L14 pop regulation

L14 pop regulation - BILD 3 July 16, 2010 POPULATION...

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BILD 3 July 16, 2010 Woodruff: population regulation 1 POPULATION REGULATION Populations have enormous potential for exponential growth ( r , the intrinsic rate of increase) but clearly cannot grow for ever. Growth rates slow due to environmental constrains (K, the concept of the carrying capacity) What factors affect r ? What determines K ? N t K selected r selected r strategists vs. K strategists CORRELATES OF r AND K SELECTION r -SELECTION K-SELECTION Climate variable constant unpredictable predictable Catastrophic mortality often rare Typical density density mortality independent dependent Survivorship Type III Population size variable in t constant N < K N ~ K Competition variable keen often lax NATURAL SELECTION WILL FAVOR: r -strategist K-strategist Development rapid slower Body size small large Age of 1st. reproduction early late Reproductive strategy single multiple semelparity iteroparity Life span short long Overall ecology high r max competitive ability productivity efficiency Fig. 53-8 Male Female 100 Kestrel 80 60 40 20 0 Reduced brood size Normal brood size Enlarged brood size Parents surviving the following winter (%) Trade-offs between survival and reproduction Fig. 53-16 Population size 100 80 60 40 20 0 200 400 500 600 300 Percentage of juveniles producing lambs Reproduction of young sheep on island off Scotland
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BILD 3 July 16, 2010 Woodruff: population regulation 2 WHAT FACTORS LIMIT LOGISTIC GROWTH? DENSITY INDEPENDENT FACTORS weather catastrophe age Fish kill following sudden freeze LAKE BEFORE AFTER DECLINE A 17,000 1,000 94% B 2,000 150 93% DENSITY DEPENDENT FACTORS emigration parasitism predation competition (scramble & contest) BIRTH RATE PREDATION N Both density independent and density dependent factors operate in regulating n. They vary in their relative significance over time In different types of organisms ENVIRONMENT KEY FACTOR FAVORABLE COMPETITION UNFAVORABLE WEATHER DENSITY DEPENDENT: birds, mammals, trees DENSITY INDEPENDENT: insects, plankton D. INDEP D. DEP • Populations are regulated by a complex interaction of biotic and abiotic influences • There are two general questions about regulation of population growth: – What environmental factors stop a population from growing? – Why do some populations show radical fluctuations
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This note was uploaded on 07/28/2010 for the course BIOLOGY BILD 3 taught by Professor Davidwoodruff during the Summer '10 term at San Diego.

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L14 pop regulation - BILD 3 July 16, 2010 POPULATION...

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