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Populations Populations Dynamics Population: A group of organisms of the same species, that in live in a specific area. Biosphere Biome Ecosystem Community Population Organism Exponential Growth J-shaped curve- growth slow, then increases rapidly As the population gets larger, it grows at a faster rate Unchecked growth See Fig. 4.2 Growth Limits Limiting factors will cause population growth to slow Examples: predators, food, disease, space Can cause an S-shaped curve See Fig. 4.3 Carrying Capacity Number of organisms of 1 species that an environment can hold Increased resources, more births than deaths, population increases When a population goes past carrying capacity, limiting factors kick in --(deaths exceed births) Life Boat analogy… Reproduction Patterns Life history pattern organism’s reproductive pattern Short life history pattern: reproduce very rapidly; mature rapidly; produce many offspring; unstable environment; ex. mosquitoes Long life history pattern: slow rate of reproduction; mature slowly; few young produced; more stable environments; at or near carrying capacity; ex. elephants Limiting Factors Continued.. Density – the # of individuals in a given area Limiting Factors Impacting Population Dispersal (2 types) Density-dependent factors Density-independent factors Density-dependent factors – increasing effect as population increases Disease Competition Predators Parasites Food Crowding Stress Density-independent factors – Affect populations regardless of their density Volcanic eruptions Temperature Storms Floods Habitat disruption Human Population Why is it important to know how many people there are in the world and where they are located? Who keeps track of this? It took from the first existence of man to the year 1800 for the world population to get to 1 billion… What is the world’s population now? World Population Demographics Demography – study of human population size, density and distributions, movement, and birth and death rates Birthrate – number of live births per 1000 population in a given year Death rate – number of deaths per 1000 population in a given year Immigration – movement of individuals INTO a population Emigration - movement of individuals OUT of a population Calculating Population Rates Population Growth Rate (PGR) = birthrate – death rate If birthrate = death rate, then zero population growth, but still changing. If PGR is above zero, then more entering than leaving the population Doubling time – time needed for a population to double in size Slow double time: developed country (ex: Germany) rapid double time: developing country (ex: India) DT = 70/percent increase Age structure – the proportions of the population that are in different age levels What limiting factors should the next president of the United States be concerned with in our nation? Explain.