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Monday, August 31st Learning Goals • Compare and contrast the major types of species interactions Agenda • Ch. 3 Quiz • Interactions Notes • Study Guide Interactions Among Organisms Homework • Unit 1 Test Thursday! Ecological Niche • The role of a species in its community. It includes: − environmental conditions the species can tolerate − what it needs to grow, survive, and reproduce − how it interacts with its biotic and abiotic environment • An organism is capable of using much more of its resources or living in a wider variety of habitats than it actually does − Fundamental niche: the environmental conditions a species can tolerate and resources it is capable of using under ideal conditions. − Realized niche: the portion of the fundamental niche a species uses in the presence of other species (competition & predation) • SO, ecological niche is the total adaptations, use of resources, and lifestyle to which it is suited. 1 Niche: Fundamental vs. Realized Competition • Greater Yellowlegs • A relationship in which multiple organisms seek the same limited resources they need to survive − Food, water, space, shelter, mates, sunlight • Intraspecific competition: between members of the same species − High population density = increased competition • Interspecific competition: between members of 2 or more different species − Leads to competitive exclusion or resource partitioning Results of Competition • Two species with identical niches cannot coexist over time − When two species compete for exactly the same resources, one will be more efficient than the other at gathering those resources • Competitive Exclusion: one species completely excludes another from using the resource Results of Competition • Resource Partitioning: when species divide shared resources by specializing in different ways – EX: one species is active at night, another in the daytime – EX: one species eats small seeds, another eats large seeds 2 More Species Interactions • One of the most important species interactions is who eats whom • Predation: process by which individuals of one species (predators) capture, kill, and consume individuals of another species (prey) Adaptations of Prey • Predation pressure: prey are at risk of immediate death – Prey develops elaborate defenses against being eaten – EX: camouflage, mimicry, warning coloration, assembling in groups, chemical defenses, built in protection Adaptations of Predators • Natural selection leads to the evolution of adaptations that make predators better hunters • Individuals who are better at catching prey: – Live longer, healthier lives – Take better care of offspring • EX: keen senses, speed, intelligence, ambush, claws, teeth, venom Adaptations of Plants Against Herbivory • Exploitation in which animals feed on the tissues of plants – Widely seen in insects – May not kill the plant, but affects its growth and survival • Defenses against herbivory include – Chemicals: toxic or distasteful parts – Physical: thorns, spines, or irritating hairs – Other animals: protect the plant 3 Other Species Interactions • Symbiosis: relationship between two different species live closely together Mutualism: both species benefit − Water buffalo & tick bird, bee & flower, clown fish & anemone Commensalism: one species benefits while the other is unaffected − Barnacles on a whale, bird’s nest in a tree, moss on a tree, remora on a shark Parasitism: one species benefits while the other is harmed − Tick feeding on a dog, tapeworm & human, flea & cat Interactions help maintain ecosystems • Loss of mutualistic relationships would ripple through the biosphere until very few organisms remained − These relationships are important to the survival of both species involved • When prey species disappear, predators soon decline − Predators keep prey populations in check and maintain balance in the ecosystem 4