Bio Notes Week 10
Bio Notes Week 10 Biol 180
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This 8 page Class Notes was uploaded by Nikki Hovland on Wednesday December 2, 2015. The Class Notes belongs to Biol 180 at University of Washington taught by Scott Freeman in Summer 2015. Since its upload, it has received 61 views. For similar materials see Introductory Biology in Biology at University of Washington.
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Date Created: 12/02/15
INTRODUCTORY BIOLOGY 180 Thursday December 3 2015 Week 10 Notes Lecture 33 CompetitionCommensalism Four Types of Species Interactions Commensalism when one species benefits but the other is unaffected 0 Competition individuals use same resources thus lowering fitness for both Consumption herbivory predation parasitism one organism eatsabsorbs nutrients from another increasing consumer fitness decreased the consumed s fitness Mutualism two species interact so that both increase fitness KEY THEMES 1 species interactions affect distribution and abundance of a certain species 2 species act as agents of natural selection when they interact Coevolution occurs pattern of evolution when two species influence each others s adaptations over time coevolutionarv arms race repeating cycle of reciprocal adaptation 3 outcome of interactions among species is dynamic and conditional Commensalism Commensalism is very conditional commensals gain fitness advantage but do not affect the species they depend on interactions can change depending on situation and actions of each species Competition competition lowers fitness of individuals because competitors use resources gt resources now not available to help other individuals 39ntraspecific competition between members of one species food space sun etc increases as pop density increases INTRODUCTORY BIOLOGY 180 Thursday December 3 2015 interspecific competition between individuals of different species as different species use same limiting resources occurs when niches of two species overlap symmetric competition if both species experience decrease in fitness due to overlap of niches gt both species may stay in overlap area even if reduced numbers asymmetric competition one species suffers greater fitness decrease than the other depends on amount of niche overlap competitive exclusion principle two species that occupy same niche cannot coexist one with die out to extinction ie explanation for why Neanderthals went extinct fundamental niche total theoretical range of environmental conditions a species can tolerate realized niche portion of fundamental niche that species ACTUALLY occupies given limiting factors like competition common experiment for studying competition one competitor is removed and response by remaining competitor observed fitness trade off if individuals are good at outcompeting others for a certain resource then they probably are not good at enduring droughts fighting disease or preventing predation since competition is interaction strong natural selection on both species to avoid it evolutionary change to reduce amount of niche overlap gt reduced competition niche differentiation evolutionary change in resource use caused by competition over time also called resource partitioning character displacement evolutionary change that occurs in species traits to exploit different resources makes niche differentiation possible INTRODUCTORY BIOLOGY 180 Thursday December 3 2015 Lecture 34 Mutualism and Coevolution mutualism are interactions ie bees and flower pollination and benefit both species although not always nice sometimes can turn into interactions when species cheats ie like deceit flowers that provide no nectar to bees mutualisms are DYNAMIC example mycorrhizal fungi and plants fungi grow on roots fungi do not produce own food heterotrophs have cell wall eukaryotes fungi fix nitrogen and phosphorous for plants and plants provide nutrients for it to eat photosynthate biomass is hard to measure because large amount of it is underground and on roots difficult to harvest plants would experience rapid selection for defense mechanism if fungi were just stealing from plants nitrogen fixing is extremely energy intensive COMMON RESEARCH STRATEGY for species interactions asses fitness costs benefits by removing one species are observing effect on other s survival and reproduction and compare to a normal interaction between the two species outcome of interaction depends on the CONDITIONS like the other interactions costs and benefits of species are fluid species interactions can change from parasitism to mutualism to competition SUMMARY TABLE OF INTERACTIONS ON PAGE 1136 INTRODUCTORY BIOLOGY 180 Thursday December 3 2015 Lecture 35 Communities Disturbance and Succession community structure has 4 key things total number of species relative abundance of each sum of interactions among those species physical attributes of community abiotic and biotic factors climax community the final stage of the development of a community in which the community is stable and does not change over time proposed by Clements ie if a fire occurs the climax community would reconstitute itself in predictable stages if communities are predictable then the same ranges of species should always be found living together Gleason proposed that a community is neither stable nor predictable Clement s hypothesis too extreme gt Gleason is more correct chance and history also play a large role in determining which species live in a certain area although biotic interactions and climate are important too removing a particular structural species from a community can have HUGE effects on the rest of the community community structure may change completely if single predatorherbivore removed added keystone species species that has much greater impact on distributionabundance of other species in community than its own abundance and total biomass of species would suggest like the seastar preying on mussel species gt affects sea star and mussel population AND indirectly affecting other species food web network of exchanges of energy and nutrients in ecosystem Community Dynamics INTRODUCTORY BIOLOGY 180 Thursday December 3 2015 disturbance strong short lived disruption to a community that changes distribution of living and nonliving resources the impact of disturbance depends on type of disturbance equency severity most communities usually experience a particular type of disturbance sort of predictable disturbance regime characteristic disturbances of a particular community normal disturbance regime should occur for communities to remain in good condition otherwise it will change rapidly succession the recovery following severe disturbances in which all or most of organisms are removed primary succession after disturbance removes soil and organisms in and above soil glaciers volcanic eruptions floods landslides secondary succession after disturbance removes some or all of organisms but leaves soil intact fire and logging early successional communities dominated by short lived small species that widely disperse seeds late or climax communities dominated by long lived large and good competitors for resources like light and nutrients successional pathway sequence of species that appear over time pioneering species tend to have weedy life histories weed plant adapted for growth in disturbed soils weeds thrive in secondary succession early successional species devote most energy to reproduction and not much to competition high fecundity low survivorship high reproductive rate can tolerate severe conditions after recolonization begins succession depends less on how species cope with abiotic environment and more on how they interact with each other INTRODUCTORY BIOLOGY 180 Thursday December 3 2015 existing species effect subsequent species by facilitation early species makes conditions better for later species like providing shade or nutrients tolerance existing species do not effect establishment of subsequent species inhibition presence of one species inhibits growthestablishment of another like releasing chemicals or hogging the sunlight KEY species traits and species interactions often make succession predictable history and chance events contribute a degree of unpredictability Lecture 36 Communities Species Richness and Net Primary Productivity NPP species richness simple count of how many species are present in given community species diversity weighted measure that includes species relative abundance MacArthurWilson model theory of island biogeography trend islands in the ocean tend to have lower species richness smaller number of different species than area of same size on a continent immigration rates should decline as number of species increases because individuals that arrive are probably already part of species there extinction rates should increase as species richness increases because of niche overlap and more intense competition for resources often a balance is found between immigration and extinction species richness depends on number of existing species island size remoteness of island KEY bigger island less remote gt more species gt greater species richness INTRODUCTORY BIOLOGY 180 Thursday December 3 2015 immigration rates higher on large islands less remote because immigrants more likely to find island extinction rates highest on small islands very remote because less resources and less immigrants to keep pop growing theory of island geographv important because relevant to many island habitatsreserves applies to metapopulations similar predictions about immigrationextinction testable predictions help design nature preserves make them large and close to other habitats evidence of a strong latitudinal gradient in species diversity as latitude increases diversity decreases for many taxonomic groups HighProductivity Hypothesis high productivity total amount of photosynthesis per unit area annually in tropics low latitudes ma increase diversity by increasing speciation rates and decreasing extinction rates more biomass gt more herbivores gt thus more predatorsparasites gt bigger populations gt more intense competition gt greater speculation rates as niche differentiation happens supported by global patterns tropics but not supported by estuaries and fertilized communities Energy Hypothesis high temperatures increase species diversity by increasing productivity and probability organisms can tolerate the environment high ENERGY inputs versus nutrient inputs as in the High Productivity Hypothesis is key for more speciation and less extinction Area and Age Hypothesis tropical regions have had more timespace for speciation than other areas because historically have larger land area and no ice compared to higher latitudes towards the poles INTRODUCTORY BIOLOGY 180 Thursday December 3 2015 however some evidence says tropical regions may not be as old not good enough explanation to support speciationextinction rates ecosystem species in a certain region with abiotic factors 39 parts of ecosystem linked by flow of nutrients and energy to sustain life carbon nitrogen energy enters ecosystem through primary producers primary producer autotroph can make own food from inorganic resources and TRANSFORMS energy does not create it gross primary productivity GPP total amount of chemical energy produced in certain area and time period primary producers use chemical energy for Cellular respiration use energy to stay alive and fuel cell respiration to produce ATP energy and fuel metabolic processes 39 Growth and Reproduction energy not used for cell respiration that is invested in building new tissue or offspring net primary productivity NPP some energy lost as molecular wasterheat KEY NPP GPP R Renergy for cell respiration or lost NPP represents total amount of chemical potential energy stored in organic materialbiomass IMPORTANCE OF NPP it is the amount of energy available from primary producers to all other organisms of ecosystem general pattern only small fraction of incoming sunlight converted to chemical energy and only fraction of this small amount of GPP is used to build biomass