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Chapter 12

Chapter 12. Population Ecology. Population Ecology. Ecology is the study of interactions Used to get the most accurate picture of the environment Management decisions are based on what is happening to the total population , not individual organisms. Population Ecology.

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Chapter 12

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  1. Chapter 12 Population Ecology

  2. Population Ecology • Ecology • is the study of interactions • Used to get the most accurate picture of the environment • Management decisions are based on what is happening to the total population, not individual organisms

  3. Population Ecology • Population ecology • is the study of organisms at the population level instead of just individuals

  4. Population Characteristics • Several measures describe populations • density • distribution • birthrates and death rates • age structure • sex ratio • fecundity (reproductive rate)

  5. Population Density • Number of individual organisms living within a defined area • number of prairie dogs per square mile • number of students per classroom

  6. Population Density • Important to scientists • especially when several years’ worth of data are available • allows interpretation • can assess whether population is growing, shrinking, or stabilized

  7. Population Distribution • A measure of how far apart population members live from each other (space) • Prairie dogs vs Mountain lions • Distribution is seldom uniform • Organisms usually concentrate near resources

  8. Birthrates and Death Rates • Both birthrate and death rate are gauges of overall population health • Birthrate • Number of births in comparison with number of individuals per year

  9. Birthrates and Death Rates • Death rate • Number of deaths in comparison with the number of individuals per year

  10. Factors Affecting Birthrate • Three main factors influence a population’s birthrate • age structure • mating systems • sex ratio

  11. Factors That Affect Birthrate • Age structure • makeup in terms of maturity • number of animals in each age group • A population loses many mature males • likely to have a high proportion of young males • can reduce birthrate

  12. Factors That Affect Birthrate • Mating systems • Sex ratio • number of males compared to females • A sufficient number of males must be available • Low number of males would decrease birthrate

  13. Fecundity of a Population • Number of eggs produced per female • Fertility • Production

  14. Population Growth • Several factors affect a population’s growth • birthrate versus death rate • age of maturity and gestation period • adaptability • emigration and immigration • availability of resources or carrying capacity • J – shaped Curve vs S – shaped Curve

  15. Movement of Organisms • Some wild animals are quite mobile • emigration • an individual’s movement out of a population • immigration • an individual’s movement into a population

  16. Availability of Resources • Resources in any environment are limited • Population growth is related to the availability of resources • Carrying capacity • maximum number of individual organisms that the environment is capable of sustaining

  17. Causes of Extinction • Several factors affect extinction • habitat destruction or degradation • introduced or non-native species • low numbers • pesticides • illegal killing

  18. Adaptability and Extinction • Most species that survive through time have the common trait of adaptability • Species that are capable of changing as their environments change have better chances of survival • Adaptable species can adjust • Specialized species are vulnerable

  19. Why Worry About Extinction? • Extinction is a natural process • Then why worry about species extinction? • The current rate at which species are going extinct is far from natural • Human activity has put most species in trouble • Many organisms may someday benefit humans

  20. Biomes • Climate is related to latitude and altitude • Ecosystems at similar latitudes and elevations have similar characteristics • temperature and precipitation similar • Biomes are ecosystems with similar types of vegetation and similar climate

  21. Aquatic Biomes • Among the many biomes found in or around water are • freshwater • lotic environment • lentic environment • wetlands • marine

  22. Freshwater Biome • Biome contains organisms adapted to living in or near water that is not salty • Wide variety of environmental conditions found in freshwater ecosystems • Producers • phytoplankton • zooplankton

  23. Freshwater Biome • Abiotic factors that shape the freshwater biome • water temperature • light intensity • concentration of dissolved materials • flow rate of a stream

  24. Freshwater Biome • Two different kinds of habitat in freshwater biome • lotic habitats • lentic habitats

  25. Freshwater Biome • Lotic habitats • flowing water • support little plant growth • detritus-based food webs • Lentic habitats • standing water such as ponds, lakes, swamps • regions of differing light and temperature

  26. Wetlands • Land areas that are flooded during all or part of the year • Great amount of concern about wetlands • Total area of wetlands in North America has declined

  27. Wetlands • Evidence shows wetlands are difficult to restore • Several groups are attempting to restore wetlands

  28. Marine Biome • The world’s largest biome is characterized by its salt content or salinity • oceans, bays, estuaries • Abiotic factors shaping the marine biome • light intensity • temperature • pressure

  29. Marine Biome • Great diversity of environments • intertidal zone • continental shelf • oceanic zone • estuaries

  30. Terrestrial Biomes • Biomes found on land include • desert • tundra • grassland • temperate forest • coniferous forest

  31. Desert • Temperatures • Daytime temperatures usually high • Nights usually cold • Biome with less than 10 inches of precipitation a year

  32. Desert • Desert organisms must be specially adapted to dry conditions • plants • taproots, short growing seasons • animals • get water from food, lap up dew

  33. Tundra • Northern biome • permafrost • no trees • temperatures below freezing most of year • less than 10 inches of precipitation a year • summer months produce wet and spongy environment

  34. Tundra • Plants and animals • adapted to cold and limited vegetation

  35. Grassland • Treeless biome often found in interior of continents • warm to hot summers • cold, freezing winters • periodic droughts • frequent fires

  36. Grassland • Vegetation includes grasses and other plants adapted to this environment

  37. Temperate Forest • Biome dominated by broad-leaved deciduous trees • approximately 30 inches of rain a year • four distinct seasons • Climate is less uniform than other biomes • produces variety of plant species

  38. Coniferous Forest • Evergreen forest forms broad northern belt across North America • precipitation mostly in form of snow • ranges from 15 inches to 40 inches per year • winters long and cold • summers moderate with cool nights

  39. Coniferous Forest • Dominated by coniferous trees • produce seeds in cones • needle-shaped leaves

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