Lessn 3: Liming Factrs in Ecsystems In the last lessn we examined specific factrs that affect ecsystems. In this lessn, yu will see hw these and ther factrs limit ppulans and cmmunies within ecsystems. Bitic Ptential Bitic ptential is the maximum number f ffspring that a species culd prduce if resurces were unlimited A species bitic ptential is determined by 4 factrs: Ord s Kangar Rat Kangar rats are able t breed all year lng if cnditins are favrable. Hwever, nly ne r tw breeding cycles are cmmn. Age f reprductin is usually abut 83 days ld. Gestatin is apprximately 30 days, and individual females can have tw litters per year. Litter size averages abut 3.5 yung per female. Annual survival rate in a ppulatin f kangar rats is abut 10% 1
Limiting Factrs A limiting factr is an abitic r bitic factr that prevents a species frm reaching its bitic ptential Think abut a ppulatin f white tailed deer. In yur grup, cme up with 3 specific examples f limiting factrs fr each bitic and abitic. Include a shrt explanatin f hw the factr limits the ppulatin. Limits f Tlerance survival and reprductin f an rganism depend n the presence f nutrients the ability f the rganism t withstand the abitic factrs in the envirnment law f the minimum: the nutrient in least supply is the ne that limits grwth law f tlerance: an rganism can survive within (tlerate) a certain range f an abitic factr; abve and belw the range it cannt survive greater this range f tlerance, the greater the rganism s ability t survive 2
Density Independent and Density Dependent Factrs ppulatin density refers t the number f species fund in a given area ex. The density f grizzly bears in Jasper Natinal Park is 11 bears / 1000km 2 Density independent factrs affect members f a ppulatin regardless f ppulatin density Density dependent factrs affect a ppulatin because f the density f the ppulatin Carrying capacity carrying capacity is the maximum number f individuals f a species that can be supprted at the time by an ecsystem A ppulatin can exceed the carrying capacity f the ecsystem, but nt fr lng 3
Lessn 3 Review Quesns 1. Fur factrs regulate ppulan grwth. Using an example f a nnhuman ppulan, explain hw each factr wuld affect the ppulan size. 2. Cedar waxwings are ne f the few birds that can withstand the cld and lack f available fd during ur winters. T ease the strains f winter, bird watchers in Lethbridge Wuld the seeds alter the carrying capacity f the ecsystem? Explain. (b) Prvide a hypthesis that explains why bird watchers have nted an increase in the falcn ppulan in recent years. 3. A scienst studying wlves near Canmre nces a steady decline in the ppulan f wlves fr fur cnsecuve years. Make a predicn abut hw the ppulan f wlves will affect the ppulan f mse. Give yur reasns. (b) Assuming that humans are nt the cause f the wlf ppulan decline, wuld it be reasnable t cnclude that the wlf ppulan will cnnue t decline unl there are (c) What might cause the wlf ppulan t begin increasing again? (d) Using a flw chart, explain hw changes in the wlf ppulan wuld affect the plant cmmunity surrunding Canmre. 4
1. Create a table like Table 3 and classify the fllwing infrman within it. Larger mammals generally live lnger than smaller nes. Pregnant female elephants carry their yung fr nearly 18 mnths. Elephants reach sexual maturity at 15 years. Elephants usually prduce ne ffspring each birth. Mst elephants wait mre than 5 years between births. Female elephants care fr their yung fr mre than 10 years. Mice en prduce liers f 6 r mre. Aer abut 6 weeks, mice reach sexual maturity. In a natural seng few mice are lder than 2 years. A pregnant female muse will carry her yung fr 22 days. Mice will breed every 6 weeks r less. (b) Refer t yur table and write a paragraph cmparing the bic ptenals f elephants and mice. 2. A researcher cnducts a study t find a pssible bilgical cntrl fr pine bark beetles, an insect cnsidered a pest by the frestry industry. The researcher sets up fur different studies f predatrs and the pine bark beetle. The ppulans f prey and predatr are mnitred ver many different generans. The graphs in Figure 4 shw changes in ppulans ver me. Which species is mst likely the best cntrlling agent? Give yur reasns. (b) Smemes the eggs f a predatr are eaten by its prey. Which predatr might serve as a fd surce fr its prey? Give yur reasns. 5