Biology 106 Outline:EXAM 1: Ecological niche: can be abiotic and biotic factors, role, food, where it lives, what it does, environment, can be organism or resource Fundamental niche - where it can live, ideal, suitable habitat and conditions Realized niche - where it does live, smaller populations, limitations because of competition and dispersal Limiting resources - factors that limit use of other resources which cannot be used effectively because of lack/cost of limiting resource, usually only one Resource partitioning - ghost of competition’s past, reduces competition between species Population: group of same species that lives in the same area (breed, compete) Density- number of individuals per area/volume, how many, can count or estimate (mark-recapture method) Emigration - old individuals leave population Migration - new individuals enter population Dispersion- how they are spaced/organized, pattern Clumped - group together, patches, usually for defense or resources Uniform - evenly spaced- Territoriality- individual defends own physical space Random - no pattern, unpredictable, independent Demographics: study of statistics of populations and change overtime Life tables - summaries of population’s survival patterns (d, b, life expectancy) Cohort - group of individuals (same age), life followed from birth to death Survivorship curves - graph, represents life table data, plot number of individuals alive in cohort at each age I- low d early, high d late (humans)- K selected- low fecundity, high survivorship, I II- constant III- high d early, low d late (sea life)- R selected- high fecundity, low survivorship, III Reproductive tables - fertility schedule, female cohorts, age-specific summary of reproductive rates Exponential Model: population growth in ideal, unlimited environment Short term Density independent- r doesn’t depend on N Per capita birth/death rate - (b/d) number of individuals produced per unit time by averageindividual female Equations B=bN1- B- number of births D-dN- D- number of deaths r= b-d- r- per capita growth rate ΔN/Δt= B-D Zero population growth - r=0, b and d are equal Population growth rate Additions=bN Losses=dN Change=bN-dN (b-d)N Nr dN/dt rmax=max per capita growth rate, ideal conditions (high b, low d) r=actual per capita growth rate, r<rmax, can be negative dN/dt=rmaxN or rN when N=0, r=max- most resources available, migrate in Logistic Model: population grows slowly near carrying capacity Per capita rate of increase approaches zero as k is reached Ideal Density dependent Carrying capacity - (k) max pop size an environment can withhold/sustain dN/dt=rmaxN((K-N)/K) or rmax(K-N)/K (K-N)/K is unused space r gets smaller with higher densities- more d, less b Intraspecific competition increases overtime Competition: abundance and distribution of biotic resources affect where a species can live K/2=ideal harvest, difficult to tell because k frequently changes Density dependent factors - as N increases, b decreases (stress competition, space) or d increases (predation, starvation, disease, stress) Competitive exclusion principle - 2+ species cannot coexist if one have competitive advantage at obtaining shared resources, MUST share same niche and limiting resources, interspecific Must specialize or die Interspecific affects realized niche- reduces Intraspecific doesn’t affect niche Interspecific changes overtime can affect fundamental niche Exploitation - gets resource first, differential abilities to use/extract resource Interference - directly affects other’s ability to get resource Symbiosis: when 2+ individuals of 2+ species live in direct, intimate, long term contact with each other2 Parasitism - (+/-) not always fatal, long term, many parasites on one host, one benefits at expense of another, derives nourishment from host, includes diseases (ex- mosquito) Parasitoid- specialists, lay eggs on/in host, offspring eat host, fatal, best bio control agent, super parasite Hyperparasitism- parasite of a parasite Predation - fatal, short term, 1 predator kills many prey (+/-) Herbivore- organism eats entire plant=predator, eats part of plant=parasite Mutualism - (+/+) both organisms benefit coevolution Obligate- at least 1 species cannot survive without the other Facultative- both species can survive on own Commensalism - (+/0) benefits one but neither harms nor helps the other Facilitation - species have positive effects on survival and reproduction of other species without living in same direct/intimate contact Specialists - eat certain things, only certain group for competition, invasive species biological control agent Generalists - eat anything, omnivores Trade off between two above Plant Relationships: Rhizobacteria - soil bacteria in rhizosphere Rhizosphere - soil around plant roots, has complex root secretions and microbial products Chemicals produced to stimulate plant growth Make antibiotics Absorb toxins Nitrogen cycle Ammonifying bacteria Nitrogen-fixing bacteria Nitrogen fixation Rhizobium - bacteria, N2 fixation NH3, mutualism Crop rotation between legumes and non-legumes can restore nitrogen concentration- monoculture change Mychorrhizae - fungi, mutualism with plant roots, host gives fungus sugar and fungus gives plant more water and minerals, antibiotics, and stimulates growth with chemicals Diversity: variety of different species in a community Species richness - number of different species in community Relative abundance - proportion each species represents of all individuals in a community Stability - community’s tendency to reach and maintain constant composition of species Climax community - species function as integrated unit Disturbance - event (storm, natural disaster, drought, overgrazing, human activity) that changes a community- removes organisms/alters resources Non equilibrium model - communities constantly change after being affect by disturbance3 Intermediate disturbance theory - moderate levels of disturbance foster greater species diversity than low/high levels, open up habitats Ecological succession - disturbed area is colonized
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