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