Chapter 8 Population Change

Overview of Chapter 8 o Principles of Population Ecology o Reproductive Strategies o The Human Population o Demographics of Countries o Demographics of United States

Principles of Population Ecology o Population Ecology Study of populations and why their numbers change over time Study of populations and why their numbers change over time Important for Important for Endangered species Endangered species Invasive species Invasive species o Population Group of individuals of same species living in the same geographic area at the same time Group of individuals of same species living in the same geographic area at the same time

Population Density o Population density The number of individuals of a species per unit area or volume at a given time The number of individuals of a species per unit area or volume at a given time Ex: minnows per Liter of pond water Ex: minnows per Liter of pond water o Ovals below have the same population, and different densities

Change in Population Size

Calculating Population Change Birth (b), Death (d), Immigration (i) and Emigration (e) are calculated per 1000 people Growth rate Birth rate Death rate Immigration rate Emigration rate r = (b – d) + (i – e)

Maximum Population Growth o Intrinsic Rate of Growth (Biotic Potential) Growth rate under ideal conditions Growth rate under ideal conditions J- Shaped Curve (exponential growth) J- Shaped Curve (exponential growth)

Environmental Resistance o Environmental limits (resistance) Prevent indefinite reproduction Prevent indefinite reproduction Unfavorable food, water, shelter, predation, etc. Unfavorable food, water, shelter, predation, etc. o Carrying Capacity (K) Maximum # of individuals an environment can support Maximum # of individuals an environment can support Causes leveling off of exponential growth Causes leveling off of exponential growth S- shaped curve of logistic population growth S- shaped curve of logistic population growth

Population Crash o Overshooting the carrying capacity can lead to a population crash Abrupt decline in population density Abrupt decline in population density

Factors That Affect Population Size o Density Dependent Factor Factor whose effect on a population changes as the population density changes Factor whose effect on a population changes as the population density changes Examples: Examples: Predation Predation Disease Disease Competition Competition Sometimes cause Boom-or-Bust Population Cycles Sometimes cause Boom-or-Bust Population Cycles

Boom-Or-Bust Population Cycles

Case Study- Predator Prey Dynamics on Isle Royale o As the wolf population increases, the moose population decreases (and vice versa)

Factors That Affect Population Size o Density Independent Factors Factors that affect the population size, but is not influenced by changes in population density Factors that affect the population size, but is not influenced by changes in population density Examples: Examples: Killing frost Killing frost Severe blizzard Severe blizzard Fire Fire

Reproductive Strategies r-selected species k-selected species -Small body size - Early maturity - Short life span - Large broods - Little or no parental care - Probability of long term survival is low - Mosquitoes and Dandelions - Small broods - Long life span - Slow development - Large body size - Late reproduction - Low reproductive rate - Redwood trees and human beings

Survivorship

Some populations fit two curves o Herring Gulls o Type III & Type II

Human Population o Demography Science of population structure and growth Science of population structure and growth o Human Population since 1980 is J- shaped curve

Human Population PopulationYear Reached 1 Billion Billion Billion Billion Billion Billion Billion2012

Population Increase in Mexico

Projecting Future Populations o Population is increasing o Growth rate (r) has started to decline o Projections for 2050 Low = 7.7 billion Low = 7.7 billion High = 10.6 billion High = 10.6 billion Most likely = 9.1 billion Most likely = 9.1 billion

Demographics of Countries RankCountryPopulation World7,174,611, China1,355,692, India1,236,344, United States318,892, Indonesia253,609, Brazil202,656, Pakistan196,174, Nigeria177,155, Bangladesh166,280, Russia142,470, Japan127,103,388

Demographic Stages o Pre-industrial Stage Birth and death rates high Birth and death rates high Modest population growth Modest population growth o Transitional Stage Lowered death rate Lowered death rate Rapid population growth Rapid population growth o Industrial Stage Birth rate decline Birth rate decline Population growth slow Population growth slow o Post Industrial Stage Low birth and death rates Low birth and death rates Population growth very slow Population growth very slow

Demographic Stages

Age Structure o The number and proportion of people at each age in a population

Demographics of Specific Countries

World-wide o 29% of human population is under age 15 o Could cause large increase in birth rates

Education of Immigrants into US