Chapter 20- Population and Community Dynamics

Population Distribution

• Factors that affect distribution patterns include

  • Distribution of resources (abiotic factors)

  • Interactions among members of a population (biotic factors)

Clumped

• Members of population are found in close proximity to each other

  • Most common when some abiotic factor (water, warmth) is limited supply

  • Echibited by most populations (including humans who settled in an area where food, water, and shelter were most abundant.

Random

• Individuals are evenly spread out over a defined area

  • Can occur when resources are very abundant and competition is very low

  • rarely found in natural populations

Uniform

• Individuals within the population are evenly separated

  • Occurs when there is great competition among individuals of the population for resource (e.g. food, water, space, mating partners)

Population Density

• The number of individual organism (N) in a given area (A) are volume (V)

Population Growth

The size of a population directly depends on how much and how fast it grows

• # Births (natality)

• # Death (mortality)

• # immigrations

• # emigrants

Lag phase

An adjustment period prior to rapid reproduction of the population ( starts slow as there are few individuals)

Growth Phase

A period of rapid reproduction where natality>mortality

Stationary Phase

The population reaches the carrying capacity of the environment; where natality=mortality

Death Phase

Waste accumulate, competition leads to resources running out; where natality<mortality

K selected population

• found in a relatively stable environment where crowding and competition is intense

• produce few offspring but invest energy and time into helping offspring reach marurity

• Longer life span

• ex: wolf, whales, moose

r-selected population

• competition is not significant and population sizes are variable

• reproductive rates are high, and low survivorship among young

• young mature early and often require little to no parental care

• Short life span, and often smaller body size

Growing (expansive)

• wide base, and narrow top. Many young in the population

Stable (stationary)

Base is similar width to middle and top

Declining

Narrow base and wider adult population

Sustainability

The concept of living in a way that meets our needs without compromising the health of future generations or the health of the plant.