True or False The quotient of two polynomial expressions is a rational expression. (pp. 61-68)
Announcements Exam II: all answers were accepted for number 39 If you find errors on the grading of your exam please email me (or argue any points) Do this before the 3 Exam next Thursday Exam III will cover material since Exam II and will include up to next Tuesday Exam III will be available beginning at 10am and will close at 3pm on April 14 50 questions, 2 points each, all multiple choice Your questions will come from a large pool of questions and you may not have the same questions as someone else but all questions cover the same material and difficulty level You will be able to see your score at 3:01pm Announcements The Final Exam will be available on the Pearson site from 12 noon on May 2 until 12 noon on May 5 You will have a time limit of 3.5 hours to complete it Once you begin the exam you must complete the exam then There will be 100 questions Multiple choice 1 point each The post-test will be available for the final two weeks and will help you practice/study for the Final Exam © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. iClicker (set to AA) Species richness (S), takes into account which of the following A) presence of individuals of a species B) abundance of individuals of a species C) biomass of a total species in an area D) how much better one species is compared to another E) the money in a species’ bank account Chapter 18 Community Dynamics Many processes interact to influence community structure How does the structure of a community change through time Community Structure Changes through Time Succession is the temporal change in community structure at a given location Abandoned cropland can go through succession First, grasses and weedy herbaceous plants colonize Then shrubs invade Over time, these shrubs are replaced by pine trees, eventually forming a closed-canopy forest Hardwood trees begin to occupy the understory Eventually, deciduous hardwoods dominate the landscape Figure 18.1 Time © 2015 Pearson Education, Inc. BUT… $#IT Happens Mt. St. Helens, 1980 Mt. St. Helens, 2012 © 2015 Pearson Education, Inc. Yosemite Valley, 2014 © 2015 Pearson Education, Inc. Near Sleeping Bear Dunes, Michigan, August 2015 © 2015 Pearson Education, Inc. Alligator Hill, Sleeping Bear Dunes, Fall 2015 © 2015 Pearson Education, Inc. Hurricane Katrina, 2005 © 2015 Pearson Education, Inc. Gulf Oil Spill, 2010 © 2015 Pearson Education, Inc. Tunguska Event, 1908 © 2015 Pearson Education, Inc. The Barringer Crater, Arizona Kīlauea's East Rift Zone (Puʻu ʻŌʻō) Eruption 1983 to present © 2015 Pearson Education, Inc. Glacier National Park, Montana, 2009 © 2015 Pearson Education, Inc. Japan earthquake and subsequent tsunami, 2011 © 2015 Pearson Education, Inc. Large-scale forestry in the western United States © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. Chernobyl (Чернобыль) & Pryp’yat’ (Прип'ять), Ukraine ́ after nuclear accident in 1986 Krakatoa (anak Krakatau) exploded ~1883 © 2015 Pearson Education, Inc. iClicker (set to AA) • How long does it take communities to develop over time (Choose the most reasonable) • A) just a few thousand years • B) it varies depending on many factors (biotic and abiotic factors play a huge role) • C) since a Monday a long time ago • D) billions of years Community Structure Changes through Time A sere is the sequence of communities seen in succession, from grass to shrub to forest Each of the changes is a seral stage, a point on the continuum of vegetation through time These stages often can be recognized as distinct communities, with characteristic structure and species composition Stages may last years or decades Some stage may be missed or abbreviated/altered IT MAY BE DIFFICULT TO DELINEATE STAGES! Community Structure Changes through Time Early successional species are the initial colonists, or pioneer species. Often have: high growth rates smaller size high degree of dispersal and colonization high rates of per capita population growth Community Structure Changes through Time Late successional species arrive later. Often have: longer lifespans larger size lower rates of dispersal and colonization lower rates of per capita population growth The patterns of species replacement through time are not random MUCH STRUCTURE Can be reset… Primary Succession Occurs on Newly Exposed Substrates Dunes can shift, covering existing vegetation or even buildings Plant cover stabilizes the dunes Sleeping Bear Dunes, Michigan © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. Primary Succession Occurs on Newly Exposed Substrates Plant succession on the dunes of Lake Michigan Very early ecological study (1899) Subsequent study quantified the successional patterns by examining a chronosequence of dunes determined by radiocarbon dating A chronosequence (chronosere) is a series of sites within an area that are at different successional stages (seral stages) This allows space to substitute for time Primary Succession Occurs on Newly Exposed Substrates The successional stages seen are similar to the order described earlier Pioneering species – grasses, mainly beach grass stabilize the dune with extensive rhizomes Then mat-forming shrubs colonize Subsequently, trees invade: first pine, then oak Sand has low moisture reserves Trees that need more moisture (mesophytic) rarely succeed the pines and oaks except in depressions or other areas where moisture accumulates Figure 18.4b 100 Beach grass Shrub-bunchgrass Conifers 80 Hardwoods 60 40 Percent cover 20 0 0 100 200 300 400 500 Dune age (yr) (b) Figure 18.5b Grand Pacific Gl. Muir Gl. Riggs Gl. Canada Alaska McBride Gl. 1940 1912 1948 1907 Plateau Gl. 1899 1941 1892 1931 1879 1911 Casement Gl. 1907 1931 1892 1900 1892 1879 1879 1913 1935 1949 1880 Muir Inlet Reid Gl. 1860 John 1857 Hopkins 1879 Bear Track 1860 Glacier 1845 Cove Gl. Bay 1830 1780 Bartlett Cove 1760 0 8 16 24 km Pleasant I. (b) © 2015 Pearson Education, Inc. Figure 18.5c 100 90 Alder Willow 80 Cottonwood Spruce 70 /ha) Hemlock 2 60 50 40 Basal area (m 20 10 0 55 90 110 165 225 500 (c) Site age (years) Species Diversity Changes during Succession Colonization increases species richness Species replacement results from the inability of a species to tolerate changing environmental conditions or competition Over time, species replacement decreases richness The peak in diversity during mid-successional stages is a transition period, after later successional species have arrived but before early successional species are replaced What influences the rate of displacement Species Diversity Changes during Succession Intermediate disturbance hypothesis The highest species diversity is seen at intermediate frequencies of disturbance Figure 18.24 18,000 yr B.P. 8000 yr B.P. (a) (b) © 2015 Pearson Education, Inc. Community Structure Changes over Geologic Time When the climate began to warm, the ice sheet retreated north By 8000 years B.P ., ice was restricted to areas in northern Canada Plant species began to invade formerly glacier- covered areas Pollen from tree species settled into lake sediments Cores from these sediments (dated by radiocarbon dating) can be used to map the northward advances of different genera of trees over the past 18,000 years Figure 18.25 10 6 8 12 12 14 12 14 Picea spp. Pinus strobus Spruce White pine 0 400 km 0 400 km (a) (b) 8 6 7 8 9 10 10 11 12 12 13 14 14 Quercus spp. 18 Acer spp. Oak Maple 0 400 km 0 400 km (c) (d) © 2015 Pearson Education, Inc. Figure 18.26 40,000 B.P. 18,000 B.P. 14,000 B.P. 10,000 B.P. 5000 B.P. 200 B.P. Laurentide ice sheet Deciduous forests Southeastern evergreen forests Open vegetation types Oak–hickory Oak–hickory–southern pine Oak savanna Tundra Boreal forests Mixed hardwoods Southern pine Prairie Spruce Oak–chestnut Cypress–gum Sand dune scrub Spruce–jack pine Subtropical hardwoods Jack pine–spruce Mixed conifer–northern hardwoods © 2015 Pearson Education, Inc.