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EEMB2- Ecology
UCSB EEMB Midterm
| Term | Definition |
|---|---|
| Ecology | • Study of distribution and abundance of organisms • And the factors and interaction that determine distribution and abundance |
| Aristotle in 350 BC | - Historia Animalium • Provided logical explanations for animal incidents (like mouse populations) • Much different than ideas of the time (Gods punishment) |
| Herodotus and Plato | Providential Ecology • Balance of nature |
| Graunt 1662 | father of demography |
| Leeuwenhoek | exponential population growth |
| Buffon | introduced evolution ideas |
| Malthus | socioeconomic perspective of populations |
| Quetelet | social physics |
| Verhulst | core equation for logistic growth of population |
| Farr 1843 | Farr’s rule Relationship between population density and death rate |
| Forbes 1887 and Cowles 1899 | Community regulation and succession |
| Rober Ross 1908 | Systems analysis • Mathematical model of the spread of infectious disease |
| Until 1960 | ecology was not considered an important sicence • Rachel Carson wrote silent spring • In the last 40 years, ecology has become increasingly experimental |
| abiotic components of the environment | non-living chemical and physical factors (temperature, light, nutrients, water) |
| biotic components of the environment | living (biological) factors (other organisms, competition, predation) |
| Ecosystem | energy flow and cycling of nutrients among abiotic and biotic components |
| Ecological evidence: a variety of sources | • Observation and monitoring in natural environment • Manipulative field experiments • Controlled lab experiments • Mathematical models |
| Goal of ecology | observe patterns, describe processes and use this information to predict, manage and control |
| Statistics | estimates of population parameters (numerical features of the population) o Attach level of confidence to conclusions that are the result of investigations |
| P- values (probability level) | Measures the strength of conclusions being drawn |
| Null hypothesis | assume there is no association between variables |
| Significance testing | o If P < than 0.05 (5%), then results are statistically significant o Less than 5% chance that the data is due to random chance o P-values are generated by comparing sampling data to a frequency distribution assumed by the null hypothesis |
| Frequency Distribution | o Used to determine probability, which aids ecologists in making predictions o Can have normal or inverted distributions • A lot of the time they are normal |
| Z-test statistic | how many standard deviations a datum is above or below the mean • Indicates how much higher or lower the value is from the mean |
| Why are particular species present and other not? | o It either evolved there o Or evolved somewhere else and dispersed there o If not there • Either evolved elsewhere and never dispersed • Once present but no longer there |
| biogeographic regions | o Based on taxonomic similarities of organisms living there o Boundaries are set where species composition changes dramatically over short distances |
| weather | short term state of atmospheric conditions at a particular place and time |
| climate | long term average atmospheric conditions found over time (temperature, precipitation, wind velocity) • Varies because of difference in amount of solar energy • Drives global atmospheric and oceanic circulation |
| daily cycles | rotation of Earth on its axis (24 hour days) |
| seasonal | annual cycle (fixed axial tilt of 23.5) Variation in sunlight intensity and day length give rise to seasonal variation in temperature in northern and southern hemisphere |
| why are tropics hottest | Solar radiation hits at almost right angles and acute angles near the poles Same amount of radiant heat is concentrated over smaller area at tropics At poles, solar radiation passes through deep layer of atmosphere (reflection, absorption, scattering) |
| Global air circulation patterns | air above equator is warm, rises and rains @ rainforests, heats at 30(desert), cools and rains at 60(temperate rainforests), dry cold air in polar regions |
| biomes | large scale patterns o Climate determines distribution of biomes o Terrestrial biomes are based on the structure of their dominant vegetation, aquatic biomes on their physical /chemical differences |
| transplant experiments | o Move organism and see if it can survive and reproduce in new environment o Follow through with one generation |
| successful transplant | • Potential range of a species is larger than its actual range • Lacks means of transport (dispersal) • Can move but choose not to (habitat selection) Area is inaccessible or unrecognizable as a living space |
| unsuccessful transplant | • Potential range of species is same as actual range • Limits imposed by other species • Positive effects of interdependent species • Or some other physical or chemical factor |
| factors limiting distribution | biotic interactions, other organisms, dispersal, habitat selection, abiotic factors, disturbance |
| habitat selection | o Organisms can move but choose not to live in certain habitats o Distribution may be limited by the behavior of individuals in selecting their habitat , dragonfly and tree pipit |
| dispersal examples | barnacles (water currents) and black rat / mongoose (human introduced) |
| competition | (-,-) o Competition can occur between two or more organisms or species that exploit the same types of limited resources and live in the same geographical area |
| species competition | o Intraspecific: within a species o Interspecific: between species |
| type of competition | o Interference: direct physical interaction o Exploitative: indirect interaction over resources |
| patterns indicating competition | • When species B is absent, species A lives in wider range of habitats (competitive release) • If competition is strong, the geographic ranges of the two competitions may not overlap, but have sharp boundaries |
| predation | (+,-) o Predation can limit the distribution of organisms via • Direct consumption of prey • Behavioral modifications of prey in the presence of predators |
| abiotic conditions | temperature & water (big 2)- osmoregulation, light, soil (serpentine soil & goldfield flower) |
| periodic disturbance | o Catastrophic disturbances can devastate organisms and limit distribution • Frequent May be predictable and organisms may be adapted to the disturbance Infrequent:unpredictable, organisms are not suited to deal with it |
| measuring population | total counts= impractical o Sub-sampling methods • Use quadrats • mark and recapture o indirect indicators mathematical models |
| Mark and recapture | know the formula |
| patterns of dispersal | clumped:common (unequal distribution of resources/social behavior) o Uniform • Due to interactions between individuals o Random • Chance dispersal • Resources not limiting • Rare |
| Importance of movement as loss and gain in population | dependent on spatial and temporal scales o Smaller the scale, greater importance to movement to population dynamics (immigration and emigration) |
| methods to identify population changes | • Direct observations o Not always practical for long lived organisms • View age structures o Life tables and survivorship curves mathematical models |
| exponential growth model | • All populations have potential for this In an unlimited resource environment • dN/dt = (b-d) N • dN/dt = rN |
| o Logistic growth | • No natural populations can maintain exponential growth indefinitely • Population density fluctuates around a constant As population increases, resources become limiting dN/dt= rN (K-N/K) |
| logistic growth assumptions | each individual added to population has same negative effect on population growth population approaches K smoothly • in reality there are many oscillations around K populations are large and density is important in regulation |
| limiting factors | • Any essential resource that is in short supply can limit population growth can be Density dependent (predation, disease) or independent (physical/chemical) |
| Stable equilibrium | birth = death • If perturbed population will return to initial density • Stabilizing forces dampen population fluctuations • Density dependent control |
| Unstable equilibrium | • If perturbed, will not go back to initial density • Destabilizing forces enhance population fluctuations |
| Mutualism | (+,+) o Both species benefit |
| commensalism | (+,0) o One species benefits, other is unaffected |
| ammensalism | (-, 0) o One species is harmed, other is unaffected |
| competition | (-,-) o Both are harmed |
| predation | (+,-) o One benefits, one is harmed o Parasitism is predation |
| lotka volterra models | • Possible outcomes when two species compete • Mathematical model o Based on logistic model of population growth |
| Guase experiments | o Competition between two species of yeast o Grew populations in isolation (logistic growth) o When he grew two species of yeast together, one will have logistic growth and one will go to extinction |
| Competitive Exclusion Principle | o No two species can occupy the same ecological niche simultaneously (complete competitors cannot coexist) |
| niche | biological role of an organism within the environment o Fundamental niche: multitude of conditions where a species can survive and multiply o Realized: where an organism ACTUALLY exists due to ecological constraints |
| in nature many species coexist | o Unstable environments: never reach equilibrium o Environments in which species do not compete: unlimited resources or partitioning o Fluctuating environments that reverse direction of competition before extinction occurs |
| lotka volterra predation model | o In absence of predators, prey populations grow exponentially o In absence of food, predator populations decline exponentially |
| predator-prey oscillations | o these oscillations are neutrally stable (amplitude determined by starting conditions) o follow same cycles indefinitely unless disturbed o due to time delays in response of predator density to that of prey density |
| o How do prey persist | • Prey have spatial or temporal refuge • Optimal foraging: Predators switch to other prey as original prey species fall to low abundance |
| • Antipredator strategies: adaptations | Chemical defense (coloration) Camouflage: cryptic coloration and mimicry Displays of intimidation and fighting Agility Armor Altered reproductive patterns: masting |
| community | two or more populations living in the same geographic area |
| • Individualistic hypothesis | : Gleason 1926 o Communities are chance assemblages of species with similar abiotic requirements |
| interactive hypothesis | Clements o Communities are an assemblage of dependent closely linked species |
| ecosystems | o Communities of organisms embedded in physical and chemical environments – movement of energy and material o Features • Open biological systems • One way flow of nutrients • Cycling of nutrients |
| trophic levels | defined by the # of steps through which energy passes to reach organisms in it |
| o Ecological pyramid | • Biomass decreases as rise up the trophic levels |
| o Energy pyramid | • Shows that the energy has a massive drop off • 90% drop off as you rise each trophic level vast majority is lost as heat o trophic energy level transfer efficiency = production at trophic level n/production at trophic level n-1 |
| • Top-Down effect | o Abundance of lower trophic level depends on effects of consumers from higher trophic levels |
| bottom-up effect | o Abundance of higher trophic levels depends on factors such as nutrients and prey availability from lower trophic levels |
| terrestrial trophic structure | often has 3 trophic levels o Often top down |
| aquatic trophic structure | o 4 trophic levels (nutrients high) o 3 trophic levels (nutrients low) o often bottom up |
| odd number trophic levels | resource limitation o Work from top down, but name it by the bottom level (what the bottom trophic level is limited by) |
| Even numbers of trophic levels | consumer limitation o Work from top down, but name it by the bottom level (what the bottom trophic level is limited by) |
| o Species richness | number of species in a community |
| species evenness | relative abundance of species in a community |
| o Intermediate disturbance hypothesis | severe and frequent= good colonizers (r-selected) with high reproductive rates mild and rare =good competitors (K selected) • Moderate / intermediate allows both colonizers and competitors to exist |
| • Diversity-stability Hypothesis | o Disturbance in diverse communities is dampened by large numbers of interacting species o The effect of disturbance is less than it would be in species poor communities |
| Ecological Succession | • Transition in species composition over time • Primary succession: bare soil no organisms o Volcano • Secondary succession: soil, some organisms o Fire, floods |
| o Early successional communities | are (r-selected) • Good dispersers (colonizers) and high reproductive rates |
| o Late successional communities | • Good competitors, exist near carrying capacity k-selected |
| • Directional succession | : progressively change in species composition |
| • Cyclical succession | change in species composition in which the original community is ultimately restored, depend on periodic disturbances to persist |
| o Invasive species | species that disrupt communities by a dominant colonization of a particular habitat or from loss of natural control |
| • Impacts | change in ecosystem structure and function Altered community composition Altered disturbance regimes • Which determine successional communities |
| o Process of invasion | • Introduction • Establishment • Spread • Impact |
| o Niche relationships | • With high niche overlap there is competition • Wider the average niche breadth, the fewer the number of species in the community • The narrower the average niche breadth, the more species in the community |
| niche trends | • Species often split apart to lessen competition (usually accompanied by behavioral, morphological or other species changes) |
| resource partitioning | specialization to narrow a niche and avoid competition |
| in short time scales competition | reduces diversity through extinction |
| in long time scales competition | increases diversity Niche diversification and spreading evolution |
| o Predation | • Increase richness: allowing competitively inferior species to coexist with superior competitors • Intense predation may reduce species richness by driving prey species to extinction |
| keystone species | species influence on the community is greater than originally expected, can be positive or negative • Predation experiment: starfish |
| • Equilibrium model of island biogeography | o Explains the process of succession on new islands o Species richness is positively correlated with island size and negatively correlated with distance from the mainland Turnover is high but number of species on an island remains relatively constant |
| • Equilibrium view | o Communities are structured by biotic interactions o Communities display global stability o Niche diversification determines species diversity |
| • Non equilibrium view | o Communities composition is always changing and never in balance o No global stability o Communities are patch works of disturbance, colonization and dispersal determine species diversity |
| why conserve biodiversity | stability, function, economic value, ecosystem services, environmental ethics |
| FOLLOWING ARE ADDITIONS FROM THE READING | YAY READING |
| density dependent population limiting factors | food supply, predators, pathogens, biotic factors mostly |
| density independent | extreme temperatures, other abiotic factors |
| factors that may contribute to high population densities | use of abundant resources, small body sizes, complex social organizations , newly introduced species to an area |
| habitat patches | areas of a habitat type that are surrounded by less suitable habitat areas , promoting the existence of subpopulations each patch has a probability of birth'= colonization or death=extinction |
| rescue effect | if individuals move between habitat patches, have less of a probability of extinction |
| reciprocal adaptation | coevolutlion can lead to an arms race ( species trying to 'out-evolve' eachother and be more fit) |
| aposemitism | bright colorization to warn of toxicity |
| Batesian mimicry | non toxic species resembling a toxic one to scare off predators |
| mullerian mimicry | number of aposematic species converge on a common color pattern, all benefiting from this |
| crypsis | background matching |
| homotypy | resemble inedible objects |
| guilds | groups of species that exploit the same resource, but in slightly different ways, making resource less likely to preempted |
| energy is lost in trophic levels due to | heat loss, biomass availability and indigestibility |
| trophic cascade | interactions of a single consumer that causes a progression of indirect effects across trophic levels (wolves in yellowstone) |
| alpha diversity | within a community |
| beta diversity | between communities |
| gamma diversity | regional diversity found over a range of communities or habitats |
| diversity on islands | large and near are highest > small near > large far > small far |
Created by:
hannad
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