Days 13-14 Applied population dyn

Days 13-14 Applied population dyn - Just an outline NOT all...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Just an outline NOT all you need to know Population growth: the basics: population size changes over time: N t+1 = N t + births - deaths + immigrants - emigrants to start with, we will be dealing with closed populations (no migration) per capita pop growth rate = # individuals in 1 year, divided by # in previous year: 1- = t t N N change in population size from year 0 to year 1: 1 N N = change in population size from year 1 to year 2: 1 2 N N = change in population size from year 0 to year 2: 2 2 N N N = = change in population size from year 0 to year t: N t = N t = geometric growth example: N = 100, N 1 = 160 = 1.6 keep constant for t = 15 N 15 = 100 * 1.6 15 = 115,000 can express as continuous growth rate rather than discrete (by generation) o easier to compare growth rates between populations 1 Just an outline NOT all you need to know substitute e r for t r = intrinsic rate of increase; b d exponential growth rt t e N N = also can calculate r directly from pop growth data take log of both sides: t N N r so rt N N t t ln ln ln ln- = + = and comparison: Growth constant pop size Exponential (r) Geometric ( ) Decreasing < 0 0 1 Constant 1 Increasing > 0 > 1 100 200 300 400 500 600 700 1 2 3 4 5 t N doubling time - a commonly reported measure that comes from this: N t = 2N (= doubled size) 2 Plotting: =e rt geometric is discrete: = 1.6 exponential is continuous: r = 0.47 (Draw really close together) rN dt dN = Just an outline NOT all you need to know from the previous equation, then 2 = e rt (or 2 = t ) take log of both sides and divide by r => double t r = ) 2 ln( r Population doubles in: .01 (= 1% growth rate) 69 years .02 (2%) 35 .03 (3%) 23 .04 (4%) 17 exponential (geometric) growth rates observed under certain conditions a) early in a species invasion of a new area b) population growth after a population crash c) species with boom-bust growth (many inverts, fish) d) current human population growth 3 Just an outline NOT all you need to know example: Ring-necked pheasants- 2 males, 6 females introduced to Protection Island, Washington (1937)- 5 yrs later 1,325- = 2.8 example: European rabbits- 12 pairs introduced to ranch in Australia (1859)- 6 yrs later 20,000 killed in 1 year; pop estimated > 60,000- = 4.7 max s, ideal settings, in lab:- field vole = 24 o doubling time = days yrs 79 22 . ) ln( ) 2 ln( = = - flour beetles = 10 billion (10 10 )- Daphnia (water flea) = 10 30 if r > 0, and time goes on, population size rises to infinity according to this model (1) obviously cannot go on indefinitely why not?...
View Full Document

Page1 / 17

Days 13-14 Applied population dyn - Just an outline NOT all...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online