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what drives variation
- latitude: causes incident radiation and seasonality
- timing and strength
- uneven heating causes wind
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hadley cells
- movement of air (and rain) due to earths rotation
- affects climate in different areas
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biome
- characteristic types of vegetation found across earths surface
- dictated by climate- temperature and precipitation
- latitude, weather patterns, ocean currents, topography all affect biome location
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variation in terrestrial conditions
- direction surface faces
- slope (amount of rain that soaks in, water storage)
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albedo
- refelection of a surface
- high: reflective (water, snow, ice, light colors)
- low: dark colored, forests
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size of soil particles
- bigger: causes lots of pores which allow water to move thru
- smaller: holds water in
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human activities
- gravel road (base components affect acidic environment)
- impermeable surfaces (roads)
- irrigation
- CO2 concentrations
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ecological niche
- summary of all the resources requirements and condition tolerances of a organism
- bounds on where an organism cal live, grow, and reporduce
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population ecology
studies what determines the distribution and abundance of populations
- determine sustainable harvest levels
- minimum populations sizes for threatened and endangered species
- control of pests
birth, death, immigration, emigration
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exponential growth
constantly accelerating or decelerating
each individual is predicted to add same number of new individuals (or lose)
per capital growth rate is constant
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genomic growth equation
- used to predict the change in size of a population growing exponentially, when individuals only reproduce only at a specific time each year (discrete breeding)
- generations do not overlap
generates periodic estimates of population size
N (t) = N (0) Y t
Its the RATIO thats constant, not the number added or lost from population
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exponential grown equation
used to predict the change in population size growing exponentially when individuals reproduce continuously and the generations overlap
N t = N 0 x e rt
generates instananeous estimates of populations size
r = instantaneous per capita rate of population increase
N (t) = N (0)e rt
- dN/dt = rN
- dN/dt = net rate of population change, rate at which the size of the population as a whole is changing at a given instant in time, slope of line tangent to anywhere on the curve
Nt = N0 x ert
r = lnY
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equations
- curves predicted by both models are unchanging thru time
- due to per capita rate of increase or decrease is unchanging
- biological processes contributing to population growth are unchanging too (birth, death, immigration, emigration)
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matrix modeling
- another method to predict population growth, based on geometric
- more detailed: focuses on survival and reproduction of different stages of an individual (age, size, dev. level)
- transition probabilities: likelihood of each possible transition between 2 categories
- 2 field seasons
- year 1: assign stages and count number in each
- year 2: determine probability of transition by comparing 1st year to 2nd year
- stages based on biomass (plant size)
- models run until population is stabilized and lambda is calculated
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native
exotic
invasive
non-invasive
native: evolved within a given geographic area - exotic: evolved outside a given geographic area
- invasive: rapidly spreading, dominates areas into which is spead
- non-invasive: not rapidly spreading
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invasibility
ease with which a new species enters a community
Edge vs intermediate vs center plots represent invasion, growth and today,
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biological control
introduction of natural enemies from an invasive exotic species native range to control the invaders population in a new area
controversial- expense, lack of effectiveness, bad outcomes
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Matrix model: lambda equations
Y = N (t+1)/N (t)
Y >1 : population increasing - Y < 1 : population decreasing
- Y = 1 : constant
when Y stabilizes Y = N(t+1)/N(t) is the same from timepoint to timepoint
model uses same transition likelihoods. biology driving population to increase or decrease is not changing
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density dependent factors
- things that take a bigger percentage cut out of larger populations
- must decrease reproduction/immigration, or increase death/emigration
- intraspecific competition is big factor
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intraspecific competition
- use or defense of a resource by one individual that reduces the availability of that resource to other individuals
- same species (have same needs)
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compete for
food, nutrients, water, oxygen, space, structures
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why competition harms individuals
- might be unable to get limiting resources
- must look harder and further, energy expense
- increase stress (defending territory, aggression to individuals)
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slows down population growth rates at high densities
- predators (as prey increase, predators eat them)
- parasites
- disease (higher density, increase disease)
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density dependence vs. density independent
density dependence: negative (population increases, growth rate decreases) - postiive (small populations, panda)
- density independent: effects population regardless of size, based on proportion, no logistic growth
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