Population Dynamics & Cycles in Nature. Population Dynamics Population- a group of organisms of the...
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Transcript of Population Dynamics & Cycles in Nature. Population Dynamics Population- a group of organisms of the...
Population Dynamics
& Cycles in
Nature
Population Dynamics
Population- a group of organisms of the same species that occupy a given area and reproduce
If environmental conditions are “favorable,” then the number of individuals in population should increase from one generation to next
Population density = # of organisms/area
Population Size-Growth Rate
Birth rate- # individuals born
Death rate- # individuals die
Immigration- # individuals that move in
Emigration- # individuals that move out
If…
BR + I = DR + E EQUILIBRIUM
BR + I > DR + E INCREASING
BR + I < DR + E DECREASING
Exponential GrowthExponential growth- starts out slowly but then grows rapidly to infinitely high numbers
Represented by “J curve”
This does NOT describe real populations forever
Something always limits growth eventually
Factors Affect Growth Rate
Limiting Factors: factors that stop populations from reaching their biotic potential
Space
Water
Nutrients
Competition
Disease
Natural disasters
Logistic Growth
Logistic Growth: Population growth that levels off due to environmental resistance.
Real populations can only grow exponentially for short spans. More realistic.
Seen as a “S-curve” on a graph
Carrying Capacity
Carrying Capacity- Total # of individuals that can be supported by the environment in a particular area.
The Earth has 7 billion people…how many more can it support?
World Populationhttp://www.youtube.com/watch?v=9_9SutNmfFk
Cycles in Nature
Cycling maintains homeostasis (balance) in the environment. Matter is constantly recycled.
3 Cycles to Investigate: 1. Water Cycle
2. Carbon Cycle
3. Nitrogen Cycle
Water Cycle
Evaporation: Liquid Gas
Condensation: Gas Liquid
Precipitation: Rain, Snow, Sleet, Hail
Transpiration: process through which plants lose water vapor through leaves
Ground Water: water within the earth
Water Cycle
Carbon CycleCarbon © is the molecule of life (proteins, carbs, fats, and other important molecules)
Autotrophs use photosynthesis Convert CO2 into energy-rich molecules
Autotrophs or Heterotrophs use carbon molecules for growth & energy (Cell Respiration) CO2 is released into the atmosphere
Decomposition- breakdown of dead organisms and waste, returning carbon to the soil and atmosphere.
Fossil Fuels- dead organisms that are buried in sediment; formed by pressure.
Combustion: the burning of fossil fuels.
Carbon Cycle
Nitrogen (N) CycleAir 78% (N2), organisms cannot use Nitrogen in that form.
Lightning & certain bacteria convert Nitrogen in air into more useable forms for plants and animals.
Nitrogen fixation- convert atmospheric nitrogen (N2) into ammonium (NH4+) which can be used to make organic compounds like amino acids (proteins).
Nitrogen-fixing bacteria: Some live in a symbiotic relationship with plants of the legume family (e.g., soybeans, clover, peanuts).
Nitrogen (N) Cycle
Herbivores eat plants – convert N- containing plant proteins into N – containing animal proteins
N returned to soil in urine (excess N) & when organism dies
Plants reuse these N molecules
Bacteria act on these molecules & put N back into the air
Nitrogen Cycle