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Chapter 19: Problem 20

Describe natural selection and give an example of natural selection at work in a population.

Short Answer

Expert verified
Natural selection is the process where better-adapted organisms survive and reproduce more. Example: Brown beetles surviving better than green beetles due to predation.

Step by step solution

01

- Define Natural Selection

Natural selection is the process whereby organisms better adapted to their environment tend to survive and produce more offspring. It is a key mechanism of evolution.
02

- Explain Mechanisms of Natural Selection

Describe how natural selection operates through variation, inheritance, high rate of population growth, and differential survival and reproduction.
03

- Provide an Example of Natural Selection

Consider a population of beetles where two color variations exist: green and brown. If birds can easily spot and prey on green beetles, brown beetles will survive longer and reproduce more successfully. Over time, the brown beetles become more common.
04

- Connect the Example to Natural Selection Principles

Explain how the example illustrates variation (green and brown beetles), differential survival (brown beetles are less visible to predators), and inheritance (brown beetles pass on their trait to offspring).

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Key Concepts

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

Evolution
Evolution is the process by which populations of organisms change over generations. It's one of the fundamental concepts of biology. Over long periods, small genetic changes can add up, leading to the development of new species.
Many factors influence evolution:
  • Mutations
  • Natural selection
  • Genetic drift
  • Gene flow
One of the most critical factors is natural selection, where traits that confer an advantage in survival and reproduction become more common over time.
Variation
Variation refers to the differences in traits among individuals in a population. These differences can be in appearance, behavior, or physiology. Variation is essential for evolution because it provides the raw material for natural selection to act upon.
Causes of variation include:
  • Mutations: changes in DNA
  • Gene recombination during sexual reproduction
  • Environmental influences
For example, consider a population of beetles where some are green, and some are brown. This color variation can significantly affect their survival.
Inheritance
Inheritance is the process through which traits are passed from parents to their offspring. Understanding inheritance is crucial to grasp how advantageous traits become more common over generations.
Traits are inherited through:
  • Genetic material (DNA)
  • Chromosomes and genes
  • Alleles: different versions of a gene
In our beetle example, if brown coloration provides a survival advantage, the brown beetles will likely have more offspring who inherit the brown color trait.
Differential Survival
Differential survival refers to the differences in survival rates among individuals in a population based on their traits. It's a central part of natural selection.
Not all individuals in a population will survive to reproduce. Those with advantageous traits have a higher likelihood of surviving and passing those traits to the next generation.
In the beetle example, brown beetles are less visible to predators compared to green beetles. As a result, brown beetles have a higher survival rate, leading to more brown beetles in future generations.
This differential survival ensures that beneficial traits become more common, driving the evolution of the population.

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Most popular questions from this chapter

Solve for the genetic structure of a population with 12 homozygous recessive individuals (yy), 8 homozygous dominant individuals (YY), and 4 heterozygous individuals (Yy).

Which of the following evolutionary forces can introduce new genetic variation into a population? a. natural selection and genetic drift b. mutation and gene flow c. natural selection and nonrandom mating d. mutation and genetic drift

Explain the Hardy-Weinberg principle of equilibrium theory.

One of the original Amish colonies rose from a ship of colonists that came from Europe. The ship's captain, who had polydactyly, a rare dominant trait, was one of the original colonists. Today, we see a much higher frequency of polydactyly in the Amish population. This is an example of: a. natural selection b. genetic drift c. founder effect d. \(\quad \mathrm{b}\) and \(\mathrm{c}\)

What is a cline? a. the slope of a mountain where a population lives b. the degree to which a mutation helps an individual survive c. the number of individuals in the population d. gradual geographic variation across an ecological gradient
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