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deer population dynamics What is happening to this population? 20 number of deer 18 16 14 12 10 Why doesn’t the population ever go above 18? 8 6 4 2 0 0 2 4 6 8 Year 10 12 14 Carrying Capacity The number of organisms of one species that an environment can support indefinitely. 18 is the Carrying Capacity for our population. deer population dynamics 20 number of deer 18 16 Why does population increase? 14 12 10 8 6 4 2 0 0 2 4 6 8 Year 10 12 14 Population Growth • An increase in the number of individuals in a population Unlimited resources and reproduction lead to population growth (G) Growth = Births – Deaths (G = B – D) Population Growth When births exceed deaths you see population growth. 600 500 J-Shaped Curve 400 300 Series1 200 100 0 0 2 4 6 8 10 12 Exponential Growth • Exponential growth means that as a population gets larger, it also grows at a faster rate. 600 500 J-Shaped Curve 400 300 Series1 200 100 0 0 2 4 6 8 10 12 Reproduction Patterns: Rapid life-history patterns • Rapid life-history patterns are common among organisms from changeable or unpredictable environments. 20 MINUTES! Reproduction Patterns: Slow life-history patterns • Large species that live in more stable environments usually have slow lifehistory patterns. • Reproduce and mature slowly, and are longlived. 22 MONTHS! • Maintain population sizes at or near carrying capacity. Growth Limitations • Resources such as food and water • Disease • Organism interaction • Habitat Size/space Crowding • Weather • predators When a population overshoots the carrying capacity, then limiting factors may come into effect. Deaths begin to exceed births and the population falls below carrying capacity population growth over 20 years 600 500 population S - Curve 400 300 200 100 0 0 2 4 6 8 10 year 12 14 16 18 20 Two types of limiting factors: Density-dependent and Density-independent Population density describes the number of individuals in a given area. Population Density • Let’s say our classroom is 1000 sq. ft. In 1st and 4th periods, there are 25 students in the class. The population density for 1st and 4th periods is 25 students/1000 sq ft or 0.025 students /sq ft. Density - Dependent • Density-dependent factors include disease, competition, predators, parasites, space and food. • Disease, for example, can spread more quickly in a population with members that live close together. Density - Independent • Density-independent factors can affect all populations, regardless of their density. • Most density-independent factors are abiotic factors, such as temperature, storms, floods, drought, hurricanes, volcanic eruptions, and oil spills. Organism Interactions • Population sizes are controlled by various interactions among organisms that share a community. • Predation and competition are two interactions that control populations. Predation Populations of predators and their prey experience cycles or changes in their numbers over periods of time. Lynx and Hare pelts sold to the Hudson’s Bay Company Competition • Is Density - Dependent • When only a few individuals compete for resources, no problem arises. • When a population increases to the point at which demand for resources exceeds the supply, the population size decreases. Crowding • As populations increase in size in environments that cannot support increased numbers, individual animals can exhibit a variety of stress symptoms. • These include aggression, decrease in parental care, decreased fertility, and decreased resistance to disease. • They become limiting factors for growth and keep populations below carrying capacity. Population of New Orleans, La 1970-2006 650000 population 550000 450000 350000 250000 150000 50000 -500001968 1973 1978 1983 1988 1993 1998 year 1. What is the population trend? 2. Why did this happen? 3. Is this density-dependent or independent? 2003 2008 Global population 1900 - 2046 Population in Billions 10 9 8 7 6 recorded population 5 projected population 4 3 2 1 0 1850 1900 1950 2000 2050 2100 Years 4. What type of growth is this? 5. When does growth increase? What might have happened to cause this?