AP Biology Population Ecology population ecosystem community biosphere organism

AP Biology Why Population Ecology?  Scientific goal  understanding the factors that influence the size of populations  general principles  specific cases  Practical goal  management of populations  increase population size  endangered species  decrease population size  pests  maintain population size  fisheries management maintain & maximize sustained yield

AP Biology Life takes place in populations  Population  group of individuals of same species in same area at same time  rely on same resources  interact  interbreed  rely on same resources  interact  interbreed Population Ecology: What factors affect a population?

AP Biology  Abiotic factors  sunlight & temperature  precipitation / water  soil / nutrients  Biotic factors  other living organisms  prey (food)  competitors  predators, parasites, disease  Intrinsic factors  adaptations Factors that affect Population Size

AP Biology Characterizing a Population  Describing a population  population range  pattern of Dispersion  Density of population  #individuals per unit area Immigration from Africa ~1900 Equator range

AP Biology Population Range  Geographical limitations  abiotic & biotic factors  temperature, rainfall, food, predators, etc.  habitat adaptations to polar biome adaptations to rainforest biome

AP Biology Population Dispersion  Spacing patterns within a population uniform random clumped Provides insight into the environmental associations & social interactions of individuals in population Why uniform? Why clump? Why random?

AP Biology Population Size  Changes to population size can occur by:

AP Biology Population Growth Rates  Factors affecting population growth rate  sex ratio  how many females vs. males?  generation time  at what age do females reproduce?  age structure  #females at reproductive age in cohort?

AP Biology Life table Demography  Study of a populations vital statistics and how they change over time  Life tables, Age Structure Diagrams and Survivorship Graphs Why do teenage boys pay high car insurance rates? females males What adaptations have led to this difference in male vs. female mortality?

AP Biology Age structure  Relative number of individuals of each age What do these data imply about population growth in these countries?

AP Biology Survivorship curves  Graphic representation of life table Belding ground squirrel The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females.

AP Biology Survivorship curves  Generalized strategies What do these graphs tell about survival & strategy of a species? Human (type I) Hydra (type II) Oyster (type III) Percent of maximum life span Survival per thousand I.High death rate in post-reproductive years II.Constant mortality rate throughout life span III.Very high early mortality but the few survivors then live long (stay reproductive)

AP Biology Trade-offs: survival vs. reproduction  The cost of reproduction  To increase reproduction may decrease survival: (think about…)  age at first reproduction  investment per offspring  number of reproductive cycles per lifetime  parents not equally invested  offspring mutations  Life History determined by costs and benefits of all adaptations. Natural selection favors a life history that maximizes lifetime reproductive success

AP Biology Reproductive strategies  K-selected  late reproduction  few offspring  invest a lot in raising offspring  primates  coconut  r-selected  early reproduction  many offspring  little parental care  insects  many plants K-selected r-selected

AP Biology Trade offs Number & size of offspring vs. Survival of offspring or parent Number & size of offspring vs. Survival of offspring or parent r-selected K-selected “Of course, long before you mature, most of you will be eaten.”

AP Biology Survivorship Curves with Reproductive Strategy Human (type I) Hydra (type II) Oyster (type III) Percent of maximum life span Survival per thousand K-selection r-selection

AP Biology Population Growth Rate Models  Exponential growth  Rapid growth  No constraints  Logistic growth  Environmental constraints  Limited growth

AP Biology Population Growth Math  Change in population = Births – Deaths  Per capita birth rate = b  Per capita death rate = d  # of individuals = N  Rate of population growth (r) = b – d  Survivorship = % surviving Ex: If there are 50 deer in a population, 13 die and 27 are born the next month. What is the population size the following month?  (Answer: = 14, so new population is 64) Ex: What is the birth rate for the deer? #Births/N = b  Answer: 27/50 =.54  Death rate (d) = 13/50 =.26 Ex: What is the rate of growth for the deer? r = =.28

AP Biology Exponential Growth (ideal conditions)  No environmental barriers  Growth is at maximum rate dN/dt = R max N N = # individuals R max = growth rate

AP Biology African elephant protected from hunting Whooping crane coming back from near extinction Exponential Growth  Characteristic of populations without limiting factors  introduced to a new environment or rebounding from a catastrophe

AP Biology K = carrying capacity Logistic rate of growth  Can populations continue to grow exponentially? Of course not! effect of natural controls no natural controls What happens as N approaches K?

AP Biology Logistic Growth Equation dN/dt = r max N(K-N)/K K = carrying capacity of population Ex: If a population has a carrying capacity of 900 and the r max is 1, what is the population growth when the population is 435? 1 x 435 ( )/900 = 224 What if the population is at 850? What if it is at 1010? Explain the results of each problem.

AP Biology Time (days) Number of cladocerans (per 200 ml)  Maximum population size that environment can support with no degradation of habitat  varies with changes in resources Time (years) Number of breeding male fur seals (thousands) Carrying capacity What ’ s going on with the plankton?

AP Biology Changes in Carrying Capacity  Population cycles  predator – prey interactions K K K K

AP Biology Regulation of population size  Limiting factors  density dependent  competition: food, mates, nesting sites  predators, parasites, pathogens  density independent  abiotic factors  sunlight (energy)  temperature  rainfall swarming locusts marking territory = competition competition for nesting sites

AP Biology Introduced species  Non-native species (INVASIVE)  transplanted populations grow exponentially in new area  out-compete native species  reduce diversity  examples  African honeybee  gypsy moth kudzu gypsy moth

AP Biology Zebra musselssel ecological & economic damage ~2 months  reduces diversity  loss of food & nesting sites for animals  economic damage  reduces diversity  loss of food & nesting sites for animals  economic damage

AP Biology Purple loosestrife  reduces diversity  loss of food & nesting sites for animals  reduces diversity  loss of food & nesting sites for animals

AP Biology Any Questions?