LECTURE 12 Biodiversity diverse when it contains many different species can be measured by species richness number of species within a given community species diversity is richness plus relative abundance of each species Disturbances and Community Composition Disturbance is event that removes individuals and or biomass o Categorized by intensity and frequency Succession changes in species composition of a community following a disturbance event o Primary Succession colonization of habitats that are devoid of life following severe disturbance that has removed soil Glaciers floods volcanic eruptions landslide may Very slow succession species have to colonize from elsewhere Soil formation requires breakdown of rock accumulation of organic matter o Secondary Succesion occurs when vegetation in an area has been partially or completely removed but soil is intact Fire clear cutting abandoned agricultural field storm damage o Species Interactions Facilitation when early arriving species make conditions more favorable for the later arrival of others Tolerance exisiting species do not affect the probability that subsequent species will become established Inhibition existing species inhibits the establishment of another Is it Predictable Clements o Communities are stable highly ordered and have predictable species composition o Pass through predicable stages o Climax community is best out come for community o Species cooperate to reach climax community Gleason o Communities are neither stable nor predictable o Community composition is a result of chance history and climate abiotic factors o Resulting communities are unique Pond STUDY constructed 12 ponds filled with sterilized water allowed natural colonization monitored for 1 year RESULTES o 61 species colonized the ponds o individual pond had 30 39 different species o about half appeared in all ponds but each had a unique composition so both hypotheses are correct Latitudinal gradients in biodiversity higher diversity in tropics due to a combination of greater age more time for speciation higher rainfall and high solar inputs high NPP Also biodiversity increases with the area of habitat LECTURE 13 Proximate causes mechanistic explanation how behavior occurs and developes focus on neurological hormonal skeletal muscular mechanisms Ultimate causes evolutionary explanations why behavior occurs its function effect on fitness and evolutionary origin Behaviors are innate learned or both Innate behavior developmentally fixed under strong genetic control exhibited in same form by all indivduals in a population Learned behavior a behavioral change that results from experience Fixed Action Patterns are innate show little or no variation in how they are performed are species specific once it starts typically continues until complete All FAPs are innate not all innate is a FAP Responde to releasers stimuli that causes a FAP EXAMPLE Robin s with orange feathers Question what characteristic of a robin intruder releases territorial behavior in breeding European robins Hypothesis orange feathers act as a releaser Paint orange feathers brown Results attacked orange feathers but not brown so they are a releaser for territorial behavior in European robins Classical Conditioning trained by experience to give same response to more than one stimuli Pavlovs dogs Imprinting species attachment to first moving thing they see young birds adopt first moving object as their mother occurs in a critical period is irreversible Using this to save whooping cranes Learning of Bird song innate in some bird species must be learned in a critical time period for others some species song is continuously learned and modified over lifetime lyrebird Deceptive Communication providing inaccurate or misleading information to members of a different species to increase individual fitness Ex orchid deceive their pollinators by mimicking scent and morphology of a female wasp but provide no nectar reward Foraging Behavior try to maximize behavior related to search for food Optimal foraging theory behaviors that compromise feeding costs vs feeding benefits Honeybee dance waggle portion is direction to food source length proportional to the distance and intensity is proportional to the amount of food Migration long distance movement of population associated with change in seasons