Chapter 6: Population Dynamics

population growth

rate - fig p 130

exponential growth grows at a constant rate J curve can determine a doubling time (4% annual

growth doubles population every 175 years)

arithmetic growth grows by a constant amount rate decreases over time

biological reproduction

exponential

offspring can reproduce at the same rate as parents

biotic potentialmaximum reproductive rateactual rate limited by other factors

carrying capacity

population limit

environmental resistance

growth patterns/strategiesoscillations - fig p 131 overshoot & dieback irruptive/Malthusian growth regular or irregular

logistic growth - fig p 132 constantly changing rate S-curve little resistance - exponential growth rate increasing resistance - slows growth rate

chaotic (variation of oscillation) natural fluctations may include catastophic changes no apparent mathematical pattern not necessarily random

reproductive strategy

table p132externally controlled many offspring rapid growth low trophic level little parental care/effort

intrinsically controlled few offspring slow growth high trophic level much parental care/effort

factors that effect population sizenatality: production of new individuals fecundity - ability to reproduce fertility - number of offspring produced

immigration & emigrationmortality death rate survivorship - curves - fig p 135 life expectancy - probabale life span for an individual at a certain age life span - maximum possible age

age structure histograms - fig p 135 patterns (expanding, stable, diminishing)

factors that effect population growth

extrinsic vs intrinsic

biotic vs abiotic

density dependent vs independent

may be positive or negative

pop. growth factors

density independent usually abiotic weather, climate catastrophes

fires volcanoes weather

density dependent usually biotic interspecific

predator-prey parasitism competition for resources mutualism and

commensalism intraspecific

competition for resources - individuals of a

species inhabit the same niche

mates territoriality

crowding stress shock too much competition

Human Population - fig p 144low population with respect to most speciesearly controls on size disease famine war culture

after 1600 international commerce international communication ag development power supplies medicine hygiene

Limits to growth - fig p 145Malthusian human population growth > growth rate of food supply stabilizing factors

disease & famine reduced birth rate (late marriage, no kids until you can afford them)

however: most people are too lazy/immoral to regulate birthrates voluntarily

don’t help the poor overpopulation is a cause

Marx social injustice is the problem people will regulate themselves given the opportunity and fair share poverty & overpopulation are consequences

open questions

WHAT IS THE MAXIMUM CAPACITY???What is the relationship of population growth, poverty, and env. degradation?What are the effects of technology?What are the benefits of more people?Was Malthus correct? Marx? neither? both?

Demographicsmeasurement of peopletotal populationnever actually countedappx. 6 billion top 10: China, India, US, Indonesia, Brazil,

Pakistan, Russia, Bangladesh, Nigeria, Mexico,

densitypeople per mi2 - map p 148

Population growth

natural rate = births - deaths

total rate = (births + immigration) - (deaths + emigration)

Fertility

crude birthrate - births per year per 1000total fertility rate - # of children born to an avg. women during her reproductive years highest - Ivory Coast – 7.5 lowest Italy – 1.3

birthrates for men??? - not countedzero population growth replacement rate a bit more than 2 per couple

mortalitymortality rate - deaths per 1000 per yearlife span max possible age 122?

expectancy average age a newborn can expect to attain increases as you age has risen dramatically responsible for population increase related to affluence (fig p. 151) implications - age structure - fig p 152

young support old if the bottom of the histogram thins…?

emigration & immigration

culturaleconomicdisease faminewarslaverypolitical

Controlling growth (or not)fig p 154pronatalist pleasure pride comfort economic support high infant mortality status

of men of women

culture replacement

reduction education economic status personal freedom work/career income/household budget status of women family planning

negative population growth

more resources per person less people to run the system

demographic transition

fig p. 156pattern high death and birth rates death rates drop birth rates follow later population size increases during the transition

current outlooks in transition, soon to be out stuck in transition transition will end when resources are equitably

distributed

future population

figs. p. 162 and 163

will stabilize in the next 100 years???

6 to 16 billion

What is the Carrying Capacity???

Human nutrition

needs minimum: 2000 to

2200 calories/day up to: 6000 to 7000

calories/day

problems undernourished

< 90% of minimum serious < 80% of minimum

overnourished malnourished: not enough of

the right things protein carbohydrates lipids and oils minerals vitamins

Food resourcescropsgrains tubers fruits & veggiessugar

animalsmeat & milkpoultry fish & seafood

Limited to a few (10-20) primary food sources!

Meat, milk, seafoodhigh in protein and nutrients and fatscrop useU.S.: 90% of grain is used to feed

livestock16kg of grain yields 1 kg of edible beef

overgrazingoverfishinghigh on the food pyramid!

new food sources

plantsregionalwild: hearty

“blue revolution”fish farmingfish ranching

world hungertypesfamine: short-term, severe shortagechronic shortages: under- and mal-nutrition

causesenvironmental conditionsfood distribution

politicseconomics

world food supply

how many people can be supported?

what is sustainable?

soil

regolith (weathered parent material)

organic material

water

air

soil formation

parent material is weatheredwaterbiological

material moves downward, creating layers (horizons)

rate: best is 1 mm/yr

soil horizons

figure, p. 245

layers

top soil is O & E

soil use

must consider climate

production landcrops or grazingdecreasing in developed worldincreasing in developing areas

soil degradation

erosion (7.4 million acres/yr are ruined)

desertification

conversion to non-ag

pollution

impoverishment (loss of fertility)

soil degradationcausesovergrazing – 35%deforestation – 30%cultivation – 28%overexploitation – 7%industrialization – 1%

mechanisms (graph p. 247)water erosionwind erosionchemicalphysical

soil degradation

solutionscontour tillingstrip croppingterracingground covertill reduction

agricultural resourceswaterrainfallirrigation (70% of water use)

fertilizersupplement natural cyclesinorganic, organicuse vs yield

energy (fig p 250)diversity

green revolutionchangesmore land in productiongeneticsfertilizerpesticides

benefit: greater yield/acredownsidesmall operators outreduction in diversityconcerns about bioengineering

sustainable agriculture

soil conservationlow input & low impactlower yieldecologically soundland reformreal pricingwomen’s rights

Pests

unwantedinterferingdestructive

plants or animals or fungi

pest control

biocideherbicideinsecticidefungicidenematociderodenticide

early methods

saltsmokeplantsinorganics (S, As, Hg)culturalalcoholspicespredators

modern methods

inorganicsnaturla organicsfumigantschlorinated hydrocarbonsorganophosphatescarbamatesmicrobial agentspredators and parasites

effectsgooddisease controlcrop protection

badnon-target speciesresistance and

resurgencepredator losspersistancemobilitybioaccumulationhuman health effects

alternativescrop rotationcultivationflooding/burningattract predatorsadjust planting timesavoid monoculturerepellant plantsgenetics/bioengineeringsterilizationintegrated pest management