Lecture #23Lecture #23 Date _______Date _______

• Chapter 52Chapter 52 ~ ~ Population Population EcologyEcology

• A wealthy business man owns a 10000 acre island and wants A wealthy business man owns a 10000 acre island and wants to have his own private pheasant hunting ranch so he releases to have his own private pheasant hunting ranch so he releases 100 pheasant onto the island (50 male and 50 female). The 100 pheasant onto the island (50 male and 50 female). The island is covered in wild grasses and each bird needs a island is covered in wild grasses and each bird needs a minimum of a 50 yard X 50 yard area to support them with minimum of a 50 yard X 50 yard area to support them with the resources to survive each year. Look up the clutch size the resources to survive each year. Look up the clutch size and age of fertility in the ring necked pheasant and then and age of fertility in the ring necked pheasant and then project what the population growth of the pheasant will look project what the population growth of the pheasant will look like. Assume that the pheasants have no natural predators on like. Assume that the pheasants have no natural predators on this island and that the weathy business man starts hunting in this island and that the weathy business man starts hunting in 5 years and then only kills 20 pheasants per year.5 years and then only kills 20 pheasants per year.

• The business man wants to plant a The business man wants to plant a second island with Pheasant, but the second island with Pheasant, but the second island has 3 native species of second island has 3 native species of birds that already occupy the island birds that already occupy the island and depend upon the grassland for and depend upon the grassland for survival and reproduction.survival and reproduction.

• Propose a two pronged study plan.Propose a two pronged study plan.– PART 1: a study to predict what the impact PART 1: a study to predict what the impact

would be of introducing pheasant to the would be of introducing pheasant to the island.island.

– PART 2: a study plan to monitor bird PART 2: a study plan to monitor bird populations after pheasant are introduced to populations after pheasant are introduced to determine if pheasant cause impacts to the determine if pheasant cause impacts to the native bird populations.native bird populations.

Population characteristicsPopulation characteristics• DensityDensity~ # of individuals per unit of area~ # of individuals per unit of area

•counts•counts •sample •sample size estimate •indirect size estimate •indirect indicators •mark-indicators •mark-recapturerecapture

• DispersionDispersion~ pattern of spacing~ pattern of spacing •random•random~ unpredictable, patternless ~ unpredictable, patternless

spacing (a)spacing (a) •clumped•clumped~ patchy aggregation (b)~ patchy aggregation (b) •uniform •uniform~ even spacing (c)~ even spacing (c)

DemographyDemography:: factors that affect growth & decline of populationsfactors that affect growth & decline of populations

• BirthrateBirthrate (natality, fecundity)~ # of offspring produced(natality, fecundity)~ # of offspring produced• Death rateDeath rate (mortality) (mortality)• Age structureAge structure~ relative number of individuals of each age~ relative number of individuals of each age• Survivorship curveSurvivorship curve~ plot of numbers still alive at each age~ plot of numbers still alive at each age

Population Growth ModelsPopulation Growth Models• Exponential model (red)Exponential model (red)

• idealized population in an • idealized population in an unlimited environment (J-unlimited environment (J-curve); r-selected species curve); r-selected species (r=per capita growth rate)(r=per capita growth rate)

• Logistic model (blue)Logistic model (blue) •carrying capacity (•carrying capacity (KK): ): maximum population size that a maximum population size that a particular environment can support particular environment can support (S-curve); K-selected species(S-curve); K-selected species

Population life history “strategies”Population life history “strategies”

• r-selected r-selected (opportunistic)(opportunistic)

• Short maturation & Short maturation & lifespanlifespan

• Many (small) Many (small) offspring; usually 1 offspring; usually 1 (early) reproduction; (early) reproduction; no parental careno parental care

• High death rateHigh death rate

• K-selected K-selected (equilibrial)(equilibrial)

• Long maturation & Long maturation & lifespanlifespan

• Few (large) offspring; Few (large) offspring; usually several (late) usually several (late) reproductions; reproductions; extensive parental careextensive parental care

• Low death rateLow death rate

Population limiting factorsPopulation limiting factors

• Density-dependent factorsDensity-dependent factors •competition•competition •predation •predation •stress/crowding •stress/crowding •waste accumulation •waste accumulation

• Density-independent factorsDensity-independent factors •weather/climate•weather/climate •periodic •periodic disturbancesdisturbances