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Ecology Population Ecology

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2 Populations 3. A population is a group of individuals of the same species living in an area

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Distribution Patterns Uniform distribution results from intense competition or antagonism between individuals. Random distribution occurs when there is no competition, antagonism, or tendency to aggregate. Clumping is the most common distribution because environmental conditions are seldom uniform. 3 Populations disperse in a variety of ways that are influenced by environmental and social factors

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Fig. 52.1, Campbell & Reece, 6 th ed. Clumped distribution in species acts as a mechanism against predation as well as an efficient mechanism to trap or corner prey. It has been shown that larger packs of animals tend to have a greater number of successful kills. What causes these populations of different organisms to clump together?

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Population Dispersal In rare cases, long- distance dispersal can lead to adaptive radiation For example, Hawaiian silverswords are a diverse group descended from an ancestral North American tarweed 5

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The Spread of the Africanized Honey Bee When did they first arrive in the Americas? How long did it take for them to expand their range into the US? How can you explain their success in expanding their territory? 6

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7 Estimating Population Size The Mark-and-Recapture Technique 1. 2. 3.

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Estimating Population Size The Mark-and-Recapture Technique 8

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Lets Try an Example! 9 Twenty individuals are captured at random and marked with a dye or tag and then are released back into the environment. Therefore s = # of animals marked = 20 At a later time a second group of animals is captured at random from the population

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Lets Try an Example! 10

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11 Which method would you use? 1. To determine the number of deer in the state of Virginia? 2. To determine the number of turkeys in a county? 3. To determine the number of dogs in your neighborhood? 4. To determine the number of ferrel cats in your neighborhood?

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Survivorship curves What do these graphs indicate regarding species survival rate & strategy? 025 1000 100 Human (type I) Hydra (type II) Oyster (type III) 10 1 50 Percent of maximum life span 10075 Survival per thousand I.High death rate in post-reproductive years II.Constant mortality rate throughout life span III.Very high early mortality but the few survivors then live long (stay reproductive)

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1,000 III II I 100 10 1 10050 0 Percentage of maximum life span Number of survivors (log scale) Ideal Survivorship Curves

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Population Growth Curves 14 d = delta or change N = population Size t = time B = birth rate D =death rate

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Population Growth Models

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Exponential Growth Curves 16 d = delta or change N = Population Size t = time r max = maximum per capita growth rate of population Population Size, N Time (hours) Growth Rate of E. coli

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Logistic Growth Curves 17

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Logistic Growth Curves 18 d = delta or change N = Population Size t = time K =carrying capacity r max = maximum per capita growth rate of population

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Comparison of Growth Curves 19

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Growth Curve Relationship 20

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Examining Logistic Population Growth Graph the data given as it relates to a logistic curve. Title, label and scale your graph properly. 21

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Examining Logistic Population Growth 22 Hypothetical Example of Logistic Growth Curve K = 1,000 & r max = 0.05 per Individual per Year

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Population Reproductive Strategies r-selected (opportunistic) Short maturation & lifespan Many (small) offspring; usually 1 (early) reproduction; No parental care High death rate K-selected (equilibrial) Long maturation & lifespan Few (large) offspring; usually several (late) reproductions Extensive parental care Low death rate

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24 Some populations overshoot K before settling down to a relatively stable density Some populations fluctuate greatly and make it difficult to define K How Well Do These Organisms Fit the Logistic Growth Model?

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Percent of population Rapid growth Afghanistan Slow growth United States No growth Italy Male Female Age 85+ 8084 7579 7074 6569 6064 5559 5054 4549 4044 3539 3034 2529 2024 1519 1014 59 04 Age 85+ 8084 7579 7074 6569 6064 5559 5054 4549 4044 3539 3034 2529 2024 1519 1014 59 04 100 88888866666644444422222200 Age Structure Diagrams: Always Examine The Base Before Making Predictions About The Future Of The Population

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Natural Selection This includes describing how organisms respond to the environment and how organisms are distributed. Events that occur in the framework of ecological time (minutes, months, years) translate into effects over the longer scale of evolutionary time (decades, centuries, millennia, and longer). 26

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Natural Selection 27

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Natural Processes 28

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Finch Beak Size or Shape 29

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Modes of Selection 30 http://gregladen.com/blog/2007/01/the-modes-of-natural-selection/

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Modes of Selection Disruptive- produces a bi- modal curve as the extreme traits are favored Stabilizing-reduces variance over time as the traits move closer to the mean Directional-favors a phenotypic trait (selected by the environment)

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Scenario 32 These photographs show the same location on Captiva Island following Hurricane Charley. What would happen to a population of birds who derive their diets from the tree tops? The population had a wide range of beak sizes. What would happen to the population gene pool over time if the new environment favored smaller beaks? Over time, which beak would be most represented in the population of birds?

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Selection Diagrams 33 ABC

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Beak Selection After Hurricane 34

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Hydrangea Flower Color Hydrangea react to the environment and ultimately display their phenotype based on the pH of their soil. Hydrangea flower color is affected by light and soil pH. Soil pH exerts the main influence on which color a hydrangea plant will display. 35

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Biogeographic Realms 36

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Introduced Species Whats the big deal? These species are free from predators, parasites and pathogens that limit their populations in their native habitats. These transplanted species disrupt their new community by preying on native organisms or outcompeting them for resources. 37

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Guam: Brown Tree Snake The brown tree snake was accidentally introduced to Guam as a stowaway in military cargo from other parts of the South Pacific after World War II. Since then, 12 species of birds and 6 species of lizards the snakes ate have become extinct. Guam had no native snakes. 38 Dispersal of Brown Tree Snake

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Southern U.S.: Kudzu Vine The Asian plant Kudzu was introduced by the U.S. Dept. of Agriculture with good intentions. It was introduced from Japanese pavilion in the 1876 Centennial Exposition in Philadelphia. It was to help control erosion but has taken over large areas of the landscape in the Southern U.S. 39

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New York: European Starling From the New York Times, 1990 The year was 1890 when an eccentric drug manufacturer named Eugene Schieffelin entered New York City's Central Park and released some 60 European starlings he had imported from England. In 1891 he loosed 40 more. Schieffelin's motives were as romantic as they were ill fated: he hoped to introduce into North America every bird mentioned by Shakespeare. Skylarks and song thrushes failed to thrive, but the enormity of his success with starlings continues to haunt us. This centennial year is worth observing as an object lesson in how even noble intentions can lead to disaster when humanity meddles with nature. 40

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New York: European Starling From the New York Times, 1990 (cont.) Today the starling is ubiquitous, with its purple and green iridescent plumage and its rasping, insistent call. It has distinguished itself as one of the costliest and most noxious birds on our continent. Roosting in hordes of up to a million, starlings can devour vast stores of seed and fruit, offsetting whatever benefit they confer by eating insects. In a single day, a cloud of omnivorous starlings can gobble up 20 tons of potatoes. 41

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42 Zebra Mussels The native distribution of the species is in the Black Sea and Caspian Sea in Eurasia. Zebra mussels have become an invasive species in North America, Great Britain, Ireland, Italy, Spain, and Sweden. They disrupt the ecosystems by monotypic (one type) colonization, and damage harbors and waterways, ships and boats, and water treatment and power plants.

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43 Zebra Mussels Water treatment plants are most impacted because the water intakes bring the microscopic free-swimming larvae directly into the facilities. The Zebra Mussels also cling on to pipes under the water and clog them. This shopping cart was left in zebra mussel-infested waters for a few months. The mussels have colonized every available surface on the cart. (J. Lubner, Wisconsin Sea Grant, Milwaukee, Wisconsin.)

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44 Zebra Mussel Range

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INQUIRY: Does feeding by sea urchins limit seaweed distribution? W. J. Fletcher of the University of Sydney, Australia reasoned that if sea urchins are a limiting biotic factor in a particular ecosystem, then more seaweeds should invade an area from which sea urchins have been removed. 46

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INQUIRY: Does feeding by sea urchins limit seaweed distribution? Seems reasonable and a tad obvious, but the area is also occupied by seaweed-eating mollusc called limpets. What to do? Formulate an experimental design aimed at answering the inquiry question. 47

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Predator Removal 48

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Predator Removal 49 Removing both limpets and urchins or removing only urchins increased seaweed cover dramatically

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Predator Removal 50 Almost no seaweed grew in areas where both urchins and limpets were present (red line), OR where only limpets were removed (blue line)

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Created by: Susan Ramsey Virginia Advanced Study Strategies Notable contributions by S.Meister