Population of Ecology

interspecific competition

Competition between different species

Size

Symbolically represented by N, the total number of individuals in the population.

Age structure

a description of the abundance of individuals of each age. It is often graphically expressed in an age structure diagram. Horizontal bars or tiers of the diagram represent the frequency of individuals in a particular group

Density-dependant

agents whose limiting effect becomes more intense as the population density increases. Examples include parasites and disease, competition for resources, and the toxic effect of waste products. Also, predation is frequently density-dependent. In some animals, reproductive behavior may be abandoned when populations attain high densities

Survivorship curves

describe how mortality of individuals in a species varies during their lifetimes

Type II survivorship curve

describe organisms in which the length of survivorship is random, that is, the likelihood of death is the same at any age. many rodents and certain invertebrates are examples

Type I survivorship curve

describe species in which most individuals survive to middle age after that age, mortality is high. Humans exhibit type I survivorship

Dispersion

describes how individuals in a population are distributed. They may be clumped, uniform, or random

Life history

describes its strategy for maximum fitness

Type III survivorship curve

desribe species in which most individuals die young, with only a relative few surviving to reproductive age and beyond, Type III survivorship is typical of oysters and other species that produce free-swimming larvae that make up a component of marine plankton. Only those few larvae that survive being eaten become adults

Limiting factors

elements that prevent a population from attaining its biotic potential. limiting factors are categorized into density-dependant and density-independant factors

K-related species

exhibits logistic growth (S-shaped curve), and the size of a mature population remains relatively constant.

r-related species

exhibits rapid growth (J-shaped curve)

Population Cycles

fluctuations in population size in response to carrying effects of limiting actors. For example, since many limiting factors are density-dependent,they will have a greater effect when the population size is large as compared to when the population size is small In addition, a newly introduced population may grow exponentially beyond the carrying capacity of the habitat before limiting factors inhibit growth.

Carrying capacity

max number of individuals of a population that can be sustained by a particular habitat

Biotic Potential

maximum growth rate of a population under ideal conditions, with unlimited resources and without any growth restrictions. For example some bacteria can divide every 20 minutes

Clutch size

number of offspring produced at each reproductive event

Density-independant

occur independently of the density of the population. Natural disasters are common examples

Logistic growth

occurs when limiting factors restrict the size of the population to the carrying capacity of the habitat.

Exponential growth

occurs whenever the reproductive rate is greater than zero. on a graph where population size is plotted against time, a plot of exponential growth

opportunistic species

quickly invade a habitat, quickly reproduce, then die

Growth rate

the population size at the beginning of the interval for which the births and deaths are counted. The numerator of the equation is the net increase in individuals.

Density

total number of individuals per area or volume occupied.

Gause's principle

when 2 species compete for exactly the same resources, one is likely to be more successful.