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Chapter 18: Problem 13

Which are two primary sources of genetic variation? a. mutations and sexual reproduction b. isolation and sexual reproduction c. sexual reproduction and asexual reproduction d. migration and sexual reproduction

Short Answer

Expert verified
a. mutations and sexual reproduction

Step by step solution

01

- Understanding Genetic Variation

Genetic variation refers to the diversity in gene frequencies. It is important for the adaptability and survival of species as it enables populations to adapt to changing environments.
02

- Identify the Role of Mutations

Mutations are changes in the genetic material of an organism. They introduce new genetic information into a population, providing a source of variation.
03

- Identify the Role of Sexual Reproduction

Sexual reproduction combines genetic material from two parents to create offspring with a mix of traits. This process shuffles genes and increases genetic variation.
04

- Evaluate Other Options

Isolation, migration, and types of reproduction also play roles in genetic variation, but their primary function is not solely the introduction of new genetic information as seen with mutations and sexual reproduction.
05

- Choose the Best Answer

Given the roles discussed, the best answer to identify two primary sources of genetic variation is mutations and sexual reproduction.

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Key Concepts

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

Mutations
Mutations are changes in the DNA sequence of an organism's genome. They happen randomly and can introduce new genetic information into a population.

These changes might occur during DNA replication or due to environmental factors, like radiation. Here are some key points to understand about mutations:

  • **Types of Mutations**: There are different types of mutations, such as insertions, deletions, and substitutions, which all modify the genetic code in unique ways.
  • **Impact**: Mutations can be beneficial, harmful, or neutral. Beneficial mutations might improve an organism's chance of survival and reproduction.
  • **Source of Variation**: Mutations add new genetic variants to a population, which is crucial for genetic diversity.
These genetic alterations are passed on to the next generation if they occur in reproductive cells.
Overall, mutations are essential for generating the novel traits on which natural selection can act.
Sexual Reproduction
Sexual reproduction is a biological process where genetic material from two parents combines to produce offspring. This process is key to creating genetic variation. Here鈥檚 why sexual reproduction is crucial:

  • **Gene Shuffling**: Sexual reproduction shuffles genes during meiosis, leading to the formation of unique genetic combinations.
  • **Independent Assortment**: During meiosis, chromosomes are distributed randomly into gametes, ensuring a mix of parental traits.
  • **Recombination**: Segments of DNA are exchanged between paired chromosomes, creating new gene combinations.
These mechanisms ensure that each offspring inherits a unique set of genes, different from both parents and their siblings.
As a result, populations have a wide range of traits, which helps species to adapt and survive in changing environments.
Adaptability
Adaptability refers to the ability of a population to adjust to various environmental changes. Genetic variation plays a crucial role in this process. Here's how:

  • **Survival**: Populations with high genetic diversity are more likely to have individuals with traits that can survive environmental challenges.
  • **Evolution**: Genetic variation provides raw material for evolution, allowing natural selection to increase the frequency of beneficial traits over time.
  • **Flexibility**: Diverse genetic backgrounds mean that populations can better withstand diseases, climate changes, and other stresses.
Without genetic variation from mutations and sexual reproduction, species would struggle to adapt and evolve. Hence, genetic diversity is vital for the long-term survival of species.
In summary, adaptability supported by genetic variation ensures that populations remain resilient and capable of thriving amidst adversity.

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Most popular questions from this chapter

Prior to 1800 in England, the typical moth of the species Biston betularia (peppered moth) had a light pattern. Dark colored moths were rare. By the late 19th century, the light-colored moths were rare, and the moths with dark patterns were abundant. The cause of this change was hypothesized to be selective predation by birds (J.W. Tutt, 1896). During the industrial revolution, soot and other wastes from industrial processes killed tree lichens and darkened tree trunks. Thus, prior to the pollution of the industrial revolution, dark moths stood out on light-colored trees and were vulnerable to predators. With the rise of pollution, however, the coloring of moths vulnerable to predators changed to light. Commonly used in biology textbooks, the peppered moth is a classic example of evolutionary change in action. The example describes changes in a population鈥檚 allele frequencies-a small-scale change, evolutionarily speaking. The presence of both light and dark forms within the gene pool is demonstrated by the story, but the peppered moth stays a peppered moth. Which scenario, if it were to occur, would be a model for large-scale evolutionary change? a. Conditions change such that the dark form of the moth is favored and the light form is diminished in the population due to predation. Conditions change again, the dark form is vulnerable, and the light form returns to prevalence. b. Conditions change such that the dark form of the moth is favored and the light form is eradicated in the population due to predation. Conditions change again, the dark form is vulnerable, and the dark form is eradicated due to predation. c. Conditions change such that dark form of the moth is favored and the light form is diminished in the population due to predation. Conditions change again, and both forms have equal prevalence. d. Conditions change such that dark form of the moth is favored and the light form is eradicated in the population due to predation. Conditions change again, the dark form is vulnerable. It develops an adaptation that shields it from predation.

Prior to 1800 in England, the typical moth of the species Biston betularia (peppered moth) had a light pattern. Dark colored moths were rare. By the late 19th century, the light-colored moths were rare, and the moths with dark patterns were abundant. The cause of this change was hypothesized to be selective predation by birds (J.W. Tutt, 1896). During the industrial revolution, soot and other wastes from industrial processes killed tree lichens and darkened tree trunks. Thus, prior to the pollution of the industrial revolution, dark moths stood out on light-colored trees and were vulnerable to predators. With the rise of pollution, however, the coloring of moths vulnerable to predators changed to light. In the late 1900s, England cleaned up its air, and pollution decreased. The bark of trees went from dark to light. Which of the following outcomes to the populations of peppered moth would you expect given this environmental change? a. An increase in the number of dark moths and a decrease in the number of light moths b. an increase in the number of moths overall c. an approximately equal number of light moths and dark moths d. an increase in the number of light moths and a decrease in the number of dark moths

The process of mutation, which generates genetic variation, is random. Thus, life has evolved, and continues to evolve, randomly. Which statement is an appropriately evidence-based refinement of the above? a. The process of mutation, which generates genetic variation, is random. However, the process of natural selection, which results in adaptations like the fit between a flower and its pollinator, favors variants which are better able to survive and reproduce. Natural selection is not random, so the overall process of evolution is not random, either. b. The process of mutation, which generates genetic variation, is random. However, the process of migration, which results in gene flow between populations, also generates genetic variation. Migration is not random, so the overall process of evolution is not random, either. c. The process of mutation, which generates genetic variation, is random. However, the process of sexual reproduction, which also introduces genetic variance, is not random. Because sexual reproduction is not random, the overall process of evolution is not random, either. d. The process of mutation, which generates genetic variation, is random. Whether mutations have a positive, negative, or neutral effect in terms of selective advantage is also random. Mutations and their effects are random, so the overall process of evolution is random.

Give an example of convergent evolution and explain how it supports the theory of evolution by natural selection. a. An example of convergent evolution is the development of the same function, swimming, in organisms that live in different parts of the globe, such as Arctic beluga whales and Antarctic right whales. The fact that organisms that do not come in contact with each other have developed the same traits suggests that natural selection can produce similar adaptations in organisms who share a similar environment b. An example of convergent evolution is the set of adaptations, such as better running speed or more efficient hunting, developed by a species in response to competition with a new species that moves into the same region. The fact that a species adapts after it comes into contact with a competitor suggests that natural selection works more quickly with higher selective pressures. c. An example of convergent evolution is the development of an ancestral structure, a limb, into two different modern structures, such as a hand and a flipper. The fact that natural selection can cause a structure to develop down two different pathways due to different environmental conditions supports the theory of evolution d. An example of convergent evolution is the development of the same function, flying, in organisms that do not share a recent common ancestry, such as insects and birds. The fact that wings that allow flight have developed from very different original structures suggests that the process of natural selection can produce similar adaptations in two very different types of organisms who share a similar environment

A friend says: 鈥淣atural selection is about the survival of the very fittest in a population. The fittest are those that are strongest, largest, fastest.鈥� Would you agree with that statement? Explain. What evidence from scientific disciplines can you offer to support your agreement or your disagreement? a. The statement is true. If an organism is not strong and fast, it will not survive long enough to reproduce and pass on its genes, and if it is not large and fitter than the other individuals around it then it will not be able to compete for a mate. Many seal species, for example, have only a single male who gets to mate. He must be the very fittest seal to win all the females. b. The very fittest organisms are not necessarily the ones that survive. Sometimes it is the least fit organisms that survive and reproduce. For example, in one generation the mice who are bad at foraging for seeds may reproduce prolifically and dominate the mice who are good at foraging. In this case, natural selection will select for the less-fit phenotype and spread it in the population. c. The definition of fitness is not correct. The strongest and fastest organisms are more fit than the weaker and slower ones, but large individuals are often at a disadvantage to smaller ones because they are easily spotted by predators. For example, a large rabbit will stick out on a field more than a small one and will get eaten by a hawk. d. What is meant by 鈥渇ittest鈥� is not necessarily strong, large, and fast. Fitness, as defined in evolutionary terms, has to do with survival and the reproduction of genetic material. For example, a small but showy male bird may be selected by female birds to reproduce, while a large but less colorful one is not.
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