ESCN01G - Population Ecology

Population

a group of individuals of one species in an area

Community

many populations of different kinds of organisms living in the same place

Population dynamics

one of the most important factors in questions of environmental quality and biodiversity

Living organisms

they modify the environments occupy

rapid

Without constraints, population growth can be _____

Exponential Growth

If a population has constant birth rate through time and is never limited by food or disease, it has what is known as _______________

how fast or slow the population grows

with exponential growth, the birth rate alone controls ___________________________

nothing limits its growth

A population can grow very rapidly only if __________________

few or no predators

A population that has __________, though, can grow at an exponential rate, at least for a while.

Carrying capacity

The number (or the biomass) of a species that can be supported in a certain area without depleting resources.

population crash

Shortages of food or other resources eventually lead to a ____________ or rapid dieback

Logistic Population Growth

As resources depleted, population growth rate slows and eventually stops

high rate of reproduction

Some organisms, such as dandelions, depend on a _______________ and growth to secure a place in the environment.

R-selected Species

They have a high reproductive rate but give little or no care to offspring, which have high mortality.

K-selected species

Their growth slows as the carrying capacity of their environment is approached.

A female clam, for example, can release up to 1 million eggs in her lifetime. The vast majority of young clams die before reaching maturity, but a few survive and the species persists.

How r-selected species respond to limits?

So-called K-selected organisms are usually larger, live long lives, mature slowly, produce few offspring in each generation, and have few natural predators. Elephants, for example, are not reproductively mature until they are 18 to 20 years old.

How K-selected species respond to limits?

Births + Immigration - Deaths - Emigration

4 factors that contribute to r-selected species

Birthrate or natality

The ratio of total live births to total population in a particular area over a specified period of time.

Death rate or mortality

The ratio of the total number of deaths to the total population.

Immigration

The number of organisms moving into area occupied by the population.

Emigration

The number of organisms moving out of the area occupied by the population.

Type I

Most individuals die late in life

Type II

Individuals die at a uniform rate

Type III

Most individuals die at a young age

Intrinsic

Operating within individual organisms or between organisms in the same species.

Extrinsic

Imposed from outside the population

Biotic

Effect on population dynamics caused by living organisms

Abiotic

Effect on population dynamics caused by nonliving organisms

Population Density

A measurement of the number of people in an area

Density Dependent and Density Independent

Regulatory Factors of Population

Density Independent

• Flood

• Hurricances

• Unreasonable weather

• fire

• Clear Cutting

• Pesticide Spraying

Clumped Dispersion

A pattern when individuals are aggregated in patches.

Density Dependent

• Competition for resources

• Predation

• Parasitism

• Infectious Disease

Uniform Dispersion

Evenly spaced distributions, in which members of the population maintain minimum distance from one another.

Random Dispersion

A spacing pattern based on total unpredictability. Least common pattern distribution