Population Dynamics

Principles of Population Ecology Objectives: 1.Define Population Ecology 2.Define growth rate and explain the factors that produce changes in population size 3.Explain how human population change is calculated 4.Understand how the following terms are related to population growth: intrinsic rate of increase, exponential population growth, environmental resistance, and carrying capacity. 5.State how the J-curve and S-curve relate to exponential population growth

Principles of Population Ecology Population Ecology – the branch of biology that deals with the numbers of a particular species found in an area and how and why those numbers change over time. Population ecologists ask: 1) How many are in the population? 2) Are its numbers increasing / decreasing? 3) What is its pattern of reproduction? 4) What is its pattern of mortality?

Principles of Population Ecology Population Density: Not enough to know just how many. Need to know per unit area. 20 / 100 m 2 20 / 25 m 2

Principles of Population Ecology How Do Populations Change in Size? On a global scale (closed system):

Principles of Population Ecology How Do Populations Change in Size? Global scale: r = b – d Growth rate Birth rate Death rate

Principles of Population Ecology How Do Populations Change in Size? On a local scale (open system):

Principles of Population Ecology How Do Populations Change in Size? Local scale: r = (b – d) + (i – e) Growth rate Birth rate Death rate Immigration rate Emigration rate

Principles of Population Ecology Maximum Population Growth- under ideal conditions = intrinsic rate of increase J-shaped curve (exponential growth)

Principles of Population Ecology Intrinsic rates of increase for a species depend on: Age that reproduction begins Fraction of life span during which a species can reproduce Number of reproductive periods per lifetime Number of offspring produced during reproduction

Principles of Population Ecology Environmental Resistance Exponential growth cannot occur forever. What factors prevent it from doing so? S-shaped curve (logistic growth)

Principles of Population Ecology Population growth depends on the interplay between biotic potential and environmental resistance Biotic PotentialEnvironmental Resistance Reproductive rateLack of food or nutrients Ability to migrate or disperse Lack of water Lack of suitable habitat ability to invade new habitats Adverse weather conditions Predators Defense mechanismsdisease Ability to cope with adverse conditions Parasites competitors

Principles of Population Ecology Overshooting the carrying capacity can lead to a population crash.

Reproductive Strategies Objectives: 1.Compare r-selected species to K-selected species with respect to survivorship curves

Reproductive Strategies Each species has its own unique life history strategy that represents a tradeoff between energy required for survival and energy required for reproduction. This strategy includes: Reproductive characteristics Body size Habitat requirements Migration patterns behaviors

Reproductive Strategies Life History Strategies r-selected K-selected vs. high growth rate slow growth rate small body sizelarge body size early maturitylate maturity short life spanlong life span large broodssmall broods little / no parental carehigh parental care

Reproductive Strategies Survivorship- the proportion of newborn individuals that are alive at a given age

Factors that Affect Population Size Objectives: 1.Distinguish between density-dependent and density-independent factors that affect population size and give examples of each.

Factors that Affect Population Size Density-Dependent Factors- Factors with effects on population growth that change as population density changes Examples: Predation, competition, disease.

Factors that Affect Population Size Density-Dependence and Boom-or-Bust Population Cycles

Factors that Affect Population Size Case-in-Point: Predatory Prey Dynamics on Isle Royale

Factors that Affect Population Size Density-Independent Factors- Factors that affect the size of a population regardless of population density. Examples: Extreme weather (frost, blizzard, hurricane, etc.; fire.

The Human Population Objectives: 1.Define demography and summarize the history of human population growth 2.Identify Thomas Malthus, relate his ideas on human population growth. 3.Explain why it is impossible to determine the earth’s carrying capacity for humans.

The Human Population Demography – the science of population structure and growth Demographics – the application of population statistics

The Human Population Current Population Numbers Today = ~7.1 billion Check out: The world’s birth rate has declined over the last 200 years The large increases in population are a result of decreased death rates.

The Human Population Decreases in the death rate can be attributed to: Greater food production Better medical care Improvements in water quality Sanitation practices

The Human Population Current Population Numbers Rapid growth primarily due to drop in death rate Mexico ( )

The Human Population Projecting Future Population Numbers When will zero population growth occur?

Demographics of Countries Objectives: 1.Explain how highly developed and developing countries differ in population characteristics such as infant mortality rate, total fertility rate, and age structure. 2.Interpret age structure diagrams

Demographics of Countries Most Populous Countries Insert Table 8.1

Demographics of Countries Developed vs. Developing Countries Demographics Insert Table 8.2 (note reconstruction)

Demographics of Countries Developed vs. Developing Countries Demographics Insert Table 8.2 (note reconstruction)

Demographics of Countries Demographic Stages

Demographics of Countries Age Structure of Countries Generalized Age Structure

Demographics of Countries Examples:

Demographics of Countries Examples:

Demographics of Countries Examples:

Demographics of Countries Effects of an Aging Population Reduction in productive workforce Increasing tax burden Strain on social security, health, and pension systems Lower crime rates????

Demographics of the US Case-in-Point: US Immigration