Exponential Population Growth: Concepts, Factors, and Limits, Study notes of Biology

Download Exponential Population Growth: Concepts, Factors, and Limits and more Study notes Biology in PDF only on Docsity! POPULATION GROWTH Exponential Growth Rate The exponential growth rate (G) keeps increasing over time as the population size increases A Model of Exponential Growth Population Growth Rate (G) = What does per capita mean? P op ul at io n S iz e (N )  Time  P op ul at io n S iz e (N )  Time  Per capita growth rate (r) depends on per capita birth & death rates Example: 15 births / 100 / yr 5 deaths / 100 / yr per capita growth rate = As the population increases (N) the overall growth rate increases because you are multiplying r by a larger number Growth Rate can also be expressed as a percentage Example: 15 births / 100 / yr 5 deaths / 100 / yr Birth Rate = ____% per year Death Rate = ____% per year Growth Rate = ____% per year or as doubling time 100  Per capita growth rate depends on “life History Characteristics” 1. # offspring / female 2. Age at first reproduction ~ Generation Time r = 0.1 100 600 1000 The logistic model is a simplification. In the real world . . . A. B. C. What happened when predators of deer were eliminated from the Kaibab Plateau? Limits to Growth (cont.) II. Density-Independent Factors A. B. P op ul at io n S iz e (N ) Time P op ul at io n S iz e (N ) Time HUMAN POPULATION GROWTH Historical Perspective < 10,000 B.P. Hunter-gatherer societies Population  b  d  Life expectancy  10,000 - 2,000 B.P. K increased Population  b & d still high In recent years population growth has followed somewhat different patterns in different parts of the world More Developed Countries (MDCs) 1700 - 1940 d slowly decreased: b also decreased, but lagged behind d G rose post WWII declining b caught up with d G decreased to < 0.8% The "Demographic Transition" in MDC’s (left) and LDC’s (right) Time Time When will global population stabilize? Depends on . . . a) b) Because of high fertility and bottom heavy age structure world population growth is concentrated in LDCs What is the ecological niche? For niche theory according to Dr. Seuss see http://nsm1.nsm.iup.edu/rgendron/Seuss.shtml Interspecific Competition has short- and long-term consequences 1. Short-term consequences A. Example: ants & rodents in the desert Preferred seed sizes overlap Hypothesis: Prediction: Experiment: B. Observations like these led Ecologists to develop the _____________________________ 2. Long-term consequences Populations can evolve in ways that reduce competition Example: Evolutionary change in beak size in two competing species of Galápagos finch within each species beak size varies  individuals with small bills are better at eating small seeds and vice versa What happens when two similar species occupy the same island? F re qu en cy (# o f bi rd s) Beak Size Community Ecology: Predation Ecology use the term “predator” to refer to any animal that consumes other organisms. What are the different types of predator? 1. 2. 3. 4. Predation can have short- and long-term effects s on Biological Communities 1. Short-term A. B. What happens to species diversity in the intertidal community when the seastar is removed? Why? Why is the seastar called a “keystone species?” 2. Long-term - _________________________________