Term
Predation, competition, herbivory and disease are all species interactions which can influence what? |
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Definition
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Term
For a specific generation type, we say that each female has a life span of 1 year and 1 viable breeding season and that they produce R0 female offspring that survive to breed the following year. What is this generation subtype called? |
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Definition
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Term
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Definition
Nt+1 (the net reproductive rate, or number of female offspring produced per female per generation, times the population size of females at a generation t when mutliplied give the population size of females at generation t+1) |
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Term
What is important about R0 being greater than or less than 1? |
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Definition
If R0 is less than one, the population will decrease in size and will eventually go extinct |
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Term
What is so important to note about the equilibrium point, where R0=1.0? |
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Definition
The birth rate equals the death rate (the population is perfectly stable) |
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Term
The deviation from the equilibrium plot can be expressed as z=N-Neq. What do these values mean? |
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Definition
z: deviation from equilibrium density
N: observed population size
Neq: equilibrium population size |
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Term
1-Bzt (where B equals the slope of the deviation line and z equals the deviation from equilibrium density at a given time t) is another way to express what? |
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Definition
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Term
This value (obtained from multiplying B and Neq) tells us what type of population growth we can expect with discrete generations and certain values of B and Neq |
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Definition
L
-If 0<L<1, the population approaches equilibrium without oscillations
-If 1<L<2, the population undergoes oscillations of decreasing amplitude to the equilibrium point
-If 2<L<2.57, the population exhibits stalbe limit cycles (predictable but irregular oscillations) that continue indenfinity
-If L<2.57, the population fluctuates chaotically with random changes depending on starting conditions |
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Term
What is the instantaneous rate of population growth? |
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Definition
r=b-d where r = per-capita rate of population growth |
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Term
What does the equation rN=(b-d)N express and what are its components? |
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Definition
It is the curve of geometric increase.
N: population size
r: per-capita rate of population growth
b: instantaneous birth rate
d: instantaneous death rate |
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Term
Because the presence of other organisms can limit the fertility and longevity of others, what do we often see in population growth graphs? |
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Definition
We often see a sigmoid (S-shaped) or logistic curve |
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Term
What does the equation dN/dt=rN((K-N)/K) calculate and what do its terms mean? |
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Definition
It produces a logistic curve and takes into account the carrying capacity, K, of the organism |
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Term
What is the key distinction between geometric and logistic growth? |
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Definition
There is no resource limitation in the case of geometric growth |
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Term
What did Gause show with his Paramecium studies with respect to the logistical growth model? |
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Definition
He showed that under a stable environment, the paramecium species follow a generally good logistical growth pattern |
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Term
What was a key issue in Pearl's (1927) argument that logistic growth is a law? (Hint: he studied Drosophilia which were fed by yeast) |
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Definition
Sang (1950) criticized his use of yeast since yeast is itself a growing and changing organism so the food source for the flies was not kept constant. He also only counted grown adults whereas both adults and larvae feed on yeast |
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Term
What interesting theory did Pearl and Reed generate in 1920 regarding the US population? |
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Definition
It would reach a carrying capacity of about 197 million people around 2060 |
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Term
What is the theta logistic model and how does it theoretically operate? |
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Definition
It relaxes the assumption that population growth rate decreases linearly as density increases; rN((K-N)/K) becomes r(1-(N/K)theta) |
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Term
Under the theta logistic model, 78% of population growth curve had a theta value less than 1. What does this mean? |
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Definition
When populations are below K, their growth rate is low and is also low relative to that predicted by normal logistic curves |
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Term
What do time-lag models say about animals and their population growth models? |
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Definition
R0 at a generation t may not depend on density in that generation but in the generation before that (t = -1) |
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Term
In the time-lag model, how is the equation Nt+1=R0Nt impacted? |
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Definition
This equation now becomes Nt+1=(1-Bzt-1)Nt |
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Term
How do the L values change for time-lag models of population growth? |
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Definition
- If 0<L<0.25, there is stable equilibrium with no oscillation
- If 0.25<L<1.0, there is convergent oscillation
- If L>1.0, the stable limit cycles or there is divergent oscillation to the point of extinction
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Term
What interesting facet has been discovered from experiments on the zooplankton Daphnia with regards to time delay models? |
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Definition
Daphnia raised at high temperatures showed continuous over and undershooting of its equilibrium density |
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