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Questions and Answers
What is the primary benefit of the mark-recapture method in estimating population size?
What is the primary benefit of the mark-recapture method in estimating population size?
Which factor is least likely to impact population dynamics?
Which factor is least likely to impact population dynamics?
What is a crucial component in distinguishing between exponential and logistic growth models?
What is a crucial component in distinguishing between exponential and logistic growth models?
How does a trade-off in life history traits typically influence an individual's fitness?
How does a trade-off in life history traits typically influence an individual's fitness?
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In analyzing population demographics graphically over time, which aspect is most directly visualized?
In analyzing population demographics graphically over time, which aspect is most directly visualized?
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What is the first step in the mark-recapture method for estimating population size?
What is the first step in the mark-recapture method for estimating population size?
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Which formula represents the relationship used to estimate population size in the mark-recapture process?
Which formula represents the relationship used to estimate population size in the mark-recapture process?
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During the mark-recapture process, what does 'm' represent in the estimation formula?
During the mark-recapture process, what does 'm' represent in the estimation formula?
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What does the mark-recapture method primarily rely on to estimate population size?
What does the mark-recapture method primarily rely on to estimate population size?
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In the context of the mark-recapture method, what is the purpose of marking individuals?
In the context of the mark-recapture method, what is the purpose of marking individuals?
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Study Notes
Population Ecology
- Population ecology is the study of populations in relation to their environment. This includes environmental effects on population density, distribution, age structure, and population size variation.
Learning Outcomes
- Estimate population sizes using the mark-recapture method.
- Graphically analyze population demographics over time.
- Identify survivorship curves based on demographic parameters from a life table.
- Compare and contrast exponential and logistic growth models.
- Predict changes in population sizes based on different growth models.
- Explain how life history traits impact an individual's lifetime fitness.
- Identify trade-offs in life history traits graphically.
Population Dynamics
- A population is a group of interbreeding individuals of a single species in the same area. They produce fertile offspring.
- Population dynamics study how biotic and abiotic factors influence population size fluctuations.
Estimating Population Size
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Mark-recapture method: A technique to estimate population size when counting all individuals is impossible.
- Sample a number of individuals (s).
- Mark all sampled individuals.
- Release marked individuals back into the population.
- Resample a new number of individuals (r).
- Count the number of re-sampled marked individuals (m).
- Use the formula N = (s * r) / m to estimate the population size (N).
Assumptions of Mark-Recapture Methods
- Marked and unmarked individuals have the same probability of being sampled.
- Marking doesn't affect sampling probability.
- Marked individuals mix back into the population.
- No births, deaths, immigration, or emigration during the re-sampling interval.
Population Density Changes
- Population density (number of individuals per unit area or volume) can change due to immigration, births, emigration, and deaths.
Demographics
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Demography is the study of changes in vital statistics (births and deaths) in populations over time.
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Life tables summarise survival and reproduction rates across specific age groups, focusing often on a cohort of females born at the same time to track reproductive output and their survival rates.
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Survivorship curves depict the proportion of a cohort still alive at different ages.
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Type I: Low death rate in early/mid-life, high death rate in old age (e.g., mammals)
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Type II: Constant death rate throughout life (e.g., some birds, rodents)
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Type III: High death rate in early life, low death rate in old age (e.g., many fish and insects)
Exponential Population Growth
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Exponential growth occurs in ideal, unlimited environments, in J-shaped curves, as population size increases at a constant rate.
- ΔN/Δt = rN ( change in population size to the change of time is proportional to population size and a per capita growth rate, r).
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r is the intrinsic rate of increase.
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B = births
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D = deaths
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This assumes no competition and plentiful resources.
Logistic Population Growth
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Logistic growth accounts for finite resource environments. It reaches a carrying capacity (K), the maximum population size the environment can sustain.
- dN/dt = rN [(K − N)/K] (change in population is proportional to the per capita growth rate(r), the population size (N), and the available resource to population size proportion ((K - N)/K).
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As a population approaches K, its per capita growth rate decreases, and growth slows.
Life History Traits
- Life history traits are characteristics affecting reproduction and survival schedules.
- Examples include: mass at birth, age at sexual maturity, frequency of reproduction, reproductive lifespan, number of offspring, parental investment, and age at death (longevity).
- Life history traits are related closely to lifetime fitness.
Life History Trade-offs
- Resources are limited; trade-offs exist between different life history traits.
- For instance, energy allocated to reproduction may reduce survival, and an organism may trade off producing many small offspring for fewer large offspring (r- or K-selection).
r-Selection
- Favored at low densities for high reproductive success.
- Characteristics include early maturity, short lifespan, many offspring, low offspring survival rate, and minimal parental care.
K-Selection
- Favored at high densities, near population carrying capacity (K).
- Characteristics include late maturity, longer lifespan, fewer offspring, high offspring survival rate, and high parental care.
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Description
Test your knowledge on population ecology and dynamics. This quiz covers key concepts such as estimating population sizes, analyzing demographics, and understanding different growth models. Dive into factors affecting population dynamics and learn how life history traits influence fitness.
