LIMITATION TO POPULATION GROWTH

LIMITATION TO POPULATION

GROWTH Presented by: JOHN FLORENTINO E. ECHON

MAEd-GenSci

Bataan Peninsula State University Main CampusBALANGA CITY, PHILIPPINES

ECHON, JOHN FLORENTINO E.Environmental Science

ECHON, JOHN FLORENTINO E.Environmental Science

Limiting FactorIn the context of populations, a limiting factor is a factor that causes population growth to decrease.

ECHON, JOHN FLORENTINO E.Environmental Science

Density-dependent and

Density-independent

Population density describes the number of individuals in a given

area.

Two types of limiting factors

ECHON, JOHN FLORENTINO E.Environmental Science

A limiting factor that depends on population size is called a density-dependent limiting factor.

Density-Dependent Factors

ECHON, JOHN FLORENTINO E.Environmental Science

Density-dependent limiting factors include:•   competition•   predation•   parasitism•   disease

ECHON, JOHN FLORENTINO E.Environmental Science

When populations become crowded, organisms compete for food, water space, sunlight and other essentials.

Competition among members of the same species is a density-dependent limiting factor.

Competition

ECHON, JOHN FLORENTINO E.Environmental Science

Populations in nature are often controlled by predation.The regulation of a population by predation takes place within a predator-prey relationship, one of the best-known mechanisms of population control.

Predation

ECHON, JOHN FLORENTINO E.Environmental Science

Parasites can limit the growth of a population.A parasite lives in or on another organism (the host) and consequently harms it.

Parasitism and Disease

ECHON, JOHN FLORENTINO E.Environmental Science

Density-dependent factors operate only when the population density reaches a certain level. These factors operate most strongly when a population is large and dense.They do not affect small, scattered populations as greatly.

Remember

ECHON, JOHN FLORENTINO E.Environmental Science

Density-independent limiting factors affect all populations in similar ways, regardless of the population size.

Density Independent Factor

ECHON, JOHN FLORENTINO E.Environmental Science

Examples of density-independent limiting factors include:• unusual weather• natural disasters• seasonal cycles• certain human activities—such as damming rivers and clear-cutting forests

ECHON, JOHN FLORENTINO E.Environmental Science

Density-dependent limiting factors

Density-independent limiting factors

Are usually biological in nature (competition, disease, predation).

Are usually physical in nature (hard winters, failure of rainy season).

Are more important for large organisms (which are buffered from physical environment).

2. Are more important for small organisms, because small organisms are not as well buffered against physical environment.

Are more important in physically benign and constant environments.

Are more important in extreme or highly seasonal environments than in mild, stable environments.

Can interrupt exponential growth or cause declines, and CAN regulate a population near a stable population size.

Can interrupt exponential growth or cause declines, but cannot regulate a population at a stable population size.

Let’s Compare

ECHON, JOHN FLORENTINO E.Environmental Science

Thank You for Listening

References: • highered.mheducation.com/sites/dl/free/.../

ch17_Concept_Review.doc

• http://study.com/academy/lesson/the-limiting-factors-of-population-growth.html

http://www.nhptv.org/natureworks/nwep12a.htm