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C.5 population.pptx

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2016 IB Biology New Curriculum

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C.5 population.pptx

  1. 1. C.5 Population ecology (AHL) Essential idea: Dynamic biological processes impact population density and population growth.
  2. 2. Understandings, Applications and Skills Statement Guidance C.5 U.1 Sampling techniques are used to estimate population size. C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment. C.5 U.3 Population growth slows as a population reaches the carrying capacity of the environment. C.5 U.4 The phases shown in the sigmoid curve can be explained by relative rates of natality, mortality, immigration and emigration. C.5 U.5 Limiting factors can be top down or bottom up. C.5 A.1 Evaluating the methods used to estimate the size of commercial stock of marine resources. C.5 A.2 Use of the capture-mark-release-recapture method to estimate the population size of an animal species. C.5 A.3 Discussion of the effect of natality, mortality, immigration and emigration on population size. C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices. C.5 A.5 Bottom-up control of algal blooms by shortage of nutrients and top-down control by herbivory. C.5 S.1 Modelling the growth curve using a simple organism such as yeast or species of Lemna.
  3. 3. Populations • The total number of individuals of a species in a given area. Populations are affected by four main factors C.5 A.3 Discussion of the effect of natality, mortality, immigration and emigration on population size.
  4. 4. Four Factors Influence the Size of a Population: Natality: Birth Rate (offspring produced and added to population) C.5 A.3 Discussion of the effect of natality, mortality, immigration and emigration on population size.
  5. 5. Mortality: Death Rate (individuals that die) C.5 A.3 Discussion of the effect of natality, mortality, immigration and emigration on population size.
  6. 6. Immigration:Immigration: Movement of members of the species into the areaMovement of members of the species into the area C.5 A.3 Discussion of the effect of natality, mortality, immigration and emigration on population size.
  7. 7. Emigration:Emigration: Movement of members of the species out of area to liveMovement of members of the species out of area to live elsewhere.elsewhere. C.5 A.3 Discussion of the effect of natality, mortality, immigration and emigration on population size.
  8. 8. Population Changes C.5 U.4 The phases shown in the sigmoid curve can be explained by relative rates of natality, mortality, immigration and emigration.
  9. 9. Population size oscillates around the carrying capacity (K) Time N K overshoot oscillations C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
  10. 10. • Density Dependent Limits  Food  Water  Shelter  Disease • Density Independent Limits  Natural Disasters  Humans (logging, mining, farming) Water and shelter are critical limiting factors in the desert. Fire is an example of a Density independent Limiting factor. Limits on Population Growth C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
  11. 11. C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment. This graph shows the explosion of human population over the last 10,000 years along with some relevant historical events.
  12. 12. How did we get here? • When I graduated high school there were 4 billion people. *Today there are almost 7 billion people C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
  13. 13. About 5 million years ago Hunter-gathers 1 million people C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
  14. 14. Neolithic Period (6000 B.C.) No longer a Natural Setting 100 million people C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
  15. 15. Common area 2000 years ago 300 million people C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
  16. 16. 1800’s (Carbon cycle control) Steam engineSteam engine 1 billion people C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
  17. 17. London between 1800 to 1880 • 1800 pop. 1 million • 1880 pop. 4.5 million • Improvements in medicine and public health C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
  18. 18. Life Expectance • Neolithic it was 20 • 1900 it was 30 • 1950 it was 47 • Current world average is 67 C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
  19. 19. 1800-2000? • From 1 billion to 6 billion? How??? C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
  20. 20. 1908 Control of the Nitrogen Cycle • Up until 1908 farms were dependent on organic sources for nitrogen (manure) • Haber figured out how to convert N2 into NH3 and then into NH4 + of NO3 - • Commercial fertilizers are bornFritz Haber C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
  21. 21. 1944 Plant Breeding • Improves yields • Disease resistance improvements • Less day-length sensitive • Improve sharing of ideas on plant breeding C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment.
  22. 22. C.5 U.2 The exponential growth pattern occurs in an ideal, unlimited environment. Examples of exponential population growth http://www.nature.com/scitable/knowledge/library/an-introduction-to-population-growth-84225544 Throughout the 1800's, hunters decimated the American Plains bison populations, and by 1889, only about one thousand bison remained. The US government, along with private landowners, established protected herds in the late 1800's and early 1900's. The herds started small, but with plentiful resources and few predators, they grew quickly. The bison population in northern Yellowstone National Park increased from 21 bison in 1902 to 250 in only 13 years.
  23. 23. C.5 U.3 Population growth slows as a population reaches the carrying capacity of the environment.
  24. 24. 3 Phases: 1. Exponential growth Phase 2. Transitional Phase 3. Plateau Phase Limited Growth Sigmoid (S-Shaped)Sigmoid (S-Shaped) C.5 U.3 Population growth slows as a population reaches the carrying capacity of the environment.
  25. 25. 1. Exponential Growth Phase • Population increases exponentially. • Resources are abundant. • Predators and disease are rare. C.5 U.3 Population growth slows as a population reaches the carrying capacity of the environment.
  26. 26. 2. Transitional Phase • As a result of intra-specific competition  for food, shelter, nesting space, etc.,  and the build up of waste. • The growth rate slows down.  Birth rates decline and death rate increases C.5 U.3 Population growth slows as a population reaches the carrying capacity of the environment.
  27. 27. 3. Plateau Phase • Natality and mortality are equal so population size is constant. • When the number of individuals in the population have reached the maximum which can be supported by the environment. The number is called the CARRYING CAPACITY C.5 U.3 Population growth slows as a population reaches the carrying capacity of the environment.
  28. 28. C.5 U.4 The phases shown in the sigmoid curve can be explained by relative rates of natality, mortality, immigration and emigration. Limiting factors are environmental factors that controls the maximum rate at which a process, e.g. population growth, can occur. • build-up of toxic by products of metabolism • Injury • Senescence (death from age related illness)
  29. 29. All examples of competition for resources • Injury • Senescence (death from age related illness) • build-up of toxic by products of metabolism C.5 U.4 The phases shown in the sigmoid curve can be explained by relative rates of natality, mortality, immigration and emigration.
  30. 30. • build-up of toxic by products of metabolism The effect of these limiting factors increases as the population increases. These factors are described as being density dependent limiting factors. • Injury • Senescence (death from age related illness) C.5 U.4 The phases shown in the sigmoid curve can be explained by relative rates of natality, mortality, immigration and emigration.
  31. 31. • build-up of toxic by products of metabolism The this limiting factor does not increases as the population increases. This factor is described as being a density independent limiting factor. • Injury • Senescence (death from age related illness) Examples include: •Climate / weather •Availability of light (for plants) •Natural disasters such as volcanic eruptions and fire C.5 U.4 The phases shown in the sigmoid curve can be explained by relative rates of natality, mortality, immigration and emigration.
  32. 32. C.5 U.5 Limiting factors can be top down or bottom up. A limiting factor is an environmental selection pressure that limits population growth. There are two categories of limiting factor: Top-down factors are pressures applied by other organisms at higher trophic levels. Bottom-up factors are those that involve resources or lower tropic levels. A keystone species exerts top-down influence on its community by preventing species at lower trophic levels from monopolizing critical resources, such as competition for space or food sources. http://commons.wikimedia.org/wiki/File:Tierpark_Sababurg_Wolf.jpg http://commons.wikimedia.org/wiki/File:Green_Sea_Turtle_grazing_seagrass.jpg
  33. 33. C.5 A.5 Bottom-up control of algal blooms by shortage of nutrients and top-down control by herbivory. An algal bloom is a rapid increase or accumulation in the population of algae (typically microscopic) in a water system. http://commons.wikimedia.org/wiki/File:Mar%C3%A9_vermelha.JPG
  34. 34. C.5 A.5 Bottom-up control of algal blooms by shortage of nutrients and top-down control by herbivory. http://commons.wikimedia.org/wiki/File:Algal_bloom_20040615.jpg • The water around coral-reef ecosystems is generally nutrient-poor. • Nutrients in these areas are needed in small amounts are essential for the synthesis of key proteins and other compounds, e.g. magnesium is needed to make chlorophyll. • Algae depend on photosynthesis for nutrition. • Free-living algae blooms can disrupt coral reef communities by blocking sunlight and preventing photosynthesis in the symbiotic zooxanthellae. This can cause coral bleaching (the corals eject the no longer useful zooxanthellae) which leads to the death of the corals. http://resources3.news.com.au/images/2011/04/28/1226046/589887-raw-sewerage.jpg
  35. 35. With key proteins such as chlorophyll in short supply the rate of photosynthesis and hence algal growth is limited. Nutrients are therefore a bottom-up limiting factor. Nutrient enrichment through human activity (fish farming, fertilizer or sewage outflows directly or from nearby rivers) can cause known as eutrophication – algal populations increase rapidly (blooms) due to the removal of nutrients as a limiting factor.
  36. 36. C.5 S.1 Modelling the growth curve using a simple organism such as yeast or species of Lemna. In the absent of equipment using one or more of the following resources to model population growth: •Yeast Population Growth lab and simulation by i-Biology (http://www.slideshare.net/gurustip/population-growth-9457952) •Bunny population growth by PhET (http://phet.colorado.edu/files/activities/3896/04.02 - CW - bunny simulation - 2014-07-30 - vdefinis.docx) Duckweed (Lemna sp.) is a good model organism for measuring sigmoidal population growth • Place a small number of plants in a container, e.g. a plastic cup • Count the number of fronds (leaves) every day until the surface of the container is covered, i.e. the population has ceased to increase. • Plot your results – you should obtain a sigmoidal curve • Your investigation can be extended by considering different independent variables e.g. nutrient availability and the surface area of the container.
  37. 37. Why monitor populationsWhy monitor populations?? • Determine current status of a population • Determine habitat requirements of a species • Evaluate effects of management *Complete “census” of natural populations is often very difficult! Population Sampling C.5 U.1 Sampling techniques are used to estimate population size.
  38. 38. Population vs.Population vs. SampleSample SampleTrue Population C.5 U.1 Sampling techniques are used to estimate population size.
  39. 39. RANDOM SAMPLING • A sampling procedure that assures that each element in the population has an equal chance of being selected • Sampled population should be representative of target population C.5 U.1 Sampling techniques are used to estimate population size. Sample Methods •Quadrat •Mark-Recapture •There are MANY more…
  40. 40. Quadrat Sampling • A square frame is placed in a habitat • All the individuals in the quadrat are counted • The process is repeated until the sample size is large enough C.5 U.1 Sampling techniques are used to estimate population size.
  41. 41. • Useful for small organisms or for organisms that do not move C.5 U.1 Sampling techniques are used to estimate population size.
  42. 42. Converting a population study into a graph
  43. 43. MARK-RECAPTURE (Lincoln Index) • Capture and mark known number of individuals • 2nd round of captures soon after  Time for mixing, but not mortality • Fraction of marked individuals in recapture sample is estimate of the proportion of population marked in first capture C.5 A.2 Use of the capture-mark-release-recapture method to estimate the population size of an animal species.
  44. 44. Marking methods • Paint or dye • Color band  birds • Unique markings  Large mammals; keep photo record • Toe clipping  Reptiles, amphibians, rodents • Radio Collars • Micro chips (NPS 2000) C.5 A.2 Use of the capture-mark-release-recapture method to estimate the population size of an animal species.
  45. 45. Lincoln Index Using mark-recapture sampling to estimate animal populations Population Size P =(# initially marked) x (total 2nd catch) (# of marked recaptures) Or N1 x N2 N3 C.5 A.2 Use of the capture-mark-release-recapture method to estimate the population size of an animal species.
  46. 46. Mark Recapture Lincoln Index N1 = 4 N2 = 5 N3 = 2 N1 = first capture N2 = second capture N3 = #’s of marked in second capture
  47. 47. Survey 1: N1= 12 Survey 2: N2 = 15 N3 = 4
  48. 48. • You capture and mark 150 fish in a lake. (This must be a random, representative sample.) • You release them back into the lake, allowing enough time for them to remix with the population. • You trap another 220 fish, of which 25 are recaptures (i.e., marked from the initial trapping. • What is your estimate of the total population of fish in the lake? Example:
  49. 49. • N1 = 150 • N2 = 220 • N3 = 25 • P = [(220)(150)] / 25 = 1320 FISH Example:
  50. 50. Example: • Use the Lincoln Index to monitor this mountain gorilla population over time C.5 A.2 Use of the capture-mark-release-recapture method to estimate the population size of an animal species.
  51. 51. C.5 A.2 Use of the capture-mark-release-recapture method to estimate the population size of an animal species.
  52. 52. Human Effect on the World Fish PopulationHuman Effect on the World Fish Population • Overexploitation of species affects the loss of genetic diversity and the loss in the relative species abundance of both individual and/or groups of interacting species. Overexploitation may include over fishing and over harvesting • Historically, humans have fished the oceans, which never seemed to pose a problem due to their C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.
  53. 53. A case study: The Peruvian Anchovy (Engraulis ringens) Universidad de La Serena C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.
  54. 54. The Peruvian Anchovy • This is a small (12-20cm), short-lived species maturing in 1 year • Anchovy live in the surface waters in large shoals off the coast of Peru and northern Chile • Here there are cold currents up-welling from the sea bed bringing nutrients for phytoplankton • Plankton is at the base of the food chain. C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.
  55. 55. The Peruvian Anchovy • The harvest of this fish doubled every year from 1955 to 1961 • Experts estimated the maximum harvestable yield (MSY) at 10 to 11 million tonnes per year • Through the 1960s the harvest was about this level • The biggest fishing harvest in the world • Some of the anchovy were used for human food • But a lot was ground into fishmeal for animal feed C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.
  56. 56. The collapse of the anchovy fishery • In 1972 there was an El Niño event that brought warm tropical water into the area • The up-welling stopped, • the phytoplankton growth decreased • the anchovy numbers fell and concentrated further south • The concentrated shoals of anchovy were easy targets for fishing boat eager to recuperate their harvest • The political will was not there to impose reduced quotas • Larger catches were made • No young fish were entering the population (no recruitment) • No reproduction was taking place • The fish stocks collapsed and did not recover C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.
  57. 57. Population dynamics of fisheries • A fishery is an area with an associated fish population which is harvested for its commercial or recreational value. Fisheries can be wild or farmed. • Population dynamics describes the ways in which a given population grows and shrinks over time, as controlled by birth, death, and emigration or immigration. It is the basis for understanding changing fishery patterns and issues such as habitat destruction, predation and optimal harvesting rates. • The population dynamics of fisheries is used by fisheries scientists to determine sustainable yields C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.
  58. 58. Sampling method Situation in which the method is used Usage and limitations Random sampling Not used. Ineffective as fish are too mobile. Capture-mark- release-recapture Fish are temporarily stunned with electric shocks and then counted Used in lakes and rivers, but recapture numbers are too small to be useful in open waters such as oceans. Echo sounders Can be used to estimate the size of fish shoals Only useful for schooling fish species Fish catches Age structure of landed fish can be used to estimate population size. Violators of fishing regulations designed to control the age of fish landed often do not report what they land or they dump the restricted fish causing a bias in the estimates. Estimating Fish populations C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.
  59. 59. Sampling method Situation in which the method is used Usage and limitations Random sampling Not used. Ineffective as fish are too mobile. Capture-mark- release-recapture Fish are temporarily stunned with electric shocks and then counted Used in lakes and rivers, but recapture numbers are too small to be useful in open waters such as oceans. Echo sounders Can be used to estimate the size of fish shoals Only useful for schooling fish species Fish catches Age structure of landed fish can be used to estimate population size. Violators of fishing regulations designed to control the age of fish landed often do not report what they land or they dump the restricted fish causing a bias in the estimates. Estimating Fish populations • Fish are very mobile – they pursue what is frequently a mobile food supply. • They often school so are unevenly distributed. … so how can we count/estimate their numbers? If we know how big fish population are we can fish sustainably, but ….
  60. 60. Maximum Sustainable Yield (MSY) Based upon: 1. the harvest rate 2. the recruitment rate of new (young) fish into the population • a population can be harvested at the point in their population growth rate where it is highest (the exponential phase) • Harvesting (output) balances recruitment (input) • Fixed fishing quotas will produce a constant harvesting rate (i.e. a constant number of individuals fished in a given period of time) C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.
  61. 61. Maximum Sustainable Yield (MSY) C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.
  62. 62. Maximum Sustainable Yield • The Largest possible catch without adversely affecting the ability of the population to recover. C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.
  63. 63. Problems with MSY Age structure: If all the age groups are harvested recruitment of young fish into the reproductive group will be reduced. The answer is to use a net with a big enough mesh size that lets the young fish escape Age and sustainable fishing • If a population is growing, then the relative number of younger fish will be higher (there are many potential breeding fish for the future). • If a population is in decline, then the proportion of older fish will be higher (older fish have a higher mortality and are unlikely to be as productive in breeding). C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.
  64. 64. Problems with MSY Limiting factors: If the limiting factors in the environment change so does the population growth rate • Limiting factors set the carrying capacity (K) of an environment • Increasing limiting factors will cause K to drop • Fixed quotas cannot cope with this • Data: For MSY to work accurate data in fish populations is needed (population size, age structure, recruitment rates) • Usually these are not well known C.5 A.4 Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.
  65. 65. What is required? • Nets with bigger mesh size • Regulated fishing methods • More data on fish populations (e.g. by fish tagging investigations – mark and recapture) • Constant monitoring to observe changes in environmental factors (e.g.El Niño events • Policing of fishing industry – respect of quotas • International agreements • Greater exploitation of fish farming • But this is not without its own problems (space, diseases and pollution are all associated with intensive fish culture)
  66. 66. C.1.A1 Distribution of one animal and one plant species to illustrate limits of tolerance and zones of stress. Shelford's law of tolerance is a useful tool to understand the relative abundance of a species and hence predict community structure. It plots the range of a biotic or abiotic factor that is tolerated by a species,. Because their is variability but within a population the limits of tolerance and where the zones of stress start is not always easy to measure. http://www.anselm.edu/homepage/bpenney/teaching/BI320/elements/Krohne_Shelfords.jpg
  67. 67. Bibliography / Acknowledgments

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