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Bell Ringer 1. Why is the population changing so drastically? 2. What factors are affecting the change? 3. Will the population continue to grow indefinitely? WORLD CLOCK 10 minutes Objectives • Students will use data and information about population dynamics, abiotic factors, and/or biotic factors to explain and/or analyze a change in carrying capacity and its effect on population size in an ecosystem. http://video.nationalgeographic.com/video/news/7-billion/ngm-7billion After watching this video, stop and jot the following questions: 1. Does over population concern you? 2. What would zero population growth look like? 3. How could we design a society that can sustain itself at zero population growth? 1. How does a population increase? 2. How does a population decrease? 3. What are possible consequences of a constantly increasing population? Change in Population = Exponential Growth • Exponential growth occurs when the individuals in a population reproduce at a constant rate. • Under ideal conditions with unlimited resources, a population will grow exponentially. Logistic Growth • As resources become less available, the growth of a population slows down or stops. • Logistic growth occurs when a population’s growth slows or stops after a period of exponential growth. Which graph is indicative of natural growth within a population? Can you think of an example of exponential growth? Logistic growth? Boom then stable Boom and Bust 1. Where do you see exponential growth in the world? 2. Where might you see logistic growth? Can you think of some resources that could limit population growth? Characterize these resources as abiotic or biotic? largest number of individuals a given environment can support. Limiting Resources Population size (N) Carrying capacity is the Carrying capacity (K) What does each part of the graph mean? Exponential growth Time (t) Exponential and Logistic Population Growth: J-Curves and S-Curves • As a population levels off, it often fluctuates slightly above and below the carrying capacity. Limits to Growth • Limiting factor: a factor that causes population growth to decrease. • Density-dependent factors are limiting factors that depend on population size. (usually due to biotic) • Competition • Intraspecific • interspecific • Predation • Parasitism • Disease • Food • Shelter • Water • Space Predator – Prey Relationship Darwin Lied Density-Independent Limiting Factors • Affect a population no matter what its size is (usually abiotic) • Unusual weather • Drought • Floods • Natural disasters • Seasonal cycles • Certain human activities • Damming rivers • Clear-cutting forests • Forest Fires Wolf and Moose Populations on Isle Royale Harsh Winter 60 2400 Parvovirus arrives 50 2000 400 40 1600 30 1200 20 800 10 0 1955 400 Harsh Winters 0 1960 1965 1970 1975 Moose 1980 Wolves 1985 1990 1995 Human Population Growth • Until about 500 years ago, the world’s human population remained fairly stable. • Then, as advances in medicine, agriculture, and technology occurred, the human population began growing very rapidly. Industrial Revolution • Today the world’s Today, the begins Agriculture begins Bubonic human population plague Plowing and is greater than 7 irrigation billion people, and it continues to grow, but at a slower rate. Think-Pair-Share • Are humans susceptible to the kind of resource shortages that affect the populations of the other species? • What might the ideal graph for humans look like over the next 200 years? Which of the populations show seasonal fluctuations? (The rabbit, fox, and warbler.) 1. What do you think is causing the Warbler populations to shrink? 2. How do you think the populations of the rabbits and the foxes are related? Accountability Talk • • • • • You have 5 min to respond to your question Then rotate You have 1 min to read You have 5 min to respond Repeat until the same person gets their paper back (3 more rotations) • Do you agree with your original statement? 5 minutes 1 minute 5 minutes White Board Attack!!!! 1. When brown tree snakes were first introduced to the island of Guam, they had no natural predators. These snakes ate many of the eggs of insect-eating birds. What probably occurred after the introduction of the brown tree snakes? A. The bird population increased. B. The insect population increased. C. The bird population began to seek a new food source. D. The insect population began to seek a new food source. 2. A population of organisms grows briefly and then stabilizes. What does the leveling off of the population size indicates? A. The population has reached the carrying capacity of the ecosystem B. The population has exceeded the carrying capacity of the ecosystem C. The population is affected by a densityindependent limiting factor D. The population is no longer able to adapt to environmental changes 3. The number of pythons found throughout Everglades National Park has increased in recent years. These huge snakes are not native to Florida and are believed to have been released into the wild by pet owners. Wildlife biologists have initiated attempts to capture and remove these pythons. Which statement best explains the biologists’ reason for removing these pythons from the Everglades? A. The pythons could upset the territorial boundaries of native organisms. B. The pythons could adapt to overcome diseases common to native snakes. C. The pythons could prey on native organisms and cause native populations to decline. D. The pythons could begin to interbreed with native snakes and produce a more successful species. 4. Which of the following is an example of primary succession? A. lichens growing on rocks following a volcanic eruption B. grasses growing after a forest fire C. oak trees replacing pine trees in a forest D. non-native species introduced into a climax community 5. Draw a graph (with no units or numbers) that clearly labels exponential growth, logistical growth and carrying capacity. Exit Slip 5 minutes Home Learning • Students will review and use vocabulary terms learned in today’s lesson for a minimum of 4 sentences, to describe how they observe changes the ecosystems where they live.