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BSC 108 (56)
Lecture 25

BSC 108 Lecture 25: Chapter 20 In-Class notes
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Department
Biological Sciences
Course
BSC 108
Professor
Christine J.Yates
Semester
Spring

Description
Chapter 20 In-Class Notes Communities and Ecosystems • Causes of declining biodiversity o Habitat destruction (1 )st nd o Invasive species (2 ) ▪ This can cause rapid extinction • Kudzu: Japanese plant o Took over vast expanses of the SEC landscape o Help stops erosion, but takes over landscapes in a bad way rd o Overexploitation of wildlife (3 ) • Community ecology: o Community: assemblages of species living close enough for interaction • Interspecific interaction o Interaction between specie • Interspecific competition: o May occur when two or more species in a community rely on a similar limiting resource o May limit population growth of the competing species • Ecological niche: o The sum of a total species’ use of the biotic and abiotic resources in its environment o The role they play • G. F. Gause: o Studied the effect of interspecific competition in two closely related species of protists o Growth curve: for final o o top one is logistical (in separate dishes) o bottom one is showing out competed: ▪ top one beat out bottom one ▪ the bottom species extinct o concluded that two species so similar that they compete for the same limiting resources cannot coexist in the same place ▪ Competitive exclusion principle: • two species cannot coexist in a community if their niches are identical o There are two outcomes of competition between species with identical niches: ▪ Extinction of one species ▪ Evolution of one species to use a different set of resources • Interspecific interaction: o Mutualism ▪ Both species benefit from an interaction • Win- win ▪ Difficult to recognize the benefits to some species o Predication: ▪ Interaction in which one species kills and eats another • Win-lose ▪ Many predators • Have adaptations, such as claws, teeth, fangs, stingers, or poison to help catch and subdue prey • Fast and agile • Most predators have acute sense ▪ Many types of defenses • Passive defense o Hiding • Active defenses o Escaping • Mechanical defense o Hard shells or quills ▪ Behavioral defense\ • Alarm class • Mobbing ▪ Distraction display • Direct the attention of the predator away from a vulnerable prey to another prey that is more likely to escape ▪ Passive defense: • Cryptic coloration o Camouflage ▪ Warning coloration: • Bright colors ▪ Mimicry: • Copycat adaptation o One species mimics the appearance of another ▪ Used by species to gain protection • Trophic structure: o Divides species in a community based on their main sources of nutrition ▪ A food chain is the sequence of food transfer between trophic levels. • Detritivores: o Consume detritus known as scavengers ▪ Vultures • Decomposers o Secrete enzymes that digest molecules in organic material ▪ Fungi and bacteria • Biological magnification o The process in which toxins become more concentrated in successive trophic levels of a food web • Food Web: o The feeding relationships in an ecosystem ▪ Typically, not as simple as in an unbranched food chain. • usually woven into elaborate food webs. ▪ Nature provides options • Species diversity in communities o The species diversity of a community ▪ the variety of species that make up the community. • The diversity of a community has two components: o Species richness, ▪ the total number of different species in the community o Relative abundance of the different species ▪ The number of members of that species • Disturbances in communities o D
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