Population Dynamics The study of population characteristics and how they change over time Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat. Population: group of the same species in the same place at the same time. Demography: the statistical study of populations, make predictions about how a population will change

Population A group of organisms of the same species living in the same area Three Key Characteristics of Populations Size Density Dispersion (clumped, even/uniform, random)

Size: number of individuals in an area Three Key Features of Populations Size: number of individuals in an area Every population has a carrying capacity or a maximum limit the environment can handle due to Limiting resources. Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Capacity overflow When the carrying capacity is overshot things like competition, disease, starvation, predation etc… result in a loss of individuals

Growth Rates Growth Rate: The change in population size over time The size of a population depends on the number of organisms entering (birth & immigration) and exiting it (death & emigration) Migration Types: Immigration – organisms move into a population Emigration – organisms move out of a population Types of growth rates: Positive Growth Rate Negative Growth Rate Zero Growth Rate IN OUT Population

Analyzing Growth Rates on Graphs Number of Rabbits Over Time Zero Growth Rate Positive Growth Rate Negative Growth Rate

Factors That Affect Future Population Growth Immigration + + - Population Mortality Nativity - Emigration

Graph: Exponential Growth Population grows exponentially if: Birth and death rates are constant More births than deaths Immigration = Emigration Creates a J-Shaped Curve What is happening? Growth starts out slowly Increases rapidly as the number of reproducing individuals increase Only will occur when there are NO Limiting recourses

Graph: Logistic Growth Usually, there are limits to growth… So…. As the population uses up available resources (nutrients, energy, space, etc.), the overall growth will slow or stop. Growth will slow or decrease when birth rate decreases or death rate increases. Eventually the number of births will equal the number of deaths (approaching Zero Growth Rate) Creates a S-Shaped Curve

Carrying Capacity Carrying Capacity (K): The number of individuals the environment can support in a given area Healthy populations will fluctuate around the carrying capacity

Limiting Factors Limiting Factor: Anything that restricts population size Resources (food, space, water, etc.) are limited Two main types of limiting factors Density independent factors Density dependent factors

Density Independent Factors: (does not depend on size of pop) Abiotic factors in the environment that affect populations regardless of their density Population size doesn’t matter Ex: Weather, natural disasters, seasonal cycles

Density Dependent Factors: (depends on side of pop) Biotic factors in the environment that have an increasing effect as population size increases Ex: Competition, disease, predation Usually only affects large, dense populations

Predation = Density Dependent

Limiting Factors will determine the Carrying Capacity of an environment

Growth of populations Carrying capacity: The following data was taken for a fish population in Clark Pond from 2000 to 2010. DATA TABLE Year Fish Population 2000 10 2001 50 2002 75 2003 120 2004 180 2005 60 2006 100 2007 2008 105 2009 115 2010

Use the data table from the previous slide: Graph the fish population data. Reminder: independent var goes on X axis, dependent var goes on the Y axis Hint: don’t forget a title for your graph and Label the X and Y axis.

Data analysis Generate a list of at least 4 factors (abiotic and biotic) that could affect the fish population. Why do you think the size of the population increased starting in 2001? Why do you think that the population decreased in 2004? Based on the graph, what do you think the carrying capacity of the pond is? Why? BONUS: why did growth slow down as time continued?

HOW MANY PEOPLE LIVE ON EARTH? As of 8-31-15 What type of growth rate does this look like?

GROWTH RATES REVISITED… Human CC video? We will reach a carrying capacity and it will be DISASTROUS

ZERO POPULATION GROWTH In order to achieve zero population growth, the average couple has just 2 kids

AGE STRUCTURE DIAGRAMS Shows % of people alive at each age group The U.S. has more _____ 80+ individuals. What is happening in Mexico’s older population? What % of under 5 years old is male in Sweden? A little more than 3%

POST-REPRODUCTIVE REPRODUCTIVE PRE-REPRODUCTIVE

Reading age structure diagrams B C D A Which graph is showing rapid population growth Which graph is showing no population growth Which graph is showing negative population growth

2. Density: measurement of population per unit area or unit volume Three Key Features of Populations 2. Density: measurement of population per unit area or unit volume Formula: Dp= N Pop. Density = # of individuals ÷ unit of space Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat. S

World Density for Humans

3. Dispersion: describes their spacing relative to each other clumped Three Key Features of Populations 3. Dispersion: describes their spacing relative to each other clumped even or uniform random Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Population Dispersion clumped random even (uniform)

What is the carrying capacity for the WallaWalla Deer

Life History Patterns 1. R Strategists short life span small body size reproduce quickly have many young little parental care Ex: cockroaches, weeds, bacteria

Life History Patterns 2. K Strategists long life span large body size reproduce slowly have few young provides parental care Ex: humans, elephants

Life history patterns lead to typical survivorship curves for organisms. Type I – K Strategists Most individuals live to old age (high survivorship early and middle years) Species with few offspring, long period of parental care (humans, large mammals) Type II – characteristics of both K and R Constant survivorship across life span Invertebrates, lizards, rodents, some birds Type III – R Strategists Low survivorship early followed by high survivorship in older individuals Species with large number of offspring, little or no parental care

Survivorship curves

Check for understanding Questions Why do you think is it important to study population dynamics? What are the three main characteristics of a population. Give an example of a density dependent limiting factor, make sure to explain HOW/WHY it is density dependent. Give an example of a density independent limiting factor, make sure to explain HOW/WHY it is density independent. What are limiting factors? What is a carrying capacity and how does it effect populations?