Chapter 35 Population Dynamics

Lesson Plans Day 1: Do Now Intro, Lecture 35. 1-35 Lesson Plans Day 1: Do Now Intro, Lecture 35.1-35.4 Day 2: Do now: Human population connection Lecture 35.5, 35.9-10 Lab: Bean mark and recapture, Interpreting Ecological data Quiz on 34-35 Test 34-35

Read the introduction on page 699 How were starlings introduced to North America? Why? Why is this a problem? How are starling populations and human populations similar?

The Spread of Shakespeare's Starlings The European Starling has become an abundant and destructive pest in North America Introduced in 1890 because of mention in Shakespeare Like the human population, is expanding and uncontrolled Population ecology is concerned with changes in population size and the factors that regulate populations over time

35.1 Populations are defined in several ways A population is a group of individuals of a single species that occupy the same general area Boundaries defined in relation to question being studied

POPULATION STRUCTURE AND DYNAMICS 35.2 Density and dispersion patterns are important population variables Population density is the number of individuals of a species per unit area or volume Environmental and social factors influence the spacing of individuals in various dispersion patterns Clumped Uniform Random

35.3 Idealized models help us understand population growth Exponential growth model gives an idealized picture of unregulated population growth Under ideal conditions, whole population multiplies by a constant factor

G = rN describes the J-shaped curve of exponential growth G = population growth rate r = intrinsic rate of increase Population members' maximum capacity to reproduce N = population size

Time Number of Cells 70 0 minutes 1 = 20 60 20 2 = 21 50 40 4 = 22 60 LE 36-04a Time Number of Cells 70 0 minutes 1 = 20 60 20 2 = 21 50 40 4 = 22 Number of bacterial cells (N) 60 8 = 23 40 80 16 = 24 30 100 32 = 25 120 (= 2 hours) 64 = 26 20 G = rN 3 hours 512 = 29 10 4 hours 4,096 = 212 8 hours 16,777,216 = 224 20 40 60 80 100 120 140 12 hours 68,719,476,736 = 236 Time (min)

G = rN(K - N)/K describes the S-shaped curve of logistic growth Logistic growth model represents the slowing of population growth as a result of limiting factors Limiting factors: environmental factors that restrict population growth G = rN(K - N)/K describes the S-shaped curve of logistic growth K = carrying capacity (K - N)/K accounts for the leveling off of the curve

Breeding male fur seals LE 36-04b 10 8 Breeding male fur seals (thousands) 6 4 2 1915 1925 1935 1945 Year

LE 36-04c G = rN (K - N) K G = rN K Number of individuals (N) Time

Predictions of logistic growth model for natural populations Growth rate low when population is either small or large Growth rate highest when population is at intermediate level Does not fit any natural population perfectly Useful starting point for studying population growth

Do Now: Read: Human population Connection Write 10 Facts from this article that you did not already know.

35.4 Multiple factors may limit population growth Population growth is density dependent Birth rates decline and death rates rise in response to increasing population density Organisms compete for limited resources Density affects health of organisms Abiotic factors may limit population growth before limiting factors become important

LE 36-05a 4.0 3.8 3.6 Clutch size 3.4 3.2 3.0 2.8 10 20 30 40 50 60 70 80 Density of females

Exponential growth Sudden decline LE 36-05b Exponential growth Sudden decline Number of aphids Apr May Jun Jul Aug Sep Oct Nov Dec

Most populations are regulated by a mixture of factors and show fluctuation over time

LE 36-05c 80 60 Number of females 40 20 1975 1980 1985 1990 1995 2000 Time (years)

35.5 Some populations have "boom-and-bust" cycles Some populations fluctuate in density with regularity May have complex causes Example: snowshoe hare and lynx cycles

LE 36-06 Snowshoe hare 160 120 9 Lynx Lynx population size (thousands) Hare population size (thousands) 80 6 40 3 1850 1875 1900 1925 Year

THE HUMAN POPULATION CONNECTION 35.8 Human population growth has started to slow after centuries of exponential increase The human population now stands at over 6.4 billion Even with slowing growth, predicted to reach 7.3 to 8 billion by 2025

LE 36-09a 6 5 4 Human population size (billions) 3 2 The Plague 1 8000 B.C. 4000 B.C. 3000 B.C. 2000 B.C. 1000 B.C. 1000 A.D. 2000 A.D.

What is Earth's human carrying capacity? Ecological footprint Amount of land needed to support human demands on Earth's resources Exceeds ecological capacity in many countries World is already in ecological deficit Problem is not just overpopulation, but overconsumption Possible limiting factors: food, space

Ecological footprint (ha per person) LE 36-09b 16 14 12 New Zealand 10 USA Germany Ecological footprint (ha per person) 8 Australia Netherlands Japan Canada Norway 6 Sweden UK 4 Spain World 2 China India 2 4 6 8 10 12 14 16 Available ecological capacity (ha per person)

LE 36-09c Traffic in downtown Cairo, Egypt Manhattan, New York City Refugee camp in Zaire

35.9 Birth and death rates and age structure affect population growth Demographic transition Shift from high birth rates and death rates to low birth rates and death rates Has occurred in most developed countries Population size continues to grow until birth rate equals death rate Reduced family size key Related to status of women

Birth or death rate per 1,00 0 population LE 36-10a 50 40 30 Birth or death rate per 1,00 0 population 20 Birth rate Death rate 10 1900 1925 1950 1975 2000 2025 2050 Year

Age structure of a population Proportion of individuals in different age groups Affects population's future growth Indicates social conditions Varies in developing and developed countries Demographic differences Infant mortality Life expectancy at birth

LE 36-10b Rapid growth Slow growth Decrease Afghanistan United States Italy Age Male Female Male Female Male Female 85+ 80 7579 707 6569 606 5559 505 4549 404 3539 Primary reproductive ages 303 2529 202 1519 101 59 0 8 6 4 2 2 4 6 8 6 4 2 2 4 6 6 4 2 2 4 6 Percent of population Percent of population Percent of population

35.10 Principles of population ecology have practical applications CONNECTION 35.10 Principles of population ecology have practical applications Principles of population ecology are useful in sustainable resource management Maximum sustained yield Improvement of habitat or provision of additional habitat to increase K Reduction of population size Challenged by economic and political pressures