Population Ecology

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populations, r-species, k-species, mark & recapture methods and analysis; more slides at GoAPES (http://goapes.wikispaces.com).

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Population Ecology

  1. 1. POPULATION DYNAMICS, CARRYING CAPACITY, AND CONSERVATION BIOLOGY The Walker School Environmental Science
  2. 2. Population Ecology The study of individual  species in relation to the environment. The field is concerned  with conservation and focuses on Population and Population Viability Analysis (PVA)
  3. 3. Population Viability Analysis A species-specific method of  risk assessment. Brings together species  characteristics and environmental variability to forecast population health and extinction risk. Begins with the question: “Is this  species at risk of becoming endangered? If so, why?”. A research example may  include: “What are the effects of industrial forestry on biodiversity.”
  4. 4. WHAT ARE THE MAJOR CHARACTERISTICS OF A POPULATION?
  5. 5. Populations A group of individuals of a single species that  simultaneously occupy the same general area.
  6. 6. Populations Under Study Diseases (prions, viruses, bacteria)  Vegetation (crops, orchards, forests)  Terrestrial Animals (cattle, sheep, pigs, chickens)  Aquatic Organisms (fish, shrimp)  Humans 
  7. 7. HIV Population in South Africa Arcview GIS
  8. 8. Characteristics of Populations Distribution  Numbers (size)  Age Structure  Density (#/area)  Celestichthys
  9. 9. WHAT IS BIOGEOGRAPHY?
  10. 10. Biogeography The study of the size and  distribution of biodiversity over space and time. It aims to reveal where organisms live, and at what abundance. Giant Pandas
  11. 11. Factors Explaining Species Distributions Speciation  Extinction  Continental drift  Glaciations  (associated variations in sea level, river routes) River capture 
  12. 12. Speciation & Population Types  Ranges  PhysicalStructures  Food Resources
  13. 13. Paleobiogeography goes one step further  to include paleogeographic data and considerations of plate tectonics. Uses molecular  analyses and fossils to determine the change in a species over millions of years. Hominid Evolution
  14. 14. HOW ARE POPULATIONS TRACKED?
  15. 15. Mark-Recapture Method A method commonly used in ecology to estimate population  size and population vital rates (i.e., survival, movement, and growth)
  16. 16. Lotek Wildlife GPS Monitors http://www.lotek.com/
  17. 17. The Process Researcher visits a study area and uses traps to 1. capture a group of individuals alive. Captured animals are marked with tags, collars, 2. bands, or spots of dye and then is released unharmed back into the environment. Sufficient time is allowed to pass for the marked 3. individuals to redistribute themselves among the unmarked population. Next, the researcher returns and captures another 4. sample of individuals.
  18. 18. Analysis
  19. 19. WHAT FACTORS GOVERN CHANGES IN POPULATION SIZE?
  20. 20. Demography The study of the vital statistics that affect population  size. •Size •Density •Age Distribution •Dispersion
  21. 21. Population Dispersion Patterns Clumped Uniform Random (elephants) (creosote bush) (dandelions)
  22. 22. Factors Affecting Distribution Density Dependant Density Independent Competition for Floods   Resources Hurricanes  Predation Unseasonable   Weather Parasitism  Infectious Disease Fire   Clear Cutting  Pesticide Spraying 
  23. 23. Changing and Clumping Availability and variation  of resources Provide protection in  numbers Packs have a better  chance of obtaining food Temporary groups for  mating
  24. 24. Factors that Govern Population Size Crude Birth Rate (CBR)  Crude Death Rate (CDR)  Immigration  Emigration  Population Change = (births + immigration) – (deaths + emigration)
  25. 25. Population Age Structures
  26. 26. WHAT LIMITS POPULATION GROWTH?
  27. 27. Resources and Competitors Biotic Potential (r)  Ecosystem Carrying  Capacity (K) Rate of Increase  Environmental  Resistance Carrying Capacity
  28. 28. Population Growth Curves: J-Curve & S-Curve © 2004 Brooks/Cole – Thomson Learning K Population size (N) Population size (N) Time (t) Time (t) Exponential Growth Logistic Growth
  29. 29. Population growth strives for dynamic equilibrium: Logistic Growth of a Sheep 2.0 Number of sheep (millions) 1.5 1.0 .5 1800 1825 1850 1875 1900 1925 Year
  30. 30. Organisms can exceed their carrying capacity: Exponential Growth and Crash of Reindeer 2,000 Number of reindeer 1,500 1,000 500 1910 1920 1930 1940 1950 Year
  31. 31. Reasons for Diebacks Catastrophic Loss of Resources  Introduction of New Predator  Disease 
  32. 32. WHAT KINDS OF POPULATION CHANGE CURVES DO WE FIND IN NATURE?
  33. 33. General Types of Population Curves in Nature © 2004 Brooks/Cole – Thomson Learning Irregular Stable Number of individuals Cyclic Irruptive Time
  34. 34. Cycles in Hare and Lynx Populations 160 140 Hare Population size (thousands) 120 Lynx 100 80 60 40 20 0 1845 1855 1865 1875 1885 1895 1905 1915 1925 1935 Year
  35. 35. Community Organization – Trophic Cascade Model Postulates that it is mainly predation that controls  community organization Predators control herbivores 
  36. 36. Community Organization – Bottom-Up Model Mineral nutrients control community organization  Nutrients control plant types and numbers  Plants control predators  Changes in this community are done by adding or  removing minerals
  37. 37. Activity: Radio Expeditions Species Extinctions Audio Evidence of Ivory-Billed Woodpecker  http://www.npr.org/templates/story/story.php?storyId=4814860  Audubon Bird Count, Lost Woodpecker Rediscovered  http://www.npr.org/templates/story/story.php?storyId=5067655  Slate's Explainer: Determining Species Extinction  http://www.npr.org/templates/story/story.php?storyId=5015201 
  38. 38. Activity: Radio Expeditions Species Extinctions Questions Populations are classified by size, density, age distribution, and dispersion  type. Briefly explain each of these concepts and describe one environmental factor that would limit the population growth of a bird species. Discuss the difference between an endangered and a threatened species.  Design a population count experiment to determine if a bird population is  threatened or endangered. Make sure to discuss how the study area was selected and what method will be used to estimate population. Discuss one biological intervention, economic incentive and one legislative  policy to restore an endangered bird population. Discuss what technology could be used to periodically monitor the program. 
  39. 39. WHAT TYPE OF REPRODUCTIVE PATTERNS DO SPECIES HAVE?
  40. 40. Sexual Partners Are Not Always Needed Asexual Reproduction  Sexual Reproduction 
  41. 41. Sexual Reproduction Methods Semelparity   Onetime reproductive event Iteroparity   Repeated reproduction
  42. 42. General Characteristics of r-Selected Species cockroach dandelion r-Selected Species Many small offspring Little or no parental care and protection of offspring Early reproductive age Most offspring die before reaching reproductive age Small adults Adapted to unstable climate and environmental conditions High population growth rate (r) Population size fluctuates wildly above and below carrying capacity (K) Generalist niche Low ability to compete Early successional species
  43. 43. General Characteristics of k-Selected Species K-Selected Species elephant saguaro Fewer, larger offspring High parental care and protection of offspring Later reproductive age Most offspring survive to reproductive age Larger adults Adapted to stable climate and environmental conditions Lower population growth rate (r) Population size fairly stable and usually close to carrying capacity (K) Specialist niche High ability to compete Late successional species
  44. 44. Carrying Capacity of Species Carrying capacity K K species; experience Number of individuals K selection r species; experience r selection Time
  45. 45. WHAT ROLE DOES GENETICS PLAY IN THE SIZE OF POPULATIONS?
  46. 46. Vulnerability of Populations Founders Effect  Results from the migration of a population to a geographically  isolated area. Demographic Bottleneck  Results from a natural catastrophe such as fire or a hurricane.  Genetic Drift  Results from random changes in the gene frequencies in a population.  Interbreeding  Results when individuals from a small population breed with each  other.
  47. 47. HOW DO ECOLOGISTS USE LIFE TABLES AND SURVIVORSHIP CURVES TO MONITOR POPULATIONS?
  48. 48. Death Will Come: Survivorship Curves Late Loss  Early Loss Percentage surviving (log scale) 100  Constant Loss  10 1 0 Age
  49. 49. Life Table Life Expectancy at Birth of Epidemic Malaria Area in Papua New Guinea An age-specific summary of the  survival pattern of a population. Life tables are constructed by  following a cohort from birth to death. A cohort is a group of individuals  of the same age. The table is constructed from the  number of individuals that die in each age-group during a defined time period. Life tables are graphically  displayed in survivorship curves.
  50. 50. Geographical Information Systems Used to Map Population Data Captures, stores, analyzes,  manages, and presents data that refers to or is linked to location. Geographic information system  technology can be used for scientific investigations for the environmental science, environmental impact assessment, urban planning and other purposes. Can be used for spacial  analysis and data modeling.

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