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Transcript
Chapter 31 Depend on many interactions Between living things Between living things and nonliving parts of the environment Organism relationships Nutrient/Chemical cycles Community: all of the interacting living things in an environment Various sizes They overlap and are not predetermined entities Ecosystem: all of the communities and the physical (nonliving) parts of an environment Species richness: a total listing of all the species in the area See pg 559—differences between a pine forest and rain forest Can vary from place to place in types of species and number of species Diversity: species richness and distribution It’s not just how many species are in an area What if there is only one member of a given species? What if one type of plant represents 99% of the plants in that area? Change in an ecosystem over time Can be due to: A disturbance Volcano eruption, fire, tornado Gradual change over time End of an ice age, gradual warming, continental drift, silting in a body of water Two Types Primary—have to make soil from scratch Secondary—soil and maybe some seeds already present First to appear in an area Small, quick growing, hardy, opportunistic Often lichens and mosses Can break down rock into dirt Add organic matter soil Pioneer animal species = herbivore insects followed by small insectivores Equilibrium species Larger, k-strategy individuals Deer, wolves, large trees Ecological Niche—the role an organism plays in its community Habitat—the physical place where an organism lives Both can range from very general to very specific Recall risk factors for extinction Competitive Exclusion Principle No two species can occupy the same niche at the same time Competition between two species in the same niche will eventually lead to one of the species being displaced in that area Small or large scale This can lead to specialization of niches Resource partitioning; pg 563 Increases specialization and can drive evolution Can be very subtle I’ll scratch your back if you’ll scratch mine! Both members benefit, sometimes to the point of codependence Pollinators and flowers Lichens Ants and various plant Pg 564, middle paragraph Keystone species—one species that is disproportionately important for the stability of an ecosystem Not always the most numerous Bats, grizzly bears, otters Native = indigenous to an area Exotic = nonnative Can greatly disrupt an ecosystem No natural predators or competitors Native species have not had a chance to evolve defenses Ex: myrtle trees in Hawaii, fox and rabbit in Australia, brown tree snakes in Guam, black rats in Galapagos, zebra mussels in U.S. Autotrophs—make their own food Photosynthesis—plants, algae, blue-green algae Chemosynthesis—caves and hydrothermal vents—all bacteria Heterotrophs—get food from consuming other organisms Herbivores Carnivores Omnivores Decomposers—feed on detritus Law of conservation of matter—remember??? What we have on Earth is all we have, so individual atoms MUST be recycled Many interactions between autotrophs, heterotrophs, and parts of the physical environment as well Water in ground, on ground, in air Elements sometimes sequestered in rock layers for long time periods Cycling of atoms can be quick or very slow Food chains—follow one flow of energy from autotroph herbivore carnivore (or omnivore) decomposer and back to autotroph Each step is a trophic level Number of organisms at each trophic level gets smaller and smaller—Rule of 10 Forms an ecological pyramid Food webs—follow total energy in a community with all of its twists and turns Life, physical world recycling atoms There’s a cycle for almost everything Main: Phosphorous Nitrogen Carbon Rate at which producers capture and store energy and nutrients Pg 576—deserts vs. swamps and rain forests