Energy flow in food webs
only 10% of the usable energy is transferred because usable energy lost as heat
(2nd law), not all biomass is digested & absorbed, predators expend energy to catch prey
(good: disinfection of water) ( bad: forms trihalomethanes)
Primary succession;
Secondary succession:
development of communities in a lifeless area not previously inhabited by life (lava);
life progresses where soil remains (clear cut forest, fire)
using waste heat to make electricity
symbiotic relationship where both partners benefit
symbiotic relationship where one partner benefits & the other is unaffected
relationship in which one partner obtains nutrients at the expense of the host
large distinct terrestrial region having similar climate, soil, plants & animals
Carrying capacity
the number of individuals that can be sustained in an area
R strategist
reproduce early, many small unprotected offspring
K strategist:
reproduce late, few, cared for offspring
Positive feedback
when a change in some condition triggers a response that intensifies the changing
condition (EX: warmer Earth – snow melts – less sunlight is reflected & more is absorbed, therefore warmer
Natural selection
organisms that possess favorable adaptations pass them onto the next generation
said human population cannot continue to increase. Consequences will be war, famine & disease
Doubling time
rule of 70 (70 divided by the percent growth rate)
Replacement level fertility
the number of children a couple must have to replace themselves (2.1
developed, 2.7 developing)
World Population is;
US Population;
6 1/2 billion;
300 million
Preindustrial stage
birth & death rates high, population grows slowly, infant mortality high
Transitional stage
death rate lower, better health care, population grows fast
Industrial stage
decline in birth rate, population growth slows
Postindustrial stage
low birth & death rates