Population Ecology - Population Demography o Demography: quantitative study of a population  How size changes through time  Whole populations: increasing, decreasing, remaining constant  Population broken down into parts - Study birth and death rates of a specific age - Demography and Dynamicso Population growth can be influenced by the population’s sex ration  Number of births directly related to number of females o generation times: average interval between birth of an individual and birthof its offspring  populations with short generations can increase in size more quickly than populations with long generations o in general, larger organisms have longer generation times, although there are exception - Population Demographyo Age structure  Determined by the numbers of individuals in a different age group  Cohort: group of individuals of the same age  Fecundity: number of offspring produced in a standard time  Mortality: death rate in a standard time  Age structure has a critical influence on a population’s growth rate o Life tables show probability of survival and reproduction through a cohort’s life o Survivorship: percentage of an origin population that survives to a certain age o Survivorship curves: express some aspects of age distribution- Life History o NS favors traits that maximize number of surviving offspring in next generation by an individual  2 factors allow this quantity - how long an individual lives - how many young does it produce - Terms to Findo Fly-catcher example  Cost of reproduction Researches changed the number of eggs in the nests of flycatcher birds - Birds given fewer eggs used less energy raising young and gave more eggs the next year - Birds given more eggs used more energy raising young andgave fewer eggs the next year o Importance of number and size of offspring with life history  more offspring means fewer are likely to survive to adulthood  larger offspring are more likely to survive to adulthood than smaller ones o Long lived species versus short lived species  Long lived species: wait longer to reproduce - Juveniles get more experience before expending high costs of reproduction  Short lived species: reproduce sooner - Put all of their energy into reproduction and often don’t livemuch past reproduction o Environmental limits to population growth Carrying capacity  Space Light Water Nutrients o Carrying capacity  Limit imposed by shortages of important environmental factors - Environmental Limits to Population Growth o Populations often remain same size regardless of number of offspring borno Exponential growth model applies to populations with no growth limits  r = (b-d) + (i-e)  r: rate of population increase b: birth rate  d: death rate  i: immigration e: emigration - Underwater Astonishment o Bioluminescence in dark environments o Hypnosiso More life in deep oceans than rainforests o Cephalopods o 3% of oceans explored o higher mountains underwater than above water o male squids change colors so females never see aggressive colorationo octopus can change color and texture to camouflage completely - Nature’s Grossest Creatures o Cockroaches  Support Protection Anchor muscles  Locomotion