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How do strong climates effect population growth models?
It causes them to jump around
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What does the logistic model of poppulations assume?
- 1. Birth/death and density affect growth
- 2. All individuals genetically the same
- 3. All individuals equal in terms of birth and death - age doesn't matter
This is not realistic
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Age structure alters population growth (How is this shown)
Age pyramids show the age structure they sumarize the population growth rates.
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What is a disadvantage of an age pyramid?
They can not be used for calculations you have to use a life table for that
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What do life tables summarize? and what type of life tables are they?
- Mortality and survival rates = static life table
- Survival and fecundity = cohort life table
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What is included in a static life table?
Construced by a snapshot of the whole population across different generations
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What is included in a chohort life table?
Constructed by looking at one generation through all times - can only be done for a small population
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Static life tables curves show?
- Survivorship with age
- There are 3 different types.
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What are disadvantages of static life tables?
They don't show if population is increasing because you don't know the reproductin rate.
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What is N1 in a cohort life table equation?
the initial population
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What is Lx in a cohort life table equation?
Nx/N1
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What is x in a cohort life table?
Age of the population
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What is Mx in a Cohort Life table?
Done out in the field - number of average seeds or eggs - seed per individual
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What is LxMx in a cohort life table?
survivorship corrective fecundity
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What is Ro in a Cohort Life table and how do you find it?
The average number of offspring per individual, you multiply Lx and Mx
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How do you interperet Ro?
Ro > 1
Ro = 1
Ro < 1
This is wheter a female is replacing herself or not
- 1. population is increasing
- 2. population is steady
- 3. population is decreasing
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What do populations generally do relating to survival and reproduction? What happens if they do not follow the norm?
- produce about 1 offspring per individual in the population
- If less than 1 the population will go extinct
- If more than 1 the population there will be uncontrolled growth
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How does reproduction and death balance out? (2 ways)
- High egg production low survivorship
- Low reproduction high survivorship
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What does semelparous mean?
One big bang reproduction
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What does Iteroparous mean?
repeated episodes
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What are is the best strategy for reproduction why doesn't this happen?
- Long lived, multiple reproductions, many offspring per episode, high survival of offspring (high investment / parental care), early age of first reproduction.
- if one trait is maximized another suffers there are tradeoffs
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what is the tradeoff between mortality and fecundity?
As fecundity rises so does mortality they are positively correlated.
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What are elements of R - selected environments?
- Fast growing
- Small, numerous seeds
- Single reproduction
- Short-life span
- Good dispersers
- Poor competitors
- Disturbed habitats
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What are elements of a K - selected environments?
- Slow growing
- Few, large seeds
- iteroparity
- Long-live span
- Poor dispersers
- Good competitors
- Stable, old habitats
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How did the human population grow?
Steadily till the industrial revolution then it started to grow exponentially
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When is Death > Birth?
When the population growth goes down
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What is different about human population?
- Individual natural selection
- Human population growth is often affected by unpredictable factors
- Political, ethical, religious, sociological, economic issues are important
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Why did industrialized countries growth rate slow?
Declined due to women entering professions, delaying reproduction, having fewer children.
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Problems with human growth rate are?
- Disagreement on K, the carrying capacity
- Most economies growth oriented, and depend on expanding population ( especially care of elderly )
- Population size also depends on immigration/emigration
- Limits on population size - has many negative connotations
- There is no easy answer
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Whats the norm for understanding human population growth?
Complexities
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