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Chapter 5: Populations

Chapter 5: Populations. 5.1Essential Question: How do populations grow and what factors limit that growth?. List the characteristics used to describe a population Identify factors that affect population growth Differentiate between exponential and logistic growth. I. 5.1 How Populations Grow.

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Chapter 5: Populations

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  1. Chapter 5: Populations

  2. 5.1Essential Question: How do populations grow and what factors limit that growth? • List the characteristics used to describe a population • Identify factors that affect population growth • Differentiate between exponential and logistic growth

  3. I. 5.1 How Populations Grow A. Describing Populations 1. Geographic range – the space where a population of organisms lives a. Ex: Geographic range of Pine Barrens Tree Frog (Hyla andersonii)

  4. 2. Density and Distribution a. Density – the number of individuals of a species per unit area Map of countries by human population density, per square kilometer.

  5. b. Population distribution – describes how organisms are spread across their geographic range • Ex: random, uniform, or clumped

  6. 3. Growth rate – the rate at which a population grows a. Can be positive, negative, or maintaining • The population of bumblebees in the United States has been experiencing a negative growth rate, dropping 96 percent over the past two decades • Honeybees have been experiencing similar problems

  7. 4. Age structure – the numbers of males and females in different age groups of a population a. Example of importance: regulation of the fish catch

  8. B. Population Growth 1. Birthrate and death rate a. Populations may grow if more individuals are born than die • In 2010, Osprey had a record year in terms of birthrate – 1.97 young/nest • In 2011, that number was 2.07!!! • In order to maintain the Osprey population, they need to have a birthrate of at least 0.80 young/nest Osprey Nest – Little Egg Harbor, NJ For more info: 2010 Osprey Data 2011 Osprey Data

  9. 2. Immigration and Emigration a. Immigration – when more individuals move into a populations range b. Emigration – when individuals move out of a population

  10. C. Exponential Growth 1. Organisms that reproduce rapidly a. Exponential growth – a growth pattern in which the individuals in a population reproduce at a constant rate • Example: bacteria

  11. b. When growth is graphed, it typically has a “J” pattern c. Occurs naturally when organisms enter into new environments Everglades National Park has been the site of suspected releases of Burmese pythons, with population predictions in the tens of thousands. The National Park Service reported the removal of 311 Burmese pythons from the Everglades in 2008.

  12. D. Logistic Growth 1. Defined- a growth pattern in which a population’s growth rate slows or stops, following a period of exponential growth

  13. 2. Phases of growth a. Phase 1: exponential growth – quick growth phase b. Phase 2: growth slows down c. Phase 3: growth stops 3. Logistical growth typically has an “S” pattern to it

  14. 4. Carrying capacity – the largest number of individuals of a population that a given environment can support

  15. 5.1Essential Question: How do populations grow and what factors limit that growth? • List the characteristics used to describe a population • Identify factors that affect population growth • Differentiate between exponential and logistic growth

  16. Do Now #1 (Day 2) 1. How do ecologists study populations? 2. What factors affect population growth? 3. What is carrying capacity?

  17. 5.2 Essential question: what factors limit population growth? • Identify factors that determine carrying capacity. • Identify the limiting factors that depend on population density. • Identify the limiting factors that do not depend on population density.

  18. II. 5.2 Limits to Growth • Limiting Factors • Defined: any factor that controls the size of a population • 2 types • Density-dependent limiting factors • Density-independent limiting factors

  19. 3. Density-dependent limiting factors a. Examples: • Herbivores

  20. b. Predators

  21. c. Parasites and diseases Chronic Wasting Disease

  22. d. Competition

  23. e. Overcrowding 2006 Australian Locust outbreak

  24. 4. Density-independent limiting factors a. Defined: limiting factors that depend on population density, or the number of organisms per unit area.

  25. b. Weather/Natural disasters

  26. c. Human Interaction • Competition • Our gain, but their habitat loss • Introduced species • Pollution / Global climate change GSP Widening Project Gypsy Moth– Introduced species Pollution: Gulf Coast Oil Spill 2010

  27. 5.2 Essential question: what factors limit population growth? • Identify factors that determine carrying capacity. • Identify the limiting factors that depend on population density. • Identify the limiting factors that do not depend on population density.

  28. Do Now #1 (Day 2) • List several examples of limiting factors that depend on population density. 2. List several examples of limiting factors that do not depend on population density.

  29. 5.3 Essential question: How is the human population growing? Objectives: • Discuss the trend of human population growth • Explain why population growth rates differ in countries around the world

  30. III. Human Population Growth A. Historical Overview 1. Human Exponential Growth a. 1800’s Industrial Revolution – made it easier to ship goods worldwide

  31. Industrial Revolution (cont.) b. Food sources were more reliable c. Healthcare and medicine improved. d. Sanitation and nutrition improved e. Lower death rates and higher birth rates

  32. 2. Population growth boomed in the 1950’s and 60’s

  33. 3. Population Growth Statistics a. It took 123 years for the human population to go from 1 billion in 1804 to 2 billion in 1927 b. 33 years later it reached 3 billion c. The USCB estimates that the world population exceeded 7 billion on March 12, 2012

  34. B. Patterns of Human Population growth 1. Demography – the scientific study of human populations a. Tries to explain how populations change over time

  35. b. Look at various factors • Birth rates • Death rates • Age structure India has a population of approximately 1.2 billion people. Almost half the Indian population is younger than 25.

  36. 2. The Demographic Transition • Defined: a dramatic change from high birthrates and death rates to low birthrates and death rates • Divided into 3 stages (see p. 144 in text)

  37. 3. Trends in Demography a. World population growth has slowed, but about 10 countries are increasing at faster rates • Ex: India and China (1:6 people on planet earth are Chinese )

  38. b. Birthrates and death rates in the US, Japan, and most of Europe have fallen

  39. c. Age structure allows us to see which countries or regions will grow faster or slower • Ex: Guatemala has more young children than teenagers, and more teenagers than adults

  40. d. Disease/death rates • AIDS is causing very high death rates in Africa and parts of Asia

  41. Interesting Facts • Estimated heart attack related deaths in the US /year is 6,000,000 • About 100,000 people a year die due to complications of the AIDS virus • Between 3-5 million people are infected with cholera a year, with 130,000 deaths attributed to it in 2010 • Non-disease related • About 4 people die every year due to shark attacks • About 60 people/year die from lightening strikes • In the US roughly 60 people die every year due to bee stings

  42. Disease rates of interest – Cancer?

  43. e. World Population may reach 9 billion by 2050 • Question to ponder: How many people can the planet support? 12billion? 50 billion? 100 billion?

  44. 5.3 Essential question: How is the human population growing? Objectives: • Discuss the trend of human population growth • Explain why population growth rates differ in countries around the world

  45. Do Now #2 (Day 4) 1. How has the size of the human population changed over time? 2. What do demographers study? 3. Why do population growth rates differ among countries?

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