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Neutral Stability. Vectors spiral inwards Functional response = rate at which individual predators capture and eat more prey per unit time as prey.

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Presentation on theme: "Neutral Stability. Vectors spiral inwards Functional response = rate at which individual predators capture and eat more prey per unit time as prey."— Presentation transcript:

1 Neutral Stability

2 Vectors spiral inwards

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4 Functional response = rate at which individual predators capture and eat more prey per unit time as prey density increases

5 Numerical response = increased prey density raises the predator’s population size and a greater number of predators consume An increased number of prey

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8 Moderately efficient predator Neutral stability — Vectors form a closed ellipse. Amplitude of oscillations remains constant.

9 Unstable — extremely efficient predator Vectors spiral outwards until a Limit Cycle is reached

10 Damped Oscillations — inefficient predator Vectors spiral inwards to stable equilibrium point

11 “Prudent” Predation and Optimal Yield Feeding territories Consequence of senescence

12 Industrial Melanism Numbers of Typical and Melanic Marked Moths (Biston betularia) Released and Recaptured in a Polluted Woods Near Birmingham and an Unpolluted Woods Near Dorset* __________________________________________________________ Polluted Woods Unpolluted Woods __________________________________________________________ Numbers of marked moths released Typical 64 496 Melanic 154473 Number of moths recaptured Typical16 (25%)62 (12.5%) Melanic82 (53%)30 (6.3%) __________________________________________________________ * The wild population in the polluted woods was 87% melanic. Source: From data of Kettlewell (1956).

13 Predator Escape Tactics Aspect Diversity Cryptic coloration (countershading) Disruptive coloration Flash coloration Eyespots, head mimicry Warning (aposematic) coloration Alarm signals Hawk alarm calls Selfish callers Plant secondary chemicals

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19 Selfish caller Hypotheses 1. Full up “I see you” 2. Mass pandemonium 3. Keep on moving 4. Mixed species flocks, fake alarm calls

20 Predator Escape Tactics Aspect Diversity Cryptic coloration (countershading) Disruptive coloration Flash coloration Eyespots, head mimicry Warning (aposematic) coloration Alarm signals Hawk alarm calls Selfish callers Plant secondary chemicals

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23 1. Physiological dependence on host most parasites are highly specialized many have complex life cycles with intermediate and final hosts challenge: how to infect new hosts? 2. Higher reproductive potential than host (high fecundity necessary for dispersal) 3. Parasites can kill highly infected hosts but typically do not — allow host to live 4. Infection produces an overdispersed distribution of parasites among hosts

24 Parasite Examples Assassin bugs (Triatoma) Malaria Tapeworms (Cestodes) Cholera (Shigella) transmission via dysentery Toilet seats, elevator buttons, shopping carts... Molecular mimicry “eclipsed antigens” resemble host antigens hence do not elicit formation of host antibodies Major Histocompatibility Complex Trypanosoma shed coats, change antigens Filariasis Elephantiasis (blocked lymph nodes, nematode worms carried by mosquitos)


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