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Chapter 36: Problem 1

An ecologist is planning to measure both the size and density of a population. Identify the experimental method that can best provide these data. a. mark and recapture b. mark and release c. quadrat d. life table

Short Answer

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c. quadrat

Step by step solution

01

Understand the Methods

First, understand what each experimental method entails. - Mark and recapture: Involves capturing organisms, marking them, and then releasing them to be possibly captured again. This helps estimate population size and density through statistical models.- Mark and release: Involves capturing and marking organisms but does not provide a mechanism for recapture, hence not suitable for estimating population size.- Quadrat: Involves marking off a square area to count all organisms within that area. This is effective for studying population size and density in a specific area.- Life table: Summarizes the age distribution and mortality rates of a population, not typically used for directly measuring population size or density.
02

Compare Methods

Compare the methods to see which best fit the need for measuring size and density. - Mark and recapture: Provides repeated data allowing for calculation of total population size and can infer density if the sampled area size is known.- Quadrat: Provides direct counts in a known area, allowing calculation of both population size and density directly from the sample.
03

Select the Best Method

Based on the comparisons, 'quadrat' (c) is most suitable for directly measuring both the size and density of a population. It allows ecologists to count individuals in a set area, making it feasible to calculate density (individuals per unit area) and estimate total population size by expanding the counts.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Understanding the Mark and Recapture Method
The **mark and recapture method** is a popular technique in ecological population studies. This method helps in estimating the size and density of animal populations. Ecologists capture a sample of the population, mark them uniquely, and then release them back into their habitat. After some time, they capture another sample and count how many of the marked individuals appear in this second sample.

This method relies on a simple equation to estimate population size (N):
\(N = \frac{MC}{R}\)
Here, M represents the number of animals initially marked and released, C is the total number captured in the second sample, and R is the number of recaptured animals that were marked.

Key assumptions for this method include:
  • The marked individuals mix evenly with the unmarked population.
  • There are no significant changes in the population size due to births, deaths, immigration, or emigration between marking and recapture.
  • Marked individuals don't lose their marks.

When done correctly, the mark and recapture method can provide a robust estimate of population size and help ecologists understand population dynamics.
What is Quadrat Sampling?
The **quadrat sampling** method involves marking out a specific area, known as a quadrat, to study organisms within that space. Ecologists count the number of individuals of each species within this fixed plot. By using multiple quadrats, they can estimate both population size and density.

Here鈥檚 how it works:
  • Ecologists place a square or rectangular frame (the quadrat) at random locations within the study area.
  • They count all the individuals of the species of interest within each quadrat.
  • By averaging the counts and knowing the total study area's size, they can estimate the overall population size and density.
For example, if an ecologist counts an average of 10 plants per quadrat, and the total study area is 100 times the quadrat area, they can infer there are approximately 1,000 plants in that larger area.

Quadrat sampling is particularly useful for studying populations confined to specific habitats, like plants or stationary animals. It gives precise data about local densities and can be extrapolated to estimate population sizes in larger areas.
The Role of Ecological Population Studies
**Ecological population studies** are essential for understanding the dynamics within ecosystems. They focus on population size, density, distribution, and interactions between species and their environments.

Key components of these studies include:
  • **Population size**: The total number of individuals within a population.
  • **Population density**: The number of individuals per unit area or volume.
  • **Distribution**: How individuals are spaced out across the habitat (random, uniform, or clumped).

Methods like mark and recapture and quadrat sampling are integral to these studies. By estimating population size and density, ecologists can monitor changes over time, understand species鈥� roles within ecosystems, and identify potential conservation needs.

Moreover, these studies help in predicting how populations respond to environmental changes, aiding in biodiversity conservation and ecosystem management. They provide critical data for making informed decisions to preserve natural habitats and the species that inhabit them.

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Most popular questions from this chapter

Give examples of how two different populations of organisms might have the same population density, but different dispersal patterns. a. Two populations could occupy the same range with the same number of individuals, giving different dispersal patterns. However, both the populations may be dispersed randomly throughout the range, giving identical population densities. b. Two populations could occupy the different range with the different number of individuals, giving different dispersal patterns. However, both the populations may move over this range in a herd, giving identical population densities. c. Two populations could occupy the same range with the different number of individuals, giving identical population densities. However, one population may move over this range in a herd while the other population may be dispersed randomly throughout the range. d. Two populations could occupy the same range with the same number of individuals, giving identical population densities. However, one population may move over this range in a herd while the other population may be dispersed randomly throughout the range.

The following problem extends the Hardy-Weinberg model of population dynamics that was covered in Chapter 19. It applies mathematics that would be appropriate after a second course in Algebra. While the concept applied in this problem are within the scope of the Exam the mathematical representations are not and the item is provided to allow students who are able another look at the concepts. The Hardy-Weinberg model of population dynamics is an algebraic representation of the relationships among genotype frequencies, F, and the probability of the dominant allele A, p, and the recessive allele a, q. The Hardy-Weinberg model of population dynamics is based on several assumptions. One of these assumptions is 鈥渞andom mating.鈥� If all genes in a population are equally able to reproduce, this means that all genes are equally fit and equally fertile. Consequently, the population never evolves. Populations do evolve and the Hardy-Weinberg model can be modified slightly to allow evolution to occur. Suppose that there is an initial population at generation zero and the probability of the dominant allele at that time is p0. Later, at population k the probability is different. But if the frequencies of the three different combinations of alleles is known then the probabilities pk and qk can be calculated at generation k (1) \(p_{k}=F_{k}(A A)+1 / 2 F_{k}(A a) q_{k}=F_{k}(a a)+1 / 2 F_{k}(A a)\) And since p and q are probabilities for a case where only two alleles exist, p+q=1. Then also (p+q)2=1, leading the Hardy-Weinberg equation (2) \(F_{k}(A A)=p_{k}^{2} w_{A A} / W F_{k}(A a)=2 p_{k} q_{k} w_{A a} / W F_{k}=\) \(q^{2}_{k} w_{a a} / W W=p^{2} w_{A A}+2 p q w_{A a} / q^{2} w_{a a}\) Haldane divides by the factor \(\mathrm{W}=\mathrm{F}_{\mathrm{k}}(\mathrm{A} \mathrm{A})+\mathrm{F}_{\mathrm{k}}(\mathrm{Aa})+\mathrm{F}_{\mathrm{k}}(\mathrm{aa})\) so that the probabilities that are still calculated with equation (1) to continue to satisfy the condition for p and q to represent probabilities:\((p+q)^{2}=1\) A. Justify Haldane's model in terms of what the factors \(\mathrm{w}_{\mathrm{AA}}, \mathrm{w}_{\mathrm{Aa}}\) and \(\mathrm{w}_{\mathrm{aa}}\) mean. B. Suppose that \(w_{A A}=w_{A a}=1,\) but that \(w_{\text { aa }}=0.8\) . Predict what will happen to the population over time. Fitness is determined by the environment. Moree (The American Naturalist, 86, 1952) measured the relative fitness in Drosophila melanogaster of a recessive allele that imparts black eye color as population density increases. A varying number of flies with an equal number of males and females were placed in a pint jar and progeny counted. In each experiment the population was initially heterozygous. C. Apply Haldane鈥檚 approach to calculate the probabilityp in the first generation after mating 150 female and 150 male flies that are heterozygous using wAA = wAa = 1. Rendel (Evolution, 5, 1951) conducted an investigation of the dependence of fecundity (fertility) on light in ebonyeyed D. melanogaster. A summary of some of the data that he reported is shown in the table below: D. Pose two scientific questions concerning the behavioral response indicated by the data that can be tested experimentally. E. Is there a question you can add here to wrap up this set with this LO from the list? In this case 鈥渓ight鈥� is the single environmental factor, and they two phenotypes are ebony and wild type that result from different genotypes within the population of flies.

Predict and explain the effects of human population on biodiversity many years in the future. a. Biodiversity will decline as human population increases because of habitat loss, increased pollution, and climate change. b. Biodiversity will decline as human population increases because of enhanced food supplies, medical advances, and development of renewable energy sources. c. Biodiversity will increase as human population increases because of habitat loss, increased pollution, and climate change. d. Biodiversity will increase as human population increases because of enhanced food supplies, medical advances, and development of renewable energy sources.

Describe how a researcher would best collect data in order to calculate mortality rates within a population. a. For various age groups, count the number of individuals that died and the number that survived within a defined time period. b. For various age groups, count the number of individuals that were born and the number that died within a defined time period. c. For each sex, count the number of individuals that were born and the number that survived within a defined time period. d. For each sex, count the number of individuals that died and the number that were born within a defined time period.

Honey bees are pollinators. Identify the type of symbiotic relationship that exists between honey bees and flowering plants, and explain why your reasoning. a. This is commensalism because bees help plants pollinate and, in turn, obtain nectar from the plants. b. This is a mutualistic relationship, because bees obtain nectar from the plants, but do not provide any benefits to the plants. c. This is commensalism, because bees obtain nectar from the plants, but do not provide any benefits to the plants. d. This is a mutualistic relationship, because bees help plants pollinate and, in turn, obtain nectar from the plants.
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