CTY Honors Biology Unit Lesson 8.4

- Population Growth - Factors that Affect Population Growth - Human Population Growth - Changes to Resources - Biodiversity

population

every species member in given location

geographic range

• pop. location affects size

• more resources = more organisms

density

amount of organisms in given area

distribution

how spaced out the organisms are within their boundaries

uniform

evenly spread throughout

• competition for resources

• maximizes space between

random

unpredictable distribution

• less individual interactions

*least common ex: dandelion seeds

clumped

clustered together

• clusters around resources

*most common

growth rate

population size change over time

• increase, decrease, no change

age structure

male+female at each age

• immature: before breeding

• mature: breeding

*allows predictions on growth/reductions

birth rate

num of births/time

death rate

num of death/time

growth rate

birth rate - death rate

immigration

individuals going into population

emigration

individuals exiting population

effects of population factors

• every factor must be considered

• they can oppose or support each other

ex: birth=death, immigration>emigration → growth

exponential growth

rapid growth

• ideal conditions+unlimited resources

logarithmic growth

phases of growth

*exponential growth is unsustainable

phase 1

lag phase; slow growth

phase 2

log phase; exponential growth

phase 3

population disruption; slower growth

phase 4

no size net growth *brith=death, em. = imm.

carrying capacity

max num of organisms in species habitat can handle

*factors reduce capacity

limiting factors

affect population’s environment, controlling population

biotic limiting factors

• competitors

• predators

• parasites+pathogens

abiotic limiting factors

• weather

• natural disasters

density-dependent competition

• when density is too high for food, water, mates, etc

• intra: within species, inter: between species

• affect death+birth rates, emigration

• limited resources → competition

predation

predator kills prey, prey population decreases

*herbivores predators to plants

predation effects

decreased prey → decreased predator → increased prey → increased predator

disease

• parasites+pathogens

• high population density makes spreading easier from close contact

*epidemics: a lot of animal/plants

density-independent factors

limits population regardless of density *random

• weather: hurricanes, droughts, floods

• natural disasters: fires, volcanoes, earthquakes

*affects entire population equally

human population growth

• slow growth

• 500 BC increased more

• industrial revolution (exponential growth)

• to 7 billion people

human growth reasons

• sturdy shelters]

  • weather protection

  • comfortable living at diff temps/precipitation

• easy food access

  • agriculture reduced migration

  • less energy for getting food

• healthcare/sanitation

  • avoiding diseases

  • increase life expectancy

human growth limits

• competition

  • war (many deaths)

• limited resources

  • water+food lack

  • starvation/malnutrition

• disease

  • pathogens, viruses, bacteria

  • *pandemics constantly monitered

demography

study of human populations

• birth/death rates, life expectancy, age structure

demographic transition

change from high birth/death rates to low

• 1: high, high (no change)

• 2: high, falling (improved living conditions)

• 3: falling, low (waiting longer for children)

• 4 low, low (stable)

*more developed countries are higher up in their transitions

age structure diagram

evaluates ages for population changes+predicts future changes

• organized by age+sex

*male/female age diffs, females usually live longer

rectangular shape

evenly spread across ages

• stable; no significant growth (ex: austrailia)

triangular shape

more young than old people

• population will grow once young people mature (ex: angola)

urbanization

creation of cities

• displaces flora+fauna

• destroys habitat/environment

• produces waste

urban sprawl

spread pf urbanized areas

industrial growth

building factories

• similar to urbanization

• burns fossil fuels

• produces hazardous waste

agriculture

farming

• high water demands

• soil nutrient depletion from crop monoculture

• burns fossil fuels

• fertilizer+pesticide waste

erosion

removal of soil by wind (becomes drier when carried to diff places) and water (less plants allows water to run through soil)

*loss+redeposition is a major issue for ecosystems

desertification

dry flat farmland to desert

depletion

nutrients+water removed

*avoided with planting a variety, resting soil

• monoculture: repeated crop planted

• animal grazing: animals destroy plants

deforestation

clearing of trees

• agriculture, urbanization, wood

• increases erosion+soil depletion from absence of trees/roots

*destroys habitat/allows erosion

water pollution

*only 2% freshwater

• sewage: a lot of nitrogen+bacteria

  • certain O2 consuming algae thrive from nitrogen, taking O2 from others

point source

clear, single pollution source

non-point source

multiple smaller sources without clear contributor

ex: pesticides, organic chemicals

biomagnification

pollutant concentration as it travels up food chain

biomagnification example

1. low concentration in water, higher in plants (take in a lot of water)

2. consumer gains more pollutant from eating many plants

3. add. magnification as consumers eat more of each other

water oversuse

water is a limited resources, and must be conserved

air pollution

*usually non-point (industrial waste+fossil fuels)

• smog: thick haze of pollutants over cities

• acid rain: nitrogen+sulfur with water vapor to nitric+sulfuric acids which falls as precipitation

• greenhouse gasses: contribute to climate change by trapping heat

ozone (O3) layer

O3 absorbs sun UV radiation+protects from radiation

• 1970’s: hole in ozone layer over Austrailia discovered

  • linked to CFCs (chloroflurocarbons), in aerosol, fridges, freezers

• montreal protocol: banned most CFC *concentration lessened, hole stopped growing

NASA climate change study

• global warming: average global temp increase

• severe weather/precipitation, sea levels increasing from ice levels melting

2007 IPCC climate change study

• shorter hibernation

• dealer flowering seasons

• linked to greenhouse gasses trapping heat

  • fossil fuels → more greenhouse gases

  • deforestation → less plants to take in CO2

*still being researched, sustainability is vital

biodiversity

variation of all organisms in biosphere

• ecosystem diversity: habitats+communities

• species diversity: species amount+types

• genetic diversity: in/between species

undiscovered species

• more than half species undiscovered

• 90% of arachnid species undiscovered

• 950,000 insects species known, 9 mil unknown

healthy ecosystems

balance of all present species

*slight changes have drastic changes

medecine

animals+plants produce compounds/treatments

agriculture

selective breeding strengthens wanted traits in crops (disease resistance)

development (agriculture/urban)

disrupts habitat/ecosystems

habitat fragmentation

smaller habitat pieces from broken ecosystem communities

over-hunting/fishing

• reduces biodiversity (extinct)

• invasive species (out-competes native species)

*limits now on over-hunting species

pollution

damage to environment+ecosystem

climate change

severe weather changes, sea levels increasing, ice levels decreasing, global warming

*sea ice loss → polar bears displaced

diversity hotspots

areas where greater amount of species are threatened

*most in Pacific Ocean, at least 1 in each continent

species preservation

endangered species bred+matured, then released into wild to increase numbers *zoos+aquariums

ecosystem preservation

focuses on entire hot spots → entire group+natural interactions (learning about ecosystem through organism in natural habitat) *national parks, reforestation areas, reserves, marine sanctuaries

people+preservation balance

rewards for inconvenience/cost of efforts

• financial credit for hybrid cars, solar panels

• tourist areas from preservation sites for profit

biosphere reserves

• encourages preservation

• sustainable technology development

• conservation policy creation

• human+organism needs balanced

*World Network of Biosphere Reserves allocate and organize such responsibilities

development (agriculture/urban)

disrupts ecosystems, habitats