BIOL 180 Lecture 27:02 & 04:03

Inducible nature of plant defenses constitutive

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: taste bad alkaloids - potent poisons Note: - Source of our pesticides, drugs and spices. Inducible Nature Of Plant Defenses Constitutive - Always present/produced e.g tannins - Energetically expensive. Inducible - Made when needed. - Toxins increase dramatically in many plants following defoliation by herbivores. - in area of wound or systemically throughout plant - response in minutes -> next growing season - Can substantially reduce subsequent herbivory. Responses of Herbivores To Plant Defenses 1. Evolve methods to counteract plant toxins e.g. containment, break-down - Leads to: a. specialization of insect herbivore to particular plant b. evolutionary arms race. 2. Some herbivores use chemicals to their advantage preferentially feed on plants with high concentrations and sequester chemicals to use against own predators. Ex. Interactions between cottonwood trees, beavers, and leaf beetle (Chrysomela confluens) (text) ***cost of inducible defense --> energetic cost to producing more chemical which would result in less seed production because there is less energy available for other things*** “Why Don’t Herbivores Eat More Plants”? - Levels of herbivory low in terrestrial ecosystems. 1. Top-Down Control Hypothesis - herbivore populations limited by predation and disease. 2. Bottom-up Limitation Hypothesis - plant tissues poor food sources (low N) and well defended limits herbivore densities/growth and reproduction Limits herbivore densities/growth and reproduction * Both important factor in limiting impact of herbivory. - Depends on plant species. MUTUALISM (+/+) Mutualisms = relationships that benefit both parties - Provide...
View Full Document

This note was uploaded on 02/24/2014 for the course BIOL 180 taught by Professor Freeman during the Winter '07 term at University of Washington.

Ask a homework question - tutors are online