Population Ecology Quiz

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Questions and Answers

What is the main characteristic of Type III survivorship?

  • Constant death rates across all age groups
  • Low mortality rates in young
  • Parental care leading to high survival rates
  • High mortality for the young followed by a plateau in adults (correct)

In exponential population growth, which factor does NOT influence the change in population size?

  • Industrial pollution (correct)
  • Number of deaths
  • Number of immigrants
  • Number of births

What denotes the carrying capacity (K) in a habitat?

  • The number of individuals that can migrate to a new area
  • The maximum population size that can be sustained (correct)
  • The point at which resources are infinite
  • The initial population size before growth starts

Which equation represents the change in population size over time?

<p>$ rac{dN}{dt} = B + I - D - E$ (D)</p> Signup and view all the answers

Which of the following best describes exponential growth?

<p>Characterized by a J-shaped growth curve (B)</p> Signup and view all the answers

What does 'r' represent in the context of population growth?

<p>Intrinsic growth rate of a single individual (A)</p> Signup and view all the answers

Which scenario is most likely to lead to exponential population growth?

<p>A population rebounds after a catastrophic event (C)</p> Signup and view all the answers

What is primarily responsible for limiting logistic growth?

<p>Finite resources (A)</p> Signup and view all the answers

What is the first step in the mark-recapture method for estimating population size?

<p>Mark all sampled individuals (D)</p> Signup and view all the answers

Which formula is used to estimate the population size in the mark-recapture method?

<p>$N = \frac{m imes s}{r}$ (D)</p> Signup and view all the answers

What is a key assumption made in mark-recapture methods?

<p>Marked individuals have mixed completely back into the population. (C)</p> Signup and view all the answers

What does the variable 's' represent in the mark-recapture method?

<p>Number of individuals initially sampled (B)</p> Signup and view all the answers

Which of the following factors contribute positively to changes in population size?

<p>Immigration and births (A)</p> Signup and view all the answers

After marking and releasing individuals, what is the next action to take in the mark-recapture process?

<p>Resample r individuals (A)</p> Signup and view all the answers

What is the purpose of counting the number m of re-sampled marked individuals?

<p>To estimate the total population size N (C)</p> Signup and view all the answers

What is the primary purpose of a life table in demographics?

<p>To summarize survival and reproduction rates of different age groups. (D)</p> Signup and view all the answers

Which of the following statements accurately reflects the mark-recapture method?

<p>It relies on extrapolation from a sub-sample for population size estimation. (C)</p> Signup and view all the answers

Which type of survivorship curve is characterized by a low death rate in juveniles and adults?

<p>Type I (A)</p> Signup and view all the answers

What is demography primarily concerned with studying?

<p>Changes over time in the vital statistics of populations. (C)</p> Signup and view all the answers

Why is it often impossible to count all individuals in a population?

<p>Individuals might be too dispersed or hidden. (B)</p> Signup and view all the answers

Which characteristic is NOT associated with K-selection?

<p>Have many offspring at a time (C)</p> Signup and view all the answers

What do K-selection strategies generally favor?

<p>Late age of first reproduction (D)</p> Signup and view all the answers

What is one common misconception regarding K and r strategies?

<p>They are used by all ecologists today (A)</p> Signup and view all the answers

In the context of life history trade-offs, which statement is true regarding r strategies?

<p>They have many small offspring (D)</p> Signup and view all the answers

What factor may influence the evolution of life-history traits according to the recent understanding in ecology?

<p>Total amount of resources individuals acquire (D)</p> Signup and view all the answers

What does the logistic growth model express?

<p>The relationship of population growth to carrying capacity (C)</p> Signup and view all the answers

Which statement best describes competition in K-selection environments?

<p>High competition due to density-dependent effects (B)</p> Signup and view all the answers

Which of the following is an example of a K-strategy organism?

<p>Mature trees in an old-growth forest (C)</p> Signup and view all the answers

What is a life history trait that impacts an organism's schedule of reproduction and survival?

<p>Age at death (C)</p> Signup and view all the answers

Which of the following is a characteristic of r-selection life history strategies?

<p>Mature rapidly (B)</p> Signup and view all the answers

What is one of the trade-offs observed in life history traits regarding offspring?

<p>Quality versus quantity of offspring (C)</p> Signup and view all the answers

In the logistic growth model, what is expected to happen if a population overshoots its carrying capacity K?

<p>Population crashes due to resource depletion (C)</p> Signup and view all the answers

Which of the following best describes a phenotypic negative correlation?

<p>Larger egg sizes correlate with fewer eggs (C)</p> Signup and view all the answers

What defines the r-selection in population ecology?

<p>Low density environments with high reproductive output (B)</p> Signup and view all the answers

Which factor is NOT a life history trait?

<p>Type of food consumed (D)</p> Signup and view all the answers

What do life history trade-offs imply about resource allocation?

<p>Resources must be divided among competing traits (B)</p> Signup and view all the answers

What does population ecology primarily study?

<p>The environment's effect on population density and distribution. (C)</p> Signup and view all the answers

What is the main purpose of the mark-recapture method?

<p>To estimate population size. (A)</p> Signup and view all the answers

Which factor is NOT typically analyzed in population dynamics?

<p>The cost of living in different habitats. (D)</p> Signup and view all the answers

Which curve is associated with survivorship based on life tables?

<p>Survivorship curve. (A)</p> Signup and view all the answers

What is a key difference between exponential and logistic growth models?

<p>Logistic growth accounts for environmental resistance. (C)</p> Signup and view all the answers

How can life history traits influence an individual’s fitness?

<p>By determining the individual's reproductive success. (A)</p> Signup and view all the answers

Which of the following is true regarding trade-offs in life history traits?

<p>Investment in one trait reduces investment in another. (C)</p> Signup and view all the answers

Which method is primarily used to extrapolate population sizes from a sub-sample?

<p>Mark-recapture method. (A)</p> Signup and view all the answers

Flashcards

Population ecology

The study of populations in relation to their environment, including factors like density, distribution, age structure, and population size variations.

Population dynamics

The study of how interactions between biotic(living) and abiotic (non-living) factors influence changes in a population's size.

Mark-recapture method

A method to estimate population size by capturing, marking, releasing, and recapturing individuals in a sample.

Population

A group of the same species living together in an area and can breed.

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Estimating population size

Using sampling techniques (like mark-recapture) to determine the total population size.

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Mark-recapture method: step 1

Capture and mark a sample (s) of individuals in the population.

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Mark-recapture method: step 2

Release the marked individuals back into the population.

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Mark-recapture method: step 3

Recapture another sample to determine the proportion of marked individuals.

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Sample individuals

Selecting a portion of a population for observation or study.

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Mark all sampled individuals

Identifying all selected individuals in a sample with a particular mark to distinguish them from unmarked individuals.

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Resample individuals

Taking a second sample of individuals from the same population after marking the initial individuals and releasing them.

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Count re-sampled marked individuals

Determining the number of individuals in the second sample that have already been marked.

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Population size estimation

Using the proportion of marked individuals in the second sample to estimate the total population size.

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Estimation formula

The formula used to estimate the population size: N = (s * r) / m, where s is the number of initially marked individuals, r is the number of individuals in the recapture sample, and m is the number of marked individuals in the recapture sample.

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Extrapolation

Estimating an unknown value (like population size) by assuming a pattern and applying it to the unknown value based on observations of a sample.

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Mark-Recapture Assumptions

A method for estimating population size when observing marked and unmarked individuals. Assumptions include equal sampling probability for all individuals, no impact of marking on re-sampling, complete mixing of marked individuals, and no births, deaths, immigration, or emigration during the sampling period.

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Population Density Change

Changes in the number of individuals per unit area or volume due to immigration/births and emigration/deaths.

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Demography

The study of population changes over time, focusing on vital statistics like birth and death rates.

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Life Table

A table that summarizes survival and reproduction rates for specific age groups in a population, typically using a female cohort.

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Survivorship Curve

A graph showing the proportion of individuals surviving at each age.

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Type III Survivorship Curve

A survivorship curve where a high number of offspring are produced, but mortality rates are very high early in life. This is typical for species with minimal parental care and many offspring.

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Exponential Growth

A rapid population growth pattern in an ideal environment with unlimited resources. It's characterized by a J-shaped curve on a graph.

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What is the equation for exponential growth?

dN/dt = rN

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Intrinsic Growth Rate (r)

The per capita change in population size at each time instant. It reflects how fast a population can grow under ideal conditions.

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Logistic Growth

A population growth pattern that starts exponentially but slows down as it approaches the carrying capacity of the environment.

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Carrying Capacity (K)

The maximum population size that an environment can sustainably support based on available resources.

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What are the limitations of exponential growth?

Exponential growth is unrealistic in the long term because resources are limited. Eventually, the population will reach the carrying capacity of the environment, which will limit further growth.

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What is the key difference between exponential and logistic growth?

Exponential growth assumes unlimited resources and continues indefinitely, whereas logistic growth accounts for limited resources and approaches a carrying capacity (K) where population growth slows down.

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Life history traits

Characteristics that affect an organism's reproduction and survival schedule, including things like age at maturity, number of offspring, and lifespan.

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Trade-off in Life History

The limited resources available force organisms to allocate energy to different life history traits, resulting in compromises between traits like survival and reproduction.

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r-selection

Selection that favors traits that promote rapid population growth at low densities, often with high reproductive rates and short lifespans.

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K-selection

Selection that favors traits that maximize fitness at high densities, often with fewer offspring and longer lifespans.

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Influence of density on selection

The effect of population density on the types of traits selected for: r-selection at low densities, and K-selection at high densities.

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Density-independent selection

Selection that favors traits that allow organisms to thrive in environments where population density has little impact.

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Density-dependent selection

Selection that favors traits that allow organisms to thrive in environments where competition is intense due to high population density.

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Examples of r-selection

Species exhibiting r-selected traits often include: - Rapidly colonizing new environments - High reproductive rates - Short lifespans - Minimal parental care

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Life History Trade-offs

Different species have different strategies for reproduction and survival, leading to trade-offs in resource allocation.

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r-strategy

A life history strategy favoring traits that maximize reproduction in unstable environments with low population densities.

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K-selected species

Species that exhibit traits characteristic of K-selection, such as slow growth, late reproduction, and long lifespan.

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r-selected species

Species that exhibit traits characteristic of r-selection, such as rapid growth, early reproduction, and short lifespan.

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Ecological Succession

The gradual process of change in a community's species composition over time following a disturbance.

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Study Notes

Topic 15: Population Ecology

  • Population ecology is the study of populations in relation to their environment, including factors like density, distribution, age structure, and population size variation.
  • Population dynamics investigates how biotic and abiotic factors influence population size changes.
  • A population is a group of individuals of a single species living in the same area and interbreeding to produce fertile offspring.

Learning Outcomes

  • Estimate population size 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 population growth models.
  • Evaluate growth model parameters to predict population size changes.
  • Explain how life history traits impact lifetime fitness.
  • Graphically identify trade-offs in life history traits.

Estimating Population Size

  • Often, counting all individuals in a population is impossible.
  • A sub-sample is used and extrapolated to estimate the whole population.
  • Mark-recapture method:
    • Sample a number of individuals (s).
    • Mark all sampled individuals.
    • Release the marked individuals.
    • Resample a number of individuals (r).
    • Count the number of re-sampled marked individuals (m).
    • Use the formula N = (s × r) / m to estimate population size (N).

Population Density

  • Population density is the number of individuals per unit area or volume, and it can change over time.
  • Population density change is influenced by immigration/births and emigration/deaths.
    • Change in population size = births + immigrants - deaths - emigrants

Demographics

  • Demography is the study of changes in vital statistics over time (like birth rates, death rates) within populations, especially birth rates and death rates.
  • A life table can summarize the survival and reproduction rates of individuals across specific age groups within a population.
  • A life table typically tracks a cohort (individuals born around the same time), particularly females, because they tend to be the ones producing offspring.
  • Life tables reveal constant death rates and higher reproduction rates at specific ages (e.g., age 4 in the Belding's ground squirrel example).

Survivorship Curves

  • Survivorship curves show the proportion of individuals in a cohort that remain alive at each age.
  • Type I curves show a high survival rate in juveniles and adults, followed by a sharp decline in old age (mammals, few offspring, parental care).
  • Type II curves display a relatively constant death rate across all ages (e.g., certain birds).
  • Type III curves illustrate high mortality rates for young but a leveling off of death rates among surviving individuals into adulthood (fish, many offspring, no parental care).

Modeling Population Growth

  • Exponential growth occurs in ideal, unlimited environments, where the population size increases by a constant proportion each time interval. The population size over time follows a J-shaped curve.
  • Logistic growth occurs when resources are finite. Initial growth is exponential but slows as the population approaches the carrying capacity (K), the maximum population size a particular environment can sustain, forming an S-shaped growth curve over time. Logistic growth is influenced by environmental limits that affect per capita birth rates and/or death rates

Life History Traits

  • Life history traits are the characteristics determining the schedule of reproduction and survival in an organism. Examples include:
    • Mass at birth
    • Age at sexual maturity
    • Frequency of reproduction
    • Reproductive lifespan
    • Number of offspring
    • Investment in parental care
    • Age at death (longevity)

Life History Trade-offs

  • Organisms allocate finite resources to different life history traits, often resulting in trade-offs.
  • Examples include the trade-off between the number of offspring and the resources invested in each offspring. Egg size and fecundity show phenotypic negative correlations.
  • r-selected species (low densities): Short lifespan, high reproductive rate, many small offspring, few reproductive events, high mortality rate, and minimal parental care.
  • K-selected species (high densities): Longer lifespan, low reproductive rate, few large offspring, frequent reproduction, low mortality rate and high parental care

Summary

  • Population ecology studies populations' relationship to their environment. Key aspects include population dynamics, estimating size, demographics (like survivorship curves), modeling growth (exponential/logistic), life history traits, and trade-offs between them. These factors impact population size over time.

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