Host defenses Parasitism

1 host defenses

1.1 in vertebrates
1.2 in insects
1.3 in plants

host defenses
in vertebrates

the dry skin of vertebrates such short-horned lizard prevents entry of many parasites.

the first line of defense against invading parasites in vertebrates physical barrier of tough , dry , waterproof skin, in reptiles, birds , mammals. microorganisms need moist environment survive. keeping skin dry, prevents invading organisms colonizing. human skin secretes sebum, toxic microorganisms. on other hand, larger parasites such trematodes detect chemicals produced skin locate hosts when enter water. saliva in vertebrate mouth prevents foreign organisms getting body orally. mouth contains lysozyme, enzyme found in tears , saliva. enzyme breaks down cell walls of invading microorganisms. should organism pass mouth, stomach hydrochloric acid, toxic microorganisms, next line of defense. intestinal parasites have thick, tough outer coating digested or not @ all, allowing parasite pass through stomach alive, @ point enter intestine , begin next stage of life. parasites can invade body through eyes. lashes on eyelids of mammals prevent microorganisms entering eye. tears contain enzyme lysozyme, kills invading microorganisms. once inside body, parasites must overcome immune system s serum proteins , pattern recognition receptors, intracellular , cellular, trigger adaptive immune system s lymphocytes such t cells , antibody-producing b cells. these have receptors recognize parasites.

in insects

insects adapt nests aid in parasite defense. example, 1 of key reasons why wasp polistes canadensis nests across multiple combs, rather building single comb of rest of genus, defense against infestation of tineid moths. tineid moth lays eggs within wasps nests , these eggs hatch larvae can burrow cell cell , prey on wasp pupae. adult wasps attempt remove , kill moth eggs , larvae chewing down edges of cells, coating cells oral secretion gives nest dark brownish appearance.

in plants

leaf spot on oak. spread of parasitic fungus limited defensive chemicals produced tree, resulting in circular patches of damaged tissue.

in response parasitic attack, plants undergo series of metabolic , biochemical reaction pathways enact defensive responses. example, parasitic invasion causes increase in jasmonic acid-insensitive (ja) , nahg (sa) pathway. these pathways produce chemicals induce defensive responses, such production of chemicals or defensive molecules fight off attack. different biochemical pathways activated different parasites. in general, there 2 types of responses can activated pathways. plants can either initiate specific or non-specific response. specific responses involve gene-gene recognition of plant , parasite. can mediated ability of plant’s cell receptors recognizing , binding molecules located on cell surface of parasites. once plant’s receptors recognizes parasite, plant localizes defensive compounds area creating hypersensitive response. form of defense mechanism localizes area of attack , keeps parasite spreading. furthermore, specific response against parasitic attack prevents plants wasting energy increasing defenses not needed. however, specific defensive responses target specific parasites. if plant lacks ability recognize parasite, specific defense responses not activated. nonspecific defensive responses work against parasites. these responses active on time , systematic, meaning responses not confined area of plant, rather spread throughout entirety of organism. however, nonspecific responses energy costly, since plant has ensure genes producing nonspecific responses expressed.