2 Populations


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  • Mortality (death rate) Decreases population density Emigration (number of organisms moving out) Decreases population density Natality (birth rate) Increases population density Immigration (number of organisms moving in) Increases population density
  • Many individuals die withou reproducing, predators,
  • Open-New orgs born and immigrate while others die or emigrate - Most ecosystems in nature Closed - Usually in a laboratory or game reserve situation
  • Competition for food Increase in predator population Increase in parasites Environmental resistance Factors which cause resistance to population growth Carrying capacity The population size that a habitat can sustain Lag phase Period of adaptation to new conditions Low initial numbers Exponential Growth Constant cell division High natality rate Transition Period Natality rate slows Affected by overcrowding Slowing Phase Rate of natality slows further Stationary Phase Natality = mortality Population growth stops
  • Average life expectance at birth The age half the individuals born will survive to Maximum length of life for a species Annuals - 1 year Biennials - 2 year
  • More energy into numbers = less into rearing offspring Or Less energy into numbers = more energy into rearing offspring Fish lay many eggs No parental care Few survive Mice reproduce early and often Dogs have smaller annual litters
  • Percentage of populaiton in different age clases - pre-reproductive, reproductive and post reproductive Sweden diminshing populaiton (urn shape curve) - few pre reproductive, post reproductive Mexico - expanding population - pyramid curve - most pre reproductive - very few post reproductive USA - stable - bell shape - widest at bottom - pre and reproductive similar - post reproductive less
  • Substrate - plants in rocky areas - grow between rocks
  • Optimum range When conditions are most favourable Zone of physiological stress When conditions are “uncomfortable” Upper and Lower limits of tolerance Organisms die
  • 2 Populations

    1. 1. Populations
    2. 2. Populations <ul><li>All individuals of a given species in a particular habitat </li></ul>
    3. 3. Communities <ul><li>All the organisms in a defined area </li></ul><ul><ul><ul><li>Ecosystem </li></ul></ul></ul><ul><ul><ul><ul><li>A community plus all the non-living (abiotic) components in a habitat </li></ul></ul></ul></ul>
    4. 4. Populations <ul><li>Measuring Populations </li></ul><ul><li>How populations are regulated </li></ul>
    5. 5. Measuring Populations <ul><li>Population Density </li></ul><ul><ul><li>Number of individuals per unit area </li></ul></ul>
    6. 6. Population Density <ul><li>Influenced by </li></ul><ul><ul><li>Mortality </li></ul></ul><ul><ul><li>Emigration </li></ul></ul><ul><ul><li>Natality </li></ul></ul><ul><ul><li>Immigration </li></ul></ul>
    7. 7. Population Growth <ul><li>Population density fluctuates </li></ul><ul><li>Natality + immigration = mortality + emigration </li></ul><ul><li>Mortality is usually high </li></ul>
    8. 8. Types of Populations <ul><li>Open </li></ul><ul><ul><li>Natality, mortality, immigration and emigration affect population size </li></ul></ul><ul><li>Closed </li></ul><ul><ul><li>Only natality and mortality affect population size </li></ul></ul>
    9. 9. Exponential Growth <ul><li>Under favourable conditions </li></ul><ul><li>No predators, parasites or competition </li></ul>
    10. 10. Sigmoid Growth <ul><li>Natural conditions </li></ul><ul><li>Curve flattens because of </li></ul><ul><ul><li>Competition </li></ul></ul><ul><ul><li>Predators </li></ul></ul><ul><ul><li>Parasites </li></ul></ul><ul><ul><li>Environmental resistance </li></ul></ul><ul><ul><li>Carrying capacity </li></ul></ul>
    11. 11. Closed Population Growth <ul><li>No immigration or emigration </li></ul><ul><li>Population slowly kills itself </li></ul><ul><ul><li>Lack of </li></ul></ul><ul><ul><ul><li>Food </li></ul></ul></ul><ul><ul><ul><li>Space </li></ul></ul></ul><ul><ul><ul><li>Oxygen </li></ul></ul></ul><ul><ul><ul><li>Water </li></ul></ul></ul><ul><ul><li>Poisons itself </li></ul></ul>
    12. 12. J Curve <ul><li>Closed population </li></ul><ul><li>Upper limit </li></ul><ul><ul><li>Seasonal conditions </li></ul></ul><ul><li>Never reaches carrying capacity </li></ul>
    13. 13. Survivorship <ul><li>The chance of remaining alive to pass on your genes to the next generation </li></ul><ul><li>Life expectancy </li></ul><ul><li>Life span </li></ul>
    14. 14. Survival of the species <ul><li>Most energy is put into survival of species </li></ul>
    15. 15. Age Group structure
    16. 16. Population Distribution <ul><li>Clumped </li></ul><ul><li>Random </li></ul><ul><li>Evenly spread out </li></ul>
    17. 17. Clumped Populations <ul><li>Increases competition for food and space </li></ul><ul><li>Reduces drying out </li></ul><ul><li>Greater defence </li></ul><ul><li>Easier to find mates </li></ul><ul><li>May also be due to substrate </li></ul>
    18. 18. Evenly Spread <ul><li>Animals </li></ul><ul><ul><li>By competition or aggression </li></ul></ul><ul><ul><li>Defended territories </li></ul></ul><ul><ul><li>Limits population density </li></ul></ul><ul><li>Plants </li></ul><ul><ul><li>Shading </li></ul></ul><ul><ul><li>Competition </li></ul></ul><ul><ul><li>Allelopathy </li></ul></ul>
    19. 19. Population Regulation <ul><li>Abiotic </li></ul><ul><ul><li>Tolerance </li></ul></ul><ul><ul><li>Acclimation </li></ul></ul><ul><ul><li>Geographical Barriers </li></ul></ul><ul><ul><li>Liebig’s Law of Minimum </li></ul></ul><ul><li>Biotic </li></ul><ul><ul><li>Predation, paracitism </li></ul></ul><ul><ul><li>Disease, toxic wastes </li></ul></ul><ul><ul><li>Competition, Humans </li></ul></ul>
    20. 20. Tolerance
    21. 21. Acclimation <ul><li>When tolerance limits for an organism change they acclimatise </li></ul><ul><ul><li>Slow process </li></ul></ul><ul><ul><li>Usually to seasons </li></ul></ul>
    22. 22. Liebig’s Law <ul><li>The functioning of an organism in limited or controlled by whatever essential environmental factor is in the least favourable amount </li></ul>
    23. 23. Geographical Barriers <ul><li>Mountain ranges </li></ul><ul><li>Seas and oceans </li></ul><ul><li>Rivers </li></ul>
    24. 24. Predation
    25. 25. Humans <ul><li>Over-hunting </li></ul><ul><ul><li>Extinction </li></ul></ul>
    26. 26. <ul><li>Destroy habitats </li></ul><ul><ul><li>Draining swamps </li></ul></ul><ul><ul><li>Clearing forests </li></ul></ul>
    27. 27. <ul><li>Over-use of pesticides </li></ul>
    28. 28. <ul><li>Toxic wastes </li></ul>