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91Ó°ÊÓ

A wildlife biologist examines frogs for a genetic trait he suspects may be linked to sensitivity to industrial toxins in the environment. Previous research had established that this trait is usually found in 1 of every 8 frogs. He collects and examines a dozen frogs. If the frequency of the trait has not changed, what's the probability he finds the trait in a. none of the 12 frogs? b. at least 2 frogs? c. 3 or 4 frogs? d. no more than 4 frogs?

Short Answer

Expert verified
The exact numerical answers depend on the calculations in each step. In general, the method involves applying the binomial distribution formula, i.e. calculating combinations \(C(n, k)\) and then applying these in the probability formula \(P(X=k) = C(n, k) * (p)^k * (1-p)^(n-k)\).

Step by step solution

01

Probability of trait in none of the 12 frogs

For the biologist to find none of the frogs with trait, \(k = 0\) successes in \(n = 12\) trials. Applying the binomial equation, we calculate \(P(X=0) = C(12, 0) * (0.125)^0 * (1-0.125)^{12-0}\).
02

Probability of trait in at least 2 frogs

Finding trait in at least 2 frogs means 2 or more, i.e. 2, 3, ..., 12 frogs. Instead of calculating all these probabilities separately and adding them, it's easier to calculate the probability of finding trait in 0 or 1 frog and subtract from 1. Thus, \(P(X >= 2) = 1 - [P(X=0) + P(X=1)]\), where \(P(X=0)\) is as calculated in step 1 and \(P(X=1) = C(12, 1) * (0.125)^1 * (1-0.125)^{12-1}\).
03

Probability of trait in 3 or 4 frogs

For finding trait in 3 or 4 frogs, we calculate probabilities for each case using the binomial equation and then add these values. Thus, \(P(X = 3 or 4) = P(X=3) + P(X=4)\), where \(P(X=3) = C(12, 3) * (0.125)^3 * (1-0.125)^{12-3}\) and \(P(X=4) = C(12, 4) * (0.125)^4 * (1-0.125)^{12-4}\).
04

Probability of trait in no more than 4 frogs

No more than 4 frogs means 0, 1, 2, 3 or 4 frogs. Calculating all these and adding, or calculating for 5, 6, ..., 12 frogs and subtracting from 1 gives the same result. Thus, \(P(X <= 4) = P(X=0) + P(X=1) + P(X=2) + P(X=3) + P(X=4)\), where \(P(X=0), P(X=1), P(X=3), P(X=4)\) are as calculated before, and \(P(X=2) = C(12, 2) * (0.125)^2 * (1-0.125)^{12-2}\).

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Key Concepts

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

Probability Theory
Probability theory is a fascinating field that examines the likelihood of events occurring. It forms the foundation for many statistical methods, including the binomial distribution used in the exercise above. The binomial distribution models the number of successes in a fixed number of trials, where each trial has two possible outcomes (like having the trait or not in a frog) and a constant probability of success (here, \(0.125\) or \(1/8\)).

In our scenario, each frog examined can either possess the genetic trait or not. Imagine tossing a coin 12 times, with the probability of getting heads each time being \(1/8\). The concepts of trials and successes apply similarly, making the binomial distribution an ideal tool to work out the probabilities for the wildlife biologist's queries.
  • Probability of none having the trait uses \(k = 0\) successes.
  • Probability of at least two frogs having the trait explores every possibility from two to twelve.
  • The scenarios "3 or 4 frogs" and "no more than 4 frogs" are other descriptive examples of how varied situations are approached with the same formula.
Mastering these probabilities assists in predicting patterns and probability effectively.
Genetic Traits and Probability
Genetic traits follow Mendelian inheritance patterns but can be studied using probability theory to predict how common a trait might appear in a population. Our trait of interest happens in 1 out of 8 frogs, indicating its relative rarity.

Biologists and geneticists frequently use probability to forecast genetic trait allocations in populations under study. By assessing these probabilities, they can uncover valuable insights into how traits persist or are influenced by environmental factors such as toxins.
  • Each frog either possesses the genetic allele or does not. This binary outcome is why binomial probability is so effective here.
  • The initial research informs the degree to which this trait manifests. This forms a central parameter, guiding all probability forecasts on the genetic trait propensities.
Through probability assessments, researchers can better understand genetic expressions and plan further research or conservation efforts.
Statistical Methods in Biology
In biology, statistical methods are essential for transforming data into meaningful information. This integration of statistics allows scientists to draw conclusions or predictions from tedious experimental data. Using the binomial distribution in our problem illustrates a typical application.

Biologists rely on statistics to validate their hypotheses, such as understanding the prevalence of genetic traits in a population. With our frog example, utilizing statistical methods, researchers use empirically derived probabilities to comprehend environmental impacts on species. This problem illustrates practical applications:
  • Determining the presence of a genetic condition in varying numbers of organisms.
  • Evaluating significant deviations from expected genetic conditions could suggest changes in environmental conditions or population genetics.
  • Subsequent biological strategies and decisions are driven by statistically significant outcomes.
Thus, statistical methods empower biologists to enhance conservation initiatives and broaden the understanding of biological phenomena.

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Most popular questions from this chapter

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