Lecture 052 - Population Ecology
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Colonie High AP Biology DeMarco/Goldberg Populations in their Environment organism population community ecosystem biosphere organism population community ecosystem Chapter 54 biosphere Population Ecology Life Takes Place in Populations Population group of individuals of same species in same area at same time Population Dynamics Complex interaction of biotic & abiotic influences Decline of Northern Pintail rely on same resources interact interbreed loss of habitat, predation, climatic changes affecting food availability Population Ecology study of populations in relation to Population Spacing Dispersal patterns within a population environment Provides insight into the environmental associations & social interactions of individuals in population environmental influences on population density & distribution, age structure, and variations in population size To answer: What environmental factors affect a population? clumped random First, you need to measure density & dispersion uniform Colonie High AP Biology DeMarco/Goldberg Characterizing a Population Describing a population population range pattern of spacing 1964 Equator density range 1970 1966 Population Range Geographical limitations biotic & abiotic factors habitat 1960 1965 1961 1958 1951 food, predators, temperature, rainfall, etc. 1943 1937 1956 size of population 1970 Immigration from Africa ~1900 adapted to polar region adapted to rainforest density Changes in Range Range expansions & contractions At Risk Populations Endangered species changing environment limitations to range / habitat places species at risk 15,000 years ago glacial period Alpine tundra Elevation (km) 3 km Alpine tundra Present Spruce-fir forests Woodlands 2 km Mixed conifer forest 1 km 0 km Devil’s hole pupfish Mixed conifer forest Spruce-fir forests Grassland, chaparral, and desert scrub Woodlands Iiwi Hawaiian bird Iriomote cat Socorro isopod Grassland, chaparral, and desert scrub New Guinea tree kangaroo result of competition Measuring Population Density How do we measure how many individuals in a population? number of individuals in an area mark & recapture methods difficult to count a moving target sampling populations Catalina Island mahogany tree Northern white rhinoceros Population Size Changes to population size adding & removing individuals from a population birth death immigration emigration Colonie High AP Biology DeMarco/Goldberg Population Growth Rates Factors affecting population growth rate Demography Factors that affect growth & decline of populations sex ratio how many females vs. males? Life table at what age do females reproduce? vital statistics & how they change over time generation time females males age structure how females at reproductive age in cohort? What does this tell you about the population? Survivorship Curves Generalized strategies The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females. 1000 Survival per thousand Survivorship Curves Graphic representation of life table Belding ground squirrel Human (type I) I. Hydra (type II) 100 1 0 25 50 75 Percent of maximum life span Trade-offs: Survival vs. Reproduction The cost of reproduction increase reproduction may decrease survival investment per offspring reproductive events per lifetime age at first reproduction Natural selection favors a life history that maximizes lifetime reproductive success High death rate in postreproductive years II. Constant mortality rate throughout life span Oyster (type III) 10 What do these graphs tell about survival & strategy of a species? Parental Survival Kestrel Falcons: The cost of larger broods to both male & female parents 100 III. Very high early mortality but the few survivors then live long (stay reproductive) Colonie High AP Biology DeMarco/Goldberg Trade Offs Reproductive Strategies K-selected number & size of offspring late reproduction few offspring invest a lot in raising offspring vs. survival of offspring or parent r-selected primates coconut r-selected K-selected early reproduction many offspring little parental care K-selected insects ―Of course, long before you mature, most of you will be eaten.‖ many plants r-selected Population Growth change in population = births – deaths Exponential model (ideal conditions) DN = riN growth increasing at constant rate Dt N = # of individuals r = rate of growth ri = intrinsic rate t = time d(D) = rate of change every pair has 4 offspring Exponential Growth Rate Characteristic of populations without limiting factors introduced to a new environment or rebounding from a catastrophe Whooping crane coming back from near extinction African elephant protected from hunting every pair has 3 offspring Carrying Capacity Maximum to grow exponentially? population size that environment can support with no degradation of habitat of course NOT! what sets limit? Carrying Capacity (K) maximum population size that environment can support with no degradation of habitat not fixed; varies with changes in resources varies with changes in resources 10 8 6 4 2 0 1915 1925 1935 1945 Time (years) Number of cladocerans (per 200 ml) Carrying Capacity Can populations continue Number of breeding male fur seals (thousands) intrinsic rate = maximum rate of growth 500 400 300 200 100 0 0 10 20 30 40 Time (days) 50 60 Colonie High AP Biology DeMarco/Goldberg Logistic Rate of Growth Can populations continue to grow exponentially? Logistic Model of Growth no natural controls K= carrying capacity effect of natural controls Changes in Carrying Capacity Population cycles Regulation of Population Size Limiting factors predator – prey interactions density dependent food supply, competition predators disease density independent abiotic factors sunlight temperature rainfall Isle Royale Studies Moose population on small island in Lake Superior Introduced Species Non-native species transplanted populations grow exponentially in new area out-compete native species loss of natural controls lack of predators, parasites, competitors starvation wolves winter loss reduce diversity examples African honeybee gypsy moth zebra mussel purple loosestrife snakehead fish kudzu gypsy moth Colonie High AP Biology DeMarco/Goldberg Zebra Mussel Purple Loosestrife ~2 months ecological & economic damage 1968 1978 Snakehead Fish came to North America live as an Asian delicacy entered North American rivers when dumped by owners now spreading to a river near you! reduces diversity loss of food & nesting sites for animals Biological Controls using an introduced predator (or other population growth inhibitor) to limit the population of a pest or other unwanted species can backfire as in case of Bufo marinus in Australia Overexploitation Human Population Growth North Atlantic bluefin tuna What factors have contributed to this exponential growth pattern? Population of… China: 1.35 billion India: 1.15 billion 20127 billion 20056 billion Bubonic plague "Black Death" 1650500 million Colonie High AP Biology DeMarco/Goldberg Demographic Comparisons Age Structure Relative number of individuals of each age Distribution of Population Growth Ecological Footprint World population in billions uneven11distribution of population: 90% of births 10 are in developing countries USA 9 distribution of resources: uneven wealthiest 20% 8 consumes ~90% of resources increasing gap between rich & poor 7 6 4 Developing countries 2 0 1900 Time 2000 2050 6.4 Indonesia 3.7 Nigeria 3.2 India Developed countries 1950 15.6 Brazil 5 1 30.2 Germany World total 3 over-population or over-consumption? uneven distribution: wealthiest 20% of world: 86% consumption of resources 53% of CO2 emissions 2.6 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 Acres Amount of land required to support an individual at standard of living of population Ecological Footprint—1997 deficit surplus Based on land & water area used to produce all resources each country consumes & to absorb all wastes it generates. Any Questions?
