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EcoEvo#3(ch.13Notes)
EcoEvo#3(ch.13.Fgs)
| Question | Answer |
|---|---|
| What are two examples that demonstrate that age structure is an indication of population fluctuations? | Whitefish and old-growth forest. |
| What are two examples of populations that have experienced overshoot and die-off? | Moose and wolves on Isle Royale. Both experienced wide fluctuations. The moose exceeded their carrying capacity and the population experienced massive die-offs from starvation. |
| What is the difference btw population fluctuations and cyclic population fluctuations? | Cyclic population fluctuations have over longer periods of time and ocillate up and down in regular patterns. |
| What are two examples that demonstrate that populations can exhibit remarkably regular fluctuations or "cyclic population fluctuation"? | Gyrfalcons, they showed regular 10 year cycles of abundance; and three species of grouse across Finland, all experienced population cycles every 6-7 years- they exhibit high and low populations at the same time. |
| True or false. In some cases, cyclic population fluctuations occur among species and across large geographic areas. | True. |
| True or false. Density dependence with time delays can cause populations to be inherently cyclic. | True. |
| What are examples some examples of cycles of environmental variation? | Daily, lunar or tidal, and seasonal cycles. |
| What are examples of non-cyclic environmental variations? Are they predictable? | Prolonged periods of abundant rainfall or drought, extreme heat or cold, or natural disasters such as fires and hurricanes. They are not predictable. |
| What must we conclude about irregular variation in the environment? | We must conclude that irregular variation in the environment is not likely to be the underlying cause of regular population cycles. |
| Explain "inherent periodicity". | Populations can naturally oscillate above and below their carrying capacity when they are subjected to environmental variation, even if the environmental variation is random over time. Populations tend to fluctuate up and down. |
| What is the key to making density-dependent populations cycle in the logistic models? | Incorporate a delay between a change in environmental conditions and the time the population reproduces. |
| What are two examples of delayed density-dependence? | Moose breed in Fall but birth in Spring; predator experience increase of prey, carrying capacity increases, takes weeks for predator to convert abundant prey to high reproduction. Lack of prey cause carrying capacity to decline as population increases. |
| What model do you use to demonstrate delayed density dependence? | Modified logistic model. |
| What does dN/dt mean in the delayed density dependence model? | Rate of change in the populations size. |
| What does r mean in the delayed density dependence model? | Intrinsic growth rate. |
| What does N mean in the delayed density dependence model? | The current size of the population at time t. |
| What does K mean in the delayed density dependence model? | The carrying capacity. |
| What does the delayed density dependence equation tell us about populations? | This equation tells us that the populations slows its growth when the population's size, at T(tau) time units in the past, approaches the carrying capacity. |
| What does T(tau) mean in the delayed density dependence model? | The amount of time delay. |
| When does a population approach the carrying capacity without any oscillations? | When the product of r and T(tau) is a low value (rT<0.37). |
| When does a population initially oscillate but the magnitude of the oscillations declines over time? What is this called? | When the product of r and T(tau) is an intermediate value (0.37<rT>1.57); damped oscillations. |
| When does a population continue to exhibit large oscillations over time? What is this called? | When the product of r and T(tau) is a high value (rT>1.57); stable limit cycle. |
| How do population models that incorporate time delays help us? | Incorporating time delays in population models helps us understand how time delays cause populations to oscillate in regular cycles. |
| What is an example of a specific mechanism that leads to cycles in populations? | Daphnia galeata (water fleas) store energy/nutrient reserves when population is low/abundance of food. When food is scare, those with reserves keep reproducing (even if the carrying capacity is exceeded) till they crash and the cycle starts over. |
| Name an example of a mechanisms that leads to overshooting carrying capacity. | Daphnia galeata and storing energy/nutrient reserves. |
| What is a classic example confirms that time delays between life stages cause population cycles? | A. J. Nicholson examined the effect of time delays between the larval and adult stages of the sheep blowfly. |
| True or false. Chance events can cause small populations to go extinct. | True. |
| Fill in the blank. When populations are ____, density-dependent factors cause ______growth, and when populations are _____, density-dependent factors cause _____ growth. | Large, slower; small, faster. |
| How does adding the reality of stochasticity add to our understanding of extinction? | Although populations of any size eventually have some chance of going extinct, the smallest populations face the greatest risk of extinction. |
| How does the probability of extinction in a population model do? | This model uses an exponential growth model and stochastic rates of birth and death to find that the average probability of extinction increases with decreasing population sizes (N) and longer times into the future (t). |
| What are metapopulations composed of? | Subpopulations that can experience independent population dynamics across space. |
| What makes a subpopulation into a metapopulation? | When individuals are able to move between patches, then the collection of subpopulations can be called metapopulation. |
| When do metapopulations occur in nature? | When a habitat is fragmented; also occurs as a result of human activities- clearing forests, draining large wetlands, and constructing roads, housing developments, and commercial properties- all breaking up large habitats into a number of smaller habitats |
| What is an example of a metapopulation? | Wetlands across North America- each one can contain many different species, but the terrestrial habitat between these wetlands is generally inhospitable, yet some individuals are able to disperse to other wetlands. |
| How can metapopulations persist over time? | A combination of extinction balanced by colonizations by dispersers that form new subpopulations. |
| In what case can fluctuations of abundance in one subpopulation influence the abundance of other subpopulations? | Juvenile animals disperse away from their family to find a mate- leading to individuals occasionally moving between habitat patches. |
| What does the basic model of metapopulation dynamics tell us? | This model indicates how we might increase the number of occupied habitat patches, which would increase the total number of individuals in the metapopulation given that each occupied patch is assumed to have an equal number of individuals. |
| Name two ways to increase the number of occupied habitat patches in a basic model of metapopulation dynamics. | 1) provide corridors between neighboring populations, thereby increasing the rate of colonization 2) decrease the rates of extinction by reducing the major causes of population decline in subpopulations |
| What do models and empirical research inform us that the key is to preserving populations? | 1)maintain large fragments of habitat when possible- populations in large habitats are less likely to go extinct 2)ensure that individuals can disperse to small fragments so they can be colonized- prevents small declining subpopulations from going extinct |
| Name an example of the basic model of metapopulation dynamics. | Glanville fritillary butterfly on the Aland of Islands of Finland. |
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BriawnaW
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