Defense Strategies

Evolution of chemical defenses according to the optimal defense theory presumes, in addition to costly defenses, that there is genetic variation for the defensive metabolites, that herbivory is the major selective agent for such metabolites, and that the chemical trait in question is efficient in reducing herbivory (Stamp 2003). Research on macroalgal chemical defenses has strongly emphasized the last precondition, which has mainly been studied by testing the deterrence effects of secondary metabolites in bioassays. The defensive role for the trait has been assumed on the basis of deterrence it provides. Veiy little research on the first two 

Owing to the costs of defenses, natural selection will optimize defenses. There are various aspects in this optimization, including defense allocation with respect to temporal variation in grazing pressure and within-plant defense allocation with respect to grazing risk and the value of different plant parts (reviewed in Stamp 2003). Here we will focus on both the induced defenses and within-plant allocation of defenses, because these aspects have been widely studied in macroalgae. 

The databases were compiled by conducting key-word searches in the Science 

Citation Index, and by examining the literature-cited sections of the papers obtained. The phenolic database consisted of 22 papers (22 indicated with in the reference list) 

For each study and response variable, we calculated an estimate of the magnitude of the induced response (effect size, Hedge s d) as the difference between the 

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Pohnert G (2004) Chemical Defense Strategies of Marine. 239 179-219 Ponthieux S, Paulmier C (2000) Selenium-Stabilized Carbanions. 208 113-142 Port M,see Idee J-M (2002) 222 151-171... 

Create guidance to help air transportation facilities develop a threat defense strategy and... 

Finding 4 Although the rapid detection of a chemical/ biological attack and identification of the agent used are worthwhile objectives, a defensive strategy that depends exclusively on a detection-system alarm before action is taken (i.e., employment of a detect and react strategy) has several serious limitations. 

One common characteristic of many chemical agents is that they tend to be relatively fast acting that is, victims begin to exhibit symptoms of distress within seconds to minutes after exposure to the agent. This almost-immediate showing of symptoms has implications for defensive strategies based on detection systems, since the chemical agent released in an attack would reach and produce a response... 

In a defensive strategy that is based on the detection of a chemical/biological agent in order to initiate a response, the time required for authorities to respond to an attack has three components the inherent response time of the detection system, the time required to verify the validity of a detector alarm, and the time required to decide on what action to take in response to the alarm. These three elements are discussed in more detail below. 

To minimize the time needed to make a decision on the response to choose in a detection-based defensive strategy, it is necessary to have contingency plans in place for responding appropriately to the alarm situations likely to be encountered. These plans should include an array of options of graduated intensity keyed to the quality of information available. They should include emergency changes to the operation of the HVAC system, evacuation of potentially... 

The feasibility of detection-based defensive strategies also depends on how the detectors are deployed and how they are actually used. Deployment considerations include the number and placement of detectors, whether in open spaces or in HVAC ductwork. In this respect, airport terminals are likely to be more difficult to protect by this strategy than are aircraft, owing to the vastly greater air volume and necessarily greater physical spacing between detectors in terminals. To the extent that more than one type of independent detection or verification system is needed to achieve acceptable POD and PFA, the system costs are multiplied. 

A defensive strategy against chemical/biological attacks that does not rely on a detection event to initiate a response... 

As discussed in Chapter 3, a detection-based defensive strategy could complement the non-detection-based strategy in some scenarios, particularly those involving the release of slow-acting biological agents. However, it is likely to be some years before technological detection systems become... 

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