An example of horizontal gene would be an antibiotic-resistant bacteria. This has caused a problem in the medical field because many types of antibiotic-resistant bacteria are developing in individuals, and are not able to be cured..
Module 5 Overview
Evolution and Natural Selection
This module begins your study of evolution and ecology with some of the basic concepts related to species, populations, gene pools, and genetic variety. Information obtained from population genetics is used as the basis for classifying organisms and studying evolutionary change. In this module, you will study population genetics and be able to describe how a lack of understanding of population genetics has contributed to the eugenics movement. In addition, this module will also cover the specifics of evolution and natural selection. For example, you will look at the factors influencing natural selection—the process that leads to evolution by “selecting” which genes will be passed on to the next generation.
Learning Objectives
Upon completion of this module, you should be able to:
| 8A | Differentiate between the biological species concept and the morphological species concept. | |
| 8B | Explain how hybrid plants and animals are produced. | |
| 8C | Distinguish between gene pool and genetic diversity. | |
| 8D | Relate cloning and hybridization to asexual and sexual reproduction. | |
| 8E | Explain how a lack of understanding about population genetics contributed to the eugenics movements. | |
| 8F | State why all organisms of a species are not the same. | |
| 8G | Explain how each of the following affects the genetic diversity within populations: mutation, sexual reproduction, population size, and migration. | |
| 8H | Describe three processes that could result in different populations of the same species having different gene combinations. | |
| 8I | Explain how the concepts of evolution and natural selection are related. | |
| 8J | List the five conditions to prevent frequency changes, according to the Hardy-Weinberg concept. | |
| 8K | Describe how individuals produced by sexual reproduction can have fitness different from that of their parents. | |
| 8L | Explain how natural selection can change the nature of a species. | |
| 8M | State why genetic diversity is essential for natural selection to occur. | |
| 8N | Describe how mutation and migration affect the genetic diversity of a population. | |
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Identify and describe three circumstances that can prevent a specific allele from being expressed in the phenotype of an organism. | |
| 8P | Explain why excess reproduction is important to the concept of natural selection. | |
| 8Q | Describe the contributions of the following individuals to the evolutionary thought: Lamarck, Buffon, Wallace, and Darwin. | |
| 8R | List the assumptions by Darwin that were important to his developing the theory of natural selection. | |
| 8S | Explain how survival, reproductive success, and mate selection can alter gene frequency from one generation to the next. |
Module 5 Reading Assignment
Enger, E. D., Ross, F. C., & Bailey, D. B. (2012). Concepts in biology (14th ed.). New York: McGraw-Hill. Chapter 12 and 13.
Optional Reading Assignment:
Chapter 14, The Formation of Species and Evolutionary Change.
Evolution and Natural Selection
Evolution is simply change over time, like the trees losing their leaves and mountain ranges rising and eroding; however, this is not biological evolution. Biological evolution is that all life on earth shares a common ancestor, just like you and a cousin share the same grandmother. The evolutionary process has given diversity to our environment from species, individual organisms, and molecules. Charles Darwin discovered the theory of evolution through natural selection. His process of natural selection included the following theories:
- More offspring are produced than can possibly survive.
- Traits vary among individuals, which leads to the differential rates of survival and reproduction.
- Trait differences are heritable.
The process of natural selection is when a member of the population dies and is then replaced by parents that are better-adapted to survive, who then reproduce in the environment they live in. Natural selection is known to cause adaptation, but this is not the only cause of evolution. Other causes for evolution are mutation and genetic drift, which will be further discussed. Evolution occurs by changes in inheritable traits. Our inherited traits are controlled by genes, which is why everyone on earth is different from one another. The numbers of variations and mutations in genetic material reshuffle during sexual reproduction and the migration between populations. Even though we all are different in our own way, the genome of a species is identical in all of the individuals within that species. An interesting example of this is that chimpanzees and humans are different in only 5% of their genomes.
Genetic drift is the process of genetic change of a population due to a chance or random event, rather than natural selection; this results in a change of allele frequencies over a period of time. Please watch the Genetic Drift video.
Gene flow is the process when genes exchange between a population and species. This will create a new variation and population or species. An example is when a rat from an island interacts with a city rat population. During this interaction, a gene transfer takes place between species which will formulate a new hybrid species. The horizontal gene transfer is from one organism to another, which allows the stronger genes to be transferred to the off spring so that they can survive. An example of horizontal gene would be an antibiotic-resistant bacteria. This has caused a problem in the medical field because many types of antibiotic-resistant bacteria are developing in individuals, and are not able to be cured. Horizontal transfer typically occurs in people that over-use antibiotics. When there is an overuse, the antibiotics become familiar and used to the drug, and then they will mutate to become stronger. Plasmids carry many different resistant genes that are programmed to resist antibiotic agents. The resistant strains are known today as “superbugs.” This is quickly becoming a problem in medical facilities as these “superbugs” can transfer from one patient to another.
There are many different ways to produce some form of genetic variations. In selective breeding, humans create a product that has the best genetic DNA, and then breed these genetics for production. For example, some potatoes are used for crops, and others are used to make French fries. Horses can also be breed for racing or trail-riding. Hybridization is when dissimilar individuals are brought together and both of these individuals’ best traits are used to create better offspring, in order to produce better breeds. Inbreeding is what occurs when similar, individual traits are bred in order to maintain the desired characteristics of a line. Increasing variation could cause a change to the DNA, which can lead to mutations and disorders. Genetic engineering, or manipulating DNA, is done by a scientist who knows how to remove the structure and chemical properties of a DNA strain in order to study the change in DNA. The steps in genetic engineering are the following:
- Extract the DNA from cells.
- Cut the DNA molecule into smaller pieces.
- Identify the sequence of bases in the DNA.
- Make numerous copies of the DNA.
Dolly was the first sheep to be cloned in 1997, which was a result of genetic engineering. Since then, there have been many ethical questions about cloning. Cloning is when DNA is extracted from an organism and is used to grow new cells in order to create another new organism. Another type of cloning is known as monoculture. This is widely used by farmers to produce the same crop every year, which allows the farmers to be consistent with production.
Required Presentations:
Click on the links below to view the Module 5 presentations.
Optional presentation: Chapter 14
