Biology Ch. 5 Populations

I. Population Dynamics - Biological processes constantly influence a population’s density, dispersion, and growth rate. Tent Caterpillars

A. Population Characteristics 1. Population Density - number of organisms per unit area

2. Spatial Distribution - uniform, clumped, random Clumped Uniform

3. Population Range - depends on the species’ adaptations to biotic and abiotic factors Range of the Cougar Range of the Olympic Marmot

4. Population Growth Rate - balance between birth and immigration and death and emigration Births Immigration Population Size Emigration Deaths Deaths and emigration remove individuals from a population. Births and immigration add individuals to a population.

B. Exponential Growth - shows an increasing growth rate - under ideal condition with unlimited resources

B. Exponential Growth - results in population explosion 1900 1920 1940 1960 1980 Year 2,000 4,000 6,000 8,000 Elephant Population Exponential Growth in the African Elephant Population of Kruger National Park, South Africa

B. Exponential Growth

Paramecium population C. Logistic Growth - population growth levels off at carrying capacity (S-shaped curve) 1,000 800 600 400 200 180 150 120 90 60 30 Time (days) 5 10 15 160 140 80 100 40 20 Number of Paramecium/ml Number of Daphnia/50 ml Paramecium population Daphnia population

Effects of Exceeding Carrying Capacity 1911 - 25 reindeer introduced 1938 - 2000 reindeer 1950 - 8 reindeer survived food (lichens) overgrazed St. Paul Island, Alaska Effects of Exceeding Carrying Capacity Figure: 38.6a Title: The effects of exceeding carrying capacity Caption: Exceeding carrying capacity can damage an ecosystem, reducing its ability to support the population. In 1911, 25 reindeer were introduced onto one of the Pribilof Islands (St. Paul) in the Bering Sea off Alaska. Food was plentiful, and the reindeer encountered no predators on the island. The herd grew exponentially (note the initial J shape) until it reached 2000 reindeer in 1938. At this point, the small island was seriously overgrazed, food was scarce, and the population declined dramatically. By 1950, only eight reindeer survived.

D. Reproductive Patterns R-strategists K-Strategists

1. R-Strategists - adapted to unstable environments - short life spans - produce many offspring Chum Salmon Mayfly adults emerging to mate.

1. R-Strategists - adapted to unstable environments - short life spans - produce many offspring Dandelion Chum Salmon

2. K-Strategists - adapted to more stable environments - long life spans - produce fewer offspring

II. Limits to Growth A. Limiting Factors - factors that control population growth Competition Natural Disaster Population Size Predation Unusual Weather Parasitism and Disease

II. Limits to Growth A. Limiting Factors - determine carrying capacity Competition Natural Disaster Population Size Predation Unusual Weather Parasitism and Disease

1. Density-Dependent Factors - affect populations more as density increases - competition

1. Density-Dependent Factors - affect populations more as density increases - competition, predation Year 1850 1875 1900 1925 40 80 120 160 3 6 9 Lynx population size (thousands) Hare population size (thousands) Lynx Snowshoe hare Snowshoe Hare and Lynx

1. Density-Dependent Factors - affect populations more as density increases - competition, predation, disease and parasites

2. Density-Independent Factors - affect populations regardless of density Forest Fire Tsunami Tornado

III. Human Population Growth 8000 B.C. 4000 B.C. 3000 B.C. 2000 B.C. 1000 B.C. 1000 A.D. The Plague Human population (billions) 2000 A.D. 1 2 3 4 5 6 - Humans are undergoing a population explosion.

Human Population Growth Human Population Clock

1. For most of human existence, death rates were high. A. Historical Overview 1. For most of human existence, death rates were high. 2. In 1800’s, death rate decreased due to technological advances. - agricultural improvements - advances in sanitation and medicine - birth rates remained high 3. World population is ~7.5 billion. - about 1 billion added every 12 years

- the study of population growth trends B. Demography - the study of population growth trends 1. Demographic Transition - shift from high birth and death rates to low birth and death rate

Demographic Transition in Sweden and Mexico 50 40 20 30 10 1750 1800 1850 1900 1950 2000 2050 Birth rate Death rate Year Sweden Mexico Birth or death rate per 1,000 people

- the study of population growth trends B. Demography - the study of population growth trends 1. Demographic Transition - shift from high birth and death rates to low birth and death rate - U.S., Japan, and Europe have passed through the demographic transition. - S. America, Africa, and Asia are passing through Stage II. Human Population (millions) Time (Years)

Human Population Growth Rate by Country

Rapid Growth Afghanistan 2. Age Structure and Population Growth - Age structure diagrams are used to predict population growth trends. Rapid Growth Afghanistan Slow Growth United States Decrease Italy Male Female Age 8 6 4 2 Percent of population 80–84 85 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 20–24 25–29 10–14 5–9 0–4 15–19

Age Structure Diagrams for Japan in 1950, 2005, and 2050

Population (Millions) 3. Future Population Growth - As countries complete the demographic transition, population growth will begin to slow down. Time (Years) Population (Millions)

Ecological Footprint in Relation to Available Ecological Capacity 16 14 12 10 8 6 4 2 New Zealand Australia Canada Sweden World China India Available ecological capacity (ha per person) Spain UK Japan Germany Netherlands Norway USA Ecological footprint (ha per person)

The End

3. Boom-and-Bust Population Cycle - population greatly exceeds carrying capacity resulting in a population crash Annual lake algal bloom Conditions good: Boom Conditions bad: Bust