forest For intraspecific (within a species): – species sometimes partition habitat by sexual dimorphism (smaller male hawks take smaller prey than females) 2 categories: 1. exploitative competition - individuals divide resource and suffer same ill effects (reduced birth rates, poor body condition); most fish populations 2. contest (interference) competition - some individuals do better than others in obtaining a resource (dominance, larger body size, faster, etc.); typical with carnivores Home Range and Territory – home range - the area within which an individual animal normally travels in its daily activities – geographic range (species range) - boundary of a species – individuals change home range seasonally due to weather, habitat condition, food availability, and reproductive condition – you can identify seasonal or annual home range; useful to know when an animal needs specific resources Examples: turkeys need nesting, feeding, and roosting habitat; deer in cold regions have summer grazing lands and wintering grounds in forested bottoms – territory - portion of home range defended against others of the same or closely related species; deals with space requirements Examples: most large carnivores defend a hunting area; birds use displays and songs to delineate a nesting and foraging area during the breeding season – pack territory - area defended by several individuals acting as a single unit; wolf packs – territories can be seasonal if individuals must group together during certain seasons; still have individual distance requirement that they will defend Examples: migrating birds travel as flocks, deer group together on wintering grounds