If the intensity of the distributed load acting on the beam is w = 3 kN>m, determine the reactions at the roller A and pin B.
Population Ecology Ecology: The study of… - Ernest Haeckel (1869) came up with the word “ecology” o Oikos – house/home; “study of the household” - Vick’s definition: Economics of nature - Textbook: study of the relationships of organisms to their environment and one another The Economics of Nature: - Based on distribution/abundance of organisms o Individual organisms o Populations of organisms o Communities of organisms Ecology vs. Evolution Ecologists & Evolutionary Ecologists: look to understand/explain processes that determine the distribution, diversity, and abundance of organisms Ecologists: Evolutionary Ecologists: Look for proximate answers for diversity, Look for ultimate answers for diversity, distribution, and abundance of organisms distribution, and abundance of organisms Ex: Why did the chicken cross the road A: To get away from a predator, find food, A: migration pattern of the chicken went or find a mate across the road, appendages carry it across the road, inclination to cross roads Ex: Colorado Potato Beetle is a pest in America (lg. population), not Mexico (sm. population) Proximate Causes: Ultimate Causes: - Pest Status: based on food - Pest Status: evolved to process availability, predation potatoes or endure cold conditions - Population Size: large amt of food - Population Size: evolved to live in increases population; potatoes less regions where natural enemies defended cannot survive Ecology: Changes in numbers of individuals or populations in ecosystems over a few Evolution: (Macroevolution) generations Changes in traits in populations - Scope: Populations or individuals over many generations within habitats - Scope: Traits within populations - Timescale: Days/Years - Timescale: Larger time frames Ecology Evolution Evolutionary change changes in ecology evolves abilities to survive differently Invasive Species: dispersal limitation Factors limiting Geographic Distribution - Dispersal - Behavior (Habitat selection) - Biotic factors (Other species, predation, competition, disease) - Abiotic factors (Chemical/physical) Density: number of individuals per unit area or volume - Often impractical/impossible to count all individuals in a population - Sampling techniques used to estimate densities/total population size MarkRecapture Method: scientists capture, tag, and release random sample of individuals (m) in a population - Marked individuals are given time to mix back into the population - Scientists capture second sample of individuals (n) and note how many of them are marked (x) - Population size (N) is estimated by: N = mn / x because m / N = x / n - Ex: Scientist marked 180 dolphins and waited a few days to mix them. He observed 44 dolphins the second time, 7 of which were marked. m = 180 So N = (180) (44) / 7 = 1131 n = 44 x = 7 Density is the results of interplay between processes that add individuals to a population and those that remove individuals Immigration: influx of new individuals from other areas Emigration: movement of individuals out of a population Dispersion: pattern of spacing among individuals within the boundaries of a population (clumped, uniform, random) Exponential Growth: (growth without limits) N: Population size d N d T r N R: Intrinsic rate of natural increase (= birth rate – death rate) dN/dT: Rate of change in population size Logistic Growth: (growth with limited resources) dN (K−N) =rN K: Carrying capacity dt K CH. 40 Behavior Behavior: Response to a stimulus Environmental Change Stimulus - Adjustments of behavior are often the most visible responses to environmental change - Ex: Many migratory animals change timing of migrations in response to climate change 40.1: Behavior is Controlled by the Nervous System but is Not Necessarily Deterministic An animal’s nervous system activates/coordinates behaviors: - Fixed Action Patterns: highly stereotyped animal behaviors that are expressed without prior learning; often resistant to modification by learning o Ex: begging behavior of gull chicks peck at red dot on bills; spiders’ web spinning - Ex: The ultimate cause of what the male threespined stickleback attacks other males entering his nesting territory is to increase their reproductive ability - Behaviors evolve: Natural selection favors the alleles that produce more adaptive behaviors than others o Many studies show that genes exert important effects on behavior o Ex: In Drosophila mutants for gene per altered circadian rhythms o - Biological Determinism: behaviors of animals are hardwired by genetics; individual’s genes change neural properties in fixed ways that affect behavior o Behavior is more flexible than any other biological trait b/c learning modifies behavior o Epigenetic effects on behavior lifelong influences; can be transmitted to next generation o Ex: Clams are inflexible in many of their responses to their environment 40.2: Behavior is Influenced by Development and Learning Learning: ability of individual to modify its behaviors as a consequence of individual experiences - Ex: Experiments with mice show that they learn layout/hiding places of their environment, learning that helps them escape predation by screech owls. - Learning is taught through patterns of recognition, whereas fixed action pattern is not Behavioral Imprinting: type of learning that is taught; takes place within a narrow window of time early in postnatal life and after is inflexible - Can have lifelong consequences - Examples o Geese imprint on their true parents and species to establish a strong attraction; o Speciesspecific songs of Darwin’s finches used to attract females; o Hungry adult offspring of “lowcaring” mothers wait longer than those of “high caring” mothers to go to food and spend less time eating food - Key regulatory genes in stressresponse biochemical/hormonal pathways are tagged with epigenetic marks early on in life permanently altering their stress responses - Malnutrition/abandonment early on in life affects epigenetic tagging in rats 40.3: Behavior is Integrated with the Rest of Function - Pronghorn have the highest sustained speeds in running animals o Can deliver O2 to muscles at high rates o Use O2 at high rates to make ATP in muscle cells o Use ATP at high rates to perform intense muscular work o Exceptionally large lungs/skeletal muscles, and muscle cells are tightly packed with mitochondria - Escape behavior is dependent upon ATP synthesis o Aerobic ATP is slow and resists fatigue o Anaerobic ATP is fast but subject to fast fatigue o Ex: Toads evolved enzymes for aerobic ATP production in legs whereas frogs evolved them for anaerobic ATP production, and therefore, leap away faster - Behaviors are dependent upon body size/growth o Ex: Tonal frequencies of insects’ songs vary based on body size; larger body low frequency song o Some species must grow to adult size before developing reproductive behaviors 40.4: Moving through Space Presents Distinctive Challenges Navigation: act of moving toward a destination or along a course - Trail following o Pheromone: chemical compound/mix of compounds emitted into outside environment by individuals of a species and elicits behavioral responses from other members of same species o Can use pheromones to attract members of opposite sex - Path Integration o Monitors length/compass direction of each segment and integrates the information about segment lengths/directions to determine where it is relative to its nest Orientation: adopting a position or path of locomotion relative to an environmental cue such as the sun - Sun Compass: determine where N, S, E, W are by observing sun o Ex: Pigeons observe position of the sun and also know the time of day to calculate direction using circadian clock; on cloudy days they detect Earth’s magnetic field to orient to - Many insects determine compass direction by detecting patterns of polarized light in sky o Depends on photoreceptors - Honey bee workers’ “Waggle Dance” o When worker bee finds flowers it returns to hive to communicate the path using the dance based on measurements taken of distance and direction to the flowers o Measures distance by monitoring rate flying past landmarks o Measures direction by monitoring the angle of flight relative to the compass position of the sun o If cloudy, they use atmospheric polarization patterns to determine position of sun - Migration: move periodically from one location to another to remain for a substantial period of time and later return from o Ex: Sea turtles use Earth’s magnetic field to orient themselves 40.5: Social Behavior is Widespread Society: group of individuals of a single species organized to some degree in a cooperative manner Social Behavior: behaviors of individuals that integrate them into societies and the group behaviors of entire societies - Disadvantages o Grouping makes animals more visible o diseases spread more rapidly o resources are depleted more rapidly - Advantages of Equal Status o Enhanced awareness of environment (Ex: Goshawk’s success in capturing pigeons decreases as number of pigeons in flock increase) o Discover preferred environments more efficiently - Advantages of Differing Statuses o Dominates: “wins” oneonone behavioral contests with others; has greatest chance of mating with adult females in group o Reasons above o Process of becoming dominant serves as a test of male’s strength, endurance, properties for success therefore females that mate with it ensure that their offspring are genetically well developed - Eusociality: social structure in which some members of social group are non reproductive and assist reproduction of fertile members of group, usually mother o Mostly in insects o Exemplify Altruism: any characteristic of an individual that imposes a cost on that individual while aiding another 40.6: Behavior Helps Structure Ecological Communities and Processes - Behavior helps maintain species - Behaviorally partition space into territories o Territory: region occupied by an individual that actively keeps others of same species out o Home Range: other individuals aren’t excluded o Provide familiarity (escape route, resources, etc) CostBenefit Approach: Assumes an animal has only a limited amount of time/energy and therefore cannot afford to engage in behaviors that cost more to perform than they bring benefits