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1. What is a life table? Define age-specific survival probability and fecundity.
• A table used to help measure age-specific survival probability and fecundity. Age-specific survival probability is the chance of survival of the organism from one age to the next. Fecundity rates are the number of offspring the organism will have at a particular age.
2. Other than age, what else may determine reproductive rate? In what types of animals is this most important?
• Size may also determine the reproductive rate. This concept is most important for plants, reptiles, invertebrates, and other organisms where growth continues throughout life or when it is difficult to determine age.
3. What is a cohort? How is a cohort used in a cohort table? What types of organisms are best for this?
• A cohort is a group of individuals born at the same time. It is best for shorter lived, and sessile organisms.
4. Describe a static life table. How is this different from a cohort table? What must you be able to identify about an individual to use a static life table? When is this better?
• A static life table is used to sample different cohorts during one time period, resulting in a "snapshot" of an entire population at one time.
• Must be able to age individuals or place them into groupings.
• Better to use for long living and mobile organisms.
5. What do you have to estimate to complete a cohort life table (2)? How do you calculate the estimated survivorship of each age class? What does it tell us?
• Estimate age-specific population structure (Nx) - Number alive at each age over time.
• Estimate Fecundity Schedule (Fx) - average number of offspring produced by a female of age x
• Nx/N0 - It tells use the estimated Survivorship of each age class. Proportion of original cohort that survives to start of age x. Probability that an individual survives from birth to the beginning of age x.
6. Is it possible for a cohort life table to have higher survivorship at a lower age class? Why? How is this related to how survivorship is calculated? Can it be the same though? How?
7. How is survivorship different from survival probability? How is survival probability calculated? Can an older age class have a high survival probability? How?
8. What is a survivorship curve? What are the three general types of survivorship? Give an example for each. Are survivorship curves the same for all populations of a species? Why?
• A graphing showing the proportion of individuals surviving at each age for a given species or group.
• The three general types of survivorships: Type I, Type II, and Type III.
• Type I - Most survive past juvenile stage and don't die until they are "old" (Humans, Elephants)
• Type II - Equal chance of surviving at any age. (Corals, songbirds)
• Type III - Few survive past juvenile stage but becomes stable when older (plants, fish)
9. What is the net reproductive rate of a cohort life table? How do you calculate it? Explain why this makes sense. What is the net reproductive rate when a population is increasing in size, decreasing in size, or staying the same?
• The Net Reproductive Rate is the Mean number of female offspring produced per female over her lifetime.
• If the Net Reproductive Rate is lower than 1 (R0 < 1) - There is a decrease in population size (-N)
• If the Net Reproductive Rate is higher than 1 (R0 > 1) - There is an increase in population size (N)
• If the Net Reproductive Rate is equal to 1 (R0 = 1) - There is no change in the population size.
• The Net Reproductive Rate is found by multiplying the fecundity rate and the survivorship of the organism. (Fx)(lx) = R0
10. What are some examples of characteristics used to age organisms? Sex an organism?
• Observing teeth (deer)
• Bait with tetracycline (black bears)
• Plastron rings (turtles)
• Plumage characteristics (birds)
• Some birds do not look the same between the male and female.
• Feathers and feet (Turkeys)
• Fecal matter (Turkey)
• Male geckos have hemepenal bulge and pre-anal pores
11. What information about the future can a life table estimate? (3)
• Age structure
• Population Size
• Population Growth - rate at which population size changes in given time period.
12. What are the different kinds of population growth rates? (3) Describe what factors would cause each pattern. How does this affect age structure?
• Rapid Growth, Negative Growth, Zero Growth
13. What do you need to know to predict how the population will change in the future? (2)
• Number of surviving to next time period
• Number of newborns the survivors produce in next time period.
14. How do you calculate the geometric population growth rate (λ)? What does it tell you? When λ=1, what does this mean? The further λ gets from 1, the more _________ a population is changing. What does it mean for a population growth rate to be negative?
• Λ = Nt+1/Nt
• Describes rate at which population size changes over a time period.
• When λ=1, it means that the population is stable.
• The further λ gets from 1, the more rapidly the population is changing.
• When λ is negative, the population is decreasing (Negative growth)
15. What is a stable age distribution? How does this relate to λ?
• When an organism has reached its stable age distribution, then there is no more change in the population growth. (No increase or decrease)
• Λ fluctuates in the beginning but becomes stable after a few years.
16. Last year, you measured 500 rabbits. Since then, you've recorded 200 births and 100 deaths. What will N be 3 years from your original starting date?
• Λ = 500+200-100/500 = 1.2
• N = (1.2)3 * 500 = 864
17. λ characterizes population size changes between discrete (no overlapping) generations. Describe a population that fits this pattern. What is the other pattern of population growth? Why do both curves have J-shaped curves?
• A population that fits this pattern are many plant populations and caribou populations.
• The other type of pattern is the Continuous Growth (Exponential).
• Both patterns have J-shaped curves because it is a constant proportion.
18. Describe the equation for exponential growth rate.
• Λ=er, r=ln(λ)
19. Assign λ and r to the growth pattern that they are associated with. How are they related? What are their dimensions?
• Λ = discrete growth patterns
• R = Continuous (exponential) growth patterns - per capita rate of increase = birth rate (b) - death rate (d)
• Λ=er, r=ln(λ)
• Λ is dimensionless (no units)
• R is offspring/individual
a. r = 0, then the population size 0 and λ is 0.
b. r > 0, then the population size increases and λ is 1.
c. r < 0, then the population size decreases (more die than are born) and λ is 1.
21. What is the equation to calculate the time it takes for a population double? A larger r does what to this time?
• Tdouble = ln(2)/r
• Larger r = short tdouble
22. When can a population grow exponentially? What two factors limit population growth?
• Populations can grow exponentially when the conditions are favorable.
• The two factors that limit population growth are Density-Dependent factors and density-independent factors.
23. What is density dependent population regulation? Describe a situation in which population density would affect the birth/death rates of a population?
• Density dependent population regulation are "natural" causes that changes birth/death rates.
• Some examples are intraspecific competition for resources. When the population increases exponentially, there are less resources per individual.
24. Describe density independent population regulation. Name some examples.
• Density independent population regulation are independent or unrelated causes that are separate from the population size. (Changes in the environment)
• Some examples of density independent population regulation are temperature, and precipitation. (Natural catastrophic events; wildfires, Human induced catastrophic events; oil spills)
25. A density dependence modeled can be created with a slight alteration of which model we already know? What is this model called? Give the equation.
• Density dependence can be modeled by altering the exponential growth model.
• This results in the Logistic Growth Model
• dN/dt = rN(1 - (N/K))
• Change in N causes change in brith/death rates (and thus population growth rate)
26. What is carrying capacity (K)? How does the logistic growth model curve change as it nears K? How does this affect the growth rate? How is this different from the exponential growth model?
• The Carrying Capacity (K) is the maximum population size (Nmax) that can be supported (carrying capacity of the environment)
• The closer N gets to the maximum N (K = Carrying Capacity) - the slower the population growth rate (dN/dt)
• The Logistic Growth model is different from the Exponential growth model because; dN/dt increases infinitely with increasing population in the exponential growth models.
27. What can cause the carrying capacity (K) to change? At what population size is the rate of population growth the highest?
• Logistic growth assumes that resources are constant, but if resource availability changes then K changes as well.
• Population growth is at the maximum rate when N is ½ its max.
• When N is ½ way to the maximum (1/2 K) population growth (dN/dt) is at its maximum
• If N is below ½ K the population growth rate is increasing (> dN/dt)
• If N is above ½ K the population growth rate is decreasing (< dN/dt)
• If N = K the population growth rate stops (dN/dt = 0)
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