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29 Cards in this Set
- Front
- Back
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What two items contribute to decrease in size of population? What two items contribute to increase? |
Emigration and death contribute to the decrease. Immigration and birth contribute to the increase. |
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How do we model the density independent population growth of a closed population, over one term (t)? |
We say that: N(t+1) = N(t) + B(t) - D(t) When N is the population size at t, B is birthrate at t, D is deathrate at t. |
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What are the per capita rates of birth and death? What are the letters to represent these values? |
The per person rates. We model them by dividing births or deaths in a time unit by the total number of individuals. We write b and d to represent these values, instead of B and D. |
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What is delta n? What about delta n over delta t? |
Delta n is change in population, total births - total deaths. Delta n over delta t is the change in population per some time unit. |
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What are the two types of population growth rates? |
Exponential growth - density independent. Happens when a new habitat is colonized, or when a habitat is recolonized. Logistic growth - density dependent. Most populations show this type of growth. |
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What can we say that population growth is equal to? HINT: Not the same as population growth rate. |
It is equal to (b - d)N. |
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What letter do we use to mean 'population growth per capita'? |
r |
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In exponential growth, what can we say about r? |
It is constant, while the number of individuals added in each t interval increases because the population size is increasing. |
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What is the formula to estimate future population sizes in exponentially growing populations? |
N(t) = N(0)e^(rt) N(t) is population size at t, e is base of natural log. Remember we can take ln of e to get 1. |
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What factors regulate population growth? |
Density Independent Factors: Generally abiotic, temperature, rainfall, solar radiation, etc. Density Dependent Factors: Disease, resource availability. |
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What is a logistic growth rate? |
When the population size approaches the carrying capacity K logistically. |
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What is K determined by? |
Food, water, space, soil quality, resting/nesting sites, life history strategies. |
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What is the Pearl and Reed Logistic Growth Model? |
delta N / delta t = r(0) N [(K - N) / K] Basically the initial, density independent rate of growth decreasing as we get closer to K. |
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How do populations tend to increase in real life? |
They follow the natural s curve. |
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When are regular population cycles produced? |
Lagged responses of death and birth due to density dependent factors can lead to regular fluctuations around K. The severity of the fluctuation depends on the severity of the factor that led to it and the length of the time lag. |
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What is demography? |
The study of factors that determine the size and structure of populations over time. |
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What is the age structure of a population? |
The number of individuals alive at each age group in a population. |
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What does the age structure in part dictate? |
The r of a population. It is also usually dependent on the females of the population, so those are the ones whose age structure we track. |
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What are the three types of species survival rates throughout their lives? HINT: Think of the graph of what percentage of a population survive to a percentage of that species' potential lifespan. |
I - Most individuals live to the older ages, humans. II - Survivorship is constant during the lifespan, squirrels, they die off gradually. III - Low survivorship at low age intervals, and a few individuals live much longer, turtles. |
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What are life history traits and what do they describe? |
They describe the reproductive strategies of organisms, ie. how many offspring to have and when to have them, and the timing of life cycle events - how long to spend growing before you mature. Reflect age specific patterns of energy allocation. |
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What are some of the trade-offs of life history traits that were explained in lecture? |
The trade-off between growth and reproduction Between early and late maturity Between few large and many small offspring. |
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What does the optimal life history trait strategy depend on? |
Abiotic conditions, community composition, resource availability, and how any of these factors influence age-specific probability of survival.
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Explain the trade-off between fecundity and survival. |
If there is a high adult mortality rate, higher levels of energy are allocated to the current reproduction cycle. If rate is low, then allocation of energy to reproduction is kept below a level that could impact future survival and reproduction. Ratio of adult to juvenile mortality decides optimal strategy here. |
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Explain the effects of resource availability on the offspring. |
If resources are unlimited, then the parent will invest very little into each offspring because the offspring don't need the help. If resources are limited, parent will have a few, large offspring and invest lots of parent care to increase chances of the offsprings survival. |
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What is an R-selected species? |
A species in which environmental instability reduces the population size before it approaches the carrying capacity. |
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What is a K-selected species? |
A species in which the population size is near the carrying capacity due to density dependent factors. |
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What are the characteristics of an r-species/opportunistic species? |
The individuals have high fecundity, grow quickly, reach sexual maturity quickly, produce many offspring. |
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What are the characteristics of a equilibrial species/ K-selected species. |
Individuals have high survivorship, grow slowly, invest more energy in their young, reach sexual maturity later, and have fewer offspring. |
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Are K and r selected species categorical? |
No, there is a continuum between them. |
