Ecology! Sections 40.3-40.6 43.5

Populations Population: all individuals of 1 species in area Population size : number of individuals Population density : number per area Population distribution : dispersal pattern

Distribution patterns 1) Clumped: most common, a) group around resources b) social behavior c) lack of offspring dispersal 2) Uniform (or close enough) a) territory division b) fairly uniform resources 3) Random – rare a) uniform resources b) ignore each other

Population Size Estimates 1) full count 2) Quadrats 3) Transects 4) Mark-recapture m-r good for organisms that move around a lot

Mark-recapture Based on assumption: % of recaptured individuals that are marked.. same as the % of the total population that is marked Steps: day 1 capture organisms & mark them day 2 capture organisms & see what % of the organisms are marked calculation day 2 marked = day 1 marked day 2 total total population

Population Growth Positive growth …….. birth & immigration Negative growth …… death & emigration Migration : periodic change w/ seasons Zero population growth (ZPG) : deaths = births Per capita = per individual Population growth (dN/dt) = births – deaths where d indicates change ….same as Δ N is the number of individuals, t is time so ΔN/Δt

r = net reproduction per capita per unit time N = number of individuals in population Population growth rate = r x N

Rapid Population Growth High r….have lots of babies fast, few deaths High N……large populations grow faster Exponential growth : population grows at a rate proportional to its size a) r remains constant b) ideal conditions allow max r Biotic potential : max r for a population Doubling time: time for pop to double size

Logistic Population Growth Exponential Growth slowed by 1) Density dependent limiting factors predation, parasites, disease limited resources, competition not by Density independent limiting factors weather, natural disasters, humans

Carrying capacity = Max # individuals an area can support indefinitely (D) Steady state #2 on graph Life history patterns: adaptations that influence survival, reproduction & population size

Reproduction Requires Energy Amount of available energy affects reproductive rates and success Seasonal reproduction timed to match resource availability Reproductive strategies match environment to maximize repro success

Reproductive strategies r-selected (r = net reproduction per capita per unit time) a) favor low pop density (d independent) b) quick production of many small babies c) high biotic potential so called r-selected K-selected (K = carrying capacity ) a) favor high pop density (d dependent) b) good competitors c) low biotic potential & high parental care

Life History Strategies

Environmental effect on Repro. 1) Unstable/changing environments a. can show more rapid evolution b. can select different traits each generation c. mature quickly and have lots of babies d. r-selected 2) Stable environments a. longer life span slower to mature b. produce fewer offspring c. more efficient use of E d. K-selected

Different Life Histories = Different Survivorship Curves Type I : live long & prosper (parental care) k-selected Type II : could die at any time… good luck Type III : high infant mortality r-selected

Human Population growth First 1 billion……2.5 mya growth to 2 billion…………..123 years Growth to 3 billion …………. 33 years Growth to 4, 5, 6 ………….. 14, 13, 12

Dot video http://www.populationconnection.org/resources/poped/

Fertility Rates and $$$$$$$ Total Fertility Rate (TFR) – average # children born per woman World wide TFR = 6.5 Replacement = 2.1 TFR in developed countries = at or below 2.1 TFR in developing countries = highest

Demographic Transition Model Niger, Guatemala, Afghanistan : stage 2 India, South Africa, Columbia : stage 3 Brazil, United States, China : stage 4 Germany, Japan : Stage 5

Age Structure Diagrams 3 categories of individuals: -pre-reproductive (base) -reproductive (center) -post-reproductive (top) Fast growth = wide shape Slow growth = narrow shape ZPG = straight at bottom, narrows at top Negative growth = bottom & top more narrow than center

2014 pop pyramid data https://populationeducation.org/sites/default/files/power-of-pyramids.pdf

U.S.A. https://populationeducation.org/sites/default/files/resource_files/US_Graphics_2013.pdf