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BIO120H1 (305)
Chapter 14

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University of Toronto St. George
James Thomson

Chapter 14Species InteractionsConsumerresource interactions organize biological communities into food chains consumers benefit individually and increase their numbers resource populations decrease populations are controlled from above and below their place on the food chain by consumers and resources respectively Mutualisminteraction where both parties involved benefit eg bees and flower pollination Competitioninteraction where two species share a resource and reduce the availability of it for the other species Commensalism 0 interaction where one party benefits and the other is unaffected eg bird builds its nest in a tree Amensalism 0 one party suffers and the other is unaffected eg you unknowingly crush an insect underfoot Symbiosis species interaction referring to individuals who live in close association mutualistic or parasitic Types of consumers predator captures prey and consumes it kills prey parasite attaches itself or lives within a host consuming parts of its body usually doesnt kill host parasitoid live and mature within a host eventually killing the host herbivores consume plant material are either predators when they kill the plant or parasites when they graze or browse detritivores consume dead organic matter commensalistic 0 important for nutrient recycling Resource populations adapt many evolutionary tactics suited to their environment to avoid being captured by consumers As the fitness of both depends on the delicate relationships between consumer and resource evolutionary responses constantly readjust the relationship There is however a cost to resource populations when they modify their behaviour to avoid being captured they have less habitat food resources time of day they can be active etc Parasites may live on or within the bodies on their hosts Some parasites cause deadly or debilitating illness while some may cause only moderate inconvenience and others still may actually be beneficial to their hosts eg Buchnera eats a hosts carbohydrate reserves but produces essential amino acids Most parasites have complicated life cycles to survive whatever life they have outside of a host and complicated evasive tactics to keep from being detected and destroyed by a host Virulence capacity of a parasite to invade host tissue infectiousness Crossresistance when the body develops antibodies which function against several varieties of an illness consider smallpox and cowpox Plants while they cannot flee like many resource population employ other
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