Transcript Slide 1
Objectives: 1. Know the dates of the Precambrian time period 2. Understand the ecological role of the primary producers of the Precambrian. 3. Understand how the marine organisms of the Precambrian changed the physical aspects of our planet. Precambrian • Spans from the formation of the earth 4.6 bya to 542 Mya. • The Precambrian accounts for 88% of geologic time • Precambrian fossil record is poor because many of the rocks have been metamorphosed, and the organisms are soft bodied. Archaea Bacteria • Archaebacteria emerged at least 3.5 billion years ago and are the oldest life forms. • Many live in extreme environments. Examples of Archea bacteria • Halophiles: Live in extremely salty environments • Thermophiles: Live in extreme heat • Methanogens: Obtain energy through the metabolism of methane gas Stromatalites • The oldest rock on earth (3.5 bya), located in australia include fossils of stromatalites. • Mats of blue-green algae (cyanobacteria) formed in shallow water by the trapping, and cementation of sedimentary grains. • The represent some of the most ancient forms of life. A New Atmosphere • cyanobacteria oxygen as a waste gas and so helped establish an aerobic ecosystem • They helped establish a stable oxygen rich atmosphere. • These new atmospheric conditions calmed the weather so that the extremes were less severe. Heterotrophic Bacteria • “hetero”= different • “trophic” = eating • Heterotrophic = Decomposers which use available organic matter to obtain energy. Biological Pump • Organic Carbon from dead organisms is transported by sinking particulate, some reaching the ocean floor. • Through bacterial respiration by decomposers, carbon is returned to the ocean as dissolved CO2 (Carbon dioxide) and Nitrogen is returned as N2 (nitrogen gas) • Decomposition processes are generally slower than Synthesis processes, which results in nutrients being transported from the ocean surface to the ocean floor. The Carbon and Nitrogen Cycle • Carbon Cycle: the movement of carbon between the abiotic (non-living) and biotic systems (living). • Nitrogen fixation: The process in which bacteria converts N2 gas into NH3 • Nitrification: Microbes convert NH3 into NO2 and NO3, that primary producers (cyanobacteria) can use. • Nitrogen is required to form amino acids and nucleotides. • Nitrogen is often a limiting nutrient in ecosystems.