Limiting Factors in Population Growth: Density Independent and Dependent Factors, Exams of Evolutionary biology

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LIMITING FACTORS QQ

How are population sizes limited?

QQ#1:

REVIEW: EXPLAIN THE DIFFERENCE

BETWEEN THESE TWO GRAPHS IN RELATION TO POPULATION GROWTH

 Density Independent Limiting Factors  limiting factors that do not depend upon a population’s size.  Density Dependent Limiting Factors  limiting factors that depend upon the population size.  The “density” of a population is determined by how many individuals are living in a set amount of space

TWO TYPES OF LIMITING FACTORS

 QQ#2: what do you think the difference

between these two factors are?

DENSITY INDEPENDENT FACTORS

Density Independent Factors are limiting factors that do not depend upon a population’s density. Examples include:  Natural Disasters (i.e. earthquakes)  Seasonal Variation (i.e. drought)  Human activities such as deforestation

COMPETITION

 When populations become crowded (more dense) organisms compete  They compete for food, water, space, sunlight, and other essentials.  Completion among members of the same species is a density-dependent limiting factor.

 QQ#3: what kinds of things

do you think individuals of the

same species compete for?

PREDATION

 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

PARASITISM AND

DISEASE

 A parasite lives in or on another organism (the host) and consequently harms it  Parasites/Diseases can limit the growth of a population by killing their hosts  Parasites/disease are more easily spread in highly dense populations  QQ#5: Why do you think Disease is considered a density dependent limiting factor?

CHECK FOR UNDERSTANDING

(YOU DO NOT NEED TO WRITE THESE)

 A limiting factor that affects all populations in similar ways regardless of their size might be  drought.  disease.  predation.  crowding.

CHECK FOR UNDERSTANDING

 Which of the following is a density-independent factor affecting populations?  predation  disease  a destructive hurricane  parasites