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BIOA02 Module 3 Lecture 3

8 Pages

Biological Sciences
Course Code
Monica Sauer

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Lecture 3 - Population Ecology II Tradeoffs!   Energy and time used for one activity cannot be used for anything else! It is an “investment.”   Total energy budgets (‘checking’ + ‘savings’) cannot be overdrawn Energy expended must maximize reproductive fitness!  Each species’ life history strategy is based on its probability of survival and reproduction over time. These determine  the organism’s life history traits.  • Lifespan  • Age at first reproduction  • Number of reproductive events  • Number of offspring per reproductive event  • Investment in parental care Trade­off between fecundity(total potential # of offsprings a species can have in a life time) and parental care  • Passive parental care before offspring born: 10 eggs at 100 units energy each = 1,000 total 1,000 eggs at 1  unit energy each = 1,000 total  • Active parental care after offspring born: many young = little care few young = more care One reproductive episode versus several  • One reproductive episode (go big or go home!)  • Semelparity (1 birth Semi = last round) • Devotes all stored energy  • Individual often dies immediately afterward  • Benefit: Maximum fecundity  • Risk: ZERO fitness if organism dies before is reproductive event!  • Multiple reproductive episodes (spreading the risk)  • Iteroparity (= many births)  • Only some energy devoted  Lecture 3 - Population Ecology II • Benefit: Fitness is spread out ­ one failed event ≠ zero fitness! Time reproduction to high resource periods.  • Risk: Smaller reproductive events. Early death = low fitness. Selection in Life History   Early reproduction favoured: usually organisms that put out a TON of offsprings • Adult survival rates low  • Animals do not grow larger with age  • Larger size does not increase fecundity (doesnt allow them to store resources) Later reproduction favoured: • If sexually mature adults likely to become older  • Iforganisms grow larger with age (and can store energy then devote that energy to later fecundity) • If larger organisms have higher fecundity Generation Time vs Body Sz Lecture 3 - Population Ecology II Ranges from an hour (bacteria)  to a hundred years (some turtles) thus  larger organism  = larger generation time. Life History: r vs k selection r = “reproductive” organisms • Short­lived  • Few reproductive events  • Many offspring  • Low parental care (both active and passive) k = “carrying capacity” (karrying capacity!) organisms • Long­lived  Lecture 3 - Population Ecology II • Several reproductive events  • Few offspring per event  • High parental care Typical Examples  Lecture 3 - Population Ecology II Population Dynamics:   Populations can...  Grow (increase) – Due to:  • Birth  • Immigration (from other populations)  Decline (decrease) – Due to:  • Death  • Emigration (to other populations)  Stay the same size (zero change):  • New individuals added are equal individuals who die and/or leave  • Lecture 3 - Population Ecology II Changes in Populations (assumes for a close
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