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Ecology Ch. 15
Ecology Exam 2
| Question | Answer |
|---|---|
| List three types of Growth curves | 1) Exponential 2) Geometric 3) Logistic |
| Natural population resembles | Logistic with variation. |
| Density dependent factors | Keep the population at or near carrying capacity. |
| Periodic cycles | Population high and lows occur regular periods |
| Population Oscillation Patterns | Logistic equation (dN/dt |
| Populations exhibit one of three patterns | 1) r is small <1- population approaches K and stabilizes (most familiar S-shaped curve) 2) 1 < r < 2-population exhibits damped oscillations 3) r > 2-Population exhibit limit cycles 4) r >> 2-Population exhibits chaotic pattern |
| The main intrinsic cause of population cycling is… | time delays in the responses of births and deaths to environmental change |
| Time delays… | Response of population to conditions at time is not expressed until the next time interval |
| Population thus oscillates as it… | over- and undershoots its carrying capacity |
| Strong year class of fish | Indicates good reproductive year |
| Stand of Trees | Age and type of trees indicate what forest was like in the past |
| Metapopulations | Interconnected subpopulations |
| Subpopulation | 1) Connected or separated 2) Large or small |
| If highly connected all subpopulations… | act as larger population |
| If small and separate… | they risk extinction |
| Rescue effect | 1) Large productive populations add individuals to smaller populations 2) This avoids extinction of sub pop. 3) If sampling to infrequent population could be extinct then recolonized and appear to function as rescue effect |
| Randomness is… | bad for small populations |
| Catastrophes | Reproductive failure or death (fire) |
| Physical environment variation | Natural variation (temp, precipitation) |
| Stochastic | Variation in population is stable environment (Random Death) |
| Stochastic randomness example | Coin toss Heads (live), Tails (die) |
| (Stochastic Extinction of Small Subpopulations) The probability of extinction | increases with 1) Smaller population size 2) Smaller habitat patch 3) Increased distance between subpopulations 4) Time |
| Stochastic with Density dependence | 1) Most models do not include density dependent changes in b and d 2) These improves probability of survival 3) Stochastic extinction much less likely with changing b and d |
| Why independent models matter | 1) Provide simplified idea of population 2)Habitat fragmentation 3)No movement 4) Variability of environment 5) Low numbers allow other species to take advantage of resources 6)TOO Low -Inbreeding or can’t find mates |
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jessica5998
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