© 2009 Delmar, Cengage Learning Chapter 12 Population Ecology

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning Population Ecology Population ecology –is the study of organisms at the population level instead of just individuals

© 2009 Delmar, Cengage Learning Population Characteristics Several measures describe populations –density –distribution –birthrates and death rates –age structure –sex ratio –fecundity (reproductive rate)

© 2009 Delmar, Cengage Learning Population Density Number of individual organisms living within a defined area –number of prairie dogs per square mile –number of students per classroom

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning Birthrates and Death Rates Death rate –Number of deaths in comparison with the number of individuals per year

© 2009 Delmar, Cengage Learning Factors Affecting Birthrate Three main factors influence a population’s birthrate –age structure –mating systems –sex ratio

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning Fecundity of a Population Number of eggs produced per female Fertility Production

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning Causes of Extinction Several factors affect extinction –habitat destruction or degradation –introduced or non-native species –low numbers –pesticides –illegal killing

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning Aquatic Biomes Among the many biomes found in or around water are –freshwater lotic environment lentic environment wetlands –marine

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning Freshwater Biome Abiotic factors that shape the freshwater biome –water temperature –light intensity –concentration of dissolved materials –flow rate of a stream

© 2009 Delmar, Cengage Learning Freshwater Biome Two different kinds of habitat in freshwater biome –lotic habitats –lentic habitats

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning Wetlands Evidence shows wetlands are difficult to restore –Several groups are attempting to restore wetlands

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning Marine Biome Great diversity of environments –intertidal zone –continental shelf –oceanic zone –estuaries

© 2009 Delmar, Cengage Learning Terrestrial Biomes Biomes found on land include –desert –tundra –grassland –temperate forest –coniferous forest

© 2009 Delmar, Cengage Learning Desert Temperatures –Daytime temperatures usually high –Nights usually cold Biome with less than 10 inches of precipitation a year

© 2009 Delmar, Cengage Learning Desert Desert organisms must be specially adapted to dry conditions –plants taproots, short growing seasons –animals get water from food, lap up dew

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning Tundra Plants and animals –adapted to cold and limited vegetation

© 2009 Delmar, Cengage Learning Grassland Treeless biome often found in interior of continents –warm to hot summers –cold, freezing winters –periodic droughts –frequent fires

© 2009 Delmar, Cengage Learning Grassland Vegetation includes grasses and other plants adapted to this environment

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning 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

© 2009 Delmar, Cengage Learning Coniferous Forest Dominated by coniferous trees –produce seeds in cones –needle-shaped leaves