Presented by Mr. Rainbeau How Populations Grow Presented by Mr. Rainbeau

Define Population group of individuals of the same species that live in the same area

What 3 characteristics are used to describe a population? Geographic distribution Density Growth rate

Define Population Density the number of individuals per unit area In which picture is the bird population most dense?

What factors affect population size? number of births number of deaths number of individuals that enter or leave the population immigration & emigration

Define Immigration the movement of individuals into an area causes a population to grow

Define Emigration the movement of individuals out of an area causes a population to decrease in size

Who is immigrating? Who is emigrating?

Define Exponential Growth occurs when the individuals in a population reproduce at a constant rate. J-shaped curve

What kinds of conditions are needed for exponential growth? ideal conditions, with unlimited resources plenty of food, water, space, mates, & no disease, parasites, predators

Define Logistic Growth Occurs when a population’s growth slows or stops following a period of exponential growth S-shaped curve

Define Carrying Capacity number of individuals that a given environment can support

Presented by Mr. Rainbeau Limits on Growth Presented by Mr. Rainbeau

Define Limiting Factors a factor that causes population growth to decrease

What determines the carrying capacity of an ecosystem? limiting nutrients; limiting factors (the amount of available food, water, space, and other environmental factors)

Define density-dependent limiting factors. a limiting factor that depends on population size

What are 4 examples of density-dependent limiting factors? Competition Predation Parasitism Disease

Competition When organisms compete for food, water, mates, and space

Predation – one organism feeding on another

Parasitism parasites take nutrients from their host

Disease infectious diseases are caused by bacteria or virus

Define predator-prey relationship. regulation of a population by predation mechanism of population control

Boom-and-bust curve shows exponential growth followed by a sudden collapse

Define density-independent limiting factors. affects all populations in similar ways, regardless of population size

What are 4 examples of density-independent limiting factors? Unusual weather Natural disasters Seasonal cycles Human activities

We can predict changes that may occur in a population What is the advantage of understanding the factors that influence population growth? We can predict changes that may occur in a population

III. Human Populations

1.Currently the human population has been growing exponentially Due to increasing gap between birth rates and death rates Why? a) Developments caused death rates to drop and the life expectancy to increase

17501900 population doubled 800 million to 1.6 billion (150 years) 19001965 doubled again to 3.2 billion (65 years) 2004 population reached 6.4 billion (39 years)

Population (in billions) World population estimates milestones (USCB) Population (in billions) 1 2 3 4 5 6 7 8 9 Year 1804 1927 1960 1974 1987 1999 2012 2027 2046 Years elapsed - 123 33 14 13 12 15 19

Exponential human growth cannot continue Factors that affect human populations: crowding, food, natural disasters, pollution, space, water, mates, and disease

What would happen if the human population does not level off? The Earth would not be able to provide a sufficient amount of resources to support the growing population and people would begin to die as a result of illness, starvation, and other related causes.