Population Ecology Population Types Population Growth

Game: Keeping a balance The players 5 animals Others are resources Resource signals –Food: hand over stomach –Water: hand over mouth –Shelter: hand over head to make a roof

Game: Keeping a balance Instructions Two groups faces away from each other All individuals from both groups choose a resource signal On teacher signal, everyone turns around animals try to find a resource match Resource match returns with animal and becomes a new animal If no resource match for animal, it dies and becomes a resource Record numbers at each round Repeat round 10-15x

Post-game assignment Graph the data Answer the questions: 1.Analyze the graph and discuss any trends or patterns that you see. Explain the causes of the trends. 2.Name 5 factors that affected the survival of animals. Availability of resource is considered one factor.

Calculating Population Size Natality – birth rate (B) Mortality – death rate (D) Immigration = # of individuals entering a population (I) Emigration =# of individuals leaving a population (E) Population size = B – D + I - E

Types of Populations Open - all 4 factors (natality, mortality, immigration and emigration) act on the population (true for most natural ecosystems) Closed - only birth rate and death rate affect the population (true for labs) The global population is considered a closed population. Why do you think?

Population Growth Equation Example: In 1989, the population of frogs was 500, During 1989, the following data on the frog population were obtained: Births = 100Deaths = 50 Immigration = 50Emigration = 20 Calculate the population of frogs. Population Growth = (births + immigration) – (death + emigration)

Types of Growth Exponential = growth curve increases rapidly and continues to increase (eg: humans) Logistic = growth curve reaches a plateau (eg: most natural ecosystems) Carrying capacity =maximum number of individuals that an ecosystem can support Law of minimum = the least abundant nutrient is the nutrient that limits population growth.

Types of Growth Exponential growth Logistic growth Time Carrying capacity Pop’n size Pop’n size

Population Histogram Young population: wide base, eg. Mexico Stable population: e.g. Sweden Declining population: narrow base e.g. Canada

Biotic Potential Biotic potential = max. # of offspring a species can produce

Four Factors that affect biotic potential Birth potential = max. # of offspring per birth Capacity for survival = # of offspring that reach reproductive age Procreation = # of times a species reproduces each year. Length of reproductive life = age of sexual maturity and the number of years the individual can reproduce.

FactorsVarious AnimalsHumans Birth potential Whooping crane: -2 eggs per year but usually just one survives -usually one child per birth -exception: multiple births (such as twins) Capacity for survival Procreation Length of reproductiv e life

Four Factors that affect biotic potential Birth potential = max. # of offspring per birth Capacity for survival = # of offspring that reach reproductive age Procreation = # of times a species reproduces each year. Length of reproductive life = age of sexual maturity and the number of years the individual can reproduce.

FactorsVarious AnimalsHumans Birth potential Whooping crane: -2 eggs per year but usually just one survives -usually one child per birth -exception: multiple births (such as twins) Capacity for survival Sea turtle: -many eggs are laid by the female turtle in the sand -only a few reach the ocean and some of them do not survive to reach sexual maturity -high survival rate in developed countries -much lower survival rate in developing nations Procreation Length of reproductiv e life

Four Factors that affect biotic potential Birth potential = max. # of offspring per birth Capacity for survival = # of offspring that reach reproductive age Procreation = # of times a species reproduces each year. Length of reproductive life = age of sexual maturity and the number of years the individual can reproduce.

FactorsVarious AnimalsHumans Birth potential Whooping crane: -2 eggs per year but usually just one survives -usually one child per birth -exception: multiple births (such as twins) Capacity for survival Sea turtle: -many eggs are laid by the female turtle in the sand -only a few reach the ocean and some of them do not survive to reach sexual maturity -high survival rate in developed countries -much lower survival rate in developing nations Procreation Elk: -elk only mate once a year -maximum of one time per year because of the 9 month gestation period Length of reproductiv e life

Four Factors that affect biotic potential Birth potential = max. # of offspring per birth Capacity for survival = # of offspring that reach reproductive age Procreation = # of times a species reproduces each year. Length of reproductive life = age of sexual maturity and the number of years the individual can reproduce.

FactorsVarious AnimalsHumans Birth potential Whooping crane: -2 eggs per year but usually just one survives -usually one child per birth -exception: multiple births (such as twins) Capacity for survival Sea turtle: -many eggs are laid by the female turtle in the sand -only a few reach the ocean and some of them do not survive to reach sexual maturity -high survival rate in developed countries -much lower survival rate in developing nations Procreation Elk: -elk only mate once a year -maximum of one time per year because of the 9 month gestation period Length of reproductiv e life Elephants: -African elephants reach sexual maturity at age 15 but can reproduce until they are 90 years old -sexual maturation at puberty -males continue to make sperm all their lives -females reach menopause (and then they no longer ovulate)

Limiting Factors Limiting factors: limitations imposed by the environment that prevent populations from reaching their biotic potential Classification of factors: biotic or abiotic, density dependent or independent

Factors that cause changes in populations Abiotic Factors: Determines where a species is able to live Physical and chemical components: –Light availability –Water availability –Nutrient availability –Temperature –Acidity –salinity

Law of tolerance: an organism can survive within a certain range of an abiotic factor Example: Fish survives best between certain ranges of temperature The greater the range of tolerance, the greater the organisms’ ability to survive

Factors that cause changes in populations Biotic Factors: All organisms, their remains and their products or waste Determines the species’ success Biotic factors involved interactions between individuals

Types of Interactions RelationshipDefinitionExample Competition2 individuals vide for the same resource PredationOne individual feeds on another Mutualism2 individuals benefitting from each other Parasitism1 individual benefits while the other is harmed organism living and feeding off a host Commensalism1 individual benefits with no effect on the other

Population density: number of individuals in a given area

Factors that cause changes in populations Density-independent Factors that affect a population regardless of the population size. Examples: fires and floods

Factors causing changes in population Density-dependent factors: Factors that affect a population because of the density of a population. Examples: water quality, food shortage, disease

Limiting Factors EnvironmentDensity BioticAbioticDependentIndependent Climate Food Predation Competition The spread of disease Flood/fire Destruction of habitat by humans Introduction of exotic species by humans Availability of mates Availability of light

Limiting Factors EnvironmentDensity BioticAbioticDependentIndependent ClimateYY Food Predation Competition The spread of disease Flood/fire Destruction of habitat by humans Introduction of exotic species by humans Availability of mates Availability of light

Limiting Factors EnvironmentDensity BioticAbioticDependentIndependent ClimateYY FoodYY Predation Competition The spread of disease Flood/fire Destruction of habitat by humans Introduction of exotic species by humans Availability of mates Availability of light

Limiting Factors EnvironmentDensity BioticAbioticDependentIndependent ClimateYY FoodYY PredationYY Competition The spread of disease Flood/fire Destruction of habitat by humans Introduction of exotic species by humans Availability of mates Availability of light

Limiting Factors EnvironmentDensity BioticAbioticDependentIndependent ClimateYY FoodYY PredationYY CompetitionYY The spread of disease Flood/fire Destruction of habitat by humans Introduction of exotic species by humans Availability of mates Availability of light

Limiting Factors EnvironmentDensity BioticAbioticDependentIndependent ClimateYY FoodYY PredationYY CompetitionYY The spread of diseaseYY Flood/fire Destruction of habitat by humans Introduction of exotic species by humans Availability of mates Availability of light

Limiting Factors EnvironmentDensity BioticAbioticDependentIndependent ClimateYY FoodYY PredationYY CompetitionYY The spread of diseaseYY Flood/fireYY Destruction of habitat by humans Introduction of exotic species by humans Availability of mates Availability of light

Limiting Factors EnvironmentDensity BioticAbioticDependentIndependent ClimateYY FoodYY PredationYY CompetitionYY The spread of diseaseYY Flood/fireYY Destruction of habitat by humans YY Introduction of exotic species by humans Availability of mates Availability of light

Limiting Factors EnvironmentDensity BioticAbioticDependentIndependent ClimateYY FoodYY PredationYY CompetitionYY The spread of diseaseYY Flood/fireYY Destruction of habitat by humans YY Introduction of exotic species by humans YY Availability of mates Availability of light

Limiting Factors EnvironmentDensity BioticAbioticDependentIndependent ClimateYY FoodYY PredationYY CompetitionYY The spread of diseaseYY Flood/fireYY Destruction of habitat by humans YY Introduction of exotic species by humans YY Availability of matesYY Availability of light

Limiting Factors EnvironmentDensity BioticAbioticDependentIndependent ClimateYY FoodYY PredationYY CompetitionYY The spread of diseaseYY Flood/fireYY Destruction of habitat by humans YY Introduction of exotic species by humans YY Availability of matesYY Availability of lightYY