POPULATIONS Population a group of organisms of the

POPULATIONS • Population – a group of organisms of the same species that live in a specific geographical area and interbreed

CHARACTERISTICS OF POPULATIONS Geographic Distribution • Where they live Population Density • The number of individuals in an area Growth Rate • Populations may increase, decrease, or stay the same

FACTORS INFLUENCING GROWTH # of Births # of Deaths # of Individuals that enter or leave a population • Immigration – movement of individuals into an area • Emigration – movement of individuals out of an area

WHAT DO YOU THINK WILL HAPPEN TO POPULATION SIZE IF…. • • • Population Increases The birth rate is higher than the death rate? Population Decreases The death rate is higher than the birth rate? Population Stays the same The birth rate equals the death rate? Population Decreases Individuals emigrate from the population? Individuals immigrate to the population? Population Increases

POPULATION GROWTH • Exponential growth – occurs when individuals in a population reproduce at a constant rate J – Shaped • This can only happen under ideal conditions with unlimited resources (food, water, shelter, space).

POPULATION GROWTH • Logistic growth – a population that starts with a minimum number and reaches a maximum depending on the carrying capacity of the habitat S - shaped

EXPONENTIAL GROWTH J - Shaped Draw the growth curve:

LOGISTIC GROWTH S - shaped Draw the growth curve:

CARRYING CAPACITY • Carrying capacity – the largest population that an environment can support at any given time

CARRYING CAPACITY • If a population grows over its carrying capacity, resources will be depleted, and the population will crash (because most of the population starves).

LOGISTIC GROWTH S - shaped Draw the growth curve:

EXPONENTIAL GROWTH

EXPONENTIAL GROWTH

EXPONENTIAL GROWTH

WHAT LIMITS A POPULATION’S GROWTH? • Limiting Factors – factors that cause population growth to decrease • Density-Dependent Limiting Factors: depends on population size • Examples: competition, predation, parasitism, and disease • Density-Independent Limiting Factors: affects all populations in similar ways, regardless of the population size • Examples: unusual weather, natural disasters, seasonal cycles and certain human activities – such as damming rivers and clear-cutting forests

CHECKS & BALANCES ACTIVITY This Photo by Unknown Author is licensed under CC BY-SA

OH DEER!

PREDATOR/PREY RELATIONSHIPS

PREDATOR/PREY RELATIONSHIPS

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