Energy and food web notes

Definitions Habitat Niche

Definitions Carrying Capacity Ecological Efficiency

Biomass and Energy http://www.buzzle.com/articles/biomass-pyramid-vs-energy-pyramid.html

Energy & Biomass Energy Pyramid Biomass Pyramid

10% Rule Sunlight is ultimate source of energy Loss of potential energy (heat energy) occurs when you move up the pyramid and conforms to the second law of thermodynamics (energy is transferred to surroundings as heat)

Predator/Prey relationship Predator and prey populations exhibit fluctuations described as the predator “tracking” the prey. The classic example is the snowshoe hare and lynx populations. Note that the lynx population (green) peaks slightly behind the hare population (blue), which is the lynx’s primary food source. The hare cycle is mainly driven by excess predation by the lynx, but other factors, such as a winter food shortage, may also be important. http://www.saylor.org/site/wp-content/uploads/2011/07/BIO313-Population-Cycles-v2-FINAL-Demary.pdf

Why does it matter? An absence of natural enemies allows an herbivore population to exceed carrying capacity, which results in overgrazing of the habitat. • The herbivore population subsequently crashes. • The size of the herbivore population is mainly maintained by predators so overgrazing does not occur. Weather and other environmental factors (including pathogens) also play roles in keeping prey populations down.

Symbiosis: interaction between two different species

DEMOGRAPHIC TRANSITION MODEL *predicts population trends based on birth rates and death rates *a country’s population will shift from one growth rate type to another *4 DEMOGRAPHIC TRANSITION TYPES 1. PRE-INDUSTRIAL- slow growth, (high birth and high death) difficult living, EX. AFRICA 2. TRANSITIONAL- Fast growth, High birth and less death, better living conditions, EX. MEXICO 3. INDUSTRIAL- slow growth, (low birth and low death), developing country, EX. CHINA 4. POST- INDUSTRIAL- population near or at ZERO POPULATION GROWTH, EX. RUSSIA & UNITED STATES

DEMOGRAPHIC TRANSITION TYPES/PHASES