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Transcript
Population Ecology Objective: I will apply my knowledge of population ecology to calculate populations based on field signs Different Species Playing Different Roles Biological communities differ in the types and numbers of species they contain and the ecological roles those species play. Species diversity: the number of different species it contains (species richness) combined with the abundance of individuals within each of those species (species evenness). Factors that determine species richness: • Latitude • Time • Habitat size Factors that Regulate Population Abundance and Distribution • • • • • Population size- the total number of individuals within a defined area at a given time. Population density- the number of individuals per unit area at a given time. Population distribution- how individuals are distributed with respect to one another. Population sex ratio- the ratio of males to females Population age structure- how many individuals fit into particular age categories. Population Distribution Patterns Competition • Competition- the struggle of individuals to obtain a limiting resource . Resource Patitioning Population Density and Population Change: Effects of Crowding A population’s density can affect how rapidly it can grow or decline (density dependent factors) • Ex: biotic factors like disease Some population control factors are not affected by population density (density independent factors) • Ex: abiotic factors like weather TYPES OF SPECIES 1. Native 2. Nonnative 3. Indicator 4. Keystone 5. Foundation species Native: I was here first! 1. Native: those that normally live and thrive in a particular community. 2. Nonnative (Invasive) species: those that migrate, deliberately or accidentally introduced into a community. Indicator Species: Biological Smoke Alarms 3. Indicator Species – A species that serve as early warnings of damage to a community or an ecosystem. • Ex: Presence or absence of trout species because they are sensitive to temperature and oxygen levels. eystone Species: Major Players 4. Keystone species - a species that plays a role in its community that is far more important than its relative abundance might suggest. • Help determine the types and numbers of other species in a community thereby helping Figures to sustain it. 7-4 and 7-5 Foundation Species: Other Major Players 5. Foundation species can create and enhance habitats that can benefit other species in a community. • Expansion of keystone species category. • Elephants push over, break, or uproot trees, creating forest openings promoting grass growth for other species to utilize. Theory of Island Biogeography • The theory that explains that both habitat size and distance to nearest mainland determine species richness. • Idea that immigration and extinction will reach equilibrium • Proposed by Wilson and MacArthur in mid1960s Case Study: Exploding White-Tailed Deer Populations in the United States • Since the 1930s the white-tailed deer population has exploded in the United States. • Nearly extinct prior to their protection in 1920’s. • Today 25-30 million white-tailed deer in U.S. pose human interaction problems. • Deer-vehicle collisions (1.5 million per year). • Transmit disease (Lyme disease in deer ticks).