5 - PREDATION READINGS FREEMAN 2005 Chapter 53 Pages 1220...

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PREDATION READINGS: FREEMAN, 2005 Chapter 53 Pages 1220 - 1227
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CONSUMPTION The consuming of one living thing by another. A basic eating relationship between populations of different species. Must be evaluated on the basis of its effects on populations, not on individuals. A + (consumer) / - (consumed) interaction.
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MAJOR TYPES OF CONSUMPTION Herbivory --- Eating of plants by animals. May not result in death of individual plant. Parasitoidism --- Larvae of parasitoids consume hosts. Cannibalism --- The eater and eaten belong to the same species (intraspecific predation). Parasitism --- Host provides nutrition to one or many individual parasites. Host may or may not die. Predation --- Predator kills prey and consumes all or part.
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HERBIVORY Occurs when animals eat plants. Herbivores are those animals that exclusively or primarily eat plant tissue. Generally restricted to specific parts of the plant (leaves, flowers, fruits, roots, tubers, sap); thus, leaving the rest to regenerate. Resembles predation when seed (which contains plant embryo), seedling or whole plant is consumed.
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VERTEBRATE HERBIVORES Large ungulates are the most conspicuous native herbivores in North America. Those that feed primarily on grasses and forbs are grazers. Those that feed on tree leaves are browsers.
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INVERTEBRATE HERBIVORES Half of all insect species are thought to be herbivores. Groups such as butterflies, moths, weevils, leaf beetles, gall wasps, leaf-mining flies and plant bugs are almost exclusively plant eaters. Snails, slugs, mites and millipedes are largely herbivores.
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HERBIVORY Is thought to be ecologically important, but its impact is still debated. Suggested positive impacts include: 1. Increased production and nutrient uptake. 2. Increased quality of leaf litter and soil. 3. Increased chances of successful seedling establishment. 4. Improved conditions for plant growth (pruning effect).
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Some Evolutionary Responses of Plants to Herbivory 1. Mechanical forms of protection. Microscopic crystals in tissues, thorns, hooks, spines. 2. Defensive chemicals. Strychnine, morphine, nicotine, digitoxin, etc. 3. Fruits. Attractive and tasty tissues surrounding seeds that promote dispersal.
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PARASITOIDISM Insects, usually flies and small wasps, that lay their eggs on living hosts. The larvae then feed within the body of the host, eventually causing death. Recent experimental evidence suggests that parasitoids locate their hosts by responding to airborne chemical signals from plants damaged by the host.
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PARASITOIDS A tachinid fly lays eggs on a hornworm (moth larva). The fly larvae develop by consuming the hornworm. Many species of ichneumon wasps are parasitoids.
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CANNIBALISM An individual consumes another individual of the same species.
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5 - PREDATION READINGS FREEMAN 2005 Chapter 53 Pages 1220...

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